[californiadisasters] San Diego Could Be Hurt By Type of Quake That Hit New Zealand

San Diego could be hurt by type of quake that hit New Zealand

By Gary Robbins

San Diego Union-Tribune

Originally published February 22, 2011 at 2:02 p.m., updated February 22, 2011 at 3:24 p.m

Seismologists aren't sure exactly what would happen. But they say that the sort of magnitude 6.3 earthquake that hit Christchurch, New Zealand, killing more than 75 people, could cause significant damage in the San Diego area. The greatest risk would be to unreinforced masonry buildings that have not undergone earthquake retrofitting.

"The lesson here is we still have unreinforced structures and that they could be destroyed if we had this kind of earthquake," said Tom Rockwell, a geologist at San Diego State University.

The Christchurch quake appears to have been caused by an oblique fault, one that scientists say involves movement that runs both perpendicular and parallel to the strike of the fault. It is significantly different than the Rose Canyon fault, which runs through San Diego. Rose Canyon is a strike-slip system, meaning that one side of the fault moves horizontally in relation to the other.

But both types of faults can destroy unretrofitted, unreinforced masonry buildings. And there are about 7,800 of those buildings statewide, including some in San Diego County. Most are mixed-use and commercial structures located in or near the downtown of cities. There are also 14,200 unreinforced masonry buildings that have been retrofitted. But their structural integrity isn't entirely known. Some of the masonry buildings damaged in Christchurch had been retrofitted before the quake.

"This is very sobering for us because many of our cities face a much higher seismic risk than Christchurch," said Fred Turner, a senior structural engineer at the California Seismic Safety Commission.

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View entire article here: http://www.signonsandiego.com/news/2011/feb/22/san-diego-could-be-hurt-type-quake-hit-new-zealand/?sciquest

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