by Just thought you should know
Thursday, Jun. 22, 2006 at 12:40 PM
The southern end of the San Andreas fault near Los Angeles, which has not had a major rupture for more than 300 years, is under immense stress and could produce a massive earthquake, a new study said.
The study found that, given average annual movement rates in other areas of the fault, there could be enough pent-up energy in the southern end to trigger a cataclysmic jolt of up to 10 metres.
Data taken by satellite is more complete than previous studies because measurements were taken every 20 metres instead of at ground stations 10 kilometres apart.
The observed strain rates confirm that the southern section of the San Andreas fault may be approaching the end of the interseismic phase of the earthquake cycle
A sudden lateral movement of seven to 10 metres would be among the largest ever recorded
According to the US Geological Survey (USGS), the earthquake that destroyed San Francisco in 1906 was produced by a sudden movement of the northern end of the fault of up to 6.4 metres.
There had been no recorded movement at the southern end of the fault - the 1,290km-long geological meeting point of the Pacific and the North American tectonic plates - since the dawn of European settlement in the area.
This lack of movement correlated with the predicted gaps between major earthquakes at the southern end of the fault of between 200 and 300 years.