HR: 1340h
AN: T33C-1488    [Abstracts]
TI: Empirical Relationships Among Magnitude and Surface Rupture Characteristics of Strike-Slip Faults: Effect of Fault (System) Geometry and Observation Location, Dervided From Numerical Modeling
AU: * Zielke, O
EM: olaf.zielke@asu.edu
AF: SESE, Arizona State University, Bateman Physical Science Center, F-Wing, Tempe, AZ 85281-1404, United States
AU: Arrowsmith, J
EM: ramon.arrowsmith@asu.edu
AF: SESE, Arizona State University, Bateman Physical Science Center, F-Wing, Tempe, AZ 85281-1404, United States
AB: In order to determine the magnitude of pre-historic earthquakes, surface rupture length, average and maximum surface displacement are utilized, assuming that an earthquake of a specific size will cause surface features of correlated size. The well known Wells and Coppersmith (1994) paper and other studies defined empirical relationships between these and other parameters, based on historic events with independently known magnitude and rupture characteristics. However, these relationships show relatively large standard deviations and they are based only on a small number of events. To improve these first-order empirical relationships, the observation location relative to the rupture extent within the regional tectonic framework should be accounted for. This however cannot be done based on natural seismicity because of the limited size of datasets on large earthquakes. We have developed the numerical model FIMozFric, based on derivations by Okada (1992) to create synthetic seismic records for a given fault or fault system under the influence of either slip- or stress boundary conditions. Our model features A) the introduction of an upper and lower aseismic zone, B) a simple Coulomb friction law, C) bulk parameters simulating fault heterogeneity, and D) a fault interaction algorithm handling the large number of fault patches (typically 5,000-10,000). The joint implementation of these features produces well behaved synthetic seismic catalogs and realistic relationships among magnitude and surface rupture characteristics which are well within the error of the results by Wells and Coppersmith (1994). Furthermore, we use the synthetic seismic records to show that the relationships between magntiude and rupture characteristics are a function of the observation location within the regional tectonic framework. The model presented here can to provide paleoseismologists with a tool to improve magnitude estimates from surface rupture characteristics, by incorporating the regional and local structural context which can be determined in the field: Assuming a paleoseismologist measures the offset along a fault caused by an earthquake, our model can be used to determine the probability distribution of magnitudes which are capable of producing the observed offset, accounting for regional tectonic setting and observation location.
DE: 7221 Paleoseismology (8036)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting