Hector Mine Earthquake

Preliminary Results of Rupture Process for The October 16, 1999 Hector Mine Earthquake

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

Data and analysis

We retrieved teleseismic body waves (P-waves) data recorded at IRIS-dmc stations via Internet. 9 stations were used in the waveform inversion. The data were bandpassed between 0.01 and 1.0 Hz and converted into ground displacement with a sampling time of 0.2s.

Applying a multi-time window inversion to the above data, we determined the spatio-temporal distribution of fault slip. Then the constraint of smoothness and positivity was imposed on the solution. We calculated Green's functions for teleseismic body-waves using Kikuchi and Kanamori [1991]'s method with J-B's structure.

We assumed a single fault plane :(strike, dip) = (333, 84) which is inferred from teleseismic body wave analysis (Kikuchi and Yamanaka). The rake was allowed to vary within the range of 174+-45(degree).

Result

The seismic moment Mo = 6.1 x 10**19 Nm (Mw 7.1); the source duration T = 15 s; Fault mechanism: (Strike, Dip, Slip)=(333, 84, 170) ; Hypocenter: (lat.= 34.60N, lon.= 116.27W, depth= 9 km) [Fix]. The source process is characterized by an asymmetric bilateral rupture propagation. The maximum slip amounts to 4.8 m at about 10 km South from the hypocenter.

(Yagi and Kikuchi, 1999)

Distribution of fault-slip

Star indicates the location of the initial break.

Rupture area (Map view)

Red line indicates rupture area.

Waveform comparison

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