HR: 16:00h
AN: NS24A-01    [Abstracts]
TI: Fault Connections and Probability of Multi-Fault Rupture in Southern California
AU: * Black, N M
EM: nblack@ess.ucla.edu
AF: University of California Los Angeles, Department of Earth and Space Sciences 595 E Charles Young Dr, Los Angeles, CA 90095,
AU: Jackson, D D
EM: djackson@ucla.edu
AF: University of California Los Angeles, Department of Earth and Space Sciences 595 E Charles Young Dr, Los Angeles, CA 90095,
AB: Geology and past earthquakes show that faults are discontinuous at the surface, and are often represented by complex networks of traces and splays. It is difficult to quantify fault length from mapped faults due to these intricacies in fault networks, which means it is also difficult to estimate maximum magnitude from these faults. A correct estimate of maximum magnitude is important in order to determine the magnitude distribution of a given fault line. If the fault length is underestimated then the magnitude distribution of the fault will be misrepresented. In previous work, we have looked at past earthquakes and studied the rupture patterns of these events. First we compare fault length and rupture length for post 1975 earthquakes in Southern California. We found that rupture length and fault length were often unequal and multiple faults often ruptured in a single event. Furthermore, we created a set of guidelines for estimating length from mapped faults. Second, we studied the probability of multi- fault rupture based on the distances between mapped faults. The probabilities are derived from observations of ruptures that did or did not jump available step-overs. We found that an exponential model best fit the data, and that multi-fault rupture became unlikely at distances larger than 10 km. In this study I will examine the areas between mapped faults to look for possible fault-connections and then assess the probability of multi-fault rupture. I will use micro-seismicity to determine if there are features at depth connecting faults already mapped at the surface. In regions of interest I will also use remote sensing to check for any deformation or offset at the surface. Next, we will use the findings from our previous studies to examine the probability of multi-fault rupture. Finally, these probabilities will be used to determine the frequency of large events.
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8010 Fractures and faults
DE: 8040 Remote sensing
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting