Wednesday, March 31, 2010

Rare quake hits Pinacates volcanic field

A magnitude 4.5 earthquake is reported at the south end of the Pinacates volcanic field in Sonora, about 60 miles south of Ajo, Arizona.  The quake hit the area at 2:14 a.m. local time on Tues, March 30.  [marked with the 'A' at left center]

The USGS maps of the area show no historical seismicity in the area.   

There are Indian legends of historical eruptions and at least two questionable reports of possible explosive activity in the early 20th century.  The field has 400 volcanic cones and other features documenting an eruption history extending over the past few million years.  

Yesterday's quake has a horizontal accuracy of about 26 kms so we can't be too certain that it actually occurred within the volcanic field.   

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