Off-fault deformation rate along the southern San Andreas fault at Mecca Hills, southern California, inferred from landscape modeling of curved drainages
| Autor: | Alison R. Duvall, Daniel E. J. Hobley, Lewis A. Owen, Gregory E. Tucker, Sarah A. Harbert, Charles M. Shobe, Harrison J. Gray |
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| Rok vydání: | 2017 |
| Předmět: |
geography
geography.geographical_feature_category Landscape evolution model 010504 meteorology & atmospheric sciences Drainage basin Geodetic datum Geology 010502 geochemistry & geophysics Strike-slip tectonics 01 natural sciences Tectonics Seismic hazard Shear (geology) Common spatial pattern Geomorphology Seismology 0105 earth and related environmental sciences |
| Zdroj: | Geology |
| ISSN: | 0091-7613 |
| DOI: | 10.1130/g39820.1 |
| Popis: | Quantifying off-fault deformation (OFD) rates on geomorphic timescales (10^2-10^5 yr) along strike-slip faults is critical for resolving discrepancies between geologic and geodetic slip-rate estimates, improving knowledge of seismic hazard, and understanding the influence of tectonic motion on landscapes. Quantifying OFD over these timescales is challenging without displacement markers such as offset terraces or geologic contacts. We present a landscape evolution model coupled with distributed lateral tectonic shear to show how drainage basins sheared by lateral tectonic motion can reveal OFD rates. The model shows that OFD rate can control the orientation of drainage basin topography: the faster the OFD rate, the greater the deflection of drainage basins towards a fault-parallel orientation. We apply the model to the southern San Andreas Fault near the Mecca Hills, where drainages basins change in orientation with proximity to the fault. Comparison of observed and modeled topography suggests that the OFD rate in the Mecca Hills follows an exponential-like spatial pattern with a maximum rate nearest the fault of 3.5 ± 1.5 mm/yr, which decays to approximately zero at ~600 m distance from the fault. This rate is applicable since the initiation of differential rock uplift in the Mecca Hills at approximately 760 ka. Our results suggest that OFD in this 800 m study area may be as high as 10% of total plate motion. This example demonstrates that curved drainage basins may be used to estimate OFD rates along strike slip faults. |
| Databáze: | OpenAIRE |
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