Co- and post-seismic deformation resolved from joint inversion of GPS and borehole strainmeter measurements during the 2019 Ridgecrest earthquake sequence

The 2019 Ridgecrest earthquake sequence is an exceptionally well-studied event, captured in nearly unprecedented geophysical detail. Three horizontal tensor borehole strainmeters (BSMs), ranging from ~2 to 30 kms near the trace of the rupture, offer a less-conventional and more sensitive measure of coseismic and postseismic deformation for the event. Historically, these instruments are noted as unreliable for measurements of coseismic strain because they are sensitive to small-scale, near-instrument heterogeneities, such as additional offsets triggered by dynamic strains or pore pressure effects. However, many studies compare the strains with pre-constrained forward models of slip. Our preliminary investigations show that we can better match the observed strains if we include BSM measurements in a joint inversion with GPS displacements for coseismic slip. Postseismically, the strainmeters record rapid, non-monotonic deformation that likewise does not match existing afterslip models with a single decay time. We present a new interpretation of co- and post-seismic deformation using BSM strains and GPS displacements at discrete time intervals marked by a change in sign or rate of strain accumulation. Our joint analysis resolves details of the co- and post-seismic slip history that remain otherwise hidden with more common satellite-based inversions from GPS and InSAR alone.