HR: 0800h
AN: T41B-04    [Abstracts]
TI: Further Tests of the Seismo-Lineament Method for Recognizing Seismogenic Faults at the Ground Surface
AU: * Millard, M A
EM: Mark_Millard@Baylor.edu
AF: Baylor University, Department of Geology One Bear Place #97354, Waco, TX 76798-7354, United States
AU: Campbell, R D
EM: Ryan_Campbell@Baylor.edu
AF: Baylor University, Department of Geology One Bear Place #97354, Waco, TX 76798-7354, United States
AU: Lindsay, R D
EM: Ryan_Lindsay@Baylor.edu
AF: Baylor University, Department of Geology One Bear Place #97354, Waco, TX 76798-7354, United States
AU: Secrest, S H
EM: Stephen_Secrest@Baylor.edu
AF: Baylor University, Department of Geology One Bear Place #97354, Waco, TX 76798-7354, United States
AU: Cronin, V S
EM: Vincent_Cronin@Baylor.edu
AF: Baylor University, Department of Geology One Bear Place #97354, Waco, TX 76798-7354, United States
AB: The importance of locating the surface trace of faults that can produce earthquakes is self-evident, particularly in California where avoidance of ground-rupture hazards is a legal requirement. We have developed a method that utilizes earthquake focal mechanism solutions coupled with field reconnaissance to locate the surface trace of probable seismogenic faults. We project a fault-plane solution from the boundaries of the uncertainty region around the earthquake focus to the surface of a DEM to define a seismo-lineament -- a zone within which the surface trace of the fault associated with the earthquake is likely to be located. Field work is then undertaken to evaluate the hypothesis that a seismogenic fault exists within the seismo-lineament. If a fault is found within the seismo-lineament, the fault’s orientation and direction of slip are statistically compared with the orientation and slip data from the fault-plane solution to complete the spatial correlation of the fault with the earthquake. To evaluate the effectiveness of this procedure, we selected 6 historic earthquakes that caused fault displacement of the ground surface and used the seismo-lineament method to indicate the probable location of the surface trace of the fault. Earthquakes analyzed in this study include the Parkfield (2004, M6), Denali (2002, M7.9), Hector Mine (1999, M7.1), Superstition Hills (1987, M6.2 and M6.6), and Borah Peak (1983, M7.3) earthquakes. In all 6 test cases, the actual ground-rupture zone associated with the main shock was located within the seismo-lineament. In addition to using focal-mechanism solutions associated with the main shocks to define seismo-lineaments, we have used data from several major aftershocks associated with these events. Seismo-lineaments defined by aftershocks also coincided with the surface trace of the seismogenic fault. Based on results from this study, the seismo-lineament method is likely to be useful in identifying probable seismogenic faults in areas where high-quality focal-mechanism solutions are available for small earthquakes that did not cause ground rupture. This method will be particularly useful in locating probable seismogenic faults that reach the ground surface in highland areas where there is no in-situ Holocene material available to be analyzed through trench studies.
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 8000 STRUCTURAL GEOLOGY
DE: 8002 Continental neotectonics (8107)
DE: 8010 Fractures and faults
SC: Tectonophysics [T]
MN: 2007 Joint Assembly