Simulating Local Sources of Crustal Deformation for Washington State Geothermal Prospects Using Geomechanical Models

Three geothermal prospect areas in Washington State were modeled using Poly3D, a boundary element code that simulates fault slip and volcanic magma chamber deflation which causes local stress perturbation within an elastic half-space. This work was done as a part of Play-Fairway Analysis for Washington State by the Washington Geological Survey, AltaRock Energy Inc., and Temple University. The region has complex tectonics which causes areal and 3D complexity in the crustal stress-strain field. Geodetic strain rate tensors from GPS velocities that represent surface block rotation as opposed to deep subduction were used to constrain the remote stress. 3D fault geometries were created for seismogenic faults using the earthquake catalog from the Pacific Northwest Seismic Network for the faults located at Mount St. Helens and the Wind River Valley. A magma chamber deflation model was used for Mount Baker that was best fit to a campaign geodetic survey on the volcano. The results of the modeling give insight into natural processes that cause dilational stress favorable for geothermal resources and are also used for siting temperature gradient holes.