Circular 171 — Earthquakes in New Mexico, 1849-1977

By Allan R. Sanford, Kenneth H. Olsen, Lawrence H. Jaksha , 1981, 20p.

The seismicity of New Mexico and its relation to major physiographic provinces and local geologic conditions within each province is presented. Earthquake data analyzed are 1) felt shocks before 1962 with maximum intensities of V or greater and 2) instrumentally located shocks with local magnitudes of 1.5 or greater for the period 1962-1977. Reports of felt shocks are almost exclusively from the Rio Grande rift, whereas the instrumental epicenters are distributed throughout the state. The instrumental data indicate a very low level of seismic activity in New Mexico relative to southern California. The data also reveal that earthquakes are most numerous in the Rio Grande rift although not as strong as those that occur in the High Plains and Colorado Plateau, two geologically stable provinces that border the rift. The more or less uniformly weak seismicity throughout the state suggests that earthquake activity is controlled more by local geologic conditions than by a general regional stress field. Some unusual local conditions that may be producing earthquakes are injection of magma into the crust in the Rio Grande rift near Socorro and hydrocarbon recovery practices in the High Plains of southeast New Mexico. Most activity in the High Plains and Colorado Plateau seems to be occurring along old buried faults that show no surface evidence of recent movement. The Jemez lineament, defined by a line of Pliocene and Pleistocene volcanoes through the southern part of the Colorado Plateau, across the Rio Grande rift, and into the northern High Plains, has seismic activity over much of its extent.