Studies suggest the maximum likely magnitude for a temblor on a local fault could be 7.7 By Ben Shore, ContributorEarthquakes aren’t just a San Francisco treat.
According to geology associate professor Kim Olsen, San Diego ismore active in the seismic world than many of us believe.
“There are a number of active faults in San Diego County,generally trending northwest to southeast as a result of theinteraction between the Pacific and North American plate movements,”he said.
He said we are susceptible to earthquakes because of the numerousfaults. The San Jacinto, Elsinore, La Nacion and Rose Canyon are allmajor onshore faults. Coronado Bank, San Diego Trough and SanClemente are all major offshore faults.
Because of the size and activity of these faults, a majorearthquake is projected to reach between magnitude 6.0 and magnitude7.7 on the Richter scale – a means of rating earthquakestrength and indirectly measuring released seismic energy.
This leaves San Diego vulnerable, said Olsen. If an earthquakegreater than magnitude 7.0 were to hit somewhere on the San Jacintofault, communities near the fault would be hit hard.
He said once the earthquake waves arrive in San Diego, a lot ofshaking will be concentrated in the longer, roller coaster-likewaves, which are far more damaging to a major city than other typesof earth movements.
“These waves could do damage to larger structures such as freewaybridges and high rises in Downtown San Diego,” Olsen said.
Olsen, along with other geologists, has been working on a projectcalled TeraShake that utilizes supercomputers to generate large-scalesimulations of potential damages caused by earthquakes.
Last Tuesday, a magnitude 6.0 registered on the Richter scale inCentral California. According to the U.S. Geological Survey, theearthquake caused only minor damage, but was felt throughout CentralCalifornia from Sacramento and San Francisco as far south as OrangeCounty and Los Angeles.
Moreover, earthquake activity in San Diego is increasing,according to a statement made by Thomas Demere, Curator ofPaleontology at the San Diego Natural History Museum, on the museum’sWeb site, www.sdnhm.org.
Since 1984, earthquake activity in San Diego County has doubled,according to Demere on the Web site. The last major earthquake to hitSan Diego occurred July 13, 1986. It was a magnitude 5.3 and wascentered on the Coronado Bank fault line, about 25 miles off shorefrom Solana Beach. In 1862, a temblor, centered on either the RoseCanyon or Coronado Bank faults, damaged buildings in Old Town andopened cracks in the earth near the San Diego River mouth. Historicaldescriptions suggest this was a magnitude 6.0.
Olsen said if a quake of that magnitude were to hit here again, wewouldn’t be that much more prepared. He said while California hassome of the toughest standards for building codes in the country, amagnitude 6.0 or higher would cause substantial damage, especially inDowntown San Diego.
“It would likely disrupt life significantly in that area for awhile, along with casualties and a huge bill to pay for everything,”he said.
Olsen said people should know a few rules of thumb for earthquakepreparedness. He said everyone should secure any heavy items theyhang on walls, know how to seek shelter and store emergency food andwater in a safe place.
Living on the West Coast, part of the “Ring of Fire” of earthquakeactivity, Californians are constantly in danger of being hit by largeearthquakes. And while seismologist Vladimir Keilis-Borok’s latestearthquake predictions for Southern California were miscalculated,San Diego may still be due for one very soon.
