Most earthquakes in Arizona are low magnitude and go unnoticed.  However, there is  potential for a big one.  The Arizona Geological Survey has several videos featuring earthquakes in and near Arizona.  The newest is a time-lapse animation of the Brawley earthquake swarm that occurred on 26-29, August, 2012. Brawley is in southern California, just south of the Salton Sea.

To see this video go to:  http://www.youtube.com/user/azgsweb

That link also contains several other earthquake-related videos (4 to 6 minutes long) so scroll down the page and you will see:

Earthquakes in Arizona

Time-lapse video animation of earthquakes in and around Arizona from 1852 to 2011. The apparent increase in seismic events in the latter part of the 20th century and early 21st century stems from improved seismic monitoring.  It is interesting to see where the most earthquakes occur.

Lake Mary Fault

The Lake Mary Fault, located immediately south of Flagstaff, Arizona, represents the greatest earthquake hazard to the more than 70,000 people of Flagstaff and environs. Dr. David Brumbaugh, Arizona Earthquake Information Center (AEIC) at Northern Arizona University, narrates the, “Lake Mary Fault — Potential Earthquake Threat to Flagstaff, Arizona.”

Little Chino Fault and Big Chino Fault

Filmed on location in Chino Valley, two separate  six minute videos describe the geometry and timing of seismic activity on these faults. This is an active fault area with a moderate recurrence rate on the order of tens of thousands of years. It is capable of yielding earthquakes in the range of magnitude 6 to 6.5 and presents a hazard to residents of Chino Valley and nearby Prescott, Arizona.

Earthquake Monitoring in Arizona, the role of the Arizona Integrated Seismic Network

Arizona has earthquakes. Geologist Dave Brumbaugh and seismic technician Lisa Linville, both of the Arizona Earthquake Information Center (Northern Arizona University), describe the role of the Arizona Integrated Seismic Network in monitoring earthquake activity in the Grand Canyon State. And Lisa deconstructs one of the broadband seismic stations that form the backbone of the system.

The 1887 Sonoran Earthquake

On 3 May 1887, a magnitude 7.2 earthquake rippled across Sonora, Mexico, and southern Arizona. Phil Pearthree, Chief of the Environmental Geology division of the Arizona Geological Survey, revisits that event in this video. The earthquake killed dozens of people and damaged or destroyed several hundred structures. A similar event today would disturb and disrupt population centers in northern Sonora and southeastern Arizona and New Mexico.

For more information on the 1887 earthquake, see my post: The Great Arizona-Sonora Earthquake of 1887

For more information on earthquakes and other geologic hazards, visit the AZGS Geologic Hazards Center: http://www.azgs.az.gov/hazards_earthquakes.shtml

On May 3, 1887, Southern Arizona and Sonora, Mexico were shaken by a 7.2 to 7.5 magnitude earthquake. The epicenter was located along the Pitaycachi fault in the San Bernardino Valley in Sonora, about 40 miles south of Douglas, Arizona, but shaking was felt and rumblings were heard as far north as Phoenix. Ground motion lasted up to 10 minutes.

It is reported that the earthquake caused church bells to ring as far south as Mexico City and many buildings in Mexico collapsed resulting in about a dozen deaths.

The 30-mile-long fault scarp shows displacements of up to 15 feet. According to McGarvin, 1987, “Numerous rockfalls were reported in the mountain ranges of southeastern Arizona and northern Sonora. Sparks from the crashing boulders ignited dry brush and grass, and fires quickly spread to the forests.” But the shaking was not enough to dislodge many balanced rocks in Southern Arizona (see: Precariously Balanced Rocks and earthquakes).

McGarvin goes on to say, “Nearly all the valleys experienced changes in water conditions. Wells that had been excellent sources of water went dry, whereas artesian conditions and temporary lakes were created in other areas. One of the more colorful descriptions of the event came from Charleston, Arizona (near Sierra Vista), where ‘the walls of the saloon did a two-step and the floor did a shimmey’”

This fault and resulting earthquake were the result of on-going crustal extension that formed the Basin and Range province of Sonora, Arizona, Nevada, and Idaho. The Arizona Geological Survey (AZGS) considers another earthquake of this magnitude unlikely on the Pitaycachi fault. Based on analysis of soils and morphological analysis of fault scarps, AZGS estimates that such earthquakes would occur along a particular fault once every 10,000 years in Southeastern Arizona. “However, the major earthquake that occurred in 1887 in northeastern Sonora is evidently part of a series of 5 or 6 surface-rupturing earthquakes that have occurred since 20,000 years ago in a N-S-trending zone straddling the Arizona-New Mexico border with surface ruptures averaging 3,000 to 4,000 years apart”. Pearthree, 1986, notes that such faulting has occurred from Tucson, east to the border during the last 120,000 years.

AZGS speculates that the most likely place for future earthquakes in Arizona (other than near Yuma and the San Andreas system) is in northwestern Arizona where the Basin and Range extension is more active (see map above).

References:

McGarvin, T.G., 1987, The 1887 Sonoran Earthquake: It wasn’t our fault, Fieldnotes, Arizona Bureau of Geology and Mineral Technology (now the Arizona Geological Survey), Vol. 17, no.2.

Pearthree, P.A., 1986, Late Quaternary Faulting and Seismic Hazard in Southeastern Arizona and Adjacent Portions Of New Mexico and Sonora, Mexico, Arizona Geological Survey, Open-File Report 86-8.

Sumner, J.R., 1977, The Sonoran Earthquake of 1887, Bulletin of the Seismological Society of America. Vol. 67, No. 4, pp. 1219-1223.

See also:

Arizona earthquakes, 1852-2011, a video time line

Earthquake hazard near Flagstaff assessed, Video

Where the Next Big American Earthquake and Tsunami Might Occur

Lake Mead has series of small earthquakes

Local atmospheric changes may foretell large earthquakes

And from the Arizona Geological Survey, see the earthquakes hazards page.