Turkey Earthquake

Preliminary Results of Rupture Process for The November 12, 1999 Turkey Earthquake

This earthquake is located about 110 km east of the magnitude 7.4 earthquake on August 17.

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. 17 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) = (265, 65) which is inferred from HARVARD UNIV. CMT Solution. The rake was allowed to vary within the range of -158+-45(degree).

Result

The seismic moment Mo = 5.6 x 10**19 Nm (Mw 7.1); the source duration T = 12 s; Fault mechanism: (Strike, Dip, Slip)=(265, 65, -168) ; Hypocenter: (lat.= 40.8N, lon.= 31.2E, depth= 10. km) [Fix]. The rupture propagated 10 km to the East and 20 km to the West. Average dislocation over (30 km x 20 km) is about 2.7 m. The average stress drop = 2.5 x Mo / S**1.5 = 10MPa. This stress drop is significantly larger than the typical stress drop of 3 MPa for inter-plate earthquakes, but close to the value for intra-plate earthquakes.

(Yagi and Kikuchi, 1999)

Distribution of fault-slip

Preliminary results of our inversion. (a) Focal mechanism (b) Total moment-rate function (c)Distribution of coseismic slip. Star indicates the location of the initial break.

Rupture area (Map view)

Red lines indicate major rupture area.

Hypocenter of the main shock (star) determined by the Earthquake Research Department of General Directorate of Disaster Affairs of Turkey. The focal mechanism is determined in this study.

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.