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Fault System Enables Larger Quakes In California

Posted by samzenpus on from the teaming-up dept.

Taco Cowboy writes Researchers have mapped the land at the southern end of the Hayward Fault and found that the creep continued 15 km beyond to merge with the Calaveras Fault, which was thought to be independent. "The maximum earthquake on a fault is proportional to its length, so by having the two directly connected, we can have a rupture propagating across from one to the other, making a larger quake," said lead researcher Estelle Chaussard, a postdoctoral fellow in the Berkeley Seismological Laboratory. "People have been looking for evidence of this for a long time, but only now do we have the data to prove it". The 70-kilometer-long Hayward Fault is already known as one of the most dangerous in the country because it runs through large population areas from its northern limit on San Pablo Bay at Richmond to its southern end south of Fremont. Last month the U.S. Geological Survey estimated a 14.3 percent likelihood of a magnitude 6.7 or greater earthquake on the Hayward Fault in the next 30 years, and a 7.4 percent chance on the Calaveras Fault, but there is one problem — the estimate was based on the assumption that the two faults are independent systems, and that the maximum quake on the Hayward Fault would be between magnitudes 6.9 and 7.0. Given that the Hayward and Calaveras faults are connected, the energy released in a simultaneous rupture could be 2.5 times greater, or a magnitude 7.3 quake.

3 of 63 comments (clear)

  1. Pffff... Magnitude 7? by Anonymous Coward · · Score: 2, Interesting

    Here by law anything you build has to withstand a 8.0 without structural damage. We don't even count the ones below 7.

    Regards from Chile.

    1. Re:Pffff... Magnitude 7? by beelsebob · · Score: 3, Interesting

      You realise that the way you (intelligently) make buildings survive large earthquakes is not to build ridiculously strong foundations (those actually make your problems worse). Instead, it's to design the building to move and sway with the earthquake. Hence why any large office building built today in the bay area is likely to be sat on big rollers, and/or have a weight system on the roof to damp the building.

  2. Re:Yes by Anonymous Coward · · Score: 2, Interesting

    Don't feel bad, it doesn't make the national news much: but from over pumping ground water here in Florida we now have sink holes everywhere (http://www.wsj.com/articles/SB10001424052702304172404575169014291111050). Saltwater is creeping much faster than anyone previously thought, and our springs are already all polluted (except literally a handful out of hundreds), and as if being polluted isn't enough, they are all *going dry* or have already dried up (http://www.tampabay.com/news/environment/water/floridas-vanishing-springs/1262988). Oh, and because we have no elevation anywhere and lax environmental laws on ag, ALL of our surface water is considered contaminated. Hiking in true wilderness here (what's left of it), is nearly as difficult as it is in SoCal desert with its near zero surface water. But, the voters here can't remember any more than what the last TV ad spot told them.