A local-magnitude scale for the western Great Basin-eastern Sierra Nevada from synthetic Wood-Anderson seismograms

Abstract

AbstractWe have computed synthetic Wood-Anderson seismograms for over 1100 arrivals at 10 three-component, broadband digital stations in the UNR western Great Basin-eastern Sierra Nevada network. These represent all the available records from local earthquakes over magnitude 3.5 between 1990 and June of 1993, plus selected events of smaller magnitude. There were 77 events ranging in magnitude from 2.2 to 5.9, including four events over magnitude 5. The distances considered ranged from 15 to 600 km, with the best-represented range being from 30 to 450 km. We invert these measurements to determine distance and station corrections appropriate for a local-magnitude scale, constrained by Richter's original definition that an earthquake of ML = 3 will cause a 1-mm zero to peak deflection of the Wood-Anderson seismogram at 100 km from the epicenter. The results between 30 and 450 km were essentially independent of choice of curve-fitting parameters. In the 30- to 500-km distance region, the smooth distance-correction curves were very similar to that determined by Richter (1958), which is still used for southern California earthquakes. We propose to use Richter's distance-correction curve in reporting amplitude magnitudes from our digital network.