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Earthquake Ground Motion in the San Francisco Bay Area Using Three-Dimensional Finite Difference SimulationsArthur Rodgers1 and Anders Petersson2
[email protected] [email protected], Earth and Energy Division and 2Center for Applied Scientific ComputingLawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94551 USA
Simulations were performed using LLNL-developed WPP code, the USGS 3D seismic velocity model for the San Francisco Bay Area (Brocher et al., 2006) and parallel computers operated by Livermore Computing at LLNL.
Piedmont 2007/07/20 Earthquake
Simulation of the 2007 July 20 Piedmont earthquake was done with the WPP code for 100 km x 100 km x 30 km volume with 100 m grid spacing for accurate synthetics to 0.5 Hz. Seismograms were obtained from the NCEDC for the Berkeley Digital Seismic Network (BDSN, blue triangles), Northern Hayward Fault Network (NHFN, yellow) and strong-motion instruments of the USGS Northern CA Network (green).
Comparison of observed and synthstic seismograms shows good agreement in general with satisfactory prediction of amplitudes and waveform complexity. Longer paths (> 10 km) often show the synthetics arriving ahead of the data, consistent with an earlier study (Rodgers et al., BSSA 2008).
-122˚30' -122˚00' -121˚30'
37˚30'
38˚00'BK.BDM
BK.JRSC
BK.WENL
BK.VALB
NC.CAG
NC.CPM
N
N
�
computational domain
NC.CLCB
WPP is an open-source anelastic finite difference code that runs on single or multiple processors. It’s been compiled and run on Linux, AIX and Mas OS X platforms. It can represent single or multiple point force and/or moment tensor sources. WPP features mesh refinement in the vertical direction to greatly im-prove memory and computational efficiency. We will soon have a version with non-planar free surface topography.
WPP is available to all free of charge. It can be requested and downloaded from https://computation.llnl.gov/casc/serpentine/
NC.CAG NC.CPM BK.VALBNC.CLCB
BK.WENLBK.BDMBK.JRSC
Absolute time and amplitude scaling
Hayward Fault Scenario EarthquakesWe performed simulations of scenario earthquakes on the Hayward Fault using re-ported finite rupture models from the 1995/01/17 (M 7) Kobe, Japan strike-slip earth-quake. We used finite source models from:
Wald (1996) Mw = 6.92 Sekiguchi et al. (2000) Mw = 7.02 Zeng and Anderson (2000) Mw = 6.90
Finite source models were obtained from the database maintained by Martin Mai (http://www.seismo.ethz.ch/srcmod). Simulations were performed using WPP with a 150 km x 100 km x 50 km volume with 100 m grid spacing and minimum shear veloc-ity of 500 m/s for accurate synthetics to 0.5 Hz. Seismograms were computed on the grid of stations surrounding the fault, shown below.
Horizontal component ground velocity seismograms for three rupture models with a Southern hypocenter at several locations. Records are color-coded by rupture model:
KOBE/Sekiguchi et al (2000) South
0
10
20
Dow
n D
ip (k
m)
0 10 20 30 40 50 60
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
slip (m)
KOBE/Wald (1997) South hypocenter
0
10
20
Dow
n D
ip (k
m)
0 10 20 30 40 50 60
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
slip (m)
KOBE/Zeng & Anderson (2000) South
0
10
20
Dow
n D
ip (k
m)
0 10 20 30 40
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
slip (m)
-122˚30' -122˚00' -121˚30'
37˚30'
38˚00'
0.0 0.1 0.6 1.1 3.4 8.1 16.0 31.0 60.0 116.0 150.0 200.0Peak Ground Velocity, cm/s
KOBE/Zeng & Anderson (2000) South
-122˚30' -122˚00' -121˚30'
37˚30'
38˚00'
0.0 0.1 0.6 1.1 3.4 8.1 16.0 31.0 60.0 116.0 150.0 200.0Peak Ground Velocity, cm/s
KOBE/Sekiguchi et al (2000) South
-122˚30' -122˚00' -121˚30'
37˚30'
38˚00'
KOBE/Wald (1997) South hypocenter
faultrupture
epicenter
0.0 0.1 0.6 1.1 3.4 8.1 16.0 31.0 60.0 116.0 150.0Peak Ground Velocity, cm/s
MM Intensity
Damage
Shaking light mod. strong str/sev
I
none v. lightnone none
II III IV V VI VII VIII IX X >X
none light mod. heavy very heavy
weak weaknot felt extremesevere violent
md/hv
San Josefault
parallel
faultnormal
~ 45 cm/s
East of San Jose
faultparallel
faultnormal
~ 20 cm/s
Fremont
~ 30 cm/s
Sunol
~ 45 cm/s
-123˚00' -122˚30' -122˚00' -121˚30' -121˚00'
37˚00'
37˚30'
38˚00'
38˚30'
Oakland
San Leandro
San Ramon
Livermore
San Jose
Lafayette
Hayward
East of San Jose
FremontSunol
Wald (1996) Sekiguchi et al (2000) Zeng & Anderson (2000)
BDSNNHFNUSGS
Absolute time and amplitude scaling
