Rupture Process for September 26 2003 Tokachi-oki, Japan, earthquake


Yagi, Yuji, Source rupture process of the 2003 Tokachi-oki earthquake determined by joint inversion of teleseismic body wave and strong ground motion data, submited to Earth Planet and Space, 2004 (PDF)

Poster for Source Rupture Process for September 26 2003 Tokachi-oki, Japan, earthquak (PDF) 8.5Mb


Joint Inversion was made using teleseismic data (provided by IRIS-DMC) and Strong ground motion data (provided by NIED)
On Sep. 26, 2003 (JST), a reverse-faulting earthquake (Mjma = 6.1) occurred in off Tokachi, Hokkaido, Japan , where the Pacific plate subductes west beneath the northeastern Japan island arc at rate of about 80 mm/year. The depth of hypocenter and focal mechanism show that this earthquake is a typical inter-plate earthquake. I retrieved teleseismic body waves (P-waves) and strong ground motion data recorded at IRIS-dmc stations and K-net (NIED) via Internet, respectively.

Result

The seismic moment Mo = 1.5 x 10**20 Nm (Mw 8.1);
The source duration T = 55 s;
(strike, dip, rake) = (249, 15, 130)
Hypocenter: (Lat. = 41.78N, Lon. = 144.08E, depth = 15 km).
[The epicenter of the main-shock was determined by JMA]
Maximum slip = 6.2(m)

(Yagi, IISEE, BRI, 2003)


Map View


Figure : Hypocenter determined by Hi-net (NIED).

Snapshots


Figure : Snapshots of cumulative dislocation.

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.

Waveform comparison (Teleseismic)


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.

Waveform comparison (Strong ground motion)


Figure : Comparison of the observed waveform (Black) with the calculated waveform (Red). The numbers below the station code indicate maximum amplitude in cm/sec. The start time of the traces is lined-up at 5 (s) before the P-wave arrival.

Station Map



Links


Last Updated: 2003 September 27