Sunday, November 09, 2014

Report on Duncan earthquake aftershocks

The first report on the magnitude 5.3 Duncan earthquake is posted on the Arizona Geology online magazine page at

The report author, Dr. Jeri Young, runs the Arizona Broadband Seismic Network at AZGS.  She continues to analyze the aftershocks and source mechanisms.    A summary of the article:

"A magnitude 5.3 earthquake occurred near Duncan, AZ at approximately 10 pm on June 28th, 2014. The earthquake shaking was strong and caused moderate damage in the Duncan area; it was felt throughout southeastern Arizona  and was recorded by seismometers around the globe. The earthquake began about 7 km (4.4 miles) below the surface, and we have found no evidence that the earthquake ruptured the earth’s surface. Fairly minor damage was reported in Duncan and Safford; cracks developed in concrete structures and at least one home foundation, several trailer homes were displaced, and glassware flew out of cupboards. This was the largest earthquake to occur in southeastern Arizona – southwestern New Mexico in 75 years, and it serves as a reminder that Arizona does indeed have earthquakes and earthquake hazards.

In the days immediately following the main shock, the Arizona Broadband Seismic Network (ABSN), operated by the AZGS, recorded 156 aftershocks in the M 1.6 to M 3.6 range; however, the locations of the smaller events are uncertain because they were not recorded by many seismic stations. Since June 28th, thirty aftershocks ranging from M 2.6 to M4.1 [right] have been reported by the U.S. Geological Survey; all of the earthquakes occurred at depths of approximately 5 to10 km (3 to 6 miles). The largest aftershock, an estimated M 4.1, occurred on July 11th. Some residents felt strong shaking while light damage was reported."

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