It is hoped that the study of tremor will shed light on the inner workings of fault movement and earthquakes, but the nature of tremor remains elusive. This fact is compounded by the different behavior of documented tremor throughout the world. My research at UCSC under the direction of Dr. Susan Schwartz involves the study of a specific type of tremor known as "triggered tremor". Triggered tremor refers to tremor that is thought to have been triggered in some way by powerful seismic waves that usually occur in the form of the body waves of local or teleseismic events. Strong evidence of triggered tremor has been observed in areas such as Cascadia, Japan , and along the San Andreas, but has yet to be found in the area of my study, Costa Rica. The absence or presence of tremor in Costa Rica is important not only in the study of the mechanisms of triggered tremor, but contributes to the knowledge of slow slip and tremor as whole by focusing on a subduction zone that differs from the other well documented areas of the world.
It is definitely hard to believe that this experience is over. I came into the internship full of hope and excitement and that is exactly how I am leaving it. I have learned an immense amount this summer. Not just about geology, but perhaps more importantly , about myself. I feel that I have grown both intellectually and personally. The area that this is expressed most in is independence. Being on my own this summer really helped me to value my independence and to respect the implications that it has. I experienced this the most not in living alone or being away from my friends, but through my work in the the lab. It did not take me long to realize that graduate level work is mostly self directed. You have to be truly motivated and love what you are doing or it is far too easy to fall behind. This was one of the most important hurdles that I had to overcome. My project was a little open-ended so it did not make things much easier, but I feel like I was able to overcome these obstacles and achieve something, even if they were negative results. That was another important lesson. In science, it is often a humbling reminder to find out that you don't always see what you expected to see, but that is what makes it interesting.The work was hard and the learning curve steep, but I definitely had a great time. I will never forget my experience this past summer and the friends I made during it. I am ever thankful for this opportunity that was given to me and am eagerly looking forward to what the future holds.
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.
It's been a while since my last post, but there is not much to report. I have been carefully working back through all of the data I have been processing in my continuing effort to identify triggered tremor in Costa Rica. After hours of staring at seismograms and reading papers I have come to one grand conclusion: triggered tremor is freaking hard to find....at least in Costa Rica. After checking both large teleseismic events and some moderately sized local events, I have found nothing very convincing. This doesn't necessarily mean it's not there, but I just haven't seen it yet. If I end up not finding any, it will mean interesting things for the relationship of triggered tremor to its regionally setting. I just need to find out what those interesting things are. I will also be examining the stress levels that the surface waves of the potential triggering quakes are exerting in order to define a threshold that tremor is or isn't occuring at. I can then compare this to other areas where triggered tremor has been observed
Pretty productive week. With a lot of help from Rob and a UNIX reference book that weighs about as much as I do, I was actually able to start writing some simple scripts. While it is only a meager victory, I am still proud. The scripts are limited, but the have helped me to speed up my tremor analysis quite a bit. Speaking of tremor, I totally think I found some triggered tremor in some of my data. I still have to check a bunch of other stations for the event, but it looks promising. After filtering, I had some nice packets of high frequency that corresponded with the peaks of the Love and Rayleigh waves. This is a good indication of tremor, but like I said, I still have to find it on all of the other stations. That will be the goal for this upcoming week, as well as continuing to work on scripting.
The personal side of things has been going well also. Last weekend I took a trip up to San Fransisco to see the city. To my surprise, it was freaking cold there. I swear that the wind did not stop blowing the whole time I was there. My roommate and I took a ferry out to Alcatraz and roamed around a bit. It was pretty cool (pun intended). Other than that I have just been relaxing while not working in the lab. I've been catching up on some recreational reading and enjoying the World Cup. What a crazy week for the US. I was totally pumped for the Ghana game yesterday, but we all know how that turned out. I think all of that vuvuzela noise was distracting our players. Is it just me, or does it sound like and entire bee hive is attacking the camera-man every time you turn on a game? Oh well, our team had a great run. Now I just need to find another team to root for. Any suggestions....other than Uruguay?
To begin, I think I will expound on some of my goals for the internship. In addition to the goals that Dr. Schwartz has established for me, I also have a few personal goals. Most importantly, I hope that this internship will help me definitively decide if geophysics, and more specifically research, is right for me. It is something that I have been on the fence about for a long time now. I hope to return with a better understanding of the field in general as well as with knowledge of the tools used in it. I especially would like to become more fluent in the computing aspect, as this is what seems to be limiting me most at the moment. On that note, I suppose you would like to know what I have been up to lately. Research wise, I have been doing a lot of work in sac. It was a little daunting at first, but I am starting to get the hang of it. I'm also getting more familiar with UNIX, which is always a good thing. After finding some large earthquakes to look at in the area near Costa Rica, I have been converting the station data for the days on which they occur from miniSEED to sac. Then I have been doing things such as merging,cutting,and rotating the files in order to prepare them to look for tremor. This has taken the bulk of my time largely since I lack the scripting knowledge to do this all in one fell swoop. I will be working to educate myself in this area though. I'm eager to get all of the data presentable so that I can actually start doing some science. Today I was able to look at some seismograms and use taup to calculate arrival times for various wave phases. That was pretty interesting. Once I get more data in, I will be able to examine the love waves for associated tremor.
I haven't spent all of my time in the lab though. In addition to my rigorous work schedule, I have also found time to explore Santa Cruz. I have spent a few leisurely afternoons on the beach and roaming around downtown. I also took a ride out to an old Spanish mission called San Juan Bautista. If you're a film buff, you'd recognize this as the spot where the bell tower scenes of Alfred Hitchcock's Vertigo were filmed. I recommend it if you haven't seen it. It's a classic. I'll put some pictures up later. I've also watched a fair share of the World Cup. If you haven't been watching it, you should be.
Until next time,
After meeting with Dr. Schwartz yesterday, I have a much better perspective on my research goals for the summer. To begin, I am to to become familiar with the general concepts of slow slip and tremor and how they relate to my research area in Costa Rica. I have been given various papers to look over to do that and my talk with Dr. Schwartz helped clarify much of the theory involved. I am also to gain basic familiarity with the computing software that I will be using which includes: SAC, Matlab, and possibly Antelope. In addition to this, I must be able to visually identify tremor and differentiate it form seismic noise and regular earthquakes. I found out yesterday that for now my research will be focused on triggered tremor in Costa Rica. I will be cataloging the large earthquakes that have happened in the last few years and searching for the subsequent data recorded from the stations in Cost Rica. Once I have the data, I will examine it for tremor in order to determine if it was caused or influenced in someway by the large earthquakes.
During the second third of my internship I will continue to read papers and gain familiarity with the computing software. I will also start to discuss my work at the sismology group lunches. For the final third of the internship, I will hopefully have some tangible results work with. This will help me to prepare an outline that will serve as the foundation for a later abstract. I have also been told that there could be a chance for me to go to Costa Rica to service some of the instruments. That would be awesome (fingers crossed).
Until next time,
So far the internship has been going great. The only hard thing is remembering everyone's name. Everyone has been really cool and helpful. I do seem to be losing some hair though. Must be something in the water. I've been learning a lot and am looking forward to a great summer at my host institution