Rupture Process of The Geiyo Earthquake of March 24, 2001 (Mw 6.7) (Revised on March 9, 2001)

Joint inversion was made using strong-ground-motion data (provided by K-net (NIED)) and teleseismic data (provided by IRIS-DMC). We modified the underground structure.

We examined two fault models :(strike, dip, rake) = (179, 55, -82),(344, 36, -102) which is inferred from teleseismic body wave analysis (EIC Seismological Note). The former fault plane (179, 55, -82) gives a slightly better waveform fit.

Result

The seismic moment Mo = 1.4 x 10**19 Nm (Mw 6.7);
The source duration T = 8 s;
Fault mechanism: (Strike, Dip, Slip)=(179, 55, -78) ;
Hypocenter: (lat.= 34.125N, lon.= 132.713E, depth= 50 km).
(The epicenter of the main-shock was determined by Earthquake Observation Center of ERI.)

The source process is characterized by a unilateral rupture propagation. The rupture mainly propagated 20 km to the south. Two asperities (large slip areas) are identified. The maximum dislocation is about 1.9 m.

(Yagi and Kikuchi, 2001)

Distribution of fault-slip

Fig. : (upper left) Focal mechanism; (upper right) Moment-rate function; (lower) Distribution of co seismic slip. Star indicates the location of the initial break. The contour interval is 0.15m.

Snapshot of fault-slip

Fig. : Snapshots of the interval dislocation.

Map View

Fig. : Map view of slip distribution. Hypocenter of the main-shock was determined by Earthquake Observation Center of ERI.

Waveform comparison

Fig. : Comparison of the observed teleseismic body wave (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- arrival.

Fig. : Comparison of the observed strong-ground-motion converted to ground-displacement (Black) with the calculated waveform (Red). The numbers below the station code indicate maximum amplitude in centi-meter. The start time of the traces is lined-up at 5 (s) before the first motion. [0.1-0.5 Hz, Displacement]

If you have questions, please send to yuji@eri.u-tokyo.ac.jp or kikuchi@eri.u-tokyo.ac.jp.

Last Updated: April 18, 2001

Rupture Process of The Geiyo Earthquake of March 24, 2001 (Mw 6.7)

Joint inversion was made using strong-ground-motion data (provided by K-net (NIED)) and teleseismic data (provided by IRIS-DMC).

We examined two fault models :(strike, dip, rake) = (179, 55, -82),(344, 36, -102) which is inferred from teleseismic body wave analysis (EIC Seismological Note). The former fault plane (179, 55, -82) gives a slightly better waveform fit.

Result

The seismic moment Mo = 1.2 x 10**19 Nm (Mw 6.7);
The source duration T = 8 s;
Fault mechanism: (Strike, Dip, Slip)=(179, 55, -81) ;
Hypocenter: (lat.= 34.125N, lon.= 132.713E, depth= 50 km).
(The epicenter of the main-shock was determined by Earthquake Observation Center of ERI.)

The source process is characterized by a unilateral rupture propagation. The rupture mainly propagated 20 km to the south. Two asperities (large slip areas) are identified. The maximum dislocation is about 1.1 m.

(Yagi and Kikuchi, 2001)

Distribution of fault-slip

Fig. : (upper left) Focal mechanism; (upper right) Moment-rate function; (lower) Distribution of coseismic slip. Star indicates the location of the initial break. The contour interval is 0.15m.

Snapshot of fault-slip

Fig. : Snapshots of the interval dislocation.

Map View

Fig. : Map view of slip distribution. Hypocenter of the main-shock was determined by Earthquake Observation Center of ERI.

Waveform comparison

Fig. : Comparison of the observed teleseismic body wave (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- arrival.

Fig. : Comparison of the observed strong-ground-motion converted to ground-displacement (Black) with the calculated waveform (Red). The numbers below the station code indicate maximum amplitude in centi-meter. The start time of the traces is lined-up at 5 (s) before the first motion. [0.1-0.5 Hz, Displacement]

If you have questions, please send to yuji@eri.u-tokyo.ac.jp or kikuchi@eri.u-tokyo.ac.jp.

Last Updated: March 26, 2001