Kinematics-Based Mathematical Model for Deforming Thrust Wedges |
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Authors: | Matty Mookerjee Gautam Mitra |
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Institution: | (1) Department of Geology, Sonoma State University, Rohnert Park, CA 94928, USA;(2) Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY 14627, USA |
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Abstract: | Given the wealth of data concerning the kinematics of deforming fold-thrust belts (FTBs), first-order generalizations about
how the major strain components vary within a deforming thrust wedges are considered. These generally observed strain patterns
are used to constrain a general, kinematics-based, FTB-wedge model. We considered five strain components within a deforming
thrust sheet: (1) thrust-parallel simple shear, (2) horizontal contractional strain, (3) thrust-normal reaction strain, (4)
gravitational strain, and (5) a lateral confining boundary condition. After making assumptions about how these strain components
vary within a model FTB-wedge, the incremental deformation matrix can be calculated for any given point within the deforming
wedge. Thus, the material path of a given marker can be determined and an initially spherical marker’s strain path can be
calculated as it moves through the deforming wedge. Furthermore, by illustrating various kinematic parameters of many initially
spherical markers (for example, Flinn’s k-value, incremental octahedral shear strain, transport-perpendicular stretch), we have assembled representations of the kinematic
properties of the entire model wedge. By including a flat-ramp-flat fault surface geometry for the model wedge, we are able
to examine the kinematic effects of this relatively common structural geometry. Within the fault ramp segment there are greater
incremental strain magnitudes, out-of-the-plane motion, and flattening strains. Additionally, data from this model suggests
that gravitational strains potentially have a significant effect on the strain distribution within a deforming thrust wedge.
M. Mookerjee is formerly Matthew Strine. |
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Keywords: | Thrust sheets Kinematics Strain Deformation Shear zone Thrust fault |
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