HR: 0800h
AN: P51B-0921    [Abstracts]
TI: Influence of Mechanical Stratigraphy and Strain on the Displacement-Length Scaling of Normal Faults From Alba Patera to the Northern Plains, Mars
AU: * Polit, A T
EM: polita@mines.unr.edu
AF: Geomechanics-Rock Fracture Group, Department of Geological Sciences and Engineering/172, Mackay School of Earth Sciences and Engineering, University of Nevada, Reno, NV 89557 United States
AU: Schultz, R A
EM: schultz@mines.unr.edu
AF: Geomechanics-Rock Fracture Group, Department of Geological Sciences and Engineering/172, Mackay School of Earth Sciences and Engineering, University of Nevada, Reno, NV 89557 United States
AU: Soliva, R
EM: solivaroger@yahoo.fr
AF: Université Montpellier II, Département des Sciences de la Terre et de l'Environnement, Montpellier, 34000 France
AB: Normal fault populations grow with constant displacement-length ( D-L) scaling relations when fault aspect ratio remains constant. Mechanical stratigraphy can vertically restrict faults so that fault height remains constant while fault length increases. This increase in aspect ratio (length/height) with length results in less displacement per unit length for progressively longer faults (Schultz and Fossen, 2002; Soliva and Benedicto, 2005). Gupta and Scholz (2000) have also demonstrated that strain influences D-L scaling relations such that, following saturation, the D-L ratio increases with increasing strain. To better understand the effects of mechanical stratigraphy and strain on D-L scaling, we measure the throw distributions on well preserved graben-bounding normal faults in the northeastern part of the Tharsis region on Mars. For faults in the northern plains of Mars, we find a transition from linear scaling, with D-L ratios of ~1×10^-3, to nonlinear D-L scaling as a function of length. To the south, on Alba Patera, faults follow linear D-L scaling. These faults have D-L ratios of ~5×10^-3, and accommodate larger strains (~0.89%) than the faults in the northern plains (~0.23%). Longer faults in the northern plains are restricted at a mechanical boundary 3 km deep whereas those on Alba Patera are not vertically restricted. The discrepancy in D-L ratio between the two regions is due to strain differences. On Alba Patera grabens accommodate larger strains by a change from regionally distributed to more localized deformation, with a corresponding increase in fault height and D-L ratio. Our results suggest a transition between vertical restriction of uniformly spaced grabens and downward propagation of a few grabens and the associated decrease in aspect ratio and increases in D-L ratios and extensional strain.
DE: 6225 Mars
DE: 8010 Fractures and faults
DE: 8015 Local crustal structure
DE: 8149 Planetary tectonics (5475)
SC: Planetary Sciences [P]
MN: Fall Meeting 2005