Group B, Poster #258, San Andreas Fault System (SAFS)
Fault Trace Mapping of the Central SAF from Lidar Topography
Poster Image:
Poster Presentation
2022 SCEC Annual Meeting, Poster #258, SCEC Contribution #12518 VIEW PDF
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We utilize the 2005 B4 and 2007 Earthscope lidar basemap datasets. We evaluate fault trace expression with geomorphic indicators to guide our mapping. We assign each trace a confidence ranking and categorize the trace as primary or secondary. Each fault trace is supported by geomorphic indicators with a total count of over 1,500 mapped indicators. Landscapes that preserve geomorphic indicators are likely to have higher confidence faults and more mapped secondary traces. The 3D differencing highlights the principal displacement zone and thus the primary trace over the majority of the creeping section, but does not show fine-scale details.
From a large-scale view, the primary trace in the 3D differencing generally agrees with the geomorphically mapped traces. Several sites along the creeping section are illustrative of the difference between the 3D differencing and geomorphic traces. At Mustang Ridge, strong geomorphic signals indicating activity over the past ~10 kyr show multiple sigmoidal fault traces, only one of which is active in the 3Ddifferencing. At Peach Tree Ranch, the wide fault zone is sensitive to geomorphic alteration. The 3D differencing has landslides and weaker signals that do not follow the geomorphically-defined fault traces. At Lewis Creek, large earth flows erase geomorphic indicators and add noise to the differencing. There is a strong contrast in movement, with horizontal tectonic displacements butted against vertically displaced landslides.
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We utilize the 2005 B4 and 2007 Earthscope lidar basemap datasets. We evaluate fault trace expression with geomorphic indicators to guide our mapping. We assign each trace a confidence ranking and categorize the trace as primary or secondary. Each fault trace is supported by geomorphic indicators with a total count of over 1,500 mapped indicators. Landscapes that preserve geomorphic indicators are likely to have higher confidence faults and more mapped secondary traces. The 3D differencing highlights the principal displacement zone and thus the primary trace over the majority of the creeping section, but does not show fine-scale details.
From a large-scale view, the primary trace in the 3D differencing generally agrees with the geomorphically mapped traces. Several sites along the creeping section are illustrative of the difference between the 3D differencing and geomorphic traces. At Mustang Ridge, strong geomorphic signals indicating activity over the past ~10 kyr show multiple sigmoidal fault traces, only one of which is active in the 3Ddifferencing. At Peach Tree Ranch, the wide fault zone is sensitive to geomorphic alteration. The 3D differencing has landslides and weaker signals that do not follow the geomorphically-defined fault traces. At Lewis Creek, large earth flows erase geomorphic indicators and add noise to the differencing. There is a strong contrast in movement, with horizontal tectonic displacements butted against vertically displaced landslides.
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Citation: Powell, J., Scott, C., & Arrowsmith, R. (2022, 09). Fault Trace Mapping of the Central SAF from Lidar Topography. Poster Presentation at 2022 SCEC Annual Meeting.
Keywords: Geomorphology, San Andreas Fault, Mapping, Geology, Surface Geology, Quaternary
Relevant SCEC Themes:
Stress and Deformation Over Time
Special Fault Study Areas: Focus on Earthquake Gates
