Saturday, February 27, 2010

Chile Earthquake PGV

I'm assuming they have good seismic monitoring in Chile. Hopefully, a lot of accelerometers in buildings and various types of soil conditions. This could be the best 'learning' earthquake since Taiwan! So far, the pictures have shown the collapse of some pretty shitty buildings and bridges. I'm surprised they exist, since most poor construction on swamps has already been cleared out by previous earthquakes.

There will be a lot of landslides, and soil deformation along the waterfront. You can't do much about that. From the map, it looks like the coast got hit with a PGV of about 50 cm/s. This is the 'light damage' limit for reasonable housing on firm ground, according to Taiwan results. Santiago looks like 30 cm/s.

Anything on soggy ground (and they have been getting a lot of El Nino rain) will amplify the ground motions by 10 to 100 times. The airport at Santiago looks like it got hit with more than 100 cm/s, but those things are always built on swamps! In historic times, when a village was totally destroyed by an earthquake, it was customary to move the entire town to firmer ground, so these people knew what to do!

I'm hoping for some good PGV measurements here! I'm sure this is also a test for some modern construction, such as base isolation, and energy absorbing elements. This earthquake could finally bury PGA in the big pit where it belongs!

No comments: