Geomatics, Natural Hazards and Risk
ISSN: (Print) (Online) Journal homepage: www.tandfonline.com/journals/tgnh20
Site response measurements and implications to soil
liquefaction potential using microtremor H/V in Greater
Metro Manila, Philippines
A. Daag, L. E. Aque, O. Locaba, R. Grutas & R. Solidum Jr.
To cite this article: A. Daag, L. E. Aque, O. Locaba, R. Grutas & R. Solidum Jr. (2023) Site
response measurements and implications to soil liquefaction potential using microtremor H/V
in Greater Metro Manila, Philippines, Geomatics, Natural Hazards and Risk, 14:1, 2256936, DOI:
10.1080/19475705.2023.2256936
To link to this article: https://doi.org/10.1080/19475705.2023.2256936
© 2023 The Author(s). Published by Informa
UK Limited, trading as Taylor & Francis
Group
Published online: 05 Oct 2023.
Submit your article to this journal
Article views: 1415
View related articles
View Crossmark data
Citing articles: 2 View citing articles
Full Terms & Conditions of access and use can be found at
https://www.tandfonline.com/action/journalInformation?journalCode=tgnh20
GEOMATICS, NATURAL HAZARDS AND RISK
2023, VOL. 14, NO. 1, 2256936
https://doi.org/10.1080/19475705.2023.2256936
Site response measurements and implications to soil
liquefaction potential using microtremor H/V in Greater
Metro Manila, Philippines
A. Daaga,b
, L. E. Aqueb, O. Locabab, R. Grutasb and R. Solidum , Jr.a,b
a
Department of Science and Technology (DOST), Taguig, Philippines; bDepartment of Science and
Technology - Philippine Institute of Volcanology and Seismology (DOST-PHIVOLCS), Quezon,
Philippines
ABSTRACT
ARTICLE HISTORY
This research explores the use of microtremor horizontal-to-verti­
cal spectral ratio (H/V) in obtaining site response characteristics
and investigating its relationship with soil liquefaction potential in
Greater Metro Manila. We performed single station microtremor
measurements in 61 sites along with in situ geotechnical techni­
ques to verify liquefaction potential. The resulting 238 spectral
curves were classified according to dominant features and subse­
quently grouped with the calculated liquefaction potential index
(LPI) of the soil. Based on a robust comparison of obtained pri­
mary parameters, it is revealed that the shape of the H/V curve,
its predominant period and relative amplitude are fundamentally
linked to the spatial variability and the shear strength of soils.
Therefore, areas of high seismic demand can also have high lique­
faction potential, and vice versa. We then correlated the predom­
inant period with the LPI of the soil and extracted a boundary
using simple statistical techniques to classify high and low poten­
tial for liquefaction subsequently validating its use as a comple­
mentary tool for rapid site-specific liquefaction assessment. Such
findings are a novel contribution to liquefaction studies employ­
ing rapid techniques since the application of microtremors to
liquefaction in the Philippines has not been practiced extensively.
Received 11 April 2023
Accepted 4 September 2023
KEYWORDS
Site response; microtremor
H/V; predominant period;
liquefaction; LPI
Introduction
Understanding how soils respond to strong ground shaking is a significant concern
in seismic hazard estimation across all geological environments, most specially in
metro regions where infrastructure is continuously being developed. Various factors
control the response of soils to strong earthquakes including, source proximity, nearsurface soil properties, acoustic impedance contrasts and basin configuration, to
CONTACT A. Daag
arturo.daag@phivolcs.dost.gov.ph
� 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/
licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited. The terms on which this article has been published allow the posting of the Accepted Manuscript in a repository by
the author(s) or with their consent.
2
A. DAAG ET AL.
name a few. The profound effects of amplified ground shaking in soft soils are histor­
ically demonstrated in the 1985 Ms 8.1 Mexico City earthquake and the 1989 Ms 7.2
Loma Prieta earthquake, where buildings sustained considerable damages despite
being hundreds of kilometers away from the earthquake epicenter. In the Philippines,
a comparable amplified ground shaking phenomenon was observed during the
1968 Ms 7.3 Casiguran earthquake and the 1990 Ms 7.9 Luzon earthquake where
buildings in the capital city of Manila suffered severe damages despite being located
about 225 and 120 kilometers away from the earthquake epicenters, respectively
(Rodolfo 2014; PHIVOLCS n.d.-a, n.d.-b).
In addition to damage on buildings due to amplified ground shaking, damages
associated with soil liquefaction is also a quintessential consequence of earthquakes.
Liquefaction occurs when the soil material below the water table temporarily loses
strength and behaves as a viscous liquid rather than a solid (Earthquake Engineering
Research Institute 1994), rendering structures founded on liquefiable soil to sustain
damages. Comparatively, a hallmark of both phenomena is the amplification and pro­
longing of the duration of seismic energy contributing to the severity of the damage
at the surface (Kramer 1996; Towhata 2008; Beroya and Aydin 2010; Mase et al.
2022). Although the mechanism for seismic amplification varies per location, site
response characteristics can be investigated in advance of an earthquake using micro­
tremors or ambient noise (Nakamura 1989, 2000, 2019; Mase et al. 2023).
In recent years, global applications of microtremor horizontal-to-vertical spectral
ratio (H/V) for liquefaction studies utilized the seismic vulnerability index of
Nakamura (1996, 1997) (and its variations) that basically constitute the product of
the site response parameters - predominant period of the soil and its relative ampli­
tude to quantify liquefaction prediction (Huang and Tseng 2002; Hardesty et al. 2010;
Choobbasti et al. 2015; Sathyaseelan et al. 2017; Singh et al. 2017; Herrera et al. 2018;
Ramos et al. 2019; Meneisy et al. 2020; Arango-Serna et al. 2021; Kang et al. 2021).
The relevant downside of this technique is that it is based on multiple and complex
assumptions as listed in Herrera et al. (2018) and Arango-Serna et al. (2021).
Moreover, some of the listed works have a lack in integrating a design earthquake
model which can trigger liquefaction. If present, there is a lack in the robust compari­
son of the more basic parameters which are the predominant period and its relative
amplitude with significant subsurface information that can contribute to liquefaction
occurrence. With a large set of subsurface data, the relationship of the site response
parameters with liquefaction potential can be better understood.
In this paper, the microtremor H/V was used to study potential site response on
seismic ground motion in the Greater Metro Manila area (GMMA), a densely popu­
lated region that hosts an actively seismic zone. This study also presents the first
application of the method in terms of liquefaction studies in the study area. We
focused on sites that are potentially liquefiable by virtue of liquefaction potential
index (LPI) calculated from in-situ geotechnical data acquired in conjunction with
the microtremor H/V. This is to facilitate the possible implications of site response
with liquefaction potential. Predominant period values, relative amplitudes, and soil
thicknesses are then compared with geological and geotechnical data, particularly the
soil shear-wave velocities, soil N-values, and the LPI of the soil deposit. In addition, a
GEOMATICS, NATURAL HAZARDS AND RISK
3
boundary was extracted separating high and low potentials of liquefaction with the
predominant period using simple statistical analysis which can be used as a first-pass
indication for liquefaction occurrence.
Geological setting and earthquake scenario
GMMA is a large region encompassing the provinces of Bulacan, Cavite and Metro
Manila. It lies at the southernmost extension of the Central Luzon Basin (Figure 1)
and is bounded to the west by the Manila Bay and to the east by the mountains of
Sierra Madre.
The Quaternary Alluvium is characterized by soft and unconsolidated sediments of
dominantly sand and clay interlayers of varying thickness. The alluvium is extensively
distributed along the coastal lowlands and terminates to the east as it thins out
towards the central plateau. Based on the accounts of Gervasio (1968), the formation
of the coastal lowlands started during the Pliocene, followed by its abrupt seaward
expansion at the advent of the Pleistocene. The expansion was supplied by volcanic
sediments associated with the calderagenic episodes of the Taal Caldera or Laguna de
Bay. The episodes deposited thick tuffaceous rocks and bedded tuff in the east
Figure 1. Experimental sites and geological map of Greater Metro Manila area (GMMA),
Philippines.
4
A. DAAG ET AL.
corresponding to the Guadalupe Formation. Bounding the plateau to the east is the
West Valley Fault (WVF) of the Marikina Valley Fault System (MVFS). The WVF is
an approximately 100-km north to south trending right lateral strike slip fault with
surface manifestation that runs from the mountains of Bulacan in the north to the
highlands of Tagaytay in the south.
Based on paleoseismic investigation of Nelson et al. (2000), the WVF has generated
4 surface-rupturing earthquakes over a period of <1300 years with a preferred recur­
rence interval of 400-600 years. Its last major earthquake was documented in 1658,
based on accounts of historians and priests (Mas�
o 1910). Considering the lower
bound of the recurrence interval, the WVF has a possibility for a near-future seismic
event. The Metro Manila Earthquake Impact Reduction Study (2004) and Rimando
and Knuepfer (2006) estimated a magnitude 7.2 and 7.3 earthquake, respectively,
should the WVF rupture. These magnitude estimates translate to an Intensity VIII in
the PHIVOLCS Earthquake Intensity Scale (PEIS) (Table 1).
Materials and methods
For the microtremor H/V analysis, single station microtremor measurements were
employed to sample raw ambient noise data. Essentially, it estimates the amplification
characteristics at a certain period of motion of the ground by only calculating the
ratio of the horizontal with the vertical Fourier amplitude spectra of only surface
measurements (Nakamura 1989). The technique follows the formula,
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
ðN 2 þ E2 Þ=2
H=V ¼
V
(1)
where N and E are the Fourier amplitude spectra of the horizontal components and
V is the vertical component. The resulting spectral peak corresponds to the predom­
inant period and its relative amplitude consistent to the major impedance contrast in
the subsurface profile. The microtremor H/V differs from the standard spectral ratio
such that transfer function is calculated by using only the recorded ground motions
at a single soft soil site, eliminating the need for a reference site (Nakamura 1989;
Lermo and Ch�avez-Garc�ıa 1994).
Table 1. PHIVOLCS Earthquake Intensity Scale (PEIS) with modified mercalli
Intensity (MMI) equivalent.
PEIS
Shaking
MMI
I
II
III
IV
V
VI
VII
VIII
IX
X
Scarcely Perceptible
Slightly Felt
Weak
Moderately Strong
Strong
Very Strong
Destructive
Very Destructive
Devastating
Completely Devastating
I
II
III
IV
V
VI
VII
VIII, IX
X, XI
XII
GEOMATICS, NATURAL HAZARDS AND RISK
5
For the geotechnical analysis and liquefaction potential investigations, Refraction
Microtremor (REMI) surveys and Screw Driving Sounding (SDS) tests were used.
The REMI survey was developed by Louie et al. (2001) and is used in this study to
obtain soil shear-wave velocity profiles of the subsurface. It is a non-invasive tech­
nique that analyzes and extracts dispersion characteristics of rayleigh waves deter­
mined from ambient noise recordings. Louie et al. (2001), Mase et al. (2018) and
(Daag et al. 2022) provide details on further surface wave analysis using this tech­
nique. On the other hand, the SDS test is a relatively new penetration test developed
in Japan and it is used in this study to obtain soil N-values comparable to the
Standard Penetration Test (SPT) (Orense et al. 2019; Daag et al. 2023). It is essentially
an improved and automated version of the Swedish Weight Sounding (SWS) test,
capable of classifying sands from clays by percent fines estimation with high probabil­
ity. Basically, we semi-quantitatively compared general and readily observable primary
output of the methods (for e.g. predominant period and relative amplitude against
soil shear-wave velocity and N-value) to facilitate in the understanding of the possible
relationship between site response and liquefaction potential. Supplementary depth to
groundwater table data necessary for liquefaction investigation was determined by the
Ground Penetrating Radar (GPR).
Data acquisition and processing
Majority of the sites for microtremor H/V measurements were along the coastal low­
lands of GMMA, where the soil deposits are susceptible to liquefaction. Additional
sites were acquired along the central plateau for comparison. We acquired single sta­
tion microtremor data at 61 temporary sites using the OYO McSEIS MT-NEO. It is
an all-in-one (battery and sensor) triaxial accelerometer with a natural frequency
response of 0.1 to 200 Hz. Sampling interval was set at 10 milliseconds. The recording
duration for each station was set at 20 min, with some reaching over an hour,
depending on the presence of transients. All the recordings followed the guidelines
set by the SESAME Project (SESAME 2004). Data recorded on the instrument were
stored in an SD card and transferred to the computer. Raw motion files of each sta­
tion were converted to multi-column ASCII format to be analyzed in Geopsy, an
open-source software capable of processing and visualizing multiple signals at once
(Wathelet et al. 2020). Processing parameters were kept as consistent as possible with
modifications only applied as recommended by the SESAME Project.
REMI survey and SDS test were also conducted in the proximity of the microtre­
mor measurements to obtain the shear-wave velocity and soil N-values of the shallow
subsurface, respectively for validation of the spectral curves. Both methods were also
used for the calculation of the liquefaction potential index (LPI), together with water
table depth estimates from the Ground Penetrating Radar (GPR). For the REMI sur­
vey, twelve 4.5 Hz geophones were installed on a linear array with about 4- to 8meter spacing, depending upon site conditions. A sledgehammer was used to induce
vibration and microtremor data for analysis were collected using DAQLink II seismo­
graph and Vscope software. Data processing was carried out using REMI Vspect and
Disper software to retrieve the shear wave velocity profile of the particular soil
6
A. DAAG ET AL.
deposit. For the SDS test, it involves the penetration of a rotating rod into the soil at
7 incremental loading steps (0.25 to 1.0 kN) until reaching 25 centimeters of penetra­
tion. At every 25 centimeters of penetration, several parameters are measured such as
torque, load, penetration speed, and rod friction. These parameters are then sent to
the proprietary Geoweb server where it automatically evaluates the equivalent N-val­
ues. Further details on test operations and parameter estimations are in Orense et al.
(2019) and (Daag et al. 2023). For the GPR survey, we employed the MALA ProEx
GPR using antenna center frequency of 500 MHz to resolve the shallow water table
depth. Raw data were processed in RadExplorer to obtain the radargrams.
Results and discussion
Site period distribution
Out of 61 sites, we collected 238 H/V curves. Most sites contained more than one
H/V measurement and thus, Figure 2 shows the representative site period or simply
the average of the predominant period of all measurements within the site.
The sites were classified based on predominant period from the H/V analysis.
Long period sites have predominant periods > 0.6 s; moderate period sites have pre­
dominant periods in the range of 0.2 s to 0.6 s; short period sites have predominant
periods in the range of 0.05 s to 0.2 s; and no peak sites have no identifiable H/V
peaks. The two peaks case was not observed much in this study suggesting that there
is only one major impedance contrast present in the study area. Majority (43%) of
the experimental sites are classified as moderate period sites and are distributed
throughout the coastal lowlands. Long period sites (25%) are observed mostly in the
northern coast where the environment is dominated by tidal plains and sand bars
while there are a few that are near the reclaimed area in Metro Manila indicating
that soil deposits are generally thicker and softer. On the other hand, short period
sites (15%) and sites with no peaks (18%) are found sparsely throughout the study
area but are nearing or atop the central plateau where the soft soil deposit is relatively
thin. The period distribution is consistent with the results of Narag et al. (2000) spe­
cifically within the coastal area of Metro Manila. Examples of H/V curves are pre­
sented in Figure 3 showing the distinguishable H/V curve shapes across the period
classifications.
The relationship between the predominant period of the soil, T, and the overall
soil thickness, h, down to the major impedance contrast is given by the quarter wave­
length formula,
T¼
4h
vs
(2)
where vs is the local average shear-wave velocity. Using the shear-wave velocity
obtained from the REMI survey as a constraint, overall soil thickness across the sur­
vey area is shown in Figure 4. It is important to note that the shear-wave velocity of
the major impedance contrast in and around Metro Manila is �600 to 760 m/s
GEOMATICS, NATURAL HAZARDS AND RISK
7
Figure 2. Site period distribution and relative amplitude across the study area (amplitude val­
ues from 2 to 8 scales with the dot size). for sites with multiple H/V measurements, the pre­
dominant period and their relative amplitudes were simply averaged to obtain the
representative values. Labelled sites are used as an example in this section and latter sec­
tions of the paper.
equivalent to the engineering bedrock (Metro Manila Earthquake Impact Reduction
Study 2004; Grutas and Yamanaka 2012).
Throughout the coastal lowlands, soil thickness varies from �2.5 meters near the
rocky coast of Cavite to 56 meters in Bulacan. A general increase in soil thickness is
also observed from east to west which is typical in the study area following the gentle
dipping topography of the central plateau towards Manila Bay.
In general, based on the distribution of the predominant period and amplitude as
well as the overall soil thickness across the study area, the potential for amplification
8
A. DAAG ET AL.
Figure 3. Examples of the (a) long period sites (predominant period > 0.6 s), (b) moderate period
sites (0.2 s to 0.6 s), (c) short period sites (0.05 s to 0.2 s) and (d) sites with no peaks.
of seismic ground motion is expected to be greatest towards the north in Bulacan,
surpassing earlier microtremor measurements of Abeki et al. (1996) and Narag et al.
(2000) in Metro Manila where the period and amplitude distribution is consistent
with their results. These findings in Bulacan correlate well with its topographical loca­
tion being proximal to the center of the Central Luzon Basin, thereby having thicker
soils as compared to Metro Manila and Cavite. Overall soil thickness decreases
towards the south and east as unconsolidated sediments thin out or increase in stiff­
ness. In Cavite, no amplification is expected along its rocky coastline, however, there
are a few sites that exhibit some degree of amplification in sites along the spit feature
and nearby river systems which are likely to be underlain by reworked sediments due
to coastal or fluvial activity, respectively.
GEOMATICS, NATURAL HAZARDS AND RISK
9
Figure 4. Spatially interpolated distribution of soil thickness across the study area calculated from
the predominant period and local average shear-wave velocity.
Liquefaction potential index (LPI) distribution
In this section, we determine the liquefaction potential distribution of the soil deposit
nearby microtremor H/V measurements. Soil profiles produced from the REMI sur­
veys and the SDS tests reveal shallow soil layers with varying shear strengths and
thicknesses (Figure 5). These profiles are grouped according to period classification
determined from the previous section. Groundwater table depths are also reflected in
the soil profiles showing the near-surface saturation of the soil in almost all sites.
Current practice of site-specific liquefaction assessment revolves around modifica­
tions of the ‘simplified procedure’ of Seed and Idriss (1971, 1982) using different
invasive (Cetin et al. 2004; Moss et al. 2006; Boulanger and Idriss 2012, 2016) and
non-invasive (Andrus and Stokoe 2000; Kayen et al. 2013) techniques. This simplified
10
A. DAAG ET AL.
Figure 5. Example of soil profiles showing depth vs. N-value from the SDS tests and depth vs.
shear-wave velocity from the REMI surveys grouped according to period classification. a1-a6 are
profiles in long period sites, b1-b7 are profiles in moderate period sites, c1-c6 are profiles in short
period sites, and d1-d5 are profiles in sites with no peaks.
GEOMATICS, NATURAL HAZARDS AND RISK
11
procedure involves empirical stress-based calculations where the liquefaction resist­
ance of soil is compared to a triggering mechanism acting on the soil to induce lique­
faction (Seed and Idriss 1971; Youd and Perkins 1978; Youd et al. 2001). However, in
this paper, we followed Maeda et al. (2015) in estimating liquefaction resistance for
SDS test data based on the ‘Specifications for Highway Bridges’ of Japan Road
Association (JRA) (Japan Road Association 1996). This is to duplicate their calcula­
tions since the SDS test is a relatively new technique and it is not an objective of this
paper to explore different methodologies. We also followed the procedure proposed
by Kayen et al. (2013) based on the shear-wave velocity obtained from the REMI sur­
vey since their work is comprehensive and is built on the work of Andrus and Stokoe
(2000). Both methods are independent in estimating liquefaction risk at depth.
Using the JRA approach, the liquefaction potential of the soil can be computed
through the liquefaction resistance factor (FL ), which is the ratio between the
dynamic shear stress (R) and seismic shear stress (L) as seen in Equation (3).
FL ¼
R
L
(3)
FL specifies the risk of liquefaction in depth, where values less than 1 will indicate
the possibility of the hazard. The seismic shear stress (L) is calculated using
Equation (4),
L ¼ cd khgL
rv
r0v
cd ¼ 1:0
0:015x
(4)
where khgL is the peak ground acceleration in g, cd is the reduction coefficient, x is
the depth from the surface in m, and rv and r0v as the total and effective overburden
pressure, respectively, at depth x: On the other hand, the dynamic shear stress (R) is
calculated using Equation (5),
R ¼ C w RL
(5)
where Cw is the coefficient of seismic motion and RL is the cyclic triaxial strength
ratio calculated from the SDS N-value and fines content. Since the SDS test estimates
parameters every 25 centimeters, FL can be calculated for every 25 centimeters.
Using the formula developed by Kayen et al. (2013), the potential for liquefaction
can also be evaluated by the factor of safety against liquefaction (FS ), which is
obtained by comparing the earthquake-induced seismic loading or cyclic stress ratio
on a soil layer (CSR) with the capacity of the soil to resist liquefaction with 15%
probability or cyclic resistance ratio (CRRPLð15%Þ ) as seen in Equation (6).
FS ¼
CRRPLð15%Þ
CSR
(6)
Similar to FL , FS specifies the risk of liquefaction in depth, where values less than
1 will indicate the possibility of liquefaction. The cyclic stress ratio (CSR) is expressed
by Equation (7),
12
A. DAAG ET AL.
CSR ¼ 0:65
�
�� �
amax
rv
rd
g
rv0
(7)
rd ¼ 1 0:00765z; for z < 9:2 m
rd ¼ 1:174 0:0267z; for z � 9:2 m
where amax is the peak ground acceleration in g, g is the acceleration of gravity, rd is
the reduction coefficient, z is the depth from the surface in m, and rv and rv0 as the
total and effective overburden pressure, respectively, at depth z: On the other hand,
cyclic stress ratio ðCRRÞ is calculated using Equation (8),
��
CRR ¼ exp
ð0:0073vs1 Þ2:8011
0:0099lnðr0 v0 Þ þ 0:0028FC
1:946
2:6168lnðMw Þ
0:4809/ 1 ðPL Þ
��
(8)
where vs1 is the effective stress-normalized shear-wave velocity, Mw is the simulated
moment magnitude used in this study, r0 v0 is the reference vertical overburden stress,
FC is the fines content (obtained from the SDS test). vs1 is given in Equation (10)
where Pa is a reference vertical overburden stress of 100 kPa.
�
vs1 ¼ vs
Pa
r0 v0
�0:25
(9)
In contrast to the resolution of calculating FL in the SDS test, FS can only be calcu­
lated per layer present in the shear-wave velocity profile. LPI was then calculated
using the formula of Iwasaki et al. (1984) given by,
2ð0
FL or Fs �ð10
LPI ¼
0:5zÞdz
(10)
0
where z is the soil depth. We also follow the criteria of Iwasaki et al. (1984) in lique­
faction risk (Table 2).
The descriptive statistics of the resulting LPI in terms of predominant period
values are summarized in Table 3 and their statistical distribution is presented in
Figure 6 in a box and whisker plot.
There is a super majority of the sites that have very high liquefaction potential.
These sites correspond to a minimum and maximum period range of 0.12 s to 1.31 s,
respectively, but most sites are found within 0.45 s to 0.91 s. Comparatively, sites with
high liquefaction potential are those found at a lower minimum and maximum
period range of 0.11 s to 0.78 s, but most are found within 0.19 s to 0.32 s. It is inter­
esting to note that Figure 6 shows high liquefaction potential can still occur at sites
with a predominant period at about 0.12 s. In contrast, those sites with low to very
low liquefaction potential contain sites that have no peaks up to periods of about
0.29 s. Another interesting find is that in terms of the predominant period, general
trends can be observed separating the period classes. All (but one) long period sites
GEOMATICS, NATURAL HAZARDS AND RISK
13
Table 2. Liquefaction potential index (LPI) classification and
description (after Iwasaki et al. 1984).
LPI Value
Description
0
0 to 5
5 to 15
>15
Very low
Low
High
Very high
Table 3. Summary of the descriptive statistics of the liquefaction potential classifica­
tion in terms of predominant period.
Very high
No. of values
Minimum
25% percentile
Median
75% percentile
Maximum
Mean
Std. dev.
Std. error
183
0.12
0.45
0.60
0.91
1.31
0.66
0.28
0.02
High
Low
Very low
19
0.11
0.19
0.22
0.32
0.78
0.27
0.16
0.04
13
0
0
0.07
0.21
0.21
0.09
0.08
0.02
55
0
0
0.10
0.29
0.29
0.09
0.08
0.01
Figure 6. Box and whisker plot of the sites in terms of predominant period and LPI.
have very high LPI. Those situated at moderate period sites have dominantly high to
very high LPI with a few very low LPI and one low LPI. Short period sites have dom­
inantly very low to low LPI with a few high to very high LPI. All sites with no peaks
have evidently very low LPI with a few low LPI.
14
A. DAAG ET AL.
Discussion
Comparison with soil profiles
To understand the possible link between site response and liquefaction potential, we detail
the comparison of the H/V curves in Figure 3 against the soil shear-wave velocity and Nvalue from Figure 5 which is generalized but contains necessary information to understand
characteristic trends. The H/V curves contain diagnostic key features of the subsurface
structure (Molnar et al. 2018; Molnar et al. 2022) and it is evident from the spectral curves
that there are distinct contrasts in their shapes and peaks across the period classes. We
already know that the predominant period is directly related to the overall thickness of the
soil cover from Equation (2) whereas the amplitude scales with the impedance contrast
between the soft soil and the rigid bedrock (Oubaiche et al. 2012; Uebayashi et al. 2012;
Castellaro and Mulargia 2014; Likitlersuang et al. 2020) thereby providing information as
to the stiffness of the soil compared to the bedrock. As an aid in interpreting H/V curve
shapes, we used the papers of LeBrun et al. (2004) and Beroya et al. (2009) as well as the
SESAME guidelines (SESAME 2004).
Sites a1, a2, a3 and a5 (Figure 3a) show predominant periods of 1.31 s, 1.06 s,
1.19 s and 1.03 s, respectively with amplitudes �4. These sites can have soil thick­
nesses of �38 to 56 meters. In comparison with the soil profiles (Figure 5, a1-a3 and
a5), N-values of the upper 20 meters in these sites commonly range from 0.5 to 5
corresponding to very loose sands or soft to very soft clays whereas shear-wave veloc­
ities in the same depth range show about 92 m/s to 188 m/s. In fact, it is common for
these low values to extend more than 30 meters at depth. In some areas such as in
sites a4 and a6, although the predominant period is shorter (therefore less thick
deposit), the amplitudes equate to about �7, indicative of a larger contrast in the
acoustic impedance of the soft soil layer above the bedrock. As mentioned earlier, the
engineering bedrock corresponding to the Guadalupe Formation has about �600 m/s
to 760 m/s shear-wave velocities with the difference possibly attributed to the state of
weathering. The apparent consistency of the low shear strength values and the con­
siderable thickness of the deposit demonstrated a clear singular high amplitude peak
qualitatively indicating a simple soil structure such as a homogenous single soft soil
layer over a rigid bedrock with high impedance contrast.
Moderate period sites show more variability in the shape of the H/V curves. Sites
b1, b3, b4, b5 and b7 (Figure 3b) show singular peaks which is the case for most of
the H/V curves in this classification, however site b2 has a slightly broader maximum
and site b6 has two peaks. Broad peaks and two peaks cases are characteristic of a
more complex soil structure and are most likely attributed to strong lateral heterogen­
eity or irregularities (Guillier et al. 2006; Moisidi et al. 2012). Soil profiles corre­
sponding to site b2 (Figure 5, b2) show the presence of a �2-meter-thick layer at
very shallow depths with somewhat higher N-values (17 to 25) and shear-wave vel­
ocity (450 m/s) than the layers above and below it. Another REMI survey conducted
about 45 meters away from where b2 was conducted showed thinning of this high
velocity layer from 2 meters to just 90 centimeters. On the other hand, the soil profile
in site b6, particularly the N-value profile (Figure 5, b6) shows a very dense sand (Nvalue reaching 50) present at about 5 meters then lessens at depth. Shear-wave
GEOMATICS, NATURAL HAZARDS AND RISK
15
velocity profiles taken nearby site b6 did not resolve this layer. It is questionable if
the presence of these shallow high velocity layers is sufficient to complicate H/V
curve interpretation and it was not explored in more detail. Therefore, these sites
lean towards an inconclusive analysis of the amplitudes, although the predominant
period is reliable and usable. Other reasons supplementary to the sufficiency of this
layer to complicate H/V curve interpretation is also possible such as the presence of
subsurface sloping interfaces between hard and soft layers (SESAME 2004) but was
not explored in this paper. Nevertheless, the sites in this period classification are
underlain by �13 to 30 meters of soil deposit having N-values commonly ranging
from 1 to 15 corresponding to the increased presence of stiff and medium dense soils
at the shallow subsurface. The shear-wave velocities also reflect increased values rang­
ing from �105 m/s to 250 m/s, with some layers reaching 300 m/s at depth. LPI values
in the long period and moderate period sites are dominated by high to very high LPI
with only a few low and very low LPI, as previously stated (Figure 6).
At short period sites, the location of the engineering bedrock is nearer to the sur­
face, commonly less than 15 meters as shown in the shear-wave velocity profiles in
sites c1, c3, c5 and c6 (Figure 5) coincident with the thickness calculations ranging
from �8 to 14 meters (Figure 4). These thicknesses translate to predominant periods
of 0.19 s, 0.11 s, 0.13 s and 0.10 s, respectively (Figure 3c). Soil N-value ranges are gen­
erally higher from �3 to 25 corresponding to soft to very stiff clays and loose to dense
sands. Similarly, shear-wave velocities at these sites are commonly ranging from
�200 m/s to 360 m/s, with some layers reaching 450 m/s near the surface. These values
of high shear strength at relatively lesser thickness of the soil deposit reflect a low amp­
litude peak equating to 2 to 2.5 at shorter periods from the H/V curves (Figure 3c).
Contrary to the direct relationship of the predominant period with the overall soil
thickness, short periods can also result from a low impedance contrast. This is shown
in site c2 where the soil layer has an average shear-wave velocity of 335 m/s (Figure 5,
c2). This is due to the strong tradeoff of the soil thickness and average shear-wave vel­
ocity represented in Equation (2). In this period classification, the sites are dominated
by low to very low LPI (Figure 6) but there are still sufficiently low shear strength
layers with considerable thicknesses that could generate a high to very high LPI, mani­
fested by clear, albeit low amplitude peaks in the short period range in Figure 3c.
Sites d1 to d5 have H/V curves with no observable peaks (Figure 3d). This simply
means that measurements were placed on hard rock areas or there is an insufficient
thickness of low shear strength material on top of rigid bedrock to produce a prom­
inent peak in the H/V curve. These sites were mostly observed on measurements
placed on or near the tuffaceous rocks of the Guadalupe Formation. As mentioned
earlier, LPI values in this period classification are mainly very low LPI with only a
few low LPI. It is interesting to note that with regards to those with low LPI classifi­
cation (Figure 5, d3 and d4), a �2.5- meter-thick sand layer with N-values at about 1
to 5 is enough to trigger liquefaction. In terms of shear-wave velocity, this relatively
thin layer was not resolved in much detail. It is very common in these sites that the
SDS test has only penetrated a few tens of centimeters with a select few reaching a
couple of meters. A unique limitation of the test is that its probing termination is
controlled primarily by the shallow presence of very stiff or dense material (N-values
16
A. DAAG ET AL.
Figure 7. Relationship between predominant period and SDS test penetration depth.
> 15) (Orense et al. 2019; Daag et al. 2023). Early termination of the test already sup­
plements the geology of the area indicative of a rock site.
Adding to the understanding of liquefaction at depth as well as taking advantage of the
data on the depth of the termination of the probing of the SDS test, hSDS (assuming that it
is the approximate expression of the bedrock below), a power-law regression equation was
generated (Ibs-von Seht and Wohlenberg 1999; Delgado et al. 2000; Parolai et al. 2002)
between predominant period, T, and depth in the form of,
hSDS ¼ aT b
(11)
where a and b are empirical parameters (Figure 7).
There exists a strong correlation between the predominant period and the depth of
penetration of the SDS test. This relationship was found and useful in terms of a first
approximation of the thickness of the liquefiable layer since the termination of the
SDS test at encountering N-values > 15 may suggest that material above may likely
liquefy, and the material below may be the starting depth to where the material
becomes very stiff or dense assuming that the stiffness of the soil deposit increases
linearly with depth. Some papers regard the depth of the soil material corresponding
to an N-value > 15 as an important target material for anchoring in shallow founda­
tion studies (Kishida 1966; Towhata 2008; Mittal et al. 2013).
Comparison with LPI
The correlation of the predominant period with the LPI was investigated since it is
practice to obtain the strength of the relationship by performing linear regression
GEOMATICS, NATURAL HAZARDS AND RISK
17
(Figure 8). This also complements the discussion in the previous section. Figure 8
shows that there is a moderately strong correlation between LPI and predominant
period. Scattering in the predominant period can be observed across all LPI classifica­
tions specially in the long period sites suggesting a simple linear relationship is not
achievable, although there is somewhat a linear trend that occurs in the short period
to moderate period range at 0.2 s to 0.6 s. Overlaps in the predominant period are
also observed, especially in the 0.1 s to 0.3 s period range where all LPI classifications
exist, similar to Figure 6, wherein long and moderate periods occupy very high and
high LPI respectively.
The reason behind the scattering is assumed to be a function of the distance of
long period sites to the West Valley Fault (WVF). From Equations (5) and (8), the
maximum ground acceleration at each site was factored in. Peak accelerations are
greatly controlled by the distance to the source fault. The farther the site is to the
fault, the lower the value of acceleration and the higher the value of the factor of
safety. Probabilistic peak accelerations in the study area are taken from The
Philippine Earthquake Model of PHIVOLCS (PHIVOLCS 2017) and range from 0.23
to 0.60 g. A number of long period sites are located in Bulacan in the north, far from
the WVF thus resulting in lower acceleration values. In contrast, short period and
moderate period sites are located more proximal to the WVF therefore having higher
acceleration values. Nevertheless, a minimum LPI value of 16 is observed in the long
period scattered region already corresponding to a very high LPI.
Figure 8. Predominant period against LPI showing moderately strong correlation. Red circles are
sites with very high LPI, purple circles are sites with high LPI, yellow circles are sites with low LPI
and green circles are sites with very low LPI.
18
A. DAAG ET AL.
Despite the moderately strong correlation, it appears that we can possibly extract a
boundary of the predominant period between high and low LPIs. We assume, based on
the interquartile ranges from Figure 6, that we can group very high and high LPIs and
low and very low LPIs resulting in just two classifications – high and low potential. An
LPI equal to 5 serves as the boundary between the two classes. In searching for the equiva­
lent boundary in terms of predominant period, a confusion matrix was employed to
explore the value with highest accuracy to separate the two classes (Figure 9).
A confusion matrix summarizes the classification performance of a classifier with
respect to some test data (Ting 2010). It can be as simple as a 2 � 2 matrix, listed in
one dimension by the actual class (predominant period) and in the other by the class
that the classifier assigns (LPI). We employed a Boolean logic to further simplify ana­
lysis. Values of 0 and 1 were assigned corresponding to low and high potential to
liquefaction, respectively, to both predominant period and LPI. True positives (long
period correctly predicting high LPI) are where 1s agree and true negatives (short
period correctly predicting low LPI) are where 0s agree. We arrived at 0.2 s with 94%
accuracy suggesting that in 94% of the observations, 0.2 s correctly classified high
from low LPI. This value of the predominant period may be used as a first pass indi­
cator that liquefaction potential is high in the study area. Microtremor measurements
can thereby serve as a tool to fill data gaps and complement site-specific liquefaction
delineation where in situ geotechnical data is limited or not readily available, consid­
ering the cost of a detailed geotechnical analysis.
Figure 9. Confusion matrix-derived relationship showing peak at 0.2 s with 94% accuracy. Periods
0 and 1 are equivalent to < 0.2 s and > 0.2 s, respectively. LPIs 0 and 1 are equivalent to <5 and
>5, respectively.
GEOMATICS, NATURAL HAZARDS AND RISK
19
As mentioned earlier, a hallmark to strong ground shaking and liquefaction is the
amplified and prolonged duration of seismic energy. From the earlier comparisons,
we have observed somewhat clear direct relationships in terms of the general period
classifications with the liquefaction potential. It is evident that longer predominant
periods with relatively high amplitudes can have higher potential for liquefaction and
the opposite is true that shorter predominant periods with relatively lower amplitudes
can have lower potential for liquefaction. The apparent reason for this is the link
between the predominant period with the soil N-values and shear-wave velocities.
Varying thickness and shear strength of the soil material is reflected upon the shape
of the H/V curve and its predominant period and relative amplitude.
Considerations on topography and groundwater table
It is clear that there is a possible link between site response and liquefaction potential
from the previous discussion. This section emphasizes the role of topography and
groundwater table depth in facilitating possible misinterpretations of the microtremor
H/V. Figure 10 shows the distribution of the sites in terms of topography and
groundwater table depth and Figure 11 shows the distribution of the groundwater
table across the study area.
The characteristics of thick and soft soil deposits influence seismic energy at the near
surface making the sites more prone to amplified ground shaking and liquefaction (Qodri
et al. 2021). A scenario that would oppose this statement is that if the site is located in a
topographical high (e.g. plateau, hill, mountain) but still produces a prominent peak in the
H/V curve. Such topographical position would already contradict the possibility of liquefac­
tion. Similarly, one can still obtain long periods even if the subsurface material is clay as
observed in Figure 5 or if the depth of the groundwater table is significantly deep. This
Figure 10. Plot showing summary of the distribution of the experimental sites in terms of eleva­
tion and groundwater table depth.
20
A. DAAG ET AL.
Figure 11. Distribution of water table level across the study area obtained from ground
Penetrating Radar (GPR).
suggests that an H/V curve with a prominent peak at a given period range does not neces­
sarily equate to a high LPI. Caution should therefore be exercised in using the predomin­
ant period at 0.2 s in separating high and low liquefaction potentials in a different
geological environment, and it is important that information on geology, geomorphology
and groundwater table depth must be considered foremost prior to interpreting the H/V
results when applied to liquefaction studies.
Conclusion
This research demonstrated the application of the microtremor H/V in obtaining site
response characteristics in coastal GMMA and explored the relationship of site
GEOMATICS, NATURAL HAZARDS AND RISK
21
response parameters to soil liquefaction potential. Listed below are the main findings
of the research:
� The distribution of the predominant period and its relative amplitude in coastal
GMMA ranges from no peaks observed in the rocky coast of Cavite in the south
as well as in the central plateau of Metro Manila in the east to 1.31 s with high
amplitudes in the coastal lowlands of Bulacan in the north. This translates to a
general increasing trend in overall soil thickness from east to west and south to
north. This also augments earlier microtremor data of Abeki et al. (1996) and
Narag et al. (2000) which are limited to Metro Manila.
� The distribution of the LPI grouped with the predominant period classification
reveals that long period sites (>0.6 s) have generally very high LPI, moderate
period sites (0.2 s to 0.6 s) have dominantly high to very high LPI with a few very
low LPI, short period sites (0.05 s to 0.2 s) have dominantly very low to low LPI
with a few high to very high LPI, an sites with no peaks have generally very
low LPI.
� The relationship of site response characteristics to soil liquefaction potential is the
fundamental link between shear strength properties of the soil. Variations in the
soil N-values and shear-wave velocities are generally reflected in the microtremor
H/V curves.
� Correlation of the predominant period against the LPI yielding a moderately
strong relationship (r2 ¼ 0.51) as well as the statistical extraction of a predominant
period boundary (0.2 s) from high and low liquefaction potential suggests its
potential use as a first-pass tool in liquefaction assessment. This boundary can be
useful for future studies on liquefaction assessment in coastal GMMA, specially
where subsurface data is limited or not readily available.
The microtremor H/V is a powerful technique for obtaining semi-quantitative
information of the subsurface. However, it is noted that it lacks the quantitative
layer-per-layer analysis that other in situ geotechnical techniques provide. This is par­
ticularly important in more dynamic environments where the soil deposits exhibit lat­
eral heterogeneity in properties and therefore complicating microtremor H/V
interpretation. A dense array of microtremor H/V measurements may be recom­
mended to deliver the necessary level of accuracy in those settings. Hence, the micro­
tremor H/V technique cannot replace conventional techniques in the assessment of
liquefaction, but it can serve as a useful complementary tool. We also point out that
the results of the liquefaction assessment are limited to coastal GMMA, and we rec­
ommend that a similar kind of analysis should be done in other geological
environments.
Acknowledgements
The authors are most grateful to the staff of the Liquefaction Project namely, A. T. Serrano,
M. J. V. Reyes, O. P. C. Halasan, K. S. Sochayseng, A. A. T. Magnaye, M. C. Dela Cruz, A. O.
Amandy, and E. J. M. Arnoco, for their invaluable insights and expertise for the holistic
improvement of this paper. The authors also thank M. I. T. Abigania, M. P. Dizon, D. J. L.
22
A. DAAG ET AL.
Buhay, and E. D. Mitiam for their assistance throughout the entire project duration. The
authors also express their gratitude to the SpecificEQ Project for the introduction of the meth­
odology and the software. The authors are also thankful to the Department of Education
(DepEd), particularly to the Educational Facilities Division for the administrative assistance
and comments that helped in various stages of the project. Special thanks are given to the
school principals and Division Engineers for the hospitality and assistance during the fieldwork
campaigns.
Author’s contributions
A. D. conceived this study and handled the overall project supervision, administration, and
funding acquisition. L. E. A. and O. L. carried out the data acquisition, processing and ana­
lysis, and manuscript preparation. A. D., R. G. and R. S. Jr. provided resource and review of
the manuscript.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This research was funded by the Department of Science and Technology – Philippine Council
for Industry, Energy, and Emerging Technology Research and Development (DOSTPCIEERD).
ORCID
A. Daag
http://orcid.org/0000-0002-8252-1066
Data availability statement
The data to support the findings of this study are available from the corresponding author, A.
D. upon reasonable request.
References
Abeki N, Punongbayan R, Garcia DC, Narag I, Bautista BC, Bautista MLP, Banganan EL,
Tabanlar RA, Soneja DS, Masaki K, et al. 1996. Site response evaluation of Metro Manila
using microtremor observation. In: 11th World Conference on Earthquake Engineering,
Acapulco, Mexico.
Andrus R, Stokoe K. 2000. Liquefaction resistance of soils from shear-wave velocity. J Geotech
Geoenviron Eng. 126(11):1015–1025. doi: 10.1061/(ASCE)1090-0241(2000)126:11(1015).
Arango-Serna S, Herrera M, Cruz A, Sandoval E, Thomson P, Ledezma C. 2021. Use of ambi­
ent noise records in seismic engineering: an approach to identify potentially liquefiable sites.
Soil Dyn Earthquake Eng. 148:106837. doi: 10.1016/j.soildyn.2021.106837.
Beroya M, Aydin A, Tiglao R, Lasala M. 2009. Use of microtremor in liquefaction hazard map­
ping. Eng Geol. 107(3–4):140–153. doi: 10.1016/j.enggeo.2009.05.009.
Beroya M, Aydin A. 2010. A new approach to liquefaction hazard zonation: application to
Laoag City, Northern Philippines. Soil Dyn Earthquake Eng. 30(11):1338–1351. doi: 10.
1016/j.soildyn.2010.06.007.
GEOMATICS, NATURAL HAZARDS AND RISK
23
Boulanger RW, Idriss IM. 2012. Probabilistic standard penetration test–based liquefaction–trig­
gering procedure. J Geotech Geoenviron Eng. 138(10):1185–1195. doi: 10.1061/(ASCE)GT.
1943-5606.0000700.
Boulanger RW, Idriss IM. 2016. CPT-based liquefaction triggering procedure. J Geotech
Geoenviron Eng. 142(2):04015065. doi: 10.1061/(ASCE)GT.1943-5606.0001388.
Castellaro S, Mulargia F. 2014. Simplified seismic soil classification: the Vfz matrix. Bull
Earthquake Eng. 12(2):735–754. doi: 10.1007/s10518-013-9543-3.
Cetin KO, Seed RB, Kiureghian AD, Tokimatsu K, Harder LF, Kayen RE, Moss RES. 2004.
Standard penetration test-based probabilistic and deterministic assessment of seismic soil
liquefaction potential. J Geotech Geoenviron Eng. 130(12):1314–1340. doi: 10.1061/
(ASCE)1090-0241(2004)130:12(1314).
Choobbasti A, Naghizadehrokni M, Rezaei S. 2015. Liquefaction assessment by microtremor
measurements in Babol city. In: 5th International Conference on Geotechnique,
Construction Materials and Environment.
Daag A, Halasan OP, Magnaye AA, Grutas R, Solidum R. Jr. 2022. Empirical correlation
between standard penetration resistance (SPT-N) and shear wave velocity (Vs) for soils in
Metro Manila, Philippines. Appl Sci. 12(16):8067. doi: 10.3390/app12168067.
Daag A, Sochayseng K, Arnoco EJ, Serrano A, Solidum RJ. 2023. The use of screw driving
sounding in soil assessment in Metro Manila, Philippines. Geotechnical Research. 10(2):51–
66. doi: 10.1680/jgere.22.00047.
Delgado J, L�opez Casado C, Est�evez A, Giner J, Cuenca A, Molina S. 2000. Mapping soft soils
in the Segura river valley (SE Spain): a case study of microtremors as an exploration tool. J
Appl Geophys. 45(1):19–32. doi: 10.1016/S0926-9851(00)00016-1.
Earthquake Engineering Research Institute. 1994. Earthquake basics brief no. 1. In: institute
EER, editor. Oakland (CA). p. 1–8.
Gervasio F. 1968. The geology, structures and landscape development of Manila and suburbs.
Philippine Geol. 22:178–192.
Grutas R, Yamanaka H. 2012. Shallow shear-wave velocity profiles and site response character­
istics from microtremor array measurements in Metro Manila, the Philippines. Explor
Geophys. 43(4):255–266. doi: 10.1071/EG12031.
Guillier B, Cornou C, Kristek JSB-C, Bard P-Y, F€ah D, Moczo P. 2006. Simulation of seismic
ambient vibrations: does the H/V provide quantitative information in 2D–3D structure. In:
Proceedings of the third international symposium on the effects of surface geology,
Grenoble (France).
Hardesty K, Wolf L, Bodin P. 2010. Noise to signal: a microtremor study at liquefaction sites
in the New Madrid Seismic Zone. Geophysics. 75(3): b 83–B90. doi: 10.1190/1.3374357.
Herrera M, Arango S, Cruz A, Sandoval E, Thomson P. 2018. Assessment of Nakamura meth­
odology for evaluating soil liquefaction potential. In: Geotechnical Earthquake Engineering
and Soil Dynamics V. doi: 10.1061/9780784481455.009.
Huang H, Tseng Y. 2002. Characteristics of soil liquefaction using H/V of microtremors in
Yuan-Lin area, Taiwan. Terr Atmos Ocean Sci. 13(3):325–338. doi: 10.3319/TAO.2002.13.3.
325(CCE).
Ibs-von Seht M, Wohlenberg J. 1999. Microtremor measurements used to map thickness of
soft sediments. Bull Seismol Soc Am. 89(1):250–259. doi: 10.1785/BSSA0890010250.
Iwasaki T, Arakawa T, Tokida K. 1984. Simplified procedures for assessing soil liquefaction
during earthquakes. Int J Soil Dyn Earthquake Eng. 3(1):49–58. doi: 10.1016/02617277(84)90027-5.
Japan Road Association. 1996. Specifications for highway bridges: part V. In: Seismic Design.
Earthquake Resistant Design. Vol. 228.
Kang S, Kim K, Kim B. 2021. Assessment of seismic vulnerability using the horizontal-to-verti­
cal spectral ratio (HVSR) method in Haenam, Korea. Geosci J. 25(1):71–81. doi: 10.1007/
s12303-020-0040-9.
Kayen R, Moss RES, Thompson EM, Seed RB, Cetin KO, Kiureghian AD, Tanaka Y,
Tokimatsu K. 2013. Shear-wave velocity–based probabilistic and deterministic assessment of
24
A. DAAG ET AL.
seismic soil liquefaction potential. J Geotech Geoenviron Eng. 139(3):407–419. doi: 10.1061/
(ASCE)GT.1943-5606.0000743.
Kishida H. 1966. Damage to reinforced concrete buildings in Niigata city with special reference
to foundation engineering. Soils Found. 6(1):71–88. doi: 10.3208/sandf1960.6.71.
Kramer S. 1996. Geotechnical earthquake engineering. Upper Saddle River (NJ): prentice Hall,
Inc. (Prentice-Hall International.
LeBrun B, Duval A-M, Bard P-Y, Monge O, Bour M, Vidal S, Fabriol H. 2004. Seismic micro­
zonation: a comparison between geotechnical and seismological approaches in Pointe�a-Pitre (French West Indies). Bull Earthquake Eng. 2(1):27–50. doi: 10.1023/B:BEEE.
0000038949.91495.91.
Lermo J, Ch�avez-Garc�ıa F. 1994. Are microtremors useful in site response evaluation? Bull
Seismol Soc Am. 84(5):1350–1364. doi: 10.1785/BSSA0840051350.
Likitlersuang S, Plengsiri P, Mase LZ, Tanapalungkorn W. 2020. Influence of spatial variability
of ground on seismic response analysis: a case study of Bangkok subsoils. Bull Eng Geol
Environ. 79(1):39–51. doi: 10.1007/s10064-019-01560-9.
Louie J, Abbott R, Anooshehpoor R, Biasi G, Beeston H. 2001. Refraction microtremor as an
alternative to boreholes for earthquake hazard assessments. In: AGU Fall Meeting Abstracts.
Maeda Y, Yamato S, Sugano Y, Sakai G, Suemasa N, Tanaka T. 2015. Evaluation of soil lique­
faction potential by Screw Driving Sounding test in residential areas. In: 6th International
Conference on Earthquake Geotechnical Engineering, Christchurch (New Zealand).
Mase L, Agustina S, Hardiansyah H, Farid M, Supriani F, Tanapalungkorn W, Likitlersuang S.
2023. Application of simplifed energy concept for liquefaction prediction in Bengkulu City,
Indonesia.Geotech Geol Eng. 41(3): 1999–2021. doi: 10.1007/s10706-023-02388-7.
Mase L, Likitlersuang S, Tobita T. 2018. Non-linear site response analysis of soil sites in
Northern Thailand during the Mw 6.8 Tarlay earthquake. Eng J. 22(3):291–303. doi: 10.
4186/ej.2018.22.3.291.
Mase L, Likitlersuang S, Tobita T. 2022. Verification of liquefaction potential during the strong
earthquake at the border of Thailand-Myanmar. J Earthquake Eng. 26(4):2023–2050. doi: 10.
1080/13632469.2020.1751346.
Mase LZ, Tanapalungkorn W, Likitlersuang S, Ueda K, Tobita T. 2022. Liquefaction analysis
of Izumio sands under variation of ground motions during strong earthquake in Osaka,
Japan. Soils Found. 62(5):101218. doi: 10.1016/j.sandf.2022.101218.
Mas�
o MS. 1910. Catalogue of violent and destructive earthquakes in the Philippines with an
appendix: earthquakes in the Marianas Islands (1599–1909). Manila: Bureau of Printing.
Meneisy A, Mostafa T, Omran A. 2020. Soft sediment characterization using seismic techni­
ques at Beni Suef City, Egypt. J Environ Eng Geophys. 25(3):391–401. doi: 10.32389/
JEEG19-069.
Metro Manila Earthquake Impact Reduction Study. 2004. MMEIRS final report volume 2.
[accessed 2021 Nov 14]. https://iskwiki.upd.edu.ph/reports/MMEIRS/.
Mittal RK, Mahalakshmi N, Singh S. 2013. Evaluation of liquefaction screening criterion based
on standard penetration test values. In: Structures Congress 2013: Bridging Your Passion
with Your Profession. p. 2983–2988. doi: 10.1061/9780784412848.260.
Moisidi M, Vallianatos F, Soupios P, Kershaw S. 2012. Spatial spectral variations of microtre­
mors and electrical resistivity tomography surveys for fault determination in southwestern
Crete, Greece. J Eng Geophys. 9(3):261–270. doi: 10.1088/1742-2132/9/3/261.
Molnar S, Cassidy JF, Castellaro S, Cornou C, Crow H, Hunter JA, Matsushima S, S�anchezSesma FJ, Yong A. 2018. Application of microtremor horizontal-to-vertical spectral ratio
(MHVSR) analysis for site characterization: state of the art. Surv Geophys. 39(4):613–631.
doi: 10.1007/s10712-018-9464-4.
Molnar S, Sirohey A, Assaf J, Bard P-Y, Castellaro S, Cornou C, Cox B, Guillier B, Hassani B,
Kawase H, et al. 2022. A review of the microtremor horizontal-to-vertical spectral ratio
(MHVSR) method. J Seismol. 26(4):653–685. doi: 10.1007/s10950-021-10062-9.
GEOMATICS, NATURAL HAZARDS AND RISK
25
Moss RE, Seed RB, Kayen RE, Stewart JP, Kiureghian AD, Cetin KO. 2006. CPT-based prob­
abilistic and deterministic assessment of in situ seismic soil liquefaction potential. J Geotech
Geoenviron Eng. 132(8):1032–1051. doi: 10.1061/(ASCE)1090-0241(2006)132:8(1032).
Nakamura Y. 1989. A method for dynamic characteristics estimation of subsurface using
microtremor on the ground surface. Q Rep RTRI. 30(1):25–33.
Nakamura Y. 1996. Real time information systems for seismic hazards mitigation UrEDAS,
HERAS and PIC. Q Rep RTRI. 37(3):112–127.
Nakamura Y. 1997. Seismic vulnerability indices for ground and structures using microtremor.
In: World Congress on Railway Research; Florence (Italy).
Nakamura Y. 2000. Clear identification of fundamental idea of Nakamura’s technique and
applications. In: 12th World Conference Earthquake Engineering; Auckland (New Zealand).
Nakamura Y. 2019. What is the Nakamura method? Seismol Res Lett. 90:1437–1443. doi: 10.
1785/0220180376.
Narag IC, Banganan EL, Lanuza AG, Deocampo JB, Lasala M, Olavere E, Penarubia H,
Bautista MLP, Bautista BC, Garcia DC. 2000. Microtremor observation of Metropolitan
Manila. In: International Workshop on the Integration of Data for Seismic Disaster
Mitigation in Metro Manila.
Nelson A, Personius S, Rimando R, Punongbayan R, Tu~
ngol N, Mirabueno H, Rasdas A. 2000.
Multiple large earthquakes in the past 1500 Years on a fault in Metropolitan Manila, the
Philippines. Bull Seismol Soc Am. 90(1):73–85. doi: 10.1785/0119990002.
Orense R, Mirjafari Y, Suemasa N. 2019. Screw driving sounding: a new test for field charac­
terisation. Geotech Res. 6(1):28–38. doi: 10.1680/jgere.18.00024.
Oubaiche E, Chatelain J, Bouguern B, Bensalem B, Machane D, Hellel M, Khaldaoui F,
Guillier B. 2012. Experimental relationship between ambient vibration H/V peak amplitude
and shear-wave velocity contrast. Seismol Res Lett. 83(6):1038–1046. doi: 10.1785/
0220120004.
Parolai S, Bormann P, Milkereit C. 2002. New relationships between Vs, thickness of sedi­
ments, and resonance frequency calculated by the H/V ratio of seismic noise for the
Cologne Area (Germany). Bull Seismol Soc Am. 92(6):2521–2527. doi: 10.1785/0120010248.
PHIVOLCS. 2017. The Philippine earthquake model: a probabilistic seismic hazard assessment
of the Philippines and of Metro Manila. Quezon City (Philippines): DOST-PHIVOLCS.
PHIVOLCS. n.d.-a. 1968 August 02 Ms7.3 Casiguran earthquake. [accessed 2022 Apr 24].
https://www.phivolcs.dost.gov.ph/index.php/earthquake/destructive-earthquake-of-the-philip­
pines/2-uncategorised/206-1968-august-02-ms7-3-casiguran-earthquake.
PHIVOLCS. n.d.-b. 1990 July 16 Ms7.8 Luzon earthquake. [accessed 2022 Apr 24]. https://
www.phivolcs.dost.gov.ph/index.php/earthquake/destructive-earthquake-of-the-philippines/2uncategorised/212-1990-july-16-ms7-9-luzon-earthquake.
Qodri M, Mase L, Likitlersuang S. 2021. Non-linear site response analysis of Bangkok subsoils due
to earthquakes triggered by Three Pagodas Fault. Eng J. 25(1):43–52. doi: 10.4186/ej.2021.25.1.43.
Ramos A, Viana de Fonseca A, Carrilho Gomes R. 2019. Evaluating soil liquefaction potential
using Nakamura methodology in an experimental site. In: 7th International Conference on
Earthquake Geotechnical Engineering; Rome (Italy).
Rimando R, Knuepfer P. 2006. Neotectonics of the Marikina Valley fault system (MVFS) and
tectonic framework of structures in northern and central Luzon, Philippines.
Tectonophysics. 415(1–4):17–38. doi: 10.1016/j.tecto.2005.11.009.
Rodolfo K. 2014. On the geological hazards that threaten existing and proposed reclamations
of Manila Bay. Philippine Sci Lett. 7(1):228–240.
Sathyaseelan R, Mundepi A, Kumar N. 2017. Quantifying seismic vulnerability, dynamical
shear strain and liquefaction of the Quaternary deposits in the Doon valley near the Main
Boundary Thrust in the Northwest Himalaya, India. Quat Int. 462:162–175. doi: 10.1016/j.
quaint.2017.05.018.
Seed H, Idriss I. 1971. Simplified procedure for evaluation of soil liquefaction potential. J Soil
Mech Found Div. 97(9):1249–1273. doi: 10.1061/JSFEAQ.0001662.
26
A. DAAG ET AL.
Seed H, Idriss I. 1982. Ground motions and soil liquefaction during earthquakes. In: Idriss IM,
editor. Berkeley (CA): Earthquake Engineering Research Institute.
SESAME. 2004. Guidelines for the implementation of the H/V spectral ratio technique on ambi­
ent vibrations measurements, processing and interpretation. Deliverable D23.12 No.: WP12
Singh A, Shukla A, Kumar M, Thakkar M. 2017. Characterizing surface geology, liquefaction
potential, and maximum intensity in the Kachchh Seismic Zone, Western India, through
microtremor analysis. Bull Seismol Soc Am. 107(3):1277–1292. doi: 10.1785/0120160264.
Ting K. 2010. Confusion matrix. In: Sammut C, Webb GI, editors. Encyclopedia of machine
learning. Boston, MA: Springer; p. 1061.
Towhata I. 2008. Geotechnical earthquake engineering. Heidelberg (Germany): Springer.
(Springer Series in Geomechanics and Geoengineering.
Uebayashi H, Kawabe H, Kamae K. 2012. Reproduction of microseism H/V spectral features using a
three-dimensional complex topographical model of the sediment-bedrock interface in the Osaka
sedimentary basin. Geophys J Int. 189(2):1060–1074. doi: 10.1111/j.1365-246X.2012.05408.x.
Wathelet M, Chatelain J-L, Cornou C, Giulio GD, Guillier B, Ohrnberger M, Savvaidis A.
2020. Geopsy: a user-friendly open-source tool set for ambient vibration processing. Seismol
Res Lett. 91(3):1878–1889. doi: 10.1785/0220190360.
Youd TL, Idriss IM, Andrus RD, Arango I, Castro G, Christian JT, Dobry R, Finn WDL,
Harder LF, Hynes ME, et al. 2001. Liquefaction resistance of soils: summary report from
the 1996 NCEER and 1998 NCEER/NSF workshops on evaluation of liquefaction resist­
ance of soils. J Geotech Geoenviron Eng. 127(10):817–833. doi: 10.1061/(ASCE)10900241(2001)127:10(817).
Youd TL, Perkins DM. 1978. Mapping Liquefaction-Induced Ground Failure Potential. J
Geotech Eng Div. 104(4):433–446. doi: 10.1061/AJGEB6.0000612.