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" Secondary deformation near strike-slip faults, southern California: "
J. M. Sheridan
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Latin Dissertation
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| Language of Document
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English
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| Record Number
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1113408
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TLpq304364741
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| Main Entry
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J. M. Sheridan
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| Title & Author
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Secondary deformation near strike-slip faults, southern California:\ J. M. Sheridan
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| College
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University of Oregon
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| Date
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1997
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| student score
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1997
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| Degree
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Ph.D.
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| Page No
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253
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| Abstract
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Tectonic boundaries are categorized into convergent, divergent, or transcurrent zones. Within these broadly defined zones are clusters of structural elements, such as folds and faults, with styles that are inconsistent with the overall boundary. In this dissertation I have investigated how structural elements group into natural domains, their level of variability, how strain is partitioned, and how kinematically incompatible domains interact to produce the overall boundary style. To investigate how disparate structural elements are linked I have mapped geological structures in the Mecca Hills. The Mecca Hills have been identified as a zone of transpression, located along a restraining bend in the right-lateral, strike-slip San Andreas Fault. The maps show a diversity of structural elements that accommodate a range of motions, including shortening, extension, strike-slip and oblique, which together accommodate the overall right-lateral transpression. I find strain partitioning and diverse structures that combine to accommodate inward and upward verging vertical motion and horizontal slip. Structural style and scale are influenced by early structures preserved in basement rock, strength contrasts in the overlying sedimentary rock, and the sequence and magnitude of deformation in progressively deforming rocks. To investigate the magnitude and spatial variability of structural style, I have located and constructed fault plane solutions for 20,000 earthquakes, with usd\rm M\sb{L} \le 5.0,usd along the San Jacinto Fault. Symmetric moment tensors are constructed from fault plane solutions and summed into subsets to identify the spatial limits of discordant domains. Strain due to all earthquakes is consistent with pure right-lateral strike-slip motion along the N47W striking San Jacinto Fault. However, normal, reverse, and strike-slip earthquakes occur everywhere, and they cluster at discrete scale lengths from the location uncertainty to the length of the fault. This work documents that diverse structural domains exist at different scales along fault boundaries. Strain or stress, inferred from few or spatially clustered data, may represent either local perturbations or the overall setting. In addition, the absence of discordant domains within a data set may indicate that spatial or temporal sampling is inadequate to characterize the overall setting. This dissertation includes both my previously published and unpublished co-authored materials.
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Earth sciences
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Geology
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Geophysics
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Geophysics
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San Andreas Fault
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San Jacinto Fault
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