Linking Fault Slip and Near-Surface Deformation on the Southern San Andreas Fault at Painted Canyon: Preliminary Results

Asenath Kwagalakwe, Eileen L. Evans, Gladys Pantoja, Allen M. Gontz, Yehuda Bock, Aubrey Bennett, Jennifer S. Haase, Matthew C. Brandin, Yuri Fialko, & Cornelius Waldhausen

Submitted August 30, 2026, SCEC Contribution #15276, 2026 SCEC Annual Meeting Poster #TBD

The San Andreas Fault (SAF) is a major plate-boundary fault in California characterized by spatial variations in slip behavior, ranging from fully locked to aseismically creeping. The southern San Andreas Fault (sSAF) is predominantly locked but also experiences localized surface creep and/or slow slip events. For most of the sSAF, surface creep appears to be co-located with the primary mapped trace of the fault. However, at Painted Canyon on the Coachella Valley segment of the sSAF, localized aseismic creep has been observed ~200 m away from the mapped trace of the fault. Here, we combine near-surface geophysical imaging with geodetic observations from InSAR and updated campaign GNSS to link near-surface structures with active deformation. We image the near surface (upper 5-20 m) using Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR). Preliminary ERT and GPR results resolve the mapped trace of the sSAF but are ambiguous within the offset creep zone. Updated campaign GNSS observations, from an existing alignment array that spans the main fault trace and the creep zone, include six surveys since 2007, with three additional surveys acquired since the last published GNSS dataset (2014). A buried elastic dislocation model constrained by the updated GNSS velocities indicates an average creep rate of 3.6 mm/yr and an average locking depth of 71 m, but the locking depth is poorly constrained. A locking depth below the resolution of the ERT and GPR is consistent with a lack of clear fault structures in the upper ~20 m.

Citation
Kwagalakwe, A., Evans, E. L., Pantoja, G., Gontz, A. M., Bock, Y., Bennett, A., Haase, J. S., Brandin, M. C., Fialko, Y., & Waldhausen, C. (2026, 08). Linking Fault Slip and Near-Surface Deformation on the Southern San Andreas Fault at Painted Canyon: Preliminary Results. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy