Reply to I am a earthquake seismologist. AMA. 5th anniversary of Louisa Quake

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[quote=Anonymous][quote=Anonymous][quote=Anonymous][quote=Anonymous]Ok OP. Here's a question.

In 2007(or 8) to took the Ca bar at the Ontario
Convention center 40 miles east of LA. In the middle of the exam there was a quake. The epicenter was Ontario. Sounded like a bomb going off. Shook the chandeliers. No broken windows. Over in a flash. The panic was the problem. But it wasn't that disturbing.

My exwife was sitting for the bar at the San Diego convention center. Yet there it was felt as a much more significant earth movement. And there was damage. Windows and wall cracks but damage.

Why?  SD is 100 miles at least from Ontario [/quote]

The difference could be site effects.  Ontario is inland; the San Diego convention center is on mud, which will amplify shaking.  I assume the earthquake in question was 2008-07-29 18:42:15 UTC Chino Hills CA earthquake (11:42 AM PDT).  This was much closer to Ontario.  I wonder if I have the wrong date, though.  From 2007-2009 there were only three M>4.5 earthquakes in So. CA, and only the Chino Hills earthquake occurred around when the bar was taken.

But, site effects and amplification is real.  In 1985, a magnitude 8.0 earthquake hit the west coast of mexico.  Damage was moderate in that region, but in mexico city, 300 east of the epicenter, the damage was severe.  The lakebed that is mexico city shook like jello.  That is a technical term.  More accurately, the sediments amplified the energy and generated surface waves which were of large amplitude.  Site effects.[/quote]

That's the quake. [/quote]

And that explains why La Jolla barely budged.

It was explosively loud. [/quote]

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