The 2012 Newcastle-Sydney SPAC microtremor surveys GEOSCIENCE AUSTRALIA RECORD 2014/54

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The 2012 Newcastle-Sydney SPAC
microtremor surveys
GEOSCIENCE AUSTRALIA
RECORD 2014/54
T. Volti 1, C. Collins 1, M. Asten2, T.Ikeda2 and D. Burbidge1
1. Geoscience Australia
2. Monash University
Department of Industry
Minister for Industry: The Hon Ian Macfarlane MP
Parliamentary Secretary: The Hon Bob Baldwin MP
Secretary: Ms Glenys Beauchamp PSM
Geoscience Australia
Chief Executive Officer: Dr Chris Pigram
This paper is published with the permission of the CEO, Geoscience Australia
© Commonwealth of Australia (Geoscience Australia) 2014
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ISSN 2201-702X (PDF)
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Bibliographic reference: Volti, T., Collins, C., Asten, M., Ikeda, I. & Burbidge, D. 2014. The 2012
Newcastle-Sydney SPAC microtremor surveys. Record 2014/54. Geoscience Australia, Canberra.
http://dx.doi.org/10.11636/Record.2014.054
Contents
Executive Summary..................................................................................................................................1
1 Introduction ............................................................................................................................................2
1.1 Introduction to the Vs30 method ........................................................................................................2
1.2 Limitations of the Vs30 method in estimating ground motion amplification .......................................2
1.3 Different methods leading to Vs30 estimation ...................................................................................3
1.3.1 Spectral analysis of surface waves (SASW) ..............................................................................3
1.3.2 Multi-channel analysis of surface waves (MASW) .....................................................................3
1.3.3 Active-source body-wave refraction/reflection ...........................................................................3
1.3.4 Refraction microtremor (ReMi) ...................................................................................................4
1.3.5 Spatial Autocorrelation (SPAC) and frequency-wavenumber (f-k).............................................4
1.3.6 H/V method ................................................................................................................................4
2 Vs30 in Australia ......................................................................................................................................6
2.1 Introduction ......................................................................................................................................6
2.2 SPAC method ..................................................................................................................................6
2.2.1 Introduction .................................................................................................................................6
2.2.2 SPAC inversion ..........................................................................................................................7
2.3 The Newcastle-Sydney SPAC Vs30 survey ......................................................................................8
2.3.1 Fieldwork ....................................................................................................................................8
2.3.2 Data Processing .......................................................................................................................10
2.3.3 Inversion ...................................................................................................................................13
2.3.4 GEOPSY results .......................................................................................................................15
2.3.5 Comparison with other methods ..............................................................................................16
3 Conclusions .........................................................................................................................................22
Acknowledgements ................................................................................................................................23
References .............................................................................................................................................24
Sites surveyed with SPAC- arrays information ...................................................................27
Velocity profiles from all sites ..............................................................................................31
Newcastle-Sydney SPAC microtremor survey project 2012: velocity models and
H/V spectra .............................................................................................................................................41
MASW, ReMi and S-refraction - 2013 survey...................................................................100
Site Pictures for Sydney and Newcastle SPAC, SCPT, MASW and ReMi Surveys ........102
E.1 Sydney Sites ................................................................................................................................102
E.2 Newcastle Sites ...........................................................................................................................104
The 2012 Newcastle-Sydney SPAC microtremor surveys
iii
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The 2012 Newcastle-Sydney SPAC microtremor surveys
Executive Summary
The average seismic shear wave velocity in the upper 30m of soil (Vs30) has long been recognised as
a key parameter for estimating the local ground-motion amplification from earthquakes at a particular
site. The risk of damage to buildings and infrastructure from earthquakes depends critically on this
degree of local ground amplification. Both building codes and surface hazard mapping thus require
local Vs30 information, particularly in urban areas.
The main purpose of this record is to report results from a SPAC (Spatial Autocorrelation or Spatially
Averaged Coherency) Vs30 survey that collected data at 25 sites in Newcastle and two in Sydney. The
survey was a collaboration between Geoscience Australia (GA) and Monash University (MU) with both
groups analysing the gathered data independently. The two approaches to the SPAC analysis are
compared and, where available, these results are compared with the results from a conepenetrometer test which is a direct measurement of the near surface shear wave velocity profile. The
surveyed sites were either at locations where shear-wave data have been previously obtained using
other techniques (e.g. non-invasive methods, boreholes, cone-penetrometers (SCPT)) or at locations
of existing seismic stations of the Australian National Seismic Network (ANSN) or Joint Urban
Monitoring Program (JUMP) network.
A major program of work at Geoscience Australia is to determine which method is the most effective,
efficient and accurate at estimating Vs30 for Australian conditions and consequently the response of the
sites to earthquake generated shaking. Subsurface shear wave velocity data can also be used to
correct for the local site amplification at the permanent seismic stations.
After Vs30 was estimated at all the sites, the US National Earthquake Hazard Reduction Program
(NEHRP) (Kayen et al., 2013) site classification scheme was applied and a specific class was
assigned to each site. It was found that SPAC microtremor data analysed by GA gave results which
were reasonably consistent with a) local geology and b) independent analysis of the same data set by
MU. The results from both techniques were less consistent with the SCPT data. This may be because
the non-invasive methods average the Vs30 over an area while the SCPT methods measure the site
conditions at a specific point. The results suggest that the analysis method used by GA is about as
effective at producing Vs30 estimates as MU’s method, but there are specific site conditions that may
give one or other method some difficultly. Future work should help to further resolve which SPAC
technique works more effectively at these sites.
The 2012 Newcastle-Sydney SPAC microtremor surveys
1
1 Introduction
1.1 Introduction to the Vs30 method
Seismic ground motion is controlled by a number of variables, including the characteristics of the
source, the propagation path and the near-surface geology. The amplification of seismic waves is
closely related to areas where strong acoustic impedance is present, i.e. where layers of low seismic
velocity overlie stiff soils or bedrock with a high seismic velocity. The amplification A is inversely
proportional to the square root of the product of the shear-wave velocity Vs and the density  of the
investigated soil (Aki and Richards, 2002):
A
1
Vs * 
(1)
where  is relatively constant with depth down to 100 m, and so the
Vs
profile best describes the local
site conditions. Vs averaged over the top 30m below the surface is referred to as Vs30. Vs30 is used in
the Australia Standard (Structural design actions, Part 4) to classify sites according to type of soil for
earthquake engineering purposes (Standards Australia, 2007).
There are several seismic techniques which allow Vs30 to be measured. These can be classified as
active or passive, depending on the type of wave source used. The final aim is to construct a V s30
profile by developing Vs values for individual sites pertaining to the area of interest. What the different
techniques have in common is that they are non-invasive, inexpensive and use portable equipment, in
contrast to boreholes or Seismic Cone Penetrometer (SCPT), which are expensive and limited in very
stiff soils or on rock. Both surface wave and body wave methods can be used to measure Vs. In the
case of surface waves, this can be achieved through an iterative procedure of fitting a theoretical to a
measured dispersion curve (DC). Surface wave methods differ in the way the experimental dispersion
curve is determined and the inversion to determine a Vs profile.
1.2 Limitations of the Vs30 method in estimating ground motion
amplification
Despite the widespread use of this parameter, it is accepted that site-specific seismic amplification is
too complex to be solely predicted from Vs30 (Castellaro et al., 2008). Gallipoli and Mucciarelli (2009)
report underestimates of Vs30 in materials with significant velocity contrasts and overestimates of Vs30
where basin effects are involved. Harmsen (1997) showed scattered amplification plots and concluded
that source directivity and topography also may play an important role in amplification, especially in
tectonically complex areas (Wald and Mori, 2000), and in the presence of inversions in the Vs profiles
(Di Giacomo et al. 2005). The role of sediments deeper than 30m may also be significant (Frankel et
al. 2002). Where a velocity profile is available, the square root of impedance (SRI) method
outperforms the measured Vs30 in predicting amplification (Thompson et al., 2010). Lee and Trifunac
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The 2012 Newcastle-Sydney SPAC microtremor surveys
(2010) concluded that a soil site parameter sL, where the numbers -1, 0, 1, 2 and 3 are assigned to
account for different types of local soil (rock, stiff soil, deep soil etc.) should be used simultaneously
with the geological site conditions (e.g. Kayen et al., 2013) in the scaling of the pseudo relative
velocity spectra, as in many cases Vs estimation tends to ignore the local soil site conditions.
1.3 Different methods leading to Vs30 estimation
The literature presents us with a number of methods that a) determine the dispersion curve and b)
invert for a given set of data, each method exhibiting both advantages and disadvantages. A summary
of these methods is given in Table 1.1. Active source body-wave reflection/refraction does not use the
dispersion curve, but still can provide depth to bedrock.
1.3.1 Spectral analysis of surface waves (SASW)
First introduced by Stokoe and his co-workers (Nazarian et al., 1983), SASW makes use of spectral
analysis of ground roll generated from impact wave sources to estimate the dispersion curve. The
source can be a hammer, a several-kilo weight drop, or a swept-frequency vibratory source when the
receiver spacing is small (e.g. <16m) (Kayen and Carkin, 2006). For longer receiver spacing a larger
source is required, for example a bulldozer may be used. At stiff soil sites, walking bulldozers generate
significant wave energy between 4 and 20 Hz (Rathje et al., 2002). Usually only two receivers
(geophones) are used and the spacing between receivers and source is changed many times to cover
the desired range of investigation depth.
1.3.2 Multi-channel analysis of surface waves (MASW)
MASW (Park et al., 1996a) is a faster method than SASW for evaluating near-surface Vs profiles
because multiple receivers are used. The entire range of investigation depths is covered by one or a
few generations of ground roll without changing receiver configuration. There are two types of MASW.
MASWV uses a swept source (Vibroseis) and processes data in the time domain. MASWI uses an
impulsive source like sledge hammer, and processes data in the frequency domain. MASWI is
cheaper, simpler and faster than MASWV. However, the bandwidth of recorded surface waves is often
narrower than that produced by the MASWV method. This can limit maximum investigation depth and
the resolution within the depth range.
1.3.3 Active-source body-wave refraction/reflection
Seismic refraction/reflection imaging has successfully been used in the oil industry to detect buried
hydrocarbon traps for about 85 years. Characterization of the near-surface is a much younger
application, although high quality images of the upper 80m have been produced (Williams et al.,
2005). Both P-waves and S-waves are used for refraction/reflection imaging. Simple impulsive sources
such as a sledge hammer can be used to generate both types of waves. To generate S-waves a
sledge hammer can be used to strike a wooden timber placed beneath the wheels of a vehicle at right
angles to the direction of the recording profile. The data are acquired using typical multi-channel
seismic acquisition systems with, for example, 48 or 60 geophones (Williams et al. 2003, 2005; Odum
et al., 2003, 2007).
The 2012 Newcastle-Sydney SPAC microtremor surveys
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1.3.4 Refraction microtremor (ReMi)
This is a passive-source method that uses standard refraction/reflection seismograph equipment
(Louie, 2001) that has gained popularity in recent years. A linear receiver array is used. A common
application of the method is to extend the depth of penetration of active source measurements by
combining the higher frequency dispersion curves obtained from active source measurements with the
low-frequency dispersion curve derived from the ReMi approach. A recent improvement of the method
is to actively excite surface wave energy down to f<1 Hz (Stokoe et al., 2006). The ReMi performs
poorer at high frequencies (compared with active methods) due mainly to the violation of the omnidirectional wavefield assumption, implicit in the interpretation of ReMi data.
1.3.5 Spatial Autocorrelation (SPAC) and frequency-wavenumber (f-k)
Introduced by Aki (1957) and Horike (1985), respectively, both methods, like ReMi, make use of the
ambient noise wavefield and require microtremor measurements to be carried out with several stations
(at least 7 for f-k and 4 for SPAC) located at pre-set distances and forming an array. These methods
allow estimation of the velocity structure from the dispersion curves of the Rayleigh waves, but not the
fundamental frequency directly. The SPAC method requires a broad azimuthal distribution of sources
to achieve best results (Asten, 2006). The f-k method is more reliable when a preferential source of
microtremor energy is identified. According to Flores and Gonzalez (2003), SPAC is more efficient and
more economic than the f-k method, since it requires only four (or even three) stations and presents
bigger density of samples for a given frequency interval. On the other hand, by recording synthetic
ambient noise with a dense array of sensors, Wathelet et al. (2005) concluded there is no significant
difference in the evaluation of Vs profile with the SPAC or the f-k method.
1.3.6 H/V method
First introduced by Nakamura (1989), it assumes that the spectral ratio of horizontal to vertical
component (called quasi-transfer spectrum, QTE) yields an estimation of site-effects. It is effectively a
single-station microtremor observation. The H/V technique alone is not sufficient to characterise
complex geology and in particular the absolute values of seismic amplification. The results of several
works show that this method can determine the fundamental frequency successfully, but in general the
corresponding amplitudes have significant inconsistencies (e.g. Bard, 1999). It shows poor resolution
in evaluating Vs profiles and requires a priori knowledge of the velocity structure for site resonance
studies (Chavez-Garcia et al., 2005). It is most effective in estimating the natural frequency of soft soil
sites when there is a large impedance contrast with the underlying bedrock. The main recommended
application of the H/V technique is in microzonation studies, i.e. to map the fundamental period of the
site, and to help constrain the geological and geotechnical models used for numerical computations
and calibrating site response studies at specific locations.
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Table 1.1 Comparisons between different methods to measure Vs30.
Method
Typical
Number of
Receivers
Source Type Frequency
Advantages
Disadvantages
SASW
2
Impact
Only 2 receivers
used. Effective in
many
geotechnical
engineering
projects.
Repeat measurements,
not good quality control
MASWV
12
Swept
source(
Vibroseis)
10-50 Hz
Fast, simple, byproduct of bodywave surveying,
multichannel
recording. More
detail in first few
metres.
Multiple number of
receiver (> 12) used.
Strong first arrivals
(refraction events) may
be troublesome
MASWI
12
Impact
(sledge
(hammer)
Narrower
frequency
range than
MASWV
Fast, simple, byproduct of bodywave surveying
Same as MASWV
ReMi
12
Microtremor
2-40 Hz
Fast, noninvasive,
inexpensive, uses
portable
equipment.
Resolution at
depth
Linear receiver array,
violation of the omnidirectional wavefield
assumption
Refraction/reflection
12 to 60
Impact
10-90 Hz
Good resolution
Time consuming
reflection data
processing.
Interpretation may be
affected
SPAC
4 to 7
Microtremor
2- 40 Hz
1-10 Hz
Fast, nonSource energy must be
invasive,
randomly distributed
inexpensive, uses
portable
equipment.
Resolution at
depth.
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2 Vs30 in Australia
2.1 Introduction
In recent years, there have been a number of surveys to characterize Vs30 in bedrock-dominated
terranes in Australia. The SPAC method has been used in Perth (Asten, 2003), in the Botany area of
Sydney (Asten and Dhu, 2004), Melbourne (Roberts et al., 2004) and Newcastle (Sorensen and
Asten, 2005). The SPAC method was also used to study 2D effects in Tasmania (Claprood et al.,
2007, 2011). A number of sites were surveyed using the SASW method in WA, SA, VIC and NSW
including Newcastle and Sydney (Collins et al., 2006), while the MASW method was employed in
Sydney (Lovell, 2011).
The Australian near-surface terrain is generally unconsolidated, highly weathered and variable in
nature. In the Botany Bay area, the regolith is composed of Quaternary sediments from a variety of
geological environments with a thickness typically of the order of 30-35 m or more. The shallow
geology of Melbourne is both complex and variable (Archbold, 1992) and the city of Newcastle is
underlain by extensive Quaternary alluvial deposits frequently up to 38 m thick (Douglas, 1995).
The MASWI method was found to be beneficial in sites where gradual velocity changes occur and not
sharp changes due to the bedrock. It provided accurate results at Macquarie and Prospect Hill, where
gradual velocity changes exist (Lovell, 2011). However, in the case of sharp acoustic contrast (on the
uniform sand site of St Albans), MASW showed an inability to model the high contrast between
unconsolidated/consolidated sand, and penetrated only a few metres allowing only the top uniform
layer of sand to be profiled (Lovell, 2011). On the other hand, the MASW method was successfully
used in a hydrogeological study at a reservoir dam near Melbourne (Suto, 2012) to detect a low Swave velocity anomaly, which was interpreted as drainage.
Asten and Dhu (2004) compared the H/V method with the SPAC method in Botany Area for the
complicated very soft, presumably silts over sand over sandstone setting. The site frequency in terms
of amplification of spectral acceleration was found to be ~1 Hz, for both methods. However the SPAC
gave second picks at higher frequencies, interpreted as the surficial silts. These discrepancies could
have a significant influence on estimates of damage and risk.
The SPAC method can achieve lower frequencies than other methods. In Melbourne, Roberts and
Asten (2004) achieved a minimum frequency of 2.5 Hz, giving a better depth resolution than active
methods (see Table 1.1).
2.2 SPAC method
2.2.1 Introduction
The spatial autocorrelation method (SPAC) was first proposed by Aki (1957) for horizontally
propagating waves. Assuming a unique phase velocity per frequency and the stationarity of the noise
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The 2012 Newcastle-Sydney SPAC microtremor surveys
wave field, he demonstrated that the correlation of the signals recorded at two stations separated by a
distance r can be written:
 (r ,  )  J 0 (
r
)
c( )
(1)
 is the azimuthal average of the correlation ratio,  (r ,  )   (r ,  ) /  (0,  ) , c(ω) is the phase
velocity and Jn is the Bessel function of order n.
 (r ,  ) 
T
1
 0 (t ) r (t )dt
T 0
(2)
Where  0 (t ) and  r (t ) are the recorded signals at two stations separated by distance 𝑟.
A typical distance between two stations or aperture can be of the order of 100m. But trees, streets,
buildings and other obstacles can result in an irregular shape array and it is not always possible to
have equal length aperture and good azimuthal coverage at the same time. For such imperfect arrays
the method proposed by Bettig et al. (2001) is used, grouping pairs of stations along rings of finite
thickness. A modified equation is used, and the interested reader is referred to the original paper
(Bettig et al., 2001). This modified version of SPAC is called MSPAC but for reasons of simplicity in
this report we’ll call it just SPAC.
2.2.2 SPAC inversion
The goal of SPAC inversion is to infer the parameters of the soil structure (Vs values) from the
measured SPAC ratios. Assuming an ambient vibration wave field made mostly of surface waves, the
SPAC curves are linked to the dispersion curve through equation (2). The dispersion curve is defined
for the case of vertically heterogeneous 1D models and its inversion is a classical problem (Hermann,
1987). Recently, the Neighbourhood Algorithm (NA) developed by Sambridge (1999a,b) has been
used for the inversion. This explores the parameter space more thoroughly than conventional methods
and is the method used in the present work. The misfit for the NA is calculated by comparing the
theoretical curves obtained from equation (2) and the SPAC data curves:
misfit 
1
k 1 nFk
nR
nR nFi

i 1 j 1

  cij 
2
dij
 ij2
(3)
 dij : SPAC ratio of data curves at frequency fj and for ring i
 cij : SPAC ratio of calculated curves at frequency fj and for ring i
 ij : observed variance for the sample at frequency fj and for ring i
The 2012 Newcastle-Sydney SPAC microtremor surveys
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nR: number of rings
nFi: number of frequency samples for ring i
nFk: number of frequency samples for ring k
2.3 The Newcastle-Sydney SPAC Vs30 survey
2.3.1 Fieldwork
In the city of Newcastle, sites were chosen and prioritised, based on local geology and earlier SCPT
data (Andrew McPherson, personal communication; Dhu and Jones, 2002). Figure 2.1 shows the sites
coloured by priority, namely high (red), medium (yellow) and low (green). Figure 2.2 is a site class map
based on Dhu and Jones (2002) that shows the surficial geology varying between deeper alluvial
deposits near the river, to shallower soils overlying weathered rock on the valley margins. In this
figure, warm colours (yellow, orange, red) refer to soft soil due to the high content of alluvium, sand
dunes and river deposits, whereas different degrees of weathered rock are depicted in green.
Appendix E shows the set of sites selected prior to the survey as high and low priority sites. During the
2-week survey in March 2012 we surveyed all high and medium priority sites, continuing onto the low
priority sites as time allowed. Apart from Newcastle, two other sites in Sydney were surveyed, one at
the Riverview seismic observatory, Lane Cove, and the other at the University of Western Sydney
Werrington North Campus (map not shown). Both these sites host permanent seismograph stations of
the Australian National Seismic network operated by Geoscience Australia.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
Figure 2.1 Location of the sites in the Newcastle region, where the SPAC survey took place. Red: high priority
sites. Yellow: medium priority sites. Green: low priority sites.
Figure 2.2 Map of Newcastle depicting the sites and the local geological conditions. Green: weathered rock. Light
green: Silt and clay. Yellow: Sand overlying silt and clay. Orange: Sand with interbedded silt and clay. Red: Silt
and clay with interbedded sand. Purple: Barrier sand (from Dhu and Jones, 2002).
The 2012 Newcastle-Sydney SPAC microtremor surveys
9
Seven Kelunji Echo recorders (sample rate 100 Hz) and seven Lenartz LE-3Dlite 1 Hz 3-component
seismometers were used. The most common configuration was a nested triangle (Figure 2.3a), or a
side-nested triangle or T-shape (b) when space was insufficient or along suburban streets. In total
seven sensors were used at a time, and the spacing between any two sensors varied from a few
meters to 100 m approximately, always depending on space availability. Sporting ovals were
preferable because they provided plenty of space without obstacles. No differences were observed
using the different configurations. Each day 2-3 new sites were surveyed and data recorded for each
site for 1h to 1.5h. A Guralp CMG3 ESP 120 second seismometer with an eighth Kelunji Echo
recorder was deployed at each site to record H/V data. In this report only the Kelunji data are
presented. Information about the sites surveyed with SPAC arrays and logistical notes regarding the
survey is presented in Appendix A.
Figure 2.3 Configurations used in the survey. a) centre-nested triangle b) side-nested triangle or T-shape. Red
dots correspond to the 7 individual Kelunji recorders. The numbers inside are the Kelunji recorder numbers.
2.3.2 Data Processing
SPAC curves were processed and interpreted using the GEOPSY software package
(www.geopsy.org). The modified SPAC method for non-circular arrays (Bettig et al., 2001) is
implemented within GEOPSY. Pairs of stations in the array were grouped along rings of finite
thickness. In order to obtain different curves for increasing apertures, 6 rings were used (Figure 2.4).
The processing method adopted in this study for each ring is described in Wathelet et al. (2005). The
SPAC curves were computed from the measured signals (Figure 2.5). The curves were then evaluated
for each ring and transformed to the frequency-slowness domain. The dispersion density is generated
by stacking the SPAC functions in the frequency-slowness domain. High density regions should then
correspond to the dispersion curve (Figure 2.6). The portions of the SPAC curve that correspond to
the highest dispersion density are selected and highlighted, see black dots in Figure 2.5. Solution
density in the frequency-slowness domain varied from site to site, depending on the quality of the
data.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
Figure 2.4 Azimuth-interdistance plot for each pair of stations shown in configuration (a) of Figure 2.3. The
coloured circles show the limits of the chosen rings for SPAC computation. Six rings are used.
The 2012 Newcastle-Sydney SPAC microtremor surveys
11
Figure 2.5 Spatial Autocorrelation (SPAC) curves. The black dots show the curves used after the selection based
on the dispersion density method (Figure 2.6).
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The 2012 Newcastle-Sydney SPAC microtremor surveys
Figure 2.6 Dispersion curve picked from stacked SPAC functions for site Wik01. The chosen limits of the denser
zone are delineated by thick grey lines. Min and max wavenumber are defined a priori to set the limits for the
frequency range of the dispersion curve used. Dotted line represents the upper wavenumber limit.
2.3.3 Inversion
For inversion ‘dinver’ implemented within the GEOPSY software package was used. Dinver uses the
conditional Neighbourhood Algorithm (NA) (Sambridge, 1999a, 1999b) for solving inversion problems
(Wathelet, 2008). The theoretical dispersion curve is calculated from random parameters given by the
NA (forward problem) and then the number of layers to invert is chosen. There are four parameters to
invert: P-wave velocity (Vp), Poisson ratio, S-wave velocity (Vs) and depth. Density was held constant
at 2 kg/m3 (Table 2.1). It was found that the choice of Vp did not have much influence on the inversion
process. Through trial-and-error a four-layer model appeared to provide best fit to the data set. Finally,
the misfit between the theoretical dispersion curve and recorded data is evaluated.
Figure 2.7 shows the Vs profile obtained for two different frequency ranges, suggested by (a) the
dispersion density (2-10 Hz) and (b) using all frequencies 1-40 Hz. The profile in Figure 2.7a is better
constrained (especially as depth increases) and presents a smaller misfit. An example of a SPAC
curve for the selected range is shown in Figure 2.8. Velocity profiles for all sites are shown in
Appendix B.
Table 2.1 Parameter space
Vp (m/s)
Poisson Ratio
Vs (m/s)
Depth (m)
Density(g/m3)
200-2000
0.2-0.5
40-500
1-25
2000
200-2000
0.2-0.5
40-500
5-40
2000
400-3000
0.2-0.5
200-600
1-60
2000
400-5000
0.2-0.5
200-1500
Half-space
2000
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Figure 2.7 Vs profiles for site Wik01. Inversion with a 4-layer model over (a) a narrow band of frequencies (2-10
Hz) (b) the whole range (1-40 Hz).
Figure 2.8 Spatial autocorrelation curve (red and coloured) derived from model in Figure 2.7a overlain by the
measured spatial autocorrelation curve (black), i.e. target curve, from station pairs with radius 67.89 - 67.96 m.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
2.3.4 Inversion results
The results using the GEOPSY software are summarized in Table 2.2. From a total of 27 sites only
Juc02 failed to produce a Vs30 value, resulting from large uncertainty in the dispersion curve values.
For all other sites reasonable Vs30 profiles are obtained (see Appendix B). However, for some sites
(Bar01, Brd04, Car01, Tih01 and Nld) the overall misfit was around 1. Sydh shows uncertainty in
depth of bedrock of ~5 m. For a number of sites a shallow thin layer with Vs < 100-200 m/s was
identified, whereas the bedrock was conventionally defined as the interface where Vs ~> 300 m/s.
For poorer quality data (no clear dispersion curves), no matter the frequency range used for the
inversion, the resulting SPAC curves were not very informative, even if the inversion resulted in a
smaller misfit. Therefore, for all data we followed the dispersion curve extraction procedure as
suggested in Wathelet et al., (2004) and shown in Figure 2.6.
For all Newcastle sites in our survey, the general trend shows regolith thickness decreasing with
distance from the river (east to west). In Figure 2.9, the estimated bedrock depths are plotted against
their corresponding Vs30 values. As expected, the results show that when the regolith is thin (shallow
bedrock depth), Vs30 values are higher.
When the dispersion curve showed scattered values the corresponding models showed uncertainty in
depth of interfaces (e.g. Brd12), in Vs (e.g. Brd08) or both (Tih01 at about 20 m). The uncertainty
below a certain depth (usually > 30 m), can be attributed to the low energy levels at frequencies below
~3 Hz, and the information, consequently, is minimal for these depths.
Relatively large uncertainty in shallow depths (<5 m) is observed for almost all sites. Better near
surface constraints are usually compensated for uncertainty at greater depths.
Figure 2.9 Depth to basement plotted against calculated Vs30 for all data in our survey. Results show a trend of
decreasing velocity with increasing regolith thickness.
The 2012 Newcastle-Sydney SPAC microtremor surveys
15
2.3.5 Comparison with other methods
Vs profiles, Vs30 and bedrock depths were derived from the same SPAC data set by both Geoscience
Australia (GA), using GEOPSY software, and Monash University (MU) using the software employed by
Asten (2006). The approach using the GEOPSY software used a SPAC analysis only. The MU results
utilised both the SPAC method and H/V curve-matching methods. The MU results are included as
Appendix C to this report, with a summary also available in Asten et al. (2013). Ikeda et al. (2013)
have extended this analysis to formal joint inversion of SPAC and H/V data. A comparison with earlier
work was also made with the addition of results from SCPT, SASW and previous SPAC data
(Sorensen and Asten, 2005) whenever possible.
This final comparison also includes a regolith site classification. Classification schemes developed for
Australia (Dhu and Jones, 2002) and the United States by NEHRP (Kayen et al., 2013) were
investigated. In the Australian classification scheme (Table 2.3), velocities for the last 4 classes remain
constant ~200-250 m/s. Having progressively changing velocities for each class is more suitable for
comparisons, and therefore the NEHRP system was adopted (Table 2.4).
There is an 89% correlation between the Vs30 values from the two SPAC analyses by MU and GA. For
both GA and MU interpretations (Table 2.5), the lowest Vs30 values were obtained for Brd01, Car01,
Car02, Ham02, Ham03 and Wik01. These are located in the east, close to the river, where thicker
alluvium is mapped. The highest Vs30 values were obtained for Kot01 and Brd08, which are located on
(weathered) rock.
The sites with the largest difference in Vs30 are: Brd04, Brd08, Kot01, Tih01 and Riv. Of these only
Brd04 has a discrepancy both in Vs30 and bedrock depth. The discrepancy in the remainder is due
mainly to thin (< 2m) shallow low velocity layers (<100 m/s), which are not present in the MU SPAC
models but are seen in the GA derived models. At greater depths the situation is reversed with the MU
model having greater Vs. The shallow, low velocity layers influence the Vs30 calculation more
significantly as Vs30 is the time averaged velocity over the top 30 metres.
Vs30 results from the SCPT technique correlated less well with the results from both the GA and MU
analysis. The correlation between SCPT and MU is slightly better than that of GA.
Table 2.2 Results of SPAC analysis (using GEOPSY). LF: low frequencies
Site
Misfit
Layer 1
Bedrock
Depth (m)
Comments
Dispersion Curve (DC)
Adm01 312
0.75
2.6
14
Very diffuse < 9.5 m
Not clear DC
Bar01
404
0.96
16
Diffuse
Not clear DC
Brd01
213
0.48
26
Brd02
221
0.53
24
Diffuse > 20 m
2-10 Hz. Clear DC
Brd03
232
0.57
18.5
Diffuse > 12 m
2-10 Hz clear DC
Brd04
301
1.13
12
Diffuse > 30
2.8-6.2 Hz Not clear DC
Brd08
408
0.65
5
Noisy in LF
Not clear DC- 8-20 Hz
Brd09
277
0.65
11
Diffuse > 11 m
3.5-8.5 Hz
Brd12
385
0.72
1.8
11
Well constrained
4-10 Hz
Car01
182
1
4
47
Diffuse > 47 m
Not clear DC
16
Vs30
m/s
1.4
1.7
1-10 Hz. Clear DC
The 2012 Newcastle-Sydney SPAC microtremor surveys
Site
Vs30
m/s
Misfit
Layer 1
Bedrock
Depth (m)
Comments
Dispersion Curve (DC)
Car02
192
0.79
45
Well constrained
Clear DC 1.5-6 Hz
Ham02 242
0.53
1.2
20
Well constrained
1.7–7.6 Hz Clear DC
Ham03 212
0.57
1.4
26
Removed LF picks
Iso01
302
0.82
Iso02
211
0.97
Juc01
263
0.89
Juc02
-
-
Mer04
337
0.45
Mer05
387
0.81
Nld
676
1
1.2
Nlt03
387
0.71
13
Nlts
193
0.8
19
2-3 Hz Not Clear DC
Tih01
259
1.1
16.5
Not Clear DC
Wik01
193
0.43
23
1-6 Hz Clear DC
Kot01
371
0.83
1.5
5.5
Diffuse > 6 m
Not Clear DC
Riv
692
0.79
2
5.5
Noisy in LF
Clear DC
Sydh
590
0.79
2
12
11
1-7.6 Hz Clear DC
3.3
16
Clear DC 1-10 Hz
5
14
1.8 -10 Hz Clear DC,
-
13
5
1.6
8.5
4-10 Hz Not Clear DC
Not very well constrained
2.5-10 Hz Not Clear DC
Not clear DC
Similar to MER05, better
constrained
2.6-11 Hz Clear DC
4-15 Hz Clear DC
Table 2.3 The site classification scheme from Dhu and Jones, 2002.
Site class
Vs30 (m/s)
C
Weathered rock (~1400 m/s)
D
Silt and clay (~650 m/s)
E
Sand overlying silt and clay (~250 m/s)
F
Sand with interbedded silt and clay (~200 m/s)
G
Silt and clay with interbedded sand (~250 m/s)
H
Barrier sand (~200 m/s)
Table 2.4 NEHRP Site classification (Kayen et al., 2013).
Site class
Vs30 (m/s)
A
> 1500
B+
1000 < Vs30 < 1500
B-
720 < Vs30 < 1000
C+
540 < Vs30 < 720
C-
360 < Vs30 < 540
The 2012 Newcastle-Sydney SPAC microtremor surveys
17
Site class
Vs30 (m/s)
D+
270 < Vs30 < 360
D-
180 < Vs30 < 270
E
< 180
F
Special soil conditions: liquefiable soil etc.
The deepest bedrock depths are observed at Ham03, Car01 and Car02, which are located on thicker
soil. Wik01, Iso02, Car01, Car02 and Ham02 show multiple interfaces, but only Ham02 and Wik01
show significant change in Vs at the shallower interface. Juc01 shows two similar interfaces, making it
difficult to decide which the bedrock is, and the second interface was picked as the first does not
exceed 300 m/s. The shallower bedrock depths are observed at Kot01, Brd08 and Nld, all located on
consolidated rock (Table 2.5).
At least seven out of 25 sites exhibit significant velocity contrasts at depths < 30 m. These are Brd01,
Brd12, Kot01, Brd08, Juc01, Mer05, Nlt03, Riv and Sydh.
Bedrock depths between the two SPAC methods are all in good agreement (Figure 2.11) with the
probable exception of Brd04, Mer04, and Wik01. GA modelling at Brd04 showed a large misfit (> 1)
and may not be very reliable. Bedrock depths derived from the SCPT data are not as consistent. Of
the high priority sites only Brd09 shows good agreement with SPAC, while for the remainder, the best
agreement comes from Brd01, Ntl03, Brd02 and Brd08. From the SCPT we know that in Brd03,
Ham02 and Mer04 the bedrock was not reached, while at others (Mer05, Iso02, Juc02 and Tih01) it is
possible that SCPT stopped at a shallower interface, which was interpreted as bedrock. Juc01,
located in the south-east on soft soil, has discrepancies in bedrock depth. A similar problem
concerning the maximum SCPT depth from Brd03 was noted. The depth suggested by both SPAC
interpretations was significantly shallower than the depth of bedrock derived from SCPT. Further
comparisons with different methods are needed to obtain a better estimate.
The GA inversion used a selected frequency range (depending on the SPAC curves for each site),
whereas the software used by MU inverts for all frequencies (1-40 Hz). When all frequencies are used
for GA modelling, the models produced were more uncertain especially as depth increased and gave
a correspondingly higher misfit (see Figure 2.7).
Regolith site classification for the two SPAC methodologies plus SCPT is presented in Table 2.5 and
Figure 2.12. Good correlation exists between soil classes and results from the two SPAC studies. For
sites in Newcastle and with both GA and MU models class D seems to predominate, especially
towards the eastern half of the survey area. From east to west sites show a tendency to belong to a
higher class (for SPAC methods). This is in agreement with the surficial geology as depicted in
Figure 2.2.
The SCPT data is less consistent. For example Kot01 was assigned class E, where the two SPAC
methods gave C. Similarly Nlt03 and Nld are assigned D while both SPAC methods gave C.
18
The 2012 Newcastle-Sydney SPAC microtremor surveys
Table 2.5 Comparison between SCPT and SPAC results, as obtained from both GA and MU. SASW results are
shown for the first five sites (high priority sites). For Iso01 and Brd04 previous SPAC measurements (Sorensen
and Asten, 2005) are also included in parentheses beside the corresponding GA values. * in SCPT depth denotes
only ‘reached’ depth. Depths separated by commas (GA and MU) denote two interfaces suggested for some
sites. Vs30 is in m/s and depth to bedrock in m.
Site
Vs30
Vs30
SASW/SCPT GA
Vs30
MU
Depth
SCPT
Depth
GA
Depth
MU
Class
SCPT
Class
GA
Class
MU
Mer05
360/266
387
394
6.8
8.5
11
D-
C-
C-
Brd09
270/220
277
319
11.5
11
10
D-
D+
D+
Iso01
246/256
302
334
15
10
11
D-
D+ (E)
D+
Brd04
188/184
301
205
26.7
12
22
D-
D+ (E)
D-
Wik01
177/178
193
178
36
23
35
E
D-
E
Brd01
223
213
218
27.95
26
25
D-
D-
D-
Nlt03
286
387
405
13.5
13
12
D+
C-
C-
Brd02
222
221
228
24.35
24
23
D-
D-
D-
Adm01
251
312
352
16
14
15
D-
D+
D+
Juc01
238
363
353
14.45
14
13
D-
C-
D+
Brd12
242
385
353
17.65
11
10
D-
C-
D+
Ham03
255
212
251
31.5
32
26
D-
D-
D-
Brd08
736
408
663
4
5
6
B-
C-
C+
Kot01
143
371
519
5
5.5
8
E
C-
C-
Brd03
249
232
295
24.5*
18.5
17
D-
D-
D+
Ham02
237
242
231
12.15*
20
15
D-
D-
D-
Bar01
249
404
399
11.4
16
12
D-
C-
C-
Car01
206
182
178
39.25
47
45
D-
D-
E
Car02
205
192
212
34.8
45
50
D-
D-
D-
Iso02
186
211
208
28.4
16
15
D-
D-
D-
Juc02
251
-
244
10.5
-
25
D-
-
D-
Mer04
298
337
316
15*
13
28
D+
D+
D+
Tih01
189
259
363
6.5
16.5
13
D-
D-
C-
Nld
302/302
676
559
-
1.2
2.5
-
C+
C+
NLTS
-
193
172
-
29
30
-
D-
E
RIV
768 SASW
692
971
-
5.5
6
B-
C+
B-
SYDH
-
590
675
-
12
14
-
C+
C+
The 2012 Newcastle-Sydney SPAC microtremor surveys
19
Figure 2.10 Vs30 results listed in Table 2.5 calculated using the three techniques described in the text (SCPT –
Seismic Cone Penetrometer; GA – Geoscience Australia SPAC analysis; MU – Monash University SPAC
analysis).
Figure 2.11 Depth results listed in Table 2.5 calculated using the three techniques described in the text (SCPT –
Seismic Cone Penetrometer; GA – Geoscience Australia SPAC analysis; MU – Monash University SPAC
analysis).
20
The 2012 Newcastle-Sydney SPAC microtremor surveys
Figure 2.12 Correlation between geology and site classification as calculated by 3 different methods: a. GA b. MU
and c. SCPT
The 2012 Newcastle-Sydney SPAC microtremor surveys
21
3 Conclusions
The results of a seismic survey to measure ambient background noise for the determination of V s30 at
sites in Newcastle and Sydney are presented. The data was independently analysed using the
Spatially Averaged Coherency Spectrum (SPAC) method by both collaborators in this project i.e.
Geoscience Australia (GA) and Monash University (MU). The results of both analyses are presented
and compared.
Vs30 values computed by GA correlate well with those computed by MU. The largest differences occur
at the sites Brd04, Brd08, Kot01, Tih01 and Riv. where the values differ by more than 22%. The
discrepancy is mainly due to thin (< 2m) shallow low velocity layers (<100 m/s), not present in the MU
models. A shallow low velocity layer can significantly influence the V s30 calculation.
Bedrock depths are in good agreement between both SPAC interpretations. Exceptions are Brd04,
Mer04 and Wik01. Further analysis (including the use of alternative methods) is required.
Regardless of the ‘absolute’ values for Vs30, as obtained by the two SPAC methods, a tendency exists
for lower values to predominate to the east, where the regolith is thicker, fine-grained and probably
saturated.
SCPT-derived velocities and bedrock depths show poorer agreement with SPAC and demonstrate
inconsistencies with class classification.
22
The 2012 Newcastle-Sydney SPAC microtremor surveys
Acknowledgements
The authors gratefully acknowledge the assistance provided by the owners and operators of the sites
used in this survey, in particular: Newcastle City Council, Riverview College and the University of
Western Sydney. We thank Andrew McPherson for advice on the selection of these sites for this
survey. We also thank Tatsunori Ikeda for assistance with the field work. This paper is published with
the permission of the CEO of Geoscience Australia.
The 2012 Newcastle-Sydney SPAC microtremor surveys
23
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scaling. Geophysical Research Letters, 35, L09301, doi:10.1029/2008GL033256
Williams, R. A., W. J. Stephenson, J. K. Odum, and D. M. Worley (2003). Comparison of P- and Swave velocity profiles from surface seismic refraction/reflection and downhole data. In
Contributions to Neotectonics and Seismic Hazards from Shallow Geophysical Imaging, ed. J. H.
McBride and W. J. Stephenson, special issue, Tectonophysics 368,71 -88.
Williams, R. A., W. J. Stephenson, J. K. Odum, and D. M. Worley (2005). P- and S-wave seismic
reflection and refraction measurements at CCOC. In Blind Comparisons of Shear-wave Velocities
at Closely-spaced Sites in San Jose, California, ed. M. W. Asten and D. M. Boore, 17 pp. USGS
Open File Report 2005-1169.
26
The 2012 Newcastle-Sydney SPAC microtremor surveys
Sites surveyed with SPAC- arrays
information
Appendix Table A.1 Fieldwork logistics
Survey Date
#
GA site
name
AMG E
AMG N
Longitude
Latitude
S1
13/03/2012
SYDH
290751
6261809
150.74176
-33.76148
S2
14/03/2012
RIV
329465
6255280
151.15830
-33.82727
bad
S2
30/03/2012
RIVr
329465
6255280
151.15830
-33.82727
Repeat
1
15/03/2012
MER05
381813
6354680
151.73686
-32.93808
2
15/03/2012
BRD09
151.74145
-32.93407
bad
2
20/03/2012
BRD09r
382237
6355129
151.74145
-32.93407
Repeat
3
16/03/2012
ISO-01
382682
6357695
151.74654
-32.91098
4
16/03/2012
BRD04
381488
6357119
151.73370
-32.91605
5
18/03/2012
WIK01
bad
5
21/03/2012
WIK01r
bad
5
25/03/2012
WIK01rr
6
18/03/2012
NLT03
6
20/03/2012
NLT03r
380169
6355342
151.71937
-32.93193
7
19/03/2012
BRD02
381347
6356622
151.73213
-32.92051
8
19/03/2012
BRD12
381526
6355182
151.73386
-32.93352
9
20/03/2012
BRD01
381890
6357007
151.73798
-32.91710
10
21/03/2012
HAM02
10
26/03/2012
HAM02r
11
21/03/2012
BRD03
11
24/03/2012
BRD03r
12
22/03/2012
NLD
12
24/03/2012
NLDr
13
22/03/2012
ADM01
13
24/03/2012
ADM01r
380579
6355371
151.72375
-32.93171
14
23/03/2012
HAM03
382949
6356614
151.74926
-32.92076
15
23/12/2012
BRD08
381403
6355688
151.73261
-32.92894
16
25/03/2012
KOT01
378214
6353367
151.69820
-32.94952
17
25/03/2012
JUC01
383702
6354584
151.75705
-32.93915
18
26/03/2012
CAR01
384557
6357711
151.76659
-32.91104
383311
6356783
151.75315
-32.91927
success
Repeat
bad
bad
382923
6355471
151.74883
-32.93106
Repeat
bad
381036
6356415
151.72878
-32.92235
Repeat
bad
378501
6358754
151.70198
-32.90097
Repeat
bad
The 2012 Newcastle-Sydney SPAC microtremor surveys
Repeat
27
Survey Date
#
GA site
name
AMG E
AMG N
Longitude
Latitude
19
26/03/2012
CAR02
384432
6357073
151.76517
-32.91678
20
28/03/2012
ISO_02
382903
6357447
151.74887
-32.91324
21
28/03/2012
NTLS
384128
6355550
151.76173
-32.93048
22
28/03/2012
JUC02
383420
6354580
151.75404
-32.93915
23
29/03/2012
BAR01
384462
6354733
151.76520
-32.93788
24
29/03/2012
MER04
383051
6354456
151.75007
-32.94023
25
29/03/2012
TIH01
383468
6358403
151.75503
-32.90468
success
Appendix Table A.2 fieldwork logistics (continued)
Location
Riverview Observatory
Array Type
Max
Survey GA site
side
#
name
length
TimeStart
TimeEnd
concentric
100
S1
SYDH
4.36pm
6.30pm~
common apex
100
S2
RIV
12.30pm
3.15pm
RIVr
11.31am
12.21pm
Lockyer St park
100
1
MER05
11.25am
1.15pm
Hassall St park (Darling Oval)
100
2
BRD09
3.15pm
4.05pm
BRD09r
12.45pm
1.45pm
River site cnr Maitland and Hubbard st
67.5
3
ISO-01
11.35am
12.40pm
Smith Pk
100
4
BRD04
3.05pm
4.10pm
100
5
WIK01
10.40am
11.40am
WIK01r
11.08am
WIK01rr
2.52pm
Wickam Pk
concentric
Univ. of Western Sydney
Observatory
cnr James Rd and
Mackie Ave
(vacant block)
100
6
cnr James Rd and Mackie Ave (vacant
block)
NLT03
4.01pm
1.55pm
3.05pm
NLT03r
3.20pm
4.07pm
Curley and Denny St
100
7
BRD02
10.33am
11.45am
cnr James St Melville St
100
8
BRD12
3.03pm
4.05pm
cnr Griffith Rd Chatham St (heavily treed)
93
9
BRD01
9.54am
11am
Learmonth Pk cnr
Jenner Rd Gordon Ave
100
10
HAM02
1.47pm
2.52pm
HAM02r
9.47am
10.47am
BRD03
4.32pm
5.38pm
BRD03r
2.35pm
3.35pm
NLD
12.15pm
12.45pm
District Pk cnr Bavin St
Perth st
ComptonSt. JUMP site.
28
concentric
concentric
concentric
100
38.1
11
12
The 2012 Newcastle-Sydney SPAC microtremor surveys
Location
Array Type
end court St; RTA motor concentric
school
Max
Survey GA site
side
#
name
length
53
13
TimeStart
TimeEnd
NLDr
9.50am
10.50am
ADM01
4.50pm
5.50pm
ADM01r
12.08pm
1.13pm
west of Wickam Pk. Cnr
Kent st Cleary St
T base on
Cleary St
100
14
HAM03
11.48am
12.48pm
cnr Gosford Melville St,
in park
concentric
55.4
15
BRD08
3.10pm
4.15pm
cnr Grayson Ave Casey
Ave
concentric
100
16
KOT01
9.37am
10.40am
Rowland Pk cnr Glebe
Rd union St
concentric
65.8
17
JUC01
12.47pm
1.47pm
cnr Gipps St Robertson
St
concentric
92.5
18
CAR01
12.25pm
1.25pm
cnr Cowper St Sth,
Wilson St
T base Cowper
St
100
19
CAR02
2.50pm
3.50pm
Morgan St sports gnd
concentric
96.5
20
ISO_02
10.04am
11.00am
National Pk soccer gnd
near JUMP stn
concentric
86.6
21
NTLS
12.27pm
1.27pm
cnr Railway St Llewellen T base Morgan- 100
St
Railw st
22
JUC02
3.15pm
4.15pm
Parkway Ave near Darby offcentre nested 41.5
St
23
BAR01
9.58am
11.00am
cnr Morgan St Llewellen offcentre nested 38
St
24
MER04
12.11pm
1.11pm
park between Industrial
Dr and George St
25
TIH01
2.36pm
3.36pm
concentric
76.2
Appendix Table A.3 Fieldwork logistics (end)
GA site
name
Guralp used
SYDH
Y
RIV
Observatory
RIVr
Observatory
MER05
y from 12.05pm
BRD09
Y
BRD09r
SASW Vs30
SPAC Vs30
SPAC Vs100
Comment
675
1179
JUMP station
768
971
1335
bad data – wind noise
360
384
671
bad wind noise
270
319
676
ISO-01
Y
246
334
702
BRD04
Y
188
205
486
WIK01
Y
The 2012 Newcastle-Sydney SPAC microtremor surveys
synch slip on D ; F Echo dead
29
GA site
name
Guralp used
SASW Vs30
SPAC Vs30
SPAC Vs100
Comment
WIK01rr
N
177
178
392
D element is Echo12
NLT03
Y
405
747
DEFG all synch from 3.05pm
WIK01r
NLT03r
BRD02
y from 10.44am
228
561
BRD12
y
353
728
218
543
BRD01
HAM02
2 mem cards missing
HAM02r
BRD03
231
500
295
675
helicopter at 2.38pm
559
839
JUMP site H/V data
Y
BRD03r
NLD
NLDr
N
302
ADM01
ADM01r
2 mem cards missing
N
352
741
HAM03
251
601
BRD08
663
1088
KOT01
N
519
957
JUC01
N
353
719
CAR01
178
367
CAR02
212
403
E disconnected at 1.10pm
ISO_02
Y
208
450
Guralp did not synch
NTLS
JUMP
172
451
Near JUMP stn
JUC02
Y
244
590
BAR01
N
399
821
MER04
N
316
607
TIH01
N
363
773
30
The 2012 Newcastle-Sydney SPAC microtremor surveys
Velocity profiles from all sites
The 2012 Newcastle-Sydney SPAC microtremor surveys
31
Appendix Figure B.1 Velocity profiles from the inversion. Inverted models rank by their SPAC misfit (colour scale)
for sites ADM01, BAR01 and BRD01.
32
The 2012 Newcastle-Sydney SPAC microtremor surveys
Appendix Figure B.2 Velocity profiles from the inversion. Inverted models rank by their SPAC misfit (colour scale)
for sites BRD02, BRD03 and BRD04.
The 2012 Newcastle-Sydney SPAC microtremor surveys
33
Appendix Figure B.3 Velocity profiles from the inversion. Inverted models rank by their SPAC misfit (colour scale)
for sites BRD08, BRD09 and BRD12.
34
The 2012 Newcastle-Sydney SPAC microtremor surveys
Appendix Figure B.4 Velocity profiles from the inversion. Inverted models rank by their SPAC misfit (colour scale)
for sites CAR01, CAR02 and HAM02.
The 2012 Newcastle-Sydney SPAC microtremor surveys
35
Appendix Figure B.5 Velocity profiles from the inversion. Inverted models rank by their SPAC misfit (colour scale)
for sites HAM03, ISO01 and ISO02.
36
The 2012 Newcastle-Sydney SPAC microtremor surveys
Appendix Figure B.6 Velocity profiles from the inversion. Inverted models rank by their SPAC misfit (colour scale)
for sites JUC01, KOT01 and MER04.
The 2012 Newcastle-Sydney SPAC microtremor surveys
37
Appendix Figure B.7 Velocity profiles from the inversion. Inverted models rank by their SPAC misfit (colour scale)
for sites MER05, NLD and NLT03.
38
The 2012 Newcastle-Sydney SPAC microtremor surveys
Appendix Figure B.8 Velocity profiles from the inversion. Inverted models rank by their SPAC misfit (colour scale)
for sites NLTS, TIH01 and WIK01.
The 2012 Newcastle-Sydney SPAC microtremor surveys
39
Appendix Figure B.9 Velocity profiles from the inversion. Inverted models rank by their SPAC misfit (colour scale)
for sites in Sydney area, SYDH and RIV.
40
The 2012 Newcastle-Sydney SPAC microtremor surveys
Newcastle-Sydney SPAC microtremor
survey project 2012: velocity models and H/V
spectra
Michael W. Asten BSc(Hons), PhD, FRAS
Email: [email protected]
Professorial Fellow
School of Geosciences
Monash University
Melbourne Vic 3800
The 2012 Newcastle-Sydney SPAC microtremor surveys
41
Appendix Figure C.1 Location of microtremor survey sites, Newcastle (NSW) area, with colour coding of site class
inferred from CPT data (as supplied by Geoscience Australia).
42
The 2012 Newcastle-Sydney SPAC microtremor surveys
EXPLANATION OF COLORS USED
SPAC spectra
r1=Radius inner triangle
r2=Side length inner triangle
r3=Radius outer triangle
r4=Side length outer triangle
H/V spectra
Appendix Figure C.2 Explanation of colours used in all following figures. Black line: field data. Thick red line:
modelled SPAC data (or H/V data) for the Rayleigh fundamental mode best-fit layered earth model. Thin red line:
model data for an alternative layer model. Thin red dashed line: model data for another alternative layer model.
Yellow: model data for the Rayleigh 1st higher mode. Green: model data for the Rayleigh 2nd higher mode.
The 2012 Newcastle-Sydney SPAC microtremor surveys
43
WIK01rr: SPAC and H/V data and model fits
Appendix Figure C.3 Site WIK01rr: SPAC and H/V data and model fits. Note: thin red line is a model with layer 5
increased in thickness from 30m to 164 m. This thick transition zone improves SPAC data fit slightly, but gives
poor H/V peak fit at 1.2 Hz, hence the thinner 30m transition zone is preferred.
44
The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS
RHO
2 400 130.
1.78
4 1500 140. 1.8
8 1500 180. 2.0
20 1500 200. 2.0
30 3000 700 2.14
.100 3000 700 2.14
200. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.4 Site WIK01rr velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
The 2012 Newcastle-Sydney SPAC microtremor surveys
45
RIVr: SPAC and H/V data and model fits
Appendix Figure C.5 SPAC and HVSR for site RIV. SPAC at 30 Hz resolves thickness of upper layers as 8.2 m of
Vs 535m/s. H/V spectral peak at 25 Hz is probably smeared due to sloping terrain at survey site. SPAC 4-15Hz
resolves Vs of sediments 1400 to 1900m/s. H/V spectrum peak at 1.5 Hz resolves base of Permian, estimated at
318m.
46
The 2012 Newcastle-Sydney SPAC microtremor surveys
Appendix Figure C.6 Site RIVr velocity and slowness plots versus depth. H=layer thickness, VP=compressional
wave velocity, VS=shear wave velocity, RHO=density in t/m3.
The 2012 Newcastle-Sydney SPAC microtremor surveys
47
SYDH: SPAC and H/V data and model fits
Appendix Figure C.7 SPAC and HVSR for site SYDH. Thin red line :SPAC fit for small triangle is better at f>20Hz
if Vs1,Vs2 reduced to 360m/s. But small triangle is in an erosion valley, below the observatory, hence the higher
Vs1,Vs2 (thick red line) are preferred. H/V peak at 7Hz is associated with base of soil at depth 14 to 22 m. H/V
peak at 1.1 Hz is associated with base of Permian, estimated depth 380m.
48
The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
2 1500 400. 2.
4 1500 400. 2.
8 1500 400. 2.0
8 3000 1700. 2.0
16 3000 1700 2.14
50 3000 1700 2.14
100. 3000 1900 2.6
200. 3000 1900 2.6
400 6000 3500 2.8
0. 6000 3500 2.8
Appendix Figure C.8 Site SYDH velocity and slowness plots versus depth. H=layer thickness, VP=compressional
wave velocity, VS=shear wave velocity, RHO=density in t/m3.
The 2012 Newcastle-Sydney SPAC microtremor surveys
49
MER05: SPAC and H/V data and model fits
Appendix Figure C.9 SPAC and HVSR for site MER05. SPAC and H/V give inconsistent result. Thick red line is
SPAC result (does not fit the H/V peak). Thin red line is model with soil layer thickness increased from 11 to
13.5m (which give an H/V fit but clearly not permitted by SPAC result.
50
The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
1 400 210. 1.78
1 1500 210. 1.8
1 1500 210. 2.0
8 1500 210. 2.0
64 1500 800 2.14
100 3000 1500 2.14
200. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.10 Site MER05 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3. Thick red line is the preferred
model although the model is inconsistent with H/V data. Thin red line is model with soil layer thickness increased
from 11 to 13.5m (which give an H/V fit but clearly not permitted by SPAC result.
The 2012 Newcastle-Sydney SPAC microtremor surveys
51
BRD09r: SPAC and H/V data and model fits
Appendix Figure C.11 SPAC and HVSR for site BRD09. SPAC data is improved by deleting station E from the
array.
52
The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
1 400 130. 1.78
1 1500 140. 1.8
3 1500 155. 2.0
5.5 1500 155. 2.0
32 2000 800 2.14
100 3000 1500 2.14
200. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.12 Site BRD09r velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
The 2012 Newcastle-Sydney SPAC microtremor surveys
53
ISO01: SPAC and H/V data and model fits
Appendix Figure C.13 SPAC and HVSR for site ISO_01. thin red line is a model with layer 5 included as a
(unrealistic) transition zone of thickness 130m, Vs5=800m/s. This unrealistic thick transition zone improves SPAC
data at low frequencies, but gives a marginally poorer H/V peak fit at 2 Hz, hence the absent transition zone (thick
red line) is preferred. (Similar to BRD01, NTLS. Also compare with model WIK01 and BRD02).
54
The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
2 400 135. 1.78
4 1500 135. 1.8
1 1500 200. 2.0
3.5 1500 220. 2.0
10 2000 800 2.14
20 2000 800 2.14
150. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.14 Site ISO-01 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
The 2012 Newcastle-Sydney SPAC microtremor surveys
55
BRD04: SPAC and H/V data and model fits
Appendix Figure C.15 SPAC and HVSR for site BRD04. SPAC data noisy. Has strong imaginary component near
5 Hz – probably associated with a directional source on major Griffith Rd. Thin red line shows alternative model of
similar fit, where Vs3, Vs4 reduced to 160, 170m/s.
56
The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
2 400 105. 1.78
4 1500 130. 1.8
8 1500 180. 2.0
8 1500 190. 2.0
30 1500 800 2.14
100 3000 1500 2.14
200. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Vs30 could be 185 m/s,
with equal fit
Appendix Figure C.16 Site BRD04 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
The 2012 Newcastle-Sydney SPAC microtremor surveys
57
NLT03: SPAC and H/V data and model fits
Appendix Figure C.17 SPAC and HVSR for site NLT03. Thin red line shows alternative model of similar fit, where
Vs3 reduced from 210 to 190 m/s. Inner and outer triangles give best fit with Vs3=210,190, respectively.
58
The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
1 600 190. 1.78
1 1500 190. 1.8
5 1500 210. 2.0
5 1500 230. 2.0
10 2000 1000 2.14
20 2000 1000 2.14
50. 2000 1000 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.18 Site NLT03velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
The 2012 Newcastle-Sydney SPAC microtremor surveys
59
BRD02: SPAC and H/V data and model fits
Appendix Figure C.19 SPAC and HVSR for site BRD02. thin red line is a model with layer 5 included as a
transition zone of thickness 64m, Vs5=500m/s. This thick transition zone improves SPAC data at low frequencies,
but gives poor H/V peak fit at 2 Hz, hence the absent transition zone (thick red line) is preferred. (Compare with
model WIK01 and BRD01).
60
The 2012 Newcastle-Sydney SPAC microtremor surveys
BRD02: Preferred model without transition zone
H VP VS RHO (no transition zone)
2 400 200. 1.78
4 1500 200. 1.8
8 1500 180. 2.0
10 1500 190. 2.0
1 1500 800 2.14
100 3000 1500 2.14
200. 2940 1500 2.39
400. 2940 1500 2.39
900. 2941 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.20 Site BRD02 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
The 2012 Newcastle-Sydney SPAC microtremor surveys
61
BRD02: Alternative model including a transition zone
H VP VS RHO (with transition zone at layer 5)
2 400 200. 1.78
4 1500 200. 1.8
8 1500 180. 2.0
18 1500 190. 2.0
64 1500 850 2.14
100 3000 1500 2.14
200. 2940 1500 2.39
400. 2940 1500 2.39
900. 2941 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.21 Alternative model for site BRD02 velocity and slowness plots versus depth. H=layer
thickness, VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
62
The 2012 Newcastle-Sydney SPAC microtremor surveys
BRD12: SPAC and H/V data and model fits
Appendix Figure C.22 SPAC and HVSR for site BRD12. The best fit model (thick red line) includes a transition
zone. Thin red line is an alternative model without a transition zone; this alternative model is a better fit for 33, but
poorer fit for r1, r2 and r4. The H/V data does not discriminate between the two models.
The 2012 Newcastle-Sydney SPAC microtremor surveys
63
H VP VS RHO
2 400 85. 1.78
2 1500 220. 2.
2 1500 220. 2.0
2 1500 220. 2.0
2 1500 220 2.14
30 2000 800 2.14
200. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.23 Site BRD12 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
64
The 2012 Newcastle-Sydney SPAC microtremor surveys
BRD01: SPAC and H/V data and model fits – all seismometers
ERRONEOUS DATA
Appendix Figure C.24 SPAC and HVSR for site BRD01. This is erroneous data; seismometer F has a poor
response which gives a bias on SPAC at frequencies below 2 Hz. Thick red line is the preferred model (see next
figures) from corrected data. Thin red line is a much better fit for low frequencies, but it has a very unrealistic
transition layer of 330m of Vs5=700 m/s.
The 2012 Newcastle-Sydney SPAC microtremor surveys
65
BRD01: SPAC and H/V data and model fits – seismometer F deleted
DELETION OF F GIVES
BETTER LOW-FREQ SPAC
Appendix Figure C.25 SPAC and HVSR for site BRD01. thin red line is a model with layer 5 included as a
(unrealistic) transition zone of thickness 130m, Vs5=800m/s. This unrealistic thick transition zone improves SPAC
data at low frequencies, but gives poorer H/V peak fit at 2 Hz, hence the absent transition zone (thick red line) is
preferred. (Similar to ISO01. also compare with model WIK01 and BRD02).
66
The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
2 400 210. 1.78
4 1500 210. 1.8
8 1500 180. 2.0
11 1500 180. 2.0
0.3 1500 700 2.14
100 3000 1500 2.14
200. 2940 1500 2.39
400. 2940 1500 2.39
901. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.26Site BRD01 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3. Thin red line is the erroneous
model obtained by fitting SPAC data for all seismometers. Thick red line is more likely a correct model, as
obtained by fitting SPAC curves with one seismometer deleted.
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67
HAM02: SPAC and H/V data and model fits
Appendix Figure C.27 SPAC and HVSR for site HAM02. This model (thick red line) favors inclusion of a transition
zone. Transition zone is 30m of Vs5=800m/s. Thin red line is an alternative model with transition zone (layer 5)
absent. SPAC data does not resolve the transition zone but the H/V fit at 2 Hz is improved by inclusion of the
transition zone. (Opposite case to examples of models BRD01, WIK01 and BRD02).
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HAM02: SPAC and H/V data and model fits
H VP VS RHO
4 400 185. 1.78
3 1500 155. 1.8
8 1500 220. 2.0
17 1500 285. 2.0
30 1500 800 2.14
100 3000 1500 2.14
200. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.28 Site HAM02 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3. Thick red line is the preferred
model including a transition zone at base of sediments. Thin red line is model without a transition zone.
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69
BRD03: SPAC and H/V data and model fits
Appendix Figure C.29 SPAC and HVSR for site BRD03. thin red line is a model with layer 5 included as a
transition zone of thickness 30m, Vs5=500m/s. This transition zone significantly improves SPAC data fits (thin red
line) at low frequencies, but gives wrong fit of H/V peak fit at 2.5 Hz, hence the absent transition zone (thick red
line) is preferred. (Compare with model WIK01 and BRD02).
70
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H VP VS RHO
2 1500 180. 1.78
4 1500 180. 1.8
8 1500 180. 2.0
3 1500 200. 2.0
0.1 2000 500 2.14
100 3000 1500 2.14
200. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.30 Site BRD03r velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3. Thick red line is the preferred
model without including a transition zone at base of sediments. Thin red line is model containing a transition zone.
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71
NLD (JUMP station): SPAC and H/V data and model fits
Appendix Figure C.31 SPAC and HVSR for site NLD. This poor SPAC data. Site is adjacent to road on lower side,
with ground sloping to north away from road. Topography is 3D. Expect that surficial soils are affected by road
cutting. SPAC array ilarge triangle has side length limited to 38m. Uses one station deleted due to noisy site.
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H VP VS RHO
1 600 130. 1.78
1 1500 150. 1.8
0.1 1500 150. 2.0
25 1500 700. 2.0
64 3000 1000 2.14
100 3000 2000 2.14
200. 2940 2000 2.39
400. 2940 2000 2.39
900. 2940 2000 2.39
0. 3400 2000 2.8
Appendix Figure C.32 Site NLDr velocity and slowness plots versus depth. H=layer thickness, VP=compressional
wave velocity, VS=shear wave velocity, RHO=density in t/m3.
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73
ADM01: SPAC and H/V data and model fits
Appendix Figure C.33 SPAC and HVSR for site ADM01. This poor SPAC data probably due to variable site
conditions. The locality lies between railway tracks and an open drain (creek) and has probably been used for
excavation and/or filling. Small triangle Uses one station deleted due to noisy site. Thick red line is the preferred
model which gives a degree of fit for spacings r2,r3 and r4. Thin red line uses a top layer with Vs1 reduced from
160m/s to 100m/s in order to get fit for r1 (small triangle radii). H/V shows a broad peak probably consistent with
variable site conditions.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
1.5 600 160. 1.78 ; alternative model (thin red line) has this top layer Vs=100m/s
1.5 1500 190. 1.8
2 1500 210. 2.0
10 1500 230. 2.0
8 2000 1000 2.14
16 2000 1000 2.14
50. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.34 Site ADM01r velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3. Thick red line is the preferred
model including a transition zone at base of sediments. Thin red line is model without a transition zone.
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75
HAM03: SPAC and H/V data and model fits
Appendix Figure C.35 SPAC and HVSR for site HAM03. This is a T-shaped array on an intersection of residential
streets. The small array (r1,r2) uses a slower Vs for the upper two layers (the preferred model shown by thick red
line, and shown in next figure). The larger array (r3,r4) gives an improved fit when using higher values Vs1, Vs2=
245m/s, plotted as thin red line. The H/V curve is the same for the 2 models, and does not give any indication of
existence of a transition zone.
76
The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
3 400 210. 1.78 ; alt model (thin red line Vs=245m/s
3 1500 205. 1.8
8 1500 210. 2.0
11 1500 225. 2.0
0.32 2000 500 2.14
100 3000 1500 2.14
200. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
Appendix Figure C.36 Site HAM03 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
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BRD08: SPAC and H/V data and model fits
Appendix Figure C.37 SPAC and HVSR for site BRD08. SPAC data at this site is very noisy but clearly indicates
a thin soft cover. The preferred model (thick red line) has 6.5m of soft soils with Vs=180 to 255 m/s. The H/V
observed and model curves have a peak at 10 Hz which indicates there is no transition zone. The H/V curve has
a lesser peak at 2 Hz which suggests sediments are underlain by bedrock at depth 181 m (see next figure).
(Compare with KOT01, BAR01).
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The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
1.5 600 180. 1.78
2 1500 220. 1.8
3 1500 255. 2.0
0.1 1500 300. 2.0
0.1 2000 500 2.14
75 3000 1500 2.14
100. 2940 1500 2.39
400 6000 3000 2.8
900. 6000 3000 2.8
Appendix Figure C.38 Site BRD08 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
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KOT01: SPAC and H/V data and model fits
Appendix Figure C.39 SPAC and HVSR for site KOT01. SPAC data at this site is very noisy but clearly indicates a
thin soft cover. The preferred model (thick red line) has 8m of soft soils with Vs=150 to 250 m/s. The H/V
observed and model curves have a peak at 7 Hz which indicates there is no transition zone. The H/V curve has a
lesser peak at 2 Hz which suggests sediments are underlain by bedrock at depth 183 m (see next figure).
(Compare with BRD08, BAR01).
80
The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
2 400 150. 1.78
4 1500 190. 1.8
1 1500 210. 2.0
1 1500 250. 2.0
75 3000 1500 2.14
100 3000 1500 2.14
200. 6000 3000 2.8
400. 6000 3000 2.8
900. 6000 3000 2.8
0. 6000 3000 2.8
Appendix Figure C.40 Site KOT01 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
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JUC01: SPAC and H/V data and model fits
Appendix Figure C.41 SPAC and HVSR for site JUC01. SPAC data for inner triangle and outer triangle fit different
models. Thick red line fit inner triangle and is model shown in next figure. Thin red line has Vs1,Vs2 increased
from 160m/s to 180m/s, and gives better fit for radii of outer triangle. Station D is near Glebe St and is deleted
from array, hence r4 is of dubious value. Fit for H/V requires a transition zone to fit frequency of the 3.5 Hz peak.
82
The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
2 400 160. 1.78
4 1500 165. 1.8
1 1500 260. 2.0
6 1500 260. 2.0
30 2000 800 2.14
100 3000 1500 2.14
200. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.42 Site JUC01 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
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CAR01: SPAC and H/V data and model fits
Appendix Figure C.43 SPAC and HVSR for site CAR01. Excellent SPAC data even where three stations are on
footpaths of quiet residential streets. Vs profile well resolved to depth 50m (including a small velocity inversion at
15-30m. Poor fit for r1,r2 at frequencies 4-7 Hz is due to higher mode wave propagation in this band. Thick red
line: model with total thickness of soft sediments is 47m. Thin red line, thin dashed line, show model with total
thickness changed by +-10%, hence conclude that thickness is resolved to better than 10%. Compare similar
case at CAR02. H/V spectrum shown is for station C not G due to G having anomalously high values at low
frequencies.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
1 400 105. 1.78
2 1500 105. 1.8
4 1500 140. 2.0
8 1500 220. 2.0
16 1500 200. 2.0
16 2000 250 2.14
150. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.44 Site CAR01 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
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85
CAR02: SPAC and H/V data and model fits
Appendix Figure C.45 SPAC and HVSR for site CAR02. Excellent SPAC data even all stations are on footpaths in
a T-shaped array on quiet residential streets. Vs profile well resolved to depth. Poor fit for r1,r2 at frequencies 4-7
Hz is due to higher mode wave propagation in this band. Thick red line: model with total thickness of soft
sediments is 49m. Thin red line, thin dashed line, show model with total thickness changed by +-10%, hence
conclude that thickness is resolved to better than 10%. Compare similar case at CAR01.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
1 400 120. 1.78
2 1500 120. 1.8
4 1500 180. 2.0
8 1500 220. 2.0
16 1500 260. 2.0
18 2000 260 2.14
150. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.46 Site CAR02 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
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87
ISO02: SPAC and H/V data and model fits
Appendix Figure C.47 SPAC and HVSR for site ISO_02. Depth and Vs are well resolved by SPAC to depth 39m.
H/V is not consistent; cannot explain why observed H/V shows peak at 2.5 Hz versus modelled H/V peak at 1.5
Hz. Thick red line is the: model with total thickness of soft sediments of 39m. Thin red line, thin dashed line, show
model with total thickness changed by +-10%, hence we conclude that thickness is resolved to better than 10%.
Compare similar case at CAR01, CAR02.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
1 400 135. 1.78
2 1500 135. 1.8
4 1500 140. 2.0
8 1500 200. 2.0
24 1500 280. 2.0
0.50 2000 800 2.14
150. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.48 Site ISO-02 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
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NTLS: SPAC and H/V data and model fits
Appendix Figure C.49 SPAC and HVSR for site NLTS. Thick red line: preferred model with no transition zone.
Thin red line is a model with layer 5 included as a (unrealistic) transition zone of thickness 64m, Vs5=500m/s.
This unrealistic thick transition zone improves SPAC data at low frequencies on r4, but gives a much poorer H/V
fit at the observed 1.5 Hz peak hence the absent transition zone (thick red line) is preferred. (Similar to BRD01,
ISO01. Also compare with model WIK01 and BRD02).
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The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
1.5 400 110. 1.78
4.5 1500 145. 1.8
8 1500 160. 2.0
16 1500 200. 2.0
0.32 2000 500 2.14 ; alt model h5=64m as transition zone
100 3000 1500 2.14
200. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.50 Site NTLS velocity and slowness plots versus depth. H=layer thickness, VP=compressional
wave velocity, VS=shear wave velocity, RHO=density in t/m3.
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91
JUC02: SPAC and H/V data and model fits
Appendix Figure C.51 SPAC and HVSR for site JUC02. this site uses an array on a T-junction, so geophones are
on footpaths (except for stations C and F). This has very poor SPAC data. H/V spectra show large variations from
one station to another. These problems may be due to either 2D geology, or to service conduits under the
footpaths. This plot uses H/V from station C. The presence (or not) of a transition zone is not resolvable. The
Vs30 is probably correct to about +- 20%. This site is only 300m west of site JUC01 but note it has a significantly
larger Vs than JUC01. This site has similar Vs30 to HAM02 (1km northeast) but lower Vs30 than BRD09 (1200m
WNW) and MER04 (500m WSW). The site is on trend with the drain through NTLS and may represent a
thickened sequence of sediments striking north-east through NTLS to Throsby Basin.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
2 400 160. 1.78
4 1500 165. 1.8
8 1500 240. 1.8
12 1500 240. 2.0
0.30 2000 800 2.14
100 3000 1500 2.14
200. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.52 Site JUC02 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
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93
BAR01: SPAC and H/V data and model fits
Appendix Figure C.53 SPAC and HVSR for site BAR01. this site uses an array straddling a dual carriageway, so
inner-triangle geophones are on the middle nature strip, others are on footpaths. This site has very poor SPAC
data. on the large triangle (r3,r4) where traffic drives through the array. The small triangle (r1,r2) yields useful
SPAC and the preferred model is shown with (thick red lines. This model also fits the H/V curve. The large
triangle yields poor SPAC but a model fit is possible, shown as thin red line. The model has increased Vs1,Vs2
(expected since large triangle covers compacted roadways). See next 2 figures for Vs profiles for the preferred
and alternative models. H/V curve has a secondary peak near 2 Hz which indicates a velocity contrast at about
185m depth (see comparison with KOT01, BRD08).
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The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO Preferred model fits the small triangle on nature strip at middle of dual carriageway
road
2 400 145. 1.78
4 1500 185. 1.8
1 1500 200. 2.0
5 1500 220. 2.0
75 3000 1500 2.4
100 3000 1500 2.4
200. 6000 3000 2.7
400. 6000 3000 2.7
900. 6000 3000 2.7
0. 6000 3000 2.7
Appendix Figure C.54 Site BAR01 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3. Thick red line is preferred
model from fitting SPAC from the small array. Thin red line is alternative non-preferred model using poor SPAC
from large array.
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95
MER04: SPAC and H/V data and model fits
Appendix Figure C.55 SPAC and HVSR for site MER04. The array is limited to half size, with large triangle radius
22m due to constraint by width of the street. The SPAC data is fair, but loses coherencies for frequencies <
4.5Hz, hence there is no resolution of a possible transition zone. The H/V data yields a match of model and field
data without inclusion of a transition zone.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
2 400 225. 1.78
4 1500 225. 1.8
8 1500 320. 2.0
14 1500 340. 2.0
.10 3000 800 2.14
20 3000 1000 2.14
200. 2940 1000 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.56 Site MER04 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
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97
TIH01: SPAC and H/V data and model fits
Appendix Figure C.57 SPAC and HVSR for site TIH01. The SPAC data is fair, but loses coherencies for
frequencies < 4.5Hz. This is surprising since the site is open space. It seems that closeness to Industrial Drive
(approx 20m) may be the problem. SPAC frequencies above 5 Hz resolve thickness of soft sediments to be
12.5m (thick red line, preferred model). Introduction of an unrealistic transition zone 60m of Vs=800m/s) does not
improve the fit of low frequencies on r4, hence there is no resolution of a possible transition zone.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
H VP VS RHO
2 400 105. 1.78
4 1500 145. 1.8
1 1500 270. 2.0
5.5 1500 270. 2.0
0.60 2000 800 2.14 ; alt model is h5=60m transition zone
20 3000 1500 2.14
200. 2940 1500 2.39
400. 2940 1500 2.39
900. 2940 1500 2.39
0. 3400 2000 2.8
Appendix Figure C.58 Site TIH01 velocity and slowness plots versus depth. H=layer thickness,
VP=compressional wave velocity, VS=shear wave velocity, RHO=density in t/m3.
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99
MASW, ReMi and S-refraction - 2013
survey
T. Volti, J Holzschuh, C. Harris-Pascal and C. Collins
Since the SPAC survey in 2012, a new shear-wave site classification project was undertaken in
Newcastle, in spring 2013, at most of the sites used in this report. Different methods such as MASW,
ReMi and P and S-wave refraction were used, in order to improve the interpretation at each site.
Processing was done using the Geometrics-SeisImager/WS Surface Wave Analysis Software package
for MASW and ReMi data. Table C.1 shows MASW, ReMi and S-refraction results together with the
common SPAC sites. MASW and ReMi methods tend to give lower Vs30 values than SPAC. P-wave
refraction picked mostly the water table level. S-wave refraction could be performed only in selected
sites because in most cases a second layer could not be identified. There is generally good
agreement, but a more detailed work is reserved for a further report.
Appendix Table D.1 Common results (added to the previous SPAC) from the 2013 Survey showing Vs30 and
depth to bedrock values derived from each method.
SITE
Vs30 (m/s)
Vs30
SASW/SCPT (m/s)
SPAC
GA
Vs30
(m/s)
SPAC
MU
Vs30
(m/s)
MASW
+ReMi
Vs30
(m/s)
Srefra
Depth
(m)
SCPT
Depth (m)
Depth Depth Depth (m)
(m) GA (m) MU MASW+ReMi S-refra
Mer05
360/266
387
394
341
263
6.8
8.5
11
11
7
Brd09
270/220
277
319
286
280
11.5
11
10
12
12
Iso01
246/256
302
334
308
-
15
11
10
7
-
Brd04
188/184
214
205
223
-
26.7
12
22
21
-
Wik01
177/178
193
178
184
-
36
23
34
-
-
Brd01
223
213
218
213
-
27.5
26
25
24
-
Nlt03
286
387
405
-
-
13.5
13
12
-
-
Brd02
222
221
228
226
-
24.35
24
23
21
-
Adm01
251
312
352
514
566
16
14
15
5.5
13
Juc01
238
363
353
346
333
20
14
13
8
12
Brd12
242
385
353
317
-
17.65
10.5
10
4
-
Ham03
255
212
251
227
-
31.5
26
25
21
-
Brd08
736
408
663
302
214
4
5
7
8
13
Kot01
143
371
519
372
625
5
6
8
5
7
Brd03
249
232
295
237
-
24.5
18.5
17
21
-
Ham02
237
242
231
240
-
12.15
20
15
21
-
Iso02
186
211
208
217
-
28.4
16
15
21
-
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The 2012 Newcastle-Sydney SPAC microtremor surveys
SITE
Vs30 (m/s)
Vs30
SASW/SCPT (m/s)
SPAC
GA
Vs30
(m/s)
SPAC
MU
Vs30
(m/s)
MASW
+ReMi
Vs30
(m/s)
Srefra
Depth
(m)
SCPT
Depth (m)
Depth Depth Depth (m)
(m) GA (m) MU MASW+ReMi S-refra
Riv
-
692
971
991
-
-
8
6
13
4
Sydh
-
590
675
598
-
-
22
14
-
4
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101
Site Pictures for Sydney and
Newcastle SPAC, SCPT, MASW and ReMi
Surveys
E.1 Sydney Sites
Appendix Figure E.1 SITE 1 Sydney: ANSN station RIV (-33.827409 151.158167) Saint Ignatius College,
Riverview St, Lane Cove
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Appendix Figure E.2 SITE 2 Sydney: ANSN station SYDH (-33.761858 150.741616) University of Western
Sydney, Werrington North Campus, Penrith. Yellow line = 100 m.
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103
E.2 Newcastle Sites
Appendix Figure E.3 Newcastle sites. Priority: RED=High, YELLOW=Medium, GREEN=Low. (JUMP permanent
seismic network sites marked 'J').
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The 2012 Newcastle-Sydney SPAC microtremor surveys
Appendix Figure E.4 Map of Newcastle district where sites were located.
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105
Appendix Figure E.5 Map of previous site studies undertaken in 2002, 2010 and 2012. Triangles = SASW, Stars =
SPAC (2002), Circles = SPAC (2012).
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The 2012 Newcastle-Sydney SPAC microtremor surveys
Appendix Figure E.6 Site classes from Dhu & Jones (2002). Red = barrier sand; Orange = silt & clay, interbedded
sand; Light Orange = sand, interbedded silt & clay; Yellow = sand overlying silt & clay; Light Green = silt & clay;
Dark Green = weathered rock.
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107
Appendix Figure E.7 SITE 0: NTLH (permanent ANSN JUMP station formerly NLD -32.90133 151.70391 North
Lambton Depot - Compton Street). Yellow line = 100 m.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
Appendix Figure E.8 SITE 1: Mer-05 -32.93771 151.73675 Merewether, Cnr Lockyer & James St. Circle Radius =
100 m.
Appendix Figure E.9 SITE 2: Brd-09 -32.93351 151.74045 Broadmeadow, Darling Oval, Cnr Darling & Hassall St.
Circle radius = 100 m.
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109
Appendix Figure E.10 SITE 3: Iso-01 -32.91102 151.74643, Islington Park, East of junction. of Maitland Rd (Old
Pacific Hwy) & Hubbard St. Circle radius = 100 m.
Appendix Figure E.11SITE 4: Brd-04 -32.91659 151.73513, Broadmeadow, Smith Park, cnr Griffiths Rd & Thorn
Rd. Circle radius = 100 m.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
Appendix Figure E.12 SITE 5: Wik-01 -32.91867 151.75338 Islington, Wickham Park, cnr Maitland Rd (Old Pacific
Hwy) & Albert St. Circle radius = 100 m.
Appendix Figure E.13 SITE 6:Brd-01 (-32.91734 151.73790) Broadmeadow, cnr Griffiths Rd & Chatham Rd (near
Smith Park) Circle radius = 100 m.
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111
Appendix Figure E.14SITE 7: Nlt-03 (-32.93221 151.71940) New Lambton, cnr St James Rd & Mackie Av (East of
Alder Park). Circle radius = 100 m.
Appendix Figure E.15SITE 8: Brd-02 (-32.92004 151.73215) Broadmeadow, cnr Curley Rd & Denney St (East of
District Park?). Circle radius = 100 m.
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Appendix Figure E.16 SITE 9: Adm-01 (-32.93297 151.72298) Adamstown, West End Park at Glebe Rd & Ct St
end Circle radius = 100 m.
Appendix Figure E.17 SITE 10: Juc-01 (-32.93909
and Union Street. Circle radius = 100 m.
The 2012 Newcastle-Sydney SPAC microtremor surveys
151.75791) The Junction, Rowland Park, cnr Glebe Rd
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Appendix Figure E.18SITE 11: Brd-12 (-32.93291 151.73532) Broadmeadow, Myers Park?, cnr Chatham St &
Melville Rd. Circle radius = 100 m.
Appendix Figure E.19SITE 12: Ham-03 (-32.91971 151.74963) Hamilton – west of Wickham Park, cnr Donald St
& Eva St. Circle radius = 100 m.
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Appendix Figure E.20 SITE 13: Brd-08 (-32.92883 151.73260) Broadmeadow, North of Myers Park, cnr Gosford
St & Melville Rd. Circle radius = 100 m.
Appendix Figure E.21 SITE 14: Kot-01(-32.94922 151.69786) Kotara South, North of Nebitt Park, cnr Grayson
Ave & Casey Ave. Circle radius = 100 m.
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115
Appendix Figure E.22 SITE 15: Brd-03 (-32.92282 151.72755) Broadmeadow, District Park, cnr Perth Rd & Bavin
St (near Bronte Rd) Circle radius = 100 m.
Appendix Figure E.23 SITE 16: Ham-02 (32.93132 151.74947) Hamilton, Learmonth Park, cnr Jenner Pd &
Gordon Ave. Circle radius = 100 m.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
Appendix Figure E.24Site BAR01 LOWER PRIORITY SITE 17: Bar-01 (-32.93827 151.76530). Yellow line = 100
m.
Appendix Figure E.25 Site BRD10. LOWER PRIORITY SITE 18: Brd-10 (-32.92756 151.74085). Yellow line = 100
m.
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117
Appendix Figure E.26 LOWER PRIORITY SITE 19: Brd-14 (-32.91654 151.72999) Site BRD14. Yellow line = 100
m.
Appendix Figure E.27LOWER PRIORITYSITE 20: Car-01 (-32.91130 151.76652) Yellow line = 100 m.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
Appendix Figure E.28 LOWER PRIORITY SITE 21: Car-02 (-32.91650 151.76518). Yellow line = 100 m.
Appendix Figure E.29 LOWER PRIORITY SITE 22: Ham-01 (-32.92338 151.74220). Yellow line = 100 m.
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119
Appendix Figure E.30 LOWER PRIORITY SITE 23: Iso-02 (-32.91412 151.74877) Yellow line = 100 m.
Appendix Figure E.31 LOWER PRIORITY SITE 24: Juc-02 (-32.93883 151.75422) Yellow line = 100 m.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
Appendix Figure E.32 LOWER PRIORITY SITE 25: Kot-03 (-32.94145 151.70611). Yellow line = 100 m.
Appendix Figure E.33 LOWER PRIORITY SITE 26: Lmt-01 (-32.92862 151.72137). Yellow line = 100 m.
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Appendix Figure E.34 LOWER PRIORITY SITE 27: Lmt-03 (-32.91255 151.71925). Yellow line = 100 m.
Appendix Figure E.35 LOWER PRIORITY SITE 28: Lmt-04 (-32.92277 151.72231). Yellow line = 100 m.
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Appendix Figure E.36 LOWER PRIORITY SITE 30: May-02 (-32.90465 151.74278) Yellow line = 100 m.
Appendix Figure E.37 LOWER PRIORITY SITE 31: May-03 (-32.90697 151.73836). Yellow line = 100 m.
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Appendix Figure E.38 LOWER PRIORITY SITE 32: Mer-04 (-32.94028 151.74987). Yellow line = 100 m.
Appendix Figure E.39 LOWER PRIORITY SITE 33: Nlt-04 (-32.93100 151.71535). Yellow line = 100 m.
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Appendix Figure E.40 LOWER PRIORITY SITE 34: Nlt-05 (-32.92753 151.71144). Yellow line = 100 m.
Appendix Figure E.41 LOWER PRIORITY SITE 35: Nlt-06 (-32.93275 151.71008). Yellow line = 100 m.
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Appendix Figure E.42 LOWER PRIORITY SITE 36: Nlt-07 (-32.91978 151.72118). Yellow line = 100 m.
Appendix Figure E.43 LOWER PRIORITY SITE 37: Tih-01 (-32.90452 151.75487). Yellow line = 100 m.
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The 2012 Newcastle-Sydney SPAC microtremor surveys
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