Preliminary Results of Rupture Process for May 26, 2003 HALMAHERA, INDONESIA Earthquake


Inversion was made using teleseismic data (provided by IRIS-DMC)

On May 26, 2003, a thrust-faulting earthquake (Mw = 6.9) occurred in Halmahera, Indonesia. I retrieved teleseismic body waves (P-waves) data recorded at IRIS-dmc stations via Internet. 10 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).

Result

The seismic moment Mo = 2.8 x 10**19 Nm (Mw 6.9);
The source duration T = 18 s;
(strike, dip, rake) = (167, 62, 113)
Hypocenter: (Lat. = 2.40N, Lon. = 128.81E, depth= 40 km).
[The epicenter of the main-shock was determined by USGS]

The main rupture mainly propagated 30 km to the north. Three asperities (large slip areas) are identified. The maximum dislocation is about 1.8 m at near hypocenter.

Note: Since I used the teleseismic body wave, the resolution of space is not so good. The maximum dislocation and fault area will be revised using the near-field data.
(Yagi, IISEE, 2003)

Distribution of fault-slip


Figure : (upper left) Focal mechanism; (upper right) Total moment-rate function; (lower) Distribution of coseismic slip. Star indicates the location of the initial break.

Map View


Figure: Hypocenter of the main-shock determined by USGS. Blue lines represent the extent of the fault plane used in our inversion.

Waveform comparison


Figure : Comparison of the observed waveform (Black) with the calculated waveform (Red). The numbers below the station code indicate maximum amplitude in microns. The start time of the traces is lined-up at 10 (s) before the P-wave arrival.

Figure : Teleseismic stations used in inversion. The star represents the epicenter of the main-shock.

Reference

Fukahata, Y., Y. Yagi, and 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.

Yagi, Yagi ; 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), submited to Bull. Seism. Soc. Am., 2003.

Links


If you have questions, please send to yagi@kenken.go.jp.

Last Updated: 2003 May 29