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Preearthquake and Postearthquake Creep on the Imperial Fault and the Brawley Fault Zone

Cohn, Stephen N. and Allen, Clarence R. and Gilman, Ralph and Goulty, Neil R. (1982) Preearthquake and Postearthquake Creep on the Imperial Fault and the Brawley Fault Zone. In: The Imperial Valley, California, earthquake of October 15, 1979. Geological Survey professional paper. No.1254. United States Geological Survey , Washington, DC, pp. 161-167.

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Taken together, 12 years of alinement-array data, 4 years of creepmeter records from four instruments, and 2 years of surveys from two nail files suggests that creep events on the Imperial fault 2 to 5 months before the October 15 earthquake are consistent with longterm trends and not indicative of any imminent event. No discernible creep occurred on the fault in the hours and days before the earthquake. Records of coseismic displacement imply that response of the soil to the fault slip at depth was brittle rather than plastic; they uniquely demonstrate that the minimum rate of surface fault displacement was 1.8 cm/s. Continuing measurements of afterslip show that all motion is due to discrete 0.2- to 1.5-cm creep events occurring less frequently over time. The accumulating displacement for the first 35 days after the earthquake is well approximated by linear logarithmic functions of time. Use of this accumulating displacement to predict future slip rates implies that for 6 years the afterslip rate from the 1979 earthquake should be greater than the 0.5-cm/yr average preearthquake creep rate. The maximum amount of slip on the surface trace of the Imperial fault associated with the 1979 earthquake, including afterslip, amounts to more than 60 cm.

Item Type:Book Section
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Additional Information:© 1982 USGS.
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Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences3369
Series Name:Geological Survey professional paper
Issue or Number:1254
Record Number:CaltechAUTHORS:20141204-131718712
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52401
Deposited By: Tony Diaz
Deposited On:04 Dec 2014 21:35
Last Modified:03 Oct 2019 07:42

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