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University of California, Riverside
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- PublicationRestrictedDynamic models of earthquakes on the North Anatolian fault zone under the Sea of Marmara: Effect of hypocenter location(2008-09-20)
; ; ; ; ;Oglesby, D.; Department of Earth Sciences, University of California, USA ;Mai, M.; Institute of Geophysics, ETH, Zurich, Switzerland ;Atakan, K.; Department of Earth Science, University of Bergen, Bergen, Norway ;Pucci, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; We perform three-dimensional spontaneous dynamic rupture models of potential earthquakes on the geometrically complex North Anatolian fault zone (NAFZ) under the Marmara Sea, Turkey. The NAFZ south of the city of Istanbul consists of a large-scale extensional stepover, with right lateral strike-slip segments linked by an oblique normal segment. We find that earthquakes nucleating near the stepover do not propagate across the entire fault system due to the statically unfavorable stress field on the oblique fault,and lead to moderate-size events only. However, earthquakes initiating a significant distance from the stepover cause significant dynamic unclamping of the oblique fault, and thus generate large through-going ruptures. Dynamic unclamping also produces supershear rupture propagation in the vicinity of fault discontinuities. The results emphasize that estimations of earthquake size, rupture propagation, and slip distribution cannot be decoupled from the location of the hypocenter and the orientation of the geometrically complex fault system within the tectonic stress field.158 27 - PublicationRestrictedEarthquakes on dipping faults: the effects of broken symmetry(1998)
; ; ; ;Oglesby, D.; University of California, Riverside ;Archuleta, R.; Institure for crustal studies, university of santa barbara, california ;Nielsen, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; Dynamic simulations of earthquakes on dipping faults show asymmetric near-source ground motion caused by the asymmetric geometry of such faults. The ground motion from a thrust or reverse fault is larger than that of a normal fault by a factor of 2 or more, given identical initial stress magnitudes. The motion of the hanging wall is larger than that of the footwall in both thrust (reverse) and normal earthquakes. The asymmetry between normal and thrust (reverse) faults results from time-dependent normal stress caused by the interaction of the earthquake-generated stress field with Earth’s free surface. The asymmetry between hanging wall and footwall results from the asymmetric mass and geometry on the two sides of the fault.125 20