Preliminary Result
11/14/2007 (Mw 7.7) , Tocopilla Earthquake, Chile
A. Sladen, Caltech
DATA Process and Inversion
We used the GSN broadband data downloaded from the IRIS DMC. We analyzed 33 teleseismic P waveforms and 5 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.=-69.809° Lat.=-22.178°), and the GCMT solution to determine the dip (20°). The crust model at the source is taken from Bassin et al. (2000).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 1.6 km/s, and the total seismic moment 5.92e20 N.m (Mw=7.7).
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 3.5 m slip patch at the hypocenter, and two other continuous slip patch further south. Black contours of the slip distribution are every 100 cm, and grey contours every 50 cm.
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(Slip Distribution)| SUBFAULT FORMAT | CMTSOLUTION FORMAT | SOURCE TIME FUNCTION |
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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