Updated Result
09/12/2007 (Mw 8.4) , South Sumatra Earthquake

A. Ozgun Konca and Anthony Sladen, Caltech

Location of Epicenter

Amount of Slip on Fault

View in Google Earth (requires Google Earth)

Colors show the amount of slip on diferent sections of the fault zone. Two views are shown (either view can be de-selected on the Google Earth sidebar):

  1. Circles show a 3-D map of the fault. (The fault map has been raised above the Earth's surface. Click on a circle to get the depth of that fault segment.)

  2. Image shows the projection of the fault onto the Earth's surface.

DATA Process and Inversion

This is an update of our preliminary analysis based on the results published in Konca et al. (2008). The source model is obtained by joint inversion of 37 GPS measurements at stations of the SUGAR network, 35 teleseismic body waveforms (16 P and 19 SH), and one L-band ALOS PALSAR interferogram. We used the epicenter of the USGS (Lon.=101.382° Lat.=-4.517°). This event was followed, 12 hours later, by a Mw=7.9 earthquake.


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.

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.

Fit of the InSAR data

Figure: Zoom on the section of the coastline with InSAR data related to the Mw=8.4 rupture. For each colored circle, the perimeter represents data point and the interior represents the model. The more similar the perimeter and interior colors, the better the fit of the model to the data. The red star is the epicenter of the Mw=8.4 event and the black line correspond to the surface projection of the the fault geometry used for the inversion.

Map view of the slip distribution and fit of the GPS data

Figure: Surface projection of the slip distribution and fit of the GPS data. The model GPS vectors (red arrows for vertical and green arrows for horizontal) are plotted on top the measured GPS vectors (black arrows).


(Slip Distribution)


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.

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.

Konca, A. O., J-P. Avouac, A. Sladen, A. J. Meltzner, K. Sieh, P. Fang, Z. Li, J. Galetzka, J. Genrich, M. Chlieh, D. H. Natawidjaja, Y. Bock, E. Fielding, C. Ji, and D. V. Helmberger, Partial rupture of a locked patch of the Sumatra megathrust during the 2007 earthquake sequence, Nature, 456, 631-635, 4 Dec 2008, doi:10.1038/nature07572.

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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