SCEC Award Number 21107 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Shallow Fault Slip Along the Locking to Creeping San Andreas Fault Transition Zone at Parkfield from Lidar Topographic Differencing and InSAR Displacements
Name Organization
Chelsea Scott Arizona State University
Other Participants Ramon Arrowsmith, Stephen DeLong
SCEC Priorities 1a, 3g, 1c SCEC Groups Geodesy, Geology, SAFS
Report Due Date 03/15/2022 Date Report Submitted 03/13/2022
Project Abstract
We resolved fault creep from Parkfield to the northwest along the creeping section of the Central San Andreas fault (CSAF) using topographic differencing-derived displacements and an inversion for fault creep along the upper portion of the fault surface. Our work captures the variation in shallow creep at the kilometer-scale along over 100 kilometers of fault length. We compared our resolved creep to the creep based on geodetic datasets with larger apertures such as InSAR and GPS. We found that the location and amplitude of the maximum creep varies between inversions. We originally proposed to solve for fault creep throughout the seismogenic crust with a joint topographic differencing and InSAR inversion. However, we found that this inversion did not work well due to the highly varying resolution to shallow and relatively deep creep from the input datasets. Instead, we explored the resolution to creep at depth of the InSAR and lidar datasets with the present 1-2 km aperture of the lidar data and the required aperture of future lidar datasets to capture creep variability in the middle and deeper portions of the seismogenic crust. This analysis informs future collections of high resolution topography along active faults, for example a second B4 dataset or future USGS 3DEP lidar topography.
Intellectual Merit We developed the first fault creep inversion surrounding Parkfield constrained from near-field differential lidar displacements. Thus, we constrained the geodetic creep rate near Parkfield. We considered how the relatively high-quality fit to the displacements may reflect the mechanics that guide the deformation. We also explored the data requirements to resolve deeper creep. These are critical for constraining the variation in moment accumulation with depth and seismic hazard and for planning future lidar dataset collections.
Broader Impacts (dissemination): Project PI Chelsea Scott gave a plenary presentation at the SCEC 2021 Annual Meeting on a topic related to this research.

(Instrumentation): We explored the requirements for future lidar dataset collections (for example, a second B4 or USGS 3DEP) to be able to resolve creep throughout the seismogenic zone.
Exemplary Figure Figure 1: Results of the fault creep inversion based on differential lidar displacements. (a) Map-view creep rate fields showing the ICP-derived creep rates (top), the modeled creep rate from the inversion (middle), and the residual rate (Residual = data - model; bottom). (b) Fault plane emphasizing fault curvature. (c) Along-strike creep rate. The error bars represent the variability in creep from λ values that lie within the L-curve corner.