HR: 0800h
AN: T21B-0587    [Abstracts]
TI: Transtensional Crustal State of Stress in the Eastern California Shear Zone Derived From 3D Finite Element Analysis
AU: Connolly, P
EM: Peter.Connolly@Chevron.Com
AF: Chevron Rock Mechanics Team, 1500 Louisana Street, Houston, TX 77002,
AU: * Eckert, A
EM: andreas.eckert@gpi.uni-karlsruhe.de
AF: Geophysical institute, University Of Karlsruhe Hertzstrasse 16, Karlsruhe, 76187, Germany
AB: Kinematic studies of deformation within the Eastern California Shear Zone conclude that the observed surface displacements are partitioned between a large dextral shear component of the plate boundary deformation and a smaller extensional component of the Basin & Range tectonics. Consequently, transtension is widely expressed in the ECSZ. The state of stress in the ECSZ can be generally characterised by NNE-SSW compression and WNW-ESE extension supporting the hypothesis of a current dextral transtensional stress regime in the ECSZ. However, information about relative or absolute stress magnitudes is sparse and when available, only for local areas. Furthermore, discrepancies exist as to whether the state of stress in the ECSZ represents a singular distinct regional state of stress with slip partitioning explaining different deformation styles, or if the state of stress variaes spatially and/or temporarily. This study presents an analysis of the regional state of stress in the ECSZ and especially in the Owens Valley-Airport Lake Fault Zone. Using multi-scale 3D finite element analysis we focus on how (1) gravitational potential energy differences (DGPE) from crustal thickness variations, (2) plate boundary forces and (3) fault geometries influence the 3D crustal state of stress. Comparison to independent stress orientations, magnitudes and observed tectonic regimes shows that the modelling approach reproduces the absolute crustal state of stress. The FE results are in agreement with independent data and yield a consistent state of stress in the ECSZ characterised by transtensional tectonic regimes with the major active faults being situated in corridors of strike- slip tectonics The geometrical impact of the bending segment of the SAF results in increased horizontal stresses in the Mojave Block and transfers strike-slip tectonics into the Eastern California Shear Zone to accommodate a part of the relative plate motion.
DE: 8107 Continental neotectonics (8002)
DE: 8111 Continental tectonics: strike-slip and transform
DE: 8122 Dynamics: gravity and tectonics
DE: 8164 Stresses: crust and lithosphere
DE: 8175 Tectonics and landscape evolution
SC: Tectonophysics [T]
MN: 2007 Fall Meeting