HR: 1340h
AN: S53A-1070    [Abstracts]
TI: The numerical Green`s function method (NGF): Synthesis of ground motion for finite-source scenarios in 3D media
AU: Wang, H
EM: haijiang@geophysik.uni-muenchen.de
AF: Department of Earth and Environmental Sciences, Theresienstrasse 41, Munich, 80333 Germany
AU: * Igel, H
EM: heiner.igel@lmu.de
AF: Department of Earth and Environmental Sciences, Theresienstrasse 41, Munich, 80333 Germany
AU: Zoeller, G
EM: zoeller@rz.uni-potsdam.de
AF: Institute of Physics, University of Potsdam, Am neuen Palais 10, Potsdam, 14469 Germany
AU: Holschneider, M
EM: hols@mathematik.uni-potsdam.de
AF: Institut für Mathematik, Universität Potsdam, Postfach 601553, Potsdam, 14415 Germany
AB: Deterministic earthquake scenario simulation methods are playing an increasingly important role in seismic hazard and risk estimation. The numerical calculation of the complete wavefield in the observed frequency band for a seismically active basin remains a computationally expensive task for some time. Our aim is to provide a tool with which we can calculate a large number of different finite-source scenarios for a particular fault or fault system. In order to avoid having to calculate an individual scenario for each kinematic source description we propose the concept of "numerical Greens functions" (NGFs). The basic idea: a large seismic fault is divided into subfaults of appropriate size for which synthetic Green's functions at the surface of the seismic active area are calculated and stored. With some limitations, arbitrary kinematic sources can be simulated for the whole fault or parts of it by superposition of this set of separate seismograms obtained by the stored subfault excitations. To demonstrate the functionalities of the method a strike-slip NGF data base was calculated for a simplified, vertical fault model of the Newport-Inglewood fault in the Los-Angeles Basin which has a predominantly right-lateral strike-slip fault mechanism. The fault was subdivided into 13x46 subfaults of size 1.5km x 1.5km area. Using this data base we synthesize numerous finite-source earthquake scenarios that are derived from final slip histories based that were calculated by a quasi-dynamic approach for similar fault type. This dynamic source model simulates seismicity on a 2D discrete heterogeneous strike-slip fault, which is embedded in a 3D elastic half space. The model dynamics is governed by realistic boundary conditions, static/kinetic friction laws, and aseismic creep. The dynamic rupture is approximated on a finite time scale using a constant shear-wave velocity ("quasidynamic approach"). This is in contrast to quasi-static models, where the rupture occurs instantaneously. Near-vertical aseismic barriers with high creep velocities are implemented in order to simulate fault segmentation in an effective way. These barriers store stress during a large earthquake; the postseismic release of stress generates realistic aftershock sequences following the Omori law. For the calculated scenarios and resulting complete seismograms we can extract information such as peak ground motions, static co-seismic deformation, etc. for individual scenarios, aftershock sequences, as well as eventually whole seismic cycles.
DE: 7209 Earthquake dynamics (1242)
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7290 Computational seismology
SC: Seismology [S]
MN: Fall Meeting 2005