Preliminary Result
09/12/2007 (Mw 7.9) , Central Sumatra Earthquake
A. Sladen, A. Ozgun Konca, Caltech
DATA Process and Inversion
We used the GSN broadband data downloaded from the IRIS DMC. We analyzed 19 teleseismic P waveforms and 18 teleseismic SH waveforms 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 epicenter of the USGS (Lon.=100.906° Lat.=-2.506°). We used the Harvard CMT solution to determine strike (319°) and dip (19°)Result
.Cross-section of slip distribution
Figure: The big black arrow shows the fault's strike. The colors show the slip amplitude and white arrows indicate the direction of motion of the hanging wall relative to the footwall. Contours show the rupture initiation time and the red star indicates the hypocenter location. The rupture velocity is about 2.2 km/s, and the total seismic moment 1.12e21 N.m (Mw=7.95).
Comparison of data and synthetic seismograms
Figure: The Data are shown in black and the synthetic seismograms are plotted in red. Both data and synthetic seismograms are aligned on the P 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 it is the epicentral distance.
Map view of the slip distribution
Figure: Surface projection of the slip distribution. The solution is dominated by a 7 m slip patch at the hypocenter, and a 2 m slip patch further north.
Static-field
Figure: Static-field computed from the solution of the slip inversion. The vertical component of displacement is given by the color-scale while the arrows show the horizontal component.
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| SUBFAULT FORMAT |
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,
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.
GCMT project: http://www.globalcmt.org/
USGS National Earthquake Information Center: http://neic.usgs.gov
Global Seismographic Network (GSN) is a cooperative scientific facility operated jointly by the Incorporated Research Institutions for Seismology (IRIS), the United States Geological Survey (USGS), and the National Science Foundation (NSF).
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