HR: 0800h
AN: G51C-0841    [Abstracts]
TI: Joint inversion of InSAR and teleseismic broadband waveform data using ABIC: application to the 1997 Manyi, Tibet earthquake
AU: Fukahata, Y
EM: fukahata@eps.s.u-tokyo.ac.jp
AF: University of Tokyo, Department of Earth and Planetary Science, Tokyo, 113-0033 Japan
AU: * Funning, G J
EM: gareth@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, University of California, 215 McCone Hall, Berkeley, CA 94720 United States
AU: Yagi, Y
EM: yagi-y@arsia.geo.tsukuba.ac.jp
AF: University of Tsukuba, Graduate School of Life and Environmental Sciences, Tsukuba, 305-8572 Japan
AU: Parsons, B
EM: barry@earth.ox.ac.uk
AF: University of Oxford, Department of Earth Sciences, Parks Road, Oxford, OX1 3PR United Kingdom
AB: There now exist numerous cases in which InSAR data have been used to estimate the distribution of coseismic slip on faults during earthquakes. InSAR data are largely very well suited for this task, having both high spatial resolution and large areal coverage on the ground, which translate to good spatial resolution at depth. The disadvantage with using InSAR to estimate earthquake slip is its lack of temporal resolution, limited by the long time duration between satellite passes, meaning that the evolution of slip on the fault cannot be determined. Detailed information about the temporal history of an earthquake rupture can be obtained seismologically; however such data have lower spatial resolving power than InSAR, and may be subject to tradeoffs between depth and origin time. Ideally, an earthquake source model would make use of the complimentary strengths of these two data types by inverting them simultaneously to find a model with good resolution in both space and time. In order to accommodate these two different datasets in a single inversion, we derive and utilise a method based upon Akaike's Bayesian Information Criterion (ABIC) for such a problem for the first time. The ABIC function, a statistical construct based upon the principle of maximum likelihood, has the property that when minimised numerically, the three hyperparameters that control the inversion -- two weighting parameters controlling the relative importance of the spatial and temporal smoothing constraints on the model to the observed data in the inversion, and another controlling the relative weighting of the two datasets in the inversion -- can be obtained objectively, and an optimal inverse model thus generated. We apply this technique to the M_w 7.6, 8th November 1997 Manyi earthquake in central northern Tibet. The input datasets are three short-interval ERS-2 interferograms from adjacent tracks that cover the coseismic deformation, and vertical component (P-wave) data from 10 Global Seismic Network stations at teleseismic distances from the epicentre. The Manyi fault is approximated by a 180 km x 18 km vertical fault, divided into 6 x 6 km subfaults. We invert both datasets separately, and then jointly, using the ABIC method. We find that the InSAR data place a very strong constraint on the spatial pattern of fault slip obtained, with the joint model bearing a strong resemblance to that of the InSAR-only model. Although the slip pattern for the joint model strongly differs from that obtained by inverting the seismic data alone, we find that it can be accommodated by the seismic data with very little degradation to the fit from that obtained by the seismic-only model. The slip history of the earthquake is consistent with that proposed in published seismic studies, with bilateral rupture for the first 20 seconds, followed by 32 seconds of unilateral westward rupture. The ABIC method is therefore demonstrated to be an excellent technique for objectively combining datasets, and has a lot of promise for further joint inversion studies of this kind.
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 7215 Earthquake source observations (1240)
SC: Geodesy [G]
MN: Fall Meeting 2005