Geophysical Research Letters
Supporting Information for
Ambient Noise Based Monitoring of Seismic Velocity Changes Associated
with the 2014 Mw 6.0 South Napa Earthquake
Taka’aki Taira1, Florent Brenguier2, Qingkai Kong1
1Berkeley
2Institut
Seismological Laboratory, University of California, Berkeley, CA 94720 USA
des Sciences de la Terre, Université Joseph Fourier, Maison des Géosciences, Grenoble, France
Contents of this file
Figures S1 to S7
Table S1
1
Figure S1. Map view of 12 seismic stations (triangles) and the 2014 Mw 6.0
South Napa epicenter (star).
2
Figure S2. Time histories of relative velocity change dv/v inferred from
vertical-vertical component of noise correlation functions (NCFs) with two
sigma standard deviations for stack of 5 days in the time intervals (a)
September 2010 through May 2015 and (b) July 2014 through May 2015.
Note that the dv/v was plotted at the end of the time window for stacking
NCFs. Red dashed line is the occurrence time of the 2014 Mw 6.0 South Napa
earthquake. Blue dashed lines indicate the 95th percentile range of dv/v
distribution obtained from the time interval September 1, 2010 through
August 23, 2014.
3
Figure S3. Time histories of relative velocity change dv/v for pair of NHCB057 with a stack of 50 days in the time intervals (a) September 2010 through
May 2015 and (b) August 2013 through May 2015. Red dashed line is the
occurrence time of the 2014 Mw 6.0 South Napa earthquake. Blue dashed
lines indicate the 95th percentile range of dv/v distribution obtained from a
one-year of dv/v measurements prior to the South Napa mainshock. Gray
area indicates the first 50-75 days of the post-South Napa earthquake period
where the median dv/v was evaluated as the coseismic dv/v (orange dashed
line). Note that the dv/v measurements in the first 50-75 day postseismic
period only include post-South Napa earthquake seismic data. Note also that
the dv/v values plotted within the first 50 days following the South Napa
mainshock included the pre- and post-mainshock data and the gradual decay
of dv/v in this period is an artifact.
4
5
Figure S4. Example for histograms of station dv/v obtained through the
Jackknife test for (a) station CVS and (b) station NTO. Dashed lines on each
panel indicate the 95th percentile range.
6
Figure S5. Volumetric strain changes at depths of (a) 0 km and (b) 10 km
(color scales are saturated). Triangles are seismic stations and the star is the
epicenter of the 2014 South Napa earthquake.
7
Figure S6. Peak ground velocity (PGV) measurement from the California
Integrated Seismic Network
(http://www.cisn.org/shakemap/nc/shake/72284586/pgv.html). Triangles are
seismic stations and the star is the epicenter of the 2014 South Napa
earthquake.
8
Figure S7. (a) dv/v measurements (gray circle) with the estimated seasonal
component (red line). Also shown are the residual velocity changes (green
squares) between dv/v and the seasonal component. (b) Daily precipitation
collected at the Napa region (station code ALT) extracted from
http://cdec.water.ca.gov.
9
Table S1. Locations of sites and their sensors installed and installation types.
Station
Latitude
Longitude
Elevation
Deptha
of site (m)
(m)
Sensor
Installation
type
CVSb
38.3453
-122.4584
333
-
STS2
Surface
NAPC
38.4395
-122.2527
739
-
L4
Surface
NHC
38.4395
-122.3577
5
-
L4
Surface
NLHb
38.1228
-122.1492
193
-
L4
Surface
NMI
38.0760
-122.2585
50
-
L4
Surface
NSP
38.2002
-122.4644
183
-
L4
Surface
NTO
38.1436
-122.4497
25
-
L4
Surface
NVA
38.4156
-122.1165
831
-
L4
Surface
B057b
38.0273
-122.5655
33
213
Sonde-2
Borehole
CMABb
38.0689
-122.2291
25
142
GS-11D
Borehole
PETB
38.1189
-122.5011
1
113
GS-11D
Borehole
VALB
38.1215
-122.2753
5
156
HS-1
Borehole
a Depth of borehole sensor from the surface (m).
b Three-component seismic data were analyzed in this study.
10