Small Quakes Shake Valley

By John Larson

SOCORRO – The ground has been rumbling under the Socorro area in recent weeks.
The second local earthquake of greater than 2.0 magnitude in the last two weeks was felt last Sunday in the Lemitar area.
The epicenter of the quake was about seven miles northeast of Socorro and 3.1 miles below the surface. In the last 10 days of August, a swarm of micro-earthquakes occurred, keeping the seismologists busy, but not noticeable to residents.
The first quake to shake up Socorro this month was August 19. According to measurements taken by instruments operated by the New Mexico Tech Geophysics Program and U.S. Geological Survey, the 2.6 magnitude quake occurred at 7:57 p.m.
It was centered about three miles northeast of Socorro. Many residents also heard the quake rumble. As of early Tuesday, New Mexico Tech seismic technician Jana Stankova-Pursley had identified hundreds of small earthquakes, most much too small to be felt, in the area associated with the recent activity.
The chairman of the Earth and Environmental Science Department, Dr. Rick Aster, told the Mountain Mail that the epicenter was only about four miles below the surface.
“That’s why it was felt so strongly in the immediate Socorro area even though it was a tiny earthquake,” Aster said. “It also created a loud boom that was heard throughout the area.”
Within two hours following the event, two aftershocks smaller than magnitude 1.0 had occurred, Stankova-Pursley said.
The recent earthquakes appear to be similar to hundreds of such quakes that have been documented in the area during the past several decades, Aster said.
The quakes, just east of the Rio Grande, are linked to a thin lens of molten rock – known as the Socorro Magma Body – situated 12 miles under the surface in the Belen-Socorro area.
Aster said the pancake shaped “blister” is slowly inflating and stressing the rocks above it, causing the ground above it to rise one to two millimeters a year.
“This inflation, and rising, probably in association with shallow heated water, causes shallow earthquakes, generally in the 1.0 or 2.0 magnitude range,” he said.
Records at New Mexico Tech show that the Socorro region averages six earthquakes a year with a magnitude of 2.0.
The strongest recorded earthquake was recorded in 1906, and measured near 6.0 in magnitude.
“This is the most seismically active area in New Mexico,” Aster said. “And the Socorro magma body is the most studied geologic feature of its kind in the world.”

Small Quakes Shake Valley