Geodetically-inferred strain rates in the Western US and comparison with stress orientations and geologic moment rates
Kaj M. JohnsonSubmitted April 19, 2022, SCEC Contribution #11842
We develop an elasticity-based method for using GNSS-derived velocities to estimate continuous surface velocity and strain rate fields and uncertainties. The method uses distributed body forces in a thin elastic sheet and builds on similar previous methods. We also allow for discontinuities in velocity across creeping faults using the solution for dislocations in a thin elastic plate. We apply the method to the the western U.S. and systematically compare our derived strain rate field with published crustal stress orientations and with fault slip rates from the 2014 US National Seismic Hazard Model (NSHM) geologic deformation model. We identify systematic differences in orientations of maximum horizontal shortening rate and maximum horizontal compressive stress in the Pacific Northwest region and along much of the San Andreas Fault system. In the Pacific Northwest, the maximum horizontal stress orientations are rotated counterclockwise 40-90 degrees relative to the maximum horizontal strain rate directions. Along the San Andreas Fault system, the maximum horizontal stresses are rotated systematically 25-40 degrees clockwise (closer to fault normal) relative to the strain rates. We also find that total geodetic moment rates are higher than geologic model moment rates for all regions of the western US except within the Western Transverse Region, and the northern and southern San Andreas Fault system.
Citation
Johnson, K. M. (2022). Geodetically-inferred strain rates in the Western US and comparison with stress orientations and geologic moment rates. Journal of Geophysical Research, (submitted).
