Friday, January 17, 2014

Happy 20th Birthday Northridge Earthquake


An M6.7 blind thrust earthquake right under an urban centre.  This is almost a 'saturation' earthquake in terms of PGV, the worst being the M7 Kobe earthquake.  An M7 thrust ruptures the whole crust, although there is a very small 'hammer zone' at the top, it is the worst shaking you can expect on moderately firm ground, or a layer of soft soil.  The larger earthquakes activate large soil basins, and make them the worst PGV, especially those standing waves.

I am proud to say that nothing was learned in this earthquake, except something about really bad steel joints.  It was on an unknown fault, so they went on a frenzy finding more faults.  The next big earthquake will still be on an unknown fault!

Almost any place in the world could be hit by this sort of earthquake.  That is why we live with a true 'minimum hazard'.  The only thing you can do is to be sure you can take a hit.

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