Earthquake Measures

[BMart006]

How does one determine peak ground accelerations recorded from previous earthquakes (e.g. the Ridgecrest quakes from a few weeks ago)? I'd like to be able to compare actual criteria seen to what structures were designed to (or should have been). I wasn't able to find much more than reported magnitude from USGS, but it'd be great to get PGA for that week or a time history of one of the more major shakes.

 

[WARose]

Correlating Richter magnitude to PGA is (of course) hard to do because it is very site dependent.

However, one equation I have seen a few times is:

log[sub]10[/sub](PGA)= -2.1+0.81(M)-0.027(M[sup]2[/sup])

where M=Earthquake Magnitude (Richter scale)

 

[TLHS]

If you go into the USGS record you can see a PGA contour.

https://earthquake.usgs.gov/earthquakes/eventpage/ci38457511/executive

Go to 'interactive map,' then on the layers thing in the top right you can select PGV and PGA contours if you'd like. You can get similar information with the shakemap tool off the same initial URL.

They probably have tabulated values somewhere as well.

You can use the same tool to search for earthquakes meeting various criteria.

 

[GC_Hopi]

The time history is at the bottom of the USGS page that TLHS posted. Here is the link to the Ridgecrest earthquake. Be sure that you determine the impact of SSI at your site or state your assumption regarding SSI. Improper assumptions/no regard for SSI would make your results erroneous, kind of like assuming 50 ksi yield for A36 steel.