HR: 16:40h
AN: S12E-03    [PDF]
TI: Pattern and Rates of Faulting in the 1932-1954 Portion of the Central Nevada Seismic Belt
AU: * Bell, J W
EM: jbell@unr.edu
AF: Nevada Bureau of Mines and Geology, University Of Nevada, Reno, NV 89557 United States
AU: Caskey, S J
EM: caskey@sfsu.edu
AF: Department of Geosciences, San Francisco State University, San Francisco, CA 94132 United States
AU: Ramelli, A R
EM: ramelli@unr.edu
AF: Nevada Bureau of Mines and Geology, University Of Nevada, Reno, NV 89557 United States
AU: Guerrieri, L
EM: guerrier@anpa.it
AF: Agenzia Nazionale per la Protezione dell'Ambiente, Via Brancati, 48, Roma, 00144 Italy
AB: The 1932-1954 portion of the central Nevada seismic belt (CNSB) is a concentration of historical surface faulting in the Basin and Range province, forming a linear, nearly continuous 300-km-long rupture zone. We have integrated the results of previous studies with new paleoseismic and exploratory trenching data from seven faulting sites to investigate the seismogenic behavior of the CNSB. In particular, we looked for evidence of older, similar, belt-like patterns or elevated slip rates that could indicate whether this part of the CNSB is a zone of focused, long-term crustal strain. Our results show that the continuous rupture belt produced by six earthquakes in 1932 and 1954 was not replicated in at least the last 10-20 kyrs. Based on the timing and mapped distribution of paleoseismic rupture zones, several similar, but not identical, belt-like combinations are possible, though each requires apparent gaps in the along-strike pattern. Faults in this portion of the CNSB have moderate- to low-slip rates in the range of 0.09-0.50 mm/yr, similar to most late Quaternary faults in the western Basin and Range. Although long-term (Holocene) strain accumulation does appear to increase from east to west into the CNSB at the latitude of the 1954 sequence, the CNSB is not a belt of concentrated or elevated crustal strain compared with areas to the west. We conclude that the results best support the belt migration model proposed originally by Wallace (1984) in which temporal tectonic pulses migrate regionally, and perhaps activate different belt-like combinations of late Quaternary faults in an as yet unknown pattern of migration. The increase in the distribution of Holocene fault activity from east to west into the CNSB is consistent with a marked increase in the GPS velocity field at the latitude of the 1954 rupture sequence. However, a comparison of the total paleoseismic extension rate across the belt (0.57-1.22 mm/yr) with the published GPS rate (2.56-2.91 mm/yr) shows that there is a factor of 2 to 5 discrepancy in the rates.
DE: 7221 Paleoseismology
DE: 7223 Seismic hazard assessment and prediction
DE: 7230 Seismicity and seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting