Cruz Chronicles V

July 26th, 2010

Great week last week. The seismo-group went on a camping trip on Monday and Tuesday. We went to the area around Big Sur to explore some California geology. It was awesome and beautiful (see pics below). The trip was also accompanied by the standard geology death march up a mountain. I seriously feared for my life...but I made it and the view was totally worth it. Some lesser individuals failed to complete the hike, but I was triumphant. On Thursday I went up to San Francisco with a couple of guys from the department to do some field work on an exposed fault surface. It was a great surface with some really defined slickenlines and striations. Nicholas and Jamie repelled down the cliff face and put tape on the striations. They then scanned the surface  with a LIDAR machine that uses the reflected light to create an image of a surface. The tape was used to get a better view of the striations in the scan. They would then use the orientation of the striations to get an idea of the stress on the fault. The trip wasn't complete until I had a go at repelling of course. It was totally easy. I mean, I was like freaking Batman going down that cliff...okay, who am I kidding? I was terrified, but it was an awesome experience. After that we loaded up everything in the Subaru and headed back. Side Note: Why does every geologist own a dilapidated Subaru? This one was smoking by the time we got to the site and an unidentified object fell off of it when the trunk was slammed. I don't know about you, but I smell a marketing deal. As far as my research goes, things are starting to come together. I received data for the Chile earthquake that occurred earlier this year and had high hopes for identifying triggered tremor in it, but alas, I haven't found any. So far I have found only one convincing event that has produced tremor. It occurred in Sumatra in 2007. I have been examining peak ground velocities for local and teleseismic events in hopes that it would yield some time between the ground velocity and triggered tremor, but there doesn't seem to be a connection in Costa Rica. The event with the highest PGV did not induce tremor. My next step is to view background ambient tremor activity to see if a relatively high level of background tremor is more conducive to triggering tremor than PGV. After that I will  compare what I have found to observations elsewhere such as Cascadia, Taiwan, and New Zealand to see if their are any similarities or differences.