EARTHQUAKE POTENTIAL ALONG THE WASATCH FAULT: TESTING ACCELERATING MOMENT RELEASE (AMR) ALONG ACTIVE NORMAL FAULTS

Many large earthquakes are preceded by an increase in regional seismicity known as “accelerating moment release” (AMR). The detection of ongoing AMR can be interpreted as a signal that a fault is near the end of its seismic cycle. This study examines the phenomena known as "accelerating moment release" (AMR) along the Wasatch Fault. However, AMR has not been used on normal faults. We use the Wasatch Fault and 1983 Borah Peak earthquake as test cases for identifying AMR on normal faults. Scenario events are based on the segmentation model of the 2002 National Seismic Hazard Maps, which includes multi-segment events. A backslip dislocation model is used to calculate an approximate geologically-constrained loading pattern that defines the regions of precursory AMR for each scenario. Seismic data from the ANSS Composite Catalog do not show a significant ongoing AMR signal for any scenario event along the Wasatch Fault. This result may be a function of the small number of intermediate events due to the low strain rate. However, a possible AMR signal is seen in analysis of precursory seismic events of the 1983 Borah Peak earthquake. We are now in process of reanalyzing these data to better understand how they may apply to the Salt Lake City segment of the Wasatch Fault