Arizona's earthquake hazards

It's a good time to review Arizona's earthquake hazards. Some of the largest historical earthquakes originated outside the state boundaries but the ground shaking did damage in Arizona.

The 1887 magnitude 7.4 quake that originated 40 miles southeast of Douglas, killed 51 in Sonora and did significant damage across southeast Arizona. [top, earthquakes since 1850 in and around Arizona]

The 1940 magnitude 7.1 Imperial Valley event in southern California did serious damage in Yuma.

The Flagstaff area suffered moderate damage from 3 earthquakes in the early 1900's.

Arizona is impacted by shaking from the San Andreas fault system in California, from the Intermountain Seismic Belt that extends south from Utah, and Basin & Range faulting in Sonora, Mexico.

In addition, the San Francisco volcanic field around Flagstaff with 600 volcanoes, has been active for 6 million years with the last eruption less than 1,000 years ago. It is the most seismically active region in the state.

The possible meltdown of nuclear reactors in Japan is prompting questions of the safety of other reactors in seismically active areas. In Arizona, the Palo Verde Nuclear Generating Station sits in the "low" earthquake hazard area, west of Phoenix, just south of the I-10 marker on the map at right. [bottom, earthquake hazard of Arizona based on rates of historical activity, number of potentially active faults, and estimated slip rates for those faults. From the Arizona Geology newsletter, 2000]