HR: 09:00h
AN: T41F-05    [Abstracts]
TI: Fault Drag Along Normal Faults in Unconsolidated Sediments
AU: * Exner, U
EM: ulrike.exner@univie.ac.at
AF: Department of Geodynamics and Sedimentology, University of Vienna, Althanstrasse 14, Vienna, 1090, Austria
AU: Grasemann, B
EM: bernhard.grasemann@univie.ac.at
AF: Department of Geodynamics and Sedimentology, University of Vienna, Althanstrasse 14, Vienna, 1090, Austria
AU: Pretsch, H
EM: a9808469@unet.univie.ac.at
AF: Department of Geodynamics and Sedimentology, University of Vienna, Althanstrasse 14, Vienna, 1090, Austria
AB: A displacement gradient along the strike of a fault plane results in the formation of fault drag in layers of the adjacent host rock. We investigated normal faults in Lower Miocene (Sarmatian-Pannonian) clastic sediments in a quarry at St. Margarethen, Burgenland, Austria, situated at the Eastern margin of the Eisenstadt Basin, a subbasin of the Vienna Basin complex. The N-S trending faults crosscut a barely lithified sequence of conglomerates, fine-grained sands and silts. These marker horizons display normal offset along the conjugate fault set, which is often, but not exclusively, restricted to the conglomerate beds. A significant amount of rotation of the faults can be inferred, as largest offsets are accumulated at the more inclined fault planes, whereas steeper faults show least displacement. Associated with increasing amount of offset, pronounced reverse drag of the faulted sedimentary layers can be observed both in footwall and hanging wall, often accommodated by re-orientation of the conglomerate pebbles. Rotation and fault linkage resulted in the formation of longer faults with varying dip angles crosscutting several conglomerate beds and the intercalated sand and silt layers. In the vicinity of the fault tips, individual pebbles are intensively cracked, which we interpret as an indicator for stress concentration at the fault tips. Comparing the geometry of the observed fault drag with results from numerical models we try to estimate the initial shape and orientation of the fault planes, as well as the amount of rotation and background strain which led to their finite geometry. Extrapolating the results to basin-scale faults, we may deduce valuable parameters for the interpretation of reflection seismic images, where structural details may be blurred or below seismic resolution.
DE: 8010 Fractures and faults
DE: 8169 Sedimentary basin processes
SC: Tectonophysics [T]
MN: 2007 Fall Meeting