Broadband Strong Ground Motion Simulation Of The 17 August And 12 November 1999, Turkey Earthquakes

The main objective of this study is to determine the source characteristics of the Duzce and Kocaeli Earthquakes such as source size, asperity location and asperity size and also compare these findings with empirical scaling relations obtained from worldwide earthquakes. The possibility of supershear rupture propagation during the Duzce earthquake proposed by Bouchon et.al.(2001) is also examined by performing numerous inversions changing the first time-window propagation velocities at each time. Besides these, results may contribute to the relation between coseismic slip distribution at the fault plane and the distribution of surface ruptures. The waveform inversion of the 12 November 1999 Duzce, Turkey Earthquake was performed for the frequency range of 0.1-0.5 Hz. using the multiple time-window linear waveform inversion methodology. For the inversion, strong motion records of the Duzce Earthquake from 8 stations within 50 km epicentral distance were used. An approximate 41 x 13 km size fault plane was assumed and subdivided into 52 subfaults. Hypocenter is at a depth of 10km, located in the bottom left hand-side of the plane, approximately 7 km away from the center of the fault plane. In order to calculate the theoretical Green's function between each subfault and each station in 1D velocity structure, the discrete wave number method of Bouchon (1981) together with the reflection-transmission matrix method (Kennett and Kerry, 1979) were used. The best source model was determined by an asperity near the hypocenter and a second asperity closer to the surface in the eastern part of the fault plane. First time-window propagation velocity was found as 4.3km/s in the eastern propagation, where it is 2.9km/s in the western propagation. A simplified version of this source model was used for getting higher frequency simulation through Empirical Green's Function (EGF) Method. The distribution of the coseismic slip in the fault plane is consistent with the surface dislocation. However the displacement values measured at surface show larger values than the final slip values found at the shallower portion of the fault plane. In order to get the broadband simulation of the 17 August 1999 Kocaeli earthquake, the EGF simulation has been performed using the available aftershock records as Green's function. The source process results of the Kocaeli Earthquake obtained by Sekiguchi et.al. (2002) was used to set up an initial source model for the forward simulation of this earthquake.