P-wave velocity in Precambrian basement (Pg) and P-wave time terms in and around Albuquerque Basin, New Mexico

Abstract

A time-term method of analyzing seismic refraction data was used to process 62 time-distance pairs observed on a 13 station seismic network from 10 shot points in and around Albuquerque Basin, New Mexico. The time terms derived from the analysis range from 1.50 seconds at the Albuquerque volcanoes down to -.047 seconds at the Albuquerque Seismological Laboratory. In a general way the time terms correlate with the geologic foundation beneath the site: Large values are calculated for stations and shots within the basin, intermediate values on consolidated sedimentary rocks and Tertiary intrusions, and the smallest on Precambrian outcrops. The P-wave (Pg) velocity in bedrock was found to be 6.0 ± .02 km/s. This falls approximately midway between higher velocities reported to the east and west of Albuquerque Basin and lower velocities reported to the north and south. These numbers will be valuable in future efforts to accurately locate shallow nearby earthquakes and for studies seeking to unravel seismic complexities deeper in the crust.