Central California shaken by earthquake
23 December 2003
A magnitude 6.5 earthquake shook Central California at about 6:15am (AEST) this morning - about 11:15am California time on 22 December. More than 30 after shocks followed, the largest measured at 4.7 by the US Geological Survey.
"Earthquakes of this size in California would usually be felt up to 400 km from the epicentre," said Geoscience Australia seismologist, Dr Cvetan Sinadinovski. "You could expect some damage to buildings from a shallow earthquake above magnitude 5, so this one certainly had the potential to cause some structural damage."
There have been reports of building movement in Los Angeles, about 350 kilometres south of the epicentre, and also San Francisco, about 450 kilometres to the north.
The earthquake struck 35 kilometres WNW of Paso Robles, a city with a population of about 24,000 where there are reports of some casualties and major structural damage to brick buildings in the older part of the town. There are also reports of damage to a major tourist attraction, the Hearst Castle, which is located very near to the epicentre.
"This area of California is prone to very large earthquakes. The most recent major damaging earthquakes were a magnitude 6.8 at Northridge in 1994 (near Los Angeles) and a magnitude 7.1 at Loma Prieta, near San Francisco, in 1989," said Dr John Schneider of Geoscience Australia's Risk Research Group.
"We would expect many aftershocks to continue in the area for up to a week. The San Andreas Fault, which runs the length of the Californian coast, is a tectonic plate boundary and the source of frequent large earthquakes. This earthquake occurred about 75 kilometres west of the San Andreas Fault along a small fault that, historically, has had no major earthquakes," said Dr Schneider.
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