HR: 0800h
AN: S51D-1044    [Abstracts]
TI: Design of a Composite Attenuation Relation for the Dead Sea Area Based on 3D Modeling of Elastic Wave Propagation
AU: * Oth, A
EM: adrien.oth@gpi.uni-karlsruhe.de
AF: Geophysical Institute, Karlsruhe University, Hertzstr. 16, Karlsruhe, 76187 Germany
AU: Wenzel, F
EM: friedemann.wenzel@gpi.uni-karlsruhe.de
AF: Geophysical Institute, Karlsruhe University, Hertzstr. 16, Karlsruhe, 76187 Germany
AU: Wust-Bloch, H
EM: hillel@seismo.tau.ac.il
AF: Department of Geophysics and Planetary Sciences, Tel Aviv University, P.O.B. 39040, Tel Aviv, 69978 Israel
AU: Gottschaemmer, E
EM: ellen.gottschaemmer@gpi.uni-karlsruhe.de
AF: Geophysical Institute, Karlsruhe University, Hertzstr. 16, Karlsruhe, 76187 Germany
AU: Ben-Avraham, Z
EM: zvi@terra.tau.ac.il
AF: Department of Geophysics and Planetary Sciences, Tel Aviv University, P.O.B. 39040, Tel Aviv, 69978 Israel
AB: Attenuation relations are a crucial component in the prediction of ground motion generated by strong earthquakes. Even though the relations from different authors (e.g. Boore et al., 1997; Abrahamson and Silva, 1997) vary in their form, they all have in common that some engineering ground motion parameter, such as peak ground acceleration (PGA) or peak spectral acceleration (PSA), is determined by the magnitude, distance to the earthquake source, site conditions and possibly source mechanism. In general, attenuation relations parameterize distance in a way that does not take into account a change in geologic features in the region of interest. Sedimentary basins or grabens, however, may strongly influence attenuation, due to both site and basin effects. By engineering seismology practice, site effects are generally taken into account by considering the shear wave velocity structure of the top 30 meters. Basins effects, on the other hand, are caused by deep geologic structures and much harder to quantify, as this requires the consideration of a two-- or three--dimensional wave propagation model. The Dead Sea Basin (DSB) is a 15 km by 100 km, N--S elongated structure around which basin effects have been observed in damage patterns of past earthquakes (Wust--Bloch, 2002). In addition, Gottschämmer et al. (2002) showed through 3D simulation of the 1927 Jericho earthquake (M=6.2) that wave focusing effects in the DSB are indeed significant. The results of this research show that the standard attenuation relation utilized in the area is inadequate to assess the basin--related effect of the DSB. A new strategy for the parametrization of attenuation relations in graben structures is developed by looking at the statistical properties of 53 3D finite--difference simulations (Olsen, 1994) of earthquakes with magnitudes ranging from 5.5 to 7.0 at the boundary fault of the DSB. The frequency range of these simulations is restricted to frequencies lower than about 1.5 Hz. An attenuation relation is designed for the 1 Hz spectral acceleration, modifying the Joyner--Boore relations by adding coefficients suited for three different source--to--site configurations: within the DSB, beyond the DSB and path unaffected by the graben structure.
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7290 Computational seismology
SC: Seismology [S]
MN: Fall Meeting 2005