DEVELOPMENT OF A GEOLOGICALLY-INFORMED FAULT SOURCE PARAMETERS DATABASE AND UPDATES OF THE FAULT SOURCE MODEL FOR THE U.S. NATIONAL SEISMIC HAZARD MODEL

The USGS is developing a database of fault source parameters for the 2023 update of the U.S. National Seismic Hazard Model (NSHM). The database will consist of fundamental geologic information about source faults, recorded at sites or reaches along faults, including geologic slip rate, paleoearthquake recurrence, time since last event and single event displacements. Additionally, the database will include metadata that provide context for core data (e.g., age range over which the slip rates are calculated, number of earthquake cycles represented in a slip rate, etc...). We are also expanding the current NSHM fault source model to both densify the fault network and potentially represent some faults and fault zones as polygons. The fault source parameters database will be mapped onto the updated fault source model. The updated databases will improve model utility by providing: 1) an up-to-date representation of best known geologic constraints on NSHM source faults; 2) the ability to filter core geologic data based on metadata (e.g., calculate hazard using slip rates measured over the same time period); 3) the opportunity to identify potential biases in geologic observations (e.g., identification of a sampling bias of slip rates in California skewed towards 11-130 ka age range); 4) the potential to incorporate slip rate epistemic uncertainties and temporal variability into deformation models; 5) collaboration and engagement with partners and stakeholders to widen the breadth of knowledge the NSHM utilizes; and 6) a way to conduct parametric testing of relative importance of geologic inputs to deformation models and hazard calculations (e.g., the sensitivity of various types of geologic data on hazard calculations). We are currently soliciting contributions of updated geologic data for consideration in the database from the USGS nationwide, state geological surveys, academia, and the earthquake science community. The submission deadline for contributions is May 29, 2020.