Preliminary Result of the Mar 11, 2011 Mw 9.1 Honshu Earthquake
Guangfu Shao, Xiangyu Li, Chen Ji, UCSB
Takahiro Maeda, NIED
DATA Process and Inversion
We used the GSN broadband waveforms downloaded from the IRIS DMC. We
analyzed 28 teleseismic broadband P waveforms, 25 broadband SH
waveforms, and 54 long period surface waves selected based upon data
quality and azimuthal distribution. Waveforms are first converted to
displacement by removing the instrument response and then used to
constrain the slip history based on a finite fault inverse algorithm (Ji
et al, 2002). We use the hypocenter of the Japan Meteorological Agency
(JMA) (Lon.=142.860 deg.; Lat.=38.10 deg.). The fault planes are defined
using the result of our quick multiple double couple point sources
analysis.
In this study, we have calibarated the traveling times of SH and surface
waves using the March 9th event as a reference.
Result
After comparing the waveform fits based on two planes, we find that the
nodal plane (strike=198.00 deg., dip=10.00 deg.) fits the data better.
The seismic moment release based upon this plane is
0.575E+30 dyne.cm using a 1D crustal model interpolated from CRUST2.0
(Bassin et al., 2000).
Cross-section of slip distribution
Figure 1.1 Cross-section of slip distribution. the strike direction of
fault plane is indicated by the black arrow and the hypocenter location
is denoted by the red star. The slip amplitude are showed in color and
motion direction of the hanging wall relative to the footwall is
indicated by white arrows. Contours show the rupture initiation time in
seconds.
Moment rate function
Comparison of data and synthetic seismograms
Figure 2.1. Comparison of teleseismic body waves. The data is shown in
black and the synthetic seismograms are plotted in red. Both data and
synthetic seismograms are aligned on the P or SH arrivals. The number at
the end of each trace is the peak amplitude of the observation in
micro-meter. The number above the beginning of each trace is the source
azimuth and below is the epicentral distance.
Figure 2.2. Comparison of teleseismic body waves. The data is shown in
black and the synthetic seismograms are plotted in red. Both data and
synthetic seismograms are aligned on the P or SH arrivals. The number at
the end of each trace is the peak amplitude of the observation in
micro-meter. The number above the beginning of each trace is the source
azimuth and below is the epicentral distance.
Figure 3.1. Comparison of long period surface waves. The data is shown
in black and the synthetic seismograms are plotted in red. Both data and
synthetic seismograms are aligned on the earthquake origin time. The
number at the end of each trace is the peak amplitude of the observation
in millimeter. The number above the beginning of each trace is the
source azimuth and below is the epicentral distance in degrees.
Figure 3.2. Comparison of long period surface waves. The data is shown
in black and the synthetic seismograms are plotted in red. Both data and
synthetic seismograms are aligned on the earthquake origin time. The
number at the end of each trace is the peak amplitude of the observation
in millimeter. The number above the beginning of each trace is the
source azimuth and below is the epicentral distance in degrees.
Figure 3.3. Comparison of long period surface waves. The data is shown
in black and the synthetic seismograms are plotted in red. Both data and
synthetic seismograms are aligned on the earthquake origin time. The
number at the end of each trace is the peak amplitude of the observation
in millimeter. The number above the beginning of each trace is the
source azimuth and below is the epicentral distance in degrees.
Figure 4. Surface projection of the slip distribution superimposed on
ETOPO2. Red dots are the aftershocks (M>3) from JMA. Vector indicates
the plate motion. The black line indicates the major plate boundary
[Bird, 2003].
Forward prediction
Figure 5.1. Comparison between the observed coseismic GPS vectors
(black) and forward predicted static displacements (red vectors) using
the inverted slip model (Figure 1), with the horizontal components on
the left and vertical components on the right. The GPS vectors were
preliminary GPS displacement data provided by the ARIA team at JPL and
Caltech (Courtesy of Dr. Susan Owen). Red star indicates the epicenter
location and red dots are the aftershocks (M>3) downloaded from JMA.
CJ's Comments:
Not Available Yet
Slip Distribution
References
Ji, C., D.J. Wald, and D.V. Helmberger, Source description of the
1999 Hector Mine, California earthquake; Part I: Wavelet domain
inversion theory and resolution analysis, Bull. Seism. Soc. Am., Vol 92, No. 4. pp. 1192-1207, 2002.
Bassin, C., Laske, G. and Masters, G., The Current Limits of Resolution
for Surface Wave Tomography in North America, EOS Trans AGU, 81, F897,
2000.
Acknowledgement and Contact Information
This work is supported by National Earthquake Information Center (NEIC)
of United States Geological Survey. This web page is built and
maintained by Dr. C. Ji at UCSB.