M3.7 Earthquake shakes NW Arizona in vicinity of recent earthquake swarm

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Contact: Michael Conway (520.209.4146 | Michael.conway@azgs.az.gov)

Tucson. A magnitude 3.7 earthquake shook northwestern Arizona south of Littlefield, Arizona, at 9:06 pm on 17 April 2016. This event is part of a swarm of more than 42 small magnitude earthquakes that began on 28 March with an M2.1 event located approximately 29 miles SSE of Littlefield, Arizona. The most recent event, M1.3, occurred at 4:58 pm (MST) on 18 April.

The M3.7 event was the largest earthquake yet and was felt in Littlefield and Mesquite, Nevada, along the remote Arizona-Nevada border. The earthquake sequence includes 2 events >ML3.0, 8 events >ML2.0 with the remainder below M2.0.  The depths of the earthquakes range from near-surface to approximately 14km.

The earthquake swarm is situated along the physiographic boundary between the Colorado Plateau and the Basin and Range Province, an area of active crustal extension and seismicity.

We anticipate additional small magnitude aftershocks in the wake of the M3.7 event.

This apparent increase in earthquake activity of northwestern Arizona may be the result of efforts by the Nevada Seismological Laboratory (NSL) to capture and record small magnitude events along the Nevada-Arizona border. The Arizona Geological Survey’s broadband seismic network, comprising 8 seismometers, is unable to record small magnitude events in northwestern Arizona.

AZGS operates the seismic network without any state or federal funding so continues to look for ways to maintain the system and to increase statewide coverage of currently undetected earthquakes.


From a report by Dr. Jeri Young, AZGS Research Geologist.