Easter Earthquake Pointed Out Some Faults - Pacific Standard

Easter Earthquake Pointed Out Some Faults

A deadly 2010 earthquake in Mexico that sealed off an overtaxed fishing ground also revealed a “treasure trove” of seismic data in California.
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Last month, Rex Dalton told us about a major earthquake in Baja Mexico that in addition to killing two people had the unfortunate local consequence of sealing off a traditional fishing spot that sustains the Cucapá Indian community.

In “Quake Rescues Reserve, Shakes Baja Fishing Town,” he noted that aftereffects of the 7.2-magnitude Easter 2010 earthquake pleased conservationists as much as it annoyed the subsistence fishermen, and for exactly the same reasons.

In the pleased column now add seismologists. The U.S. Geological Survey just announced that the El Mayor-Cucapah quake helped reveal several previously unknown faults in Southern California. Quoted in a release from USGS, California’s state geologist, John Parrish, termed the quake and its sizable aftershocks a “geological treasure trove” thanks to all the new data generated about faults in the farm-rich Coachella and Imperial valleys up to 100 miles from the epicenter.

"Every earthquake is an opportunity for new understanding,” said USGS director Marcia McNutt, “but few in recent times have created more distinct new information than the April 4, 2010 Baja quake."

Several dozen faults near the Salton Sea showed surface movement, and the USGS says only half of them had been known before. And even among the known faults, one proved to be longer than thought and another showed it was active. And lest this seem a little academic, as the USGS noted, “Knowing the existence of faults is the first step in evaluating the hazard they pose.”

This “surface movement” – 2 inches up or down is big, and hard to notice unless it breaks a road or canal – was discovered both by traditional on-foot field geology and by a non-lethal application of drone technology, NASA’s Uninhabited Aerial Vehicle Synthetic-Aperture Radar (although, in this case, the look-down radar was mounted on a plane).

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