HR: 11:20h
AN: S52A-05    [Abstracts]
TI: Comparison Between the Ruptures of the 1966 and 2004 Mw6 Parkfield Earthquakes
AU: * Archuleta, R J
EM: ralph@crustal.ucsb.edu
AF: Department of Earth Science, University of California, Santa Barbara, Santa Barbara, CA 93106 United States
AU: * Archuleta, R J
EM: ralph@crustal.ucsb.edu
AF: Institute for Crustal Studies, University of California, Santa Barbara, Santa Barbara, CA 93106-1100 United States
AU: Custodio, S
EM: susana@crustal.ucsb.edu
AF: Department of Earth Science, University of California, Santa Barbara, Santa Barbara, CA 93106 United States
AU: Custodio, S
EM: susana@crustal.ucsb.edu
AF: Institute for Crustal Studies, University of California, Santa Barbara, Santa Barbara, CA 93106-1100 United States
AU: Liu, P
EM: pcliu@crustal.ucsb.edu
AF: Institute for Crustal Studies, University of California, Santa Barbara, Santa Barbara, CA 93106-1100 United States
AB: The Parkfield section of the San Andreas Fault (SAF), California, has been the stage of at least six Mw6 earthquakes in historical time. Bakun and McEvilly (1984) observed that seismograms from the 1922, 1934 and 1966 Parkfield earthquakes were extremely similar. Only identical ruptures can generate similar seismic records. Thus Bakun and McEvilly (1984) advanced the concept of characteristic earthquakes - earthquakes of well-defined features (hypocenter, rupture area, seismic moment) that would repeat regularly in time. According to their idea, the next Parkfield earthquake was due between 1983 and 1993. As a consequence of this prediction, several geophysical instruments were deployed in the Parkfield region. The most recent Mw6 Parkfield earthquake occurred on September 2004, later than predicted. It ruptured the SAF from southeast to northwest, unlike the previous Parkfield Mw6 earthquakes. The 2004 hypocenter also does not coincide with previous Mw6 characteristic Parkfield earthquakes hypocenters. We compute rupture models for the two most recent Parkfield earthquakes (1966 and 2004) from the inversion of seismic data. Seismic data for the 2004 event is abundant and covers well the hypocentral region. Seven stations, located 3.5 km to 100 km from the epicenter, recorded the 1966 event. All of these seven stations stay to the south and southeast of the epicenter, thus offering only a partial vision of the rupture. We invert this scarce dataset in order to obtain a kinematic model for the 1966 earthquake. Because the inversion yields a non-unique solution, we compare different rupture models that explain equally well the data. The study of the variance between different acceptable models provides a good picture of the kinematic model accuracy. We compare the well-resolved slip features of the 1966 and 2004 earthquake. In particular, we investigate whether the 1966 rupture broke past the right step on the surface trace of the SAF. We focus on the main similarities and differences between the two Mw6 events, in an attempt to understand why the 2004 earthquake did not rupture as a characteristic Parkfield earthquake.
DE: 3260 Inverse theory
DE: 3275 Uncertainty quantification (1873)
DE: 7215 Earthquake source observations (1240)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
SC: Seismology [S]
MN: Fall Meeting 2005