Tuesday, July 29, 2008

What happens when the "Big One" rolls across Arizona?

Today's magnitude 5.4 earthquake in the LA basin has the phones ringing here at AZGS with reporters wanting to know about the earthquake hazards in Arizona.

In addition to our own home-grown faults, Arizona may be shaken by quakes in northern Sonora (such as happened in 1887) and by the mother of all western faults, the San Andreas.

The Southern California Earthquake Center (SCEC) ran their Terashake simulator through a number of possible earthquake models for Southern California, all but one of them evaluating a fault rupture that begins in the south and moves north. However, one simulation [right, screenshot of Terashake simulation of north to south fault rupture on th e San Andreas fault. credit SCEC] does show what happens if the fault starts rupturing in the LA basin and moves southeastward.

What you see is a broad region of ground shaking rolling into and across southern Arizona. Unfortunately, the model only goes a little ways across the border into Arizona. But it's enough to get me wondering just what is going to happen to the 5 million or so people living in the jello-like basins around Phoenix and Tucson.

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