HR: 0800h
AN: S51A-0128    [Abstracts]
TI: the Cataract Creek, Arizona, 1993 Earthquake Sequence
AU: * Brumbaugh, D S
EM: david.brumbaugh@nau.edu
AF: Northern Arizona University, Dept. of Geology, box 4099, Flagstaff, AZ 86011-4099 United States
AB: The 1993 Cataract Creek sequence was the most extensively documented seismic event in Arizona history. The sequence consisted of an mb 4.8 foreshock, followed four days later by the mb5.5 mainshock and numerous aftershocks. Analysis of the foreshock and mainshock indicated that both were normal faulting events with WNW strikes (Lay et.al.,1994). The aftershock analysis supports activity on a NW trending surface for the main shock, parallel to trends of faults of the Cataract Creek system (Sanders, 1997). Examination of the results of both previous studies suggests two further points. The distance between the foreshock and aftershock indicates that they are on separate fault surfaces; and the stress release throughout the sequence was spatially heterogeneous. The foreshock and its aftershocks clustered near the south part of the region of stress release (April 25-29). The April 29 mainshock occurred 28 kilometers to the north of the foreshock followed over the next four days by aftershocks clustered close to the mainshock. The four largest aftershocks from April 25 to May 17 occurred in the southern part of the region of stress release closer to the mb4.8 foreshock. The spatial separation of the mainshock and foreshock and their aftershocks suggests that they may represent two mainshocks of different sequences on separate faults. This would explain the difference in nodal trends of the two shocks.
DE: 7230 Seismicity and seismotectonics
DE: 7215 Earthquake parameters
SC: Seismology [S]
MN: 2004 AGU Fall Meeting