Updating the central San Andreas fault creep record with alignment array and differential lidar measurements at high spatial resolution

Catherine E. Hanagan, Stephen DeLong, Jessie Vermeer, & Travis V. Alongi

Submitted September 7, 2025, SCEC Contribution #14554, 2025 SCEC Annual Meeting Poster #TBD

The central San Andreas fault has an exceptional geodetic record, with high precision measurements of surface fault creep dating to the late 1960s from sparsely distributed (multi-km) alignment arrays (AAs) and creepmeters. Subsequent studies extend the record of fault creep for these monuments toward present day, and fill spatial gaps along-strike with additional InSAR and differential lidar point-cloud measurements. Together, the complementary records reveal spatially comprehensive and relatively consistent multi-year to multi-decade snapshots of creep rates on the order of 1-3cm/yr. However, the variability of surface creep at high (sub-meter) spatial resolution is not well-resolved. Geomorphic evidence of the fault location is not always reconciled with the location of creep inferred by geodetic methods. These differences can reveal subtle deviations from the often-inferred simple fault geometry, and may hint at long-term fault slip evolution. We update the record of creep for the central San Andreas fault by relocating and resurveying alignment arrays, providing individual high-precision monument locations across the fault with long-term, 50+ year estimates of creep rate. We also implement a new workflow for deriving creep rates from repeat airborne lidar digital elevation models at 0.5 m spatial resolution. The updated alignment array measurements provide ground-truth for the high-resolution lidar-derived creep rates, lending confidence to further analyses of the lidar differencing results. From these datasets, new, preliminary estimates of creep rate, fault location, and fault zone width demonstrate the utility of the method for capturing near-fault deformation and reveal previously unknown along-strike variability for the seemingly well-understood central San Andreas fault.

Citation
Hanagan, C. E., DeLong, S., Vermeer, J., & Alongi, T. V. (2025, 09). Updating the central San Andreas fault creep record with alignment array and differential lidar measurements at high spatial resolution. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy