San Andreas Fault Longer than Previously Estimated

Newly discovered geological features, known as 'mud pots', found south of the San Andreas fault and stretching across most of the state of California, US, now confirm a long standing prediction that the famous fault line is indeed much longer than previous evidence seemed to suggest. The finding is detailed in an analysis of the region carried out by David Lynch and Kenneth Hudnut of the US Geological Survey.

"We found a large number of mud pots and mud volcanoes, many of which were lined up beyond the accepted end of the San Andreas fault," Lynch explained.

Similarly to mud volcanoes, mud pots form when hot fluids are pushed upwards through the crust of the planet, indicating that a deep rift is present in the respective area. Lynch believes that the location of the newly found mud pots is clear indication that the San Andreas Fault has an extension towards its southernmost point.

"Some geologists knew about a few of these pots, and one even suggested many years ago that they might indicate a fault," says Lynch about the fact that researchers long predicted the existence of this southern extension. Clear evidence however, was not found until now, probably due to agriculture and other related activities that erased any evidence of the presence of these geological features.

The research team also said that the discovery of the new extension is unlikely to be linked with any additional seismic activity, since the fault is not actually growing.

"It opens up a chance for geochemical studies of fault-zone fluids to contribute to seismic hazard estimates," said Jeff McGuire of Woods Hole Oceanographic Institution, Massachusetts, while pointing out that the study of the area should provide further help in predicting future major seismic activities. Currently, the US Geological Survey is preparing for the scheduled November 2008 earthquake drill, known as the Great Southern California ShakeOut, in order to collect data regarding a potential major earthquake expected to take place in the southern region of the fault in the next decades.