Seismicity and faults in northern New Mexico
— Leigh S. House and Hans Hartse

The Los Alamos seismograph network has recorded earthquake data from north-central New Mexico for more than 20 years. Re-analysis of data for earthquakes between 1973 and 1988 and new analysis for earthquakes between 1989 and 1994 have provided a set of earthquake locations that are more accurate than previously available. Newly determined epicenters of about 580 events show that earthquakes occur in widely scattered locations through much of the area, although some occur in clusters and some are associated with fault zones. This level of detail has not been seen previously on earlier epicenter maps. Previous studies had concluded that the margins of the Rio Grande rift can not be identified from the seismicity and the new locations confirm that. The areas of greatest seismicity all lie in a roughly horseshoe-shaped zone of activity that surrounds the relatively inactive Valles Caldera and Jemez Mountains. The tectonics of this region would be better understood with additional information from the earthquakes, such as focal mechanisms.