Monday, March 9, 2009

Famous Earthquakes: Miramichi 1982


This earthquake happened when I was very freshly into work. It was a surprising earthquake, since it happened in the middle of nowhere, and it had the same magnitude as the Cornwall earthquake, which I was very 'into' at the time. I just thought of it now because of a recent earthquake there.

This earthquake had a special meaning to us in the old Geotechnical Department, since we were rich enough, and crazy enough to send a drill crew to measure horizontal stresses. It was thought to be great fun to drill right on top of the epicentre!

I never went, but I got all the reports. The most fun was that micro-earthquakes were happening right under their feet as they drilled. These would be like shotgun blasts, and would sometimes throw the drill around. I thought that if I had an accelerometer there, it would measure 2 g! That's when I started to realize that there was no physical connection between peak acceleration, and damage potential. The smaller you got, it was a higher frequency, and a very high acceleration. Peak ground veolocity, however, was constrained, since it was an integral, and had a relation to induced ground strain.

That earthquake totally turned me away from PGA, and I proceeded with my eternal conflict, with the rest of the seismic crowd.

No comments: