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Fresh time-lapse videos of historic Arizona Earthquakes 1860-2019

The recent M7.1 and M6.4 Ridgecrest, CA, earthquakes, and the 10,000+ aftershocks, caused some consternation among Arizona’s media about the likelihood of earthquakes impacting Arizona’s people, property, and infrastructure. In the days following the M7.1 event, we entertained conversations and interviews with media staff in Flagstaff, Prescott, Phoenix, Tucson and Yuma.

Our response was always the same: Arizona is Earthquake Country.  Unlike California, large magnitude earthquakes in Arizona are few and far between. But each year about 100 earthquakes originate in Arizona. Nearly all of those are less than M 2.5 and are not felt. But seismometers of the Arizona Broadband Seismic Network (ABSN) record the events and AZGS’ Jeri Young Ben-Horin adds them to the existing catalog. These small magnitude events are instrumental in better understanding Arizona’s seismic hazard and risk.

To illustrate Arizona’s earthquake activity, we made three time-lapse videos of felt earthquakes and earthquakes recorded by the ABSN. The 1860 – 2019 >M2.75 earthquake video begins in 1860 and ends in mid-July 2019 with events equal to or greater than M2.75. The two other videos include all seismic events, including events less than M2.75 and illustrate earthquake activity from 1860-2019, and rolling backwards through time from 2019-1860. The videos are just over 1-minute in length and individual scenes reflect 2.5 years of activity.  

1987-1989 L-M2.75 EQs, R-All EQs
Earthquake activity from Feb. 1987 to Dec. 1989. Left - EQ's with M2.75 or greater; right - all earthquakes

Beginning in the 1960s, there is an apparent increase in earthquake activity that ramps upward through the first decades of the 21st century, this is particularly noticeable in the two videos that include all seismic date. This is an artifact of improved seismic monitoring in Arizona and throughout the Western U.S. The videos reveal, however, that concentrations of earthquakes have shifted around the state during the past 150 years, and earthquakes can occur anywhere in Arizona.

Key for earthquake magnitudes
For keying out magnitudes in the 3 videos

And Arizona is not immune to moderate and large magnitude earthquakes. In 1887, the Great Sonoran Earthquake caused ground shaking that was felt throughout the Southwestern U.S. and northern Mexico (DuBois and Smith, 1980). More than 50 people were killed and numerous buildings were damaged across the region. The groundshaking in Tucson knocked people right off their feet and shook the Santa Catalina Mountains severely enough to raise a cloud of rock dust so thick that people believed that a massive wildfire had broken out.

The Northern Arizona Seismic Zone extending from south of Flagstaff north to Utah is a hotbed for seismic events. Between 1906 and 1912, Flagstaff was rocked by three M~6 earthquakes. Yuma has been shaken by numerous large earthquakes centered in southern California and northern Mexico. The April 2010 M7.2 El Mayor – Cucapah earthquake damaged the historic Gandolfo Annex in downtown Yuma. Some other Arizona communities that felt earthquakes in the past decade include: Phoenix Metro Area, Tucson, Duncan, Sedona, Flagstaff, Cottonwood, Jerome, Safford and Morenci.

Note. Since 2012, on the third Thursday in October, the Arizona Geological Survey and the Arizona Dept. of Emergency and Military Affairs host the Great Arizona ShakeOut earthquake preparedness event. To register for this years ShakeOut: Register !

Time-lapse videos were manufactured using ArcGIS Pro Animation module and filmed using FastStone Capture.

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