Group , Poster #115, Stress and Deformation Over Time (SDOT)

A Curvature-based Approach to Measuring Permanent Long-wavelength Off-fault Deformation: Applications to the Volcanic Tablelands, CA

Alba M. Rodriguez Padilla, & Michael E. Oskin
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Poster Presentation

2021 SCEC Annual Meeting, Poster #115, SCEC Contribution #11348 VIEW PDF
Detailed and continuous geomorphic measurements of permanent off-fault deformation accrued over geologic timescales are challenging to collect due to incomplete knowledge of the pre-faulted landscape, sparse data coverage, erosion, and limited chronologies. We quantify permanent bending strains surrounding faults at the Volcanic Tablelands in California, an extensional accommodation zone that results in flexure of the Bishop Tuff. We first detrend the regional slope from the landscape and apply a 50 m window low pass filter to a high-resolution lidar DEM to remove survey artifacts, smooth high-frequency roughness from the landscape, and remove fault scarps and channels, so that only long-wav...elength, off-fault deformation remains. We calculate bending strains for the filtered landscape. This type of analysis assumes the tuff layer deforms as a thin elastic plate, such that layer-parallel strains are directly related to the curvature of the folded surface. The Volcanic Tablelands are well suited for this thin-plate treatment because the tuff unit is much wider and longer than it is thick, and off-fault strains are small. We estimate average permanent off-fault bending strains on the order of ~10^-2, with permanent strains decreasing with distance away from faults in an inverse power-law with exponent ~1.2. We integrate strain over the plate to estimate the total strain energy absorbed by long-wavelength off-fault deformation at the Tablelands over the lifetime of the Bishop Tuff. Though our analysis is confined to the shallow crust, the lessons learned from this analysis may be extrapolated to quantify strain energy from crustal-scale folding.
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