Minor Earthquake Activity in Northern Socorro County

SAN ACACIA, N.M. -- A series of minor earthquakes measuring between the magnitudes of 2.1 and less than 1 occurred Sunday night, March 22, through Monday, March 23, near the northern Socorro County communities of San Acacia and Alamillo, located about 11 miles north of Socorro.

Seismologists at New Mexico Tech in Socorro recorded the earthquake activity on the university's array of seismic stations and fielded felt reports about the largest tremor from San Acacia area residents. Preliminary analyses of the quakes show the epicenter's location to be about three and a half miles west of San Acacia, near San Lorenzo Arroyo.

The first earthquake, which registered at magnitude 2.1, occurred at 10:03:46.8 p.m. This strongest temblor was then followed by a swarm of at least 10 smaller earthquakes, all measuring less than magnitude 1 and too small to be felt.

"The first earthquake was felt because it was fairly large and because its source was shallow--only approximately 2.5 kilometers or 1.6 miles deep," says Richard C. Aster, associate professor of geophysics and research geophysics at New Mexico Tech.

Historical and recent records of earthquakes in New Mexico show that, although the area along the Rio Grande from Socorro north to Bernardo occupies only two percent of the total area of the state, it accounts for about 45 percent of all of New Mexico's earthquake activity. Seismic records also show that the earthquake activity in the area is often dominated by swarms of temblors lasting days or weeks, some strong enough to be felt.

Aster explains that the relatively high earthquake activity in the Socorro area, an area that seismologists refer to as the "Socorro seismic anomaly," is probably attributable to the ongoing inflation of a mostly thin, yet extensive, horizontal layer of molten rock, the "Socorro magma body," residing about 12 miles below the middle Rio Grande valley, between Socorro and Bernardo.

-NMT-

George Zamora