New constraints on the geometry and evolution of the Southern San Andreas Fault and Salton Pull-apart basin
Abstract
In the recent geologic past, the Salton pull-apart basin, northern Imperial Fault (IF) and Southern San Andreas Fault (SSAF) have been part of an evolving tectonic regime, subject to strain partitioning. This part of the North American/Pacific plate boundary has the potential for generating a large earthquake. Several lines of active-source seismic reflection and refraction data in the Salton Sea were analyzed to better understand the fault interactions and evolution in this region by investigating the SSAF geometry, stratigraphy, and velocity structure. These data, collected in conjunction with the Salton Seismic Imaging Project (SSIP) include two fault-perpendicular lines: one adjacent to the southern terminus of the SSAF (Line 7), and one just south of the terminus (Line 8). We present results from Multi Channel Seismic (MCS) data along Line 7, and refraction data along Lines 7 and 8. Velocity models along these lines were constructed from the refraction data. Included in the Line 7 model is an interface representing a strong reflector observed in the MCS data, which helps to constrain the raypaths and velocities in the model. Line 7 MCS data image stratigraphic layers thickening to and dipping down to the east towards the SSAF, indicative of a westward-dipping, oblique strike-slip fault. The refraction data along this line are consistent with a westward dipping SSAF and a down the west normal component. We present velocity models for Line 7 and 8, as well as resolution tests supporting the fault's geometry. The results from these two lines and a fault parallel line suggest that the SSAF is dipping to the west and is in transtension. We propose that the SSAF has migrated northward through time, partitioning its strain onto the IF. As the IF migrates northwards it forms the Salton pull-apart basin.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.T11D2481S
- Keywords:
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- 8106 TECTONOPHYSICS Continental margins: transform;
- 8111 TECTONOPHYSICS Continental tectonics: strike-slip and transform;
- 8180 TECTONOPHYSICS Tomography;
- 8169 TECTONOPHYSICS Sedimentary basin processes