On December 26, 2004 (GMT), a thrust-faulting giant earthquake (Mw 9.0) struck off coast of northern Sumatra.
To estimate rupture process of this giant earthquake, I retrieved teleseismic body waves (P-waves) data recorded at IRIS-dmc stations via Internet.
13 stations were selected from the viewpoint of good coverage, and used in the waveform inversion with ABIC (Fukahata et al., 2003; Yagi et al., 2003).
From a broadband seismic wave, we can divide the giant earthquake into
two stages. In first stage, the rupture mainly propagated to the northwest
from hypocenter during initial 100 sec. The second rupture started about
100 sec after initial break. The second rupture generate ultra long period
seismic wave. This may imply that slow and large dislocation occurred in
the second stage. Form a high frequency component of seismic wave, I rough
estimated the duration of source process, and found that the duration may
exceed 400 sec (figure: duration of shaking = source duration + sP-Ptime). Unfortunately, the
period of seismic wave of the second stage is too long to analyze my program
set. In this web-site, I estimated a part of rupture process using waveform
that were bandpassed between 4 and 200 sec.
Yuji Yaig (IISEE, BRI, 2004)
Fukahata, Y.; Y. Yagi; M. Matsu'ura, Waveform inversion for seismic source
processes using ABIC with two sorts of prior constraints: Comparison between
proper and improper formulations, GRL, 30, 10.1029/2002GL016293, 2003.
Fukahata, Y.; A. Nishitani; M. Matsu'ura, Geodetic data inversion using
ABIC to estimate slip history during one earthquake cycle with viscoelastic
slip-response functions, Geophys. J. Int., 156, 140-153, 2004.
Yagi, Y. ; T. Mikumo; J. Pacheco, Source
rupture process of the Tecoman, Colima, Mexico earthquake of January 22, 2003,
determined by joint inversion of teleseismic body wave and near-field data
(PDF), Bull. Seism. Soc. Am., 94, 1795-1807, 2004.