Local Magnitude Determinations for Intermountain Seismic Belt Earthquakes from Broadband Digital Data

摘要

The University of Utah Seismograph Stations (UUSS) earthquake catalogs for the Utah and Yellowstone National Park regions contain two types of size measurements: local magnitude (M_L) and coda magnitude (M_C), which is calibrated against M_L. From 1962 through 1993, UUSS calculated M_L values for southern and central Intermountain Seismic Belt earthquakes using maximum peak-to-peak (p-p) amplitudes on paper records from one to five Wood–Anderson (W-A) seismographs in Utah. For M_L determinations of earthquakes since 1994, UUSS has utilized synthetic W-A seismograms from U.S. National Seismic Network and UUSS broadband digital telemetry stations in the region, which numbered 23 by the end of our study period on 30 June 2002. This change has greatly increased the percentage of earthquakes for which M_L can be determined. It is now possible to determine M_L for all M 3 earthquakes in the Utah and Yellowstone regions and earthquakes as small as M <1 in some areas.