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Crone, A. J.
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Crone, A. J.
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- PublicationRestrictedSurface Rupture and Slip Distribution of the Denali and Totschunda Faults(2004-12)
; ; ; ; ; ; ; ; ; ; ; ;Haeussler, P. J.; U.S. Geological Survey ;Schwartz, D. P.; U.S. Geological Survey ;Dawson, T. E.; U.S. Geological Survey ;Stenner, H. D.; U.S. Geological Survey ;Lienkaemper, J. J.; U.S. Geological Survey ;Sherrod, B.; U.S. Geological Survey ;Cinti, F. R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Montone, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Craw, P. A.; U.S. Geological Survey ;Crone, A. J.; State of Alaska, Department of Natural Resources, Fairbanks, Alaska ;Personius, S. F.; U.S. Geological Survey; ; ; ; ; ; ; ; ; ; The 3 November 2002 Denali fault, Alaska, earthquake resulted in 341 km of surface rupture on the Susitna Glacier, Denali, and Totschunda faults. The rupture proceeded from west to east and began with a 48-km-long break on the previously unknown Susitna Glacier thrust fault. Slip on this thrust averaged about 4 m (Crone et al., 2004). Next came the principal surface break, along 226 km of the Denali fault, with average right-lateral offsets of 4.5–5.1 m and a maximum offset of 8.8 m near its eastern end. The Denali fault trace is commonly left stepping and north side up. About 99 km of the fault ruptured through glacier ice, where the trace orientation was commonly influenced by local ice fabric. Finally, slip transferred southeastward onto the Totschunda fault and continued for another 66 km where dextral offsets average 1.6–1.8 m. The transition from the Denali fault to the Totschunda fault occurs over a complex 25-km-long transfer zone of right-slip and normal fault traces. Three methods of calculating average surface slip all yield a moment magnitude of Mw 7.8, in very good agreement with the seismologically determined magnitude of M 7.9. A comparison of strong-motion inversions for moment release with our slip distribution shows they have a similar pattern. The locations of the two largest pulses of moment release correlate with the locations of increasing steps in the average values of observed slip. This suggests that slipdistribution data can be used to infer moment release along other active fault traces.141 26 - PublicationRestrictedPaleoseismicity of Two Historically Quiescent Faults in Australia: Implications for Fault Behavior in Stable Continental Regions(2003-10)
; ; ; ; ; ;Crone, A. J.; U.S. Geological Survey, MS 966, P.O. Box 25046, Denver, Colorado 80225, USA ;De Martini, P. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Machette, M. N.; U.S. Geological Survey, MS 966, P.O. Box 25046, Denver, Colorado 80225, USA ;Okumura, K.; Department of Geography, Hiroshima University, Higashi-Hiroshima, 739, Japan ;Prescott, J. R.; Department of Physics and Mathematical Physics, University of Adelaide, Adelaide, South Australia 5005; ; ; ; Paleoseismic studies of two historically aseismic Quaternary faults in Australia confirm that cratonic faults in stable continental regions (SCR) typically have a long-term behavior characterized by episodes of activity separated by quiescent intervals of at least 10,000 and commonly 100,000 years or more. Studies of the approximately 30-km-long Roopena fault in South Australia and the approximately 30-km-long Hyden fault in Western Australia document multiple Quaternary surface-faulting events that are unevenly spaced in time. The episodic clustering of events on cratonic SCR faults may be related to temporal fluctuations of fault-zone fluid pore pressures in a volume of strained crust. The long-term slip rate on cratonic SCR faults is extremely low, so the geomorphic expression of many cratonic SCR faults is subtle, and scarps may be difficult to detect because they are poorly preserved. Both the Roopena and Hyden faults are in areas of limited or no significant seismicity; these and other faults that we have studied indicate that many potentially hazardous SCR faults cannot be recognized solely on the basis of instrumental data or historical earthquakes. Although cratonic SCR faults may appear to be nonhazardous because they have been historically aseismic, those that are favorably oriented for movement in the current stress field can and have produced unexpected damaging earthquakes. Paleoseismic studies of modern and prehistoric SCR faulting events provide the basis for understanding of the long-term behavior of these faults and ultimately contribute to better seismic-hazard assessments.199 31