Abstract

In this paper we analyze the location performance of the Montana Regional Seismic Network (MRSN) using the Seismic Network Evaluation through Simulation (SNES) method. Montana has a high level of seismicity that includes approximately 1500 locatable earthquakes annually. The MRSN comprises 38 stations deployed over an area of approximately 50,000 km2. The application of the SNES method permits us to evaluate the background noise levels of the network stations and estimate an empirical law that links the variance of P and S travel‐time residuals to hypocentral distance. This in turn permits us to assess the appropriateness of the velocity model used by the MRSN in the location routine. We constructed SNES maps for ML 1.4, 1.6, 1.8, 2.0, and 2.2, fixing the hypocentral depth at 10 km and at the 95% confidence level. Through application of the SNES method, we show that MRSN provides the best monitoring coverage in the Flathead Valley of northwestern Montana, with errors for ML 2 that are less than 2 and 6 km for epicenter and hypocentral depth, respectively. At magnitude 2.2, this seismic network is capable of locating earthquakes as deep as 150 km and provides a threshold of completeness down to magnitude 1.5 for most of western Montana. We delineate some seismogenic areas of western Montana, including the central portion of the centennial tectonic belt in extreme southwestern Montana, that are not adequately covered by the MRSN alone.

You do not currently have access to this article.