Alexis McAdams is a student at Augustana College currently completing her research at Saint Louis University under Dr. Linda Warren.
My project this summer is looking at the stress fields within subduction zones before and after great megathrust earthquakes. To do this I will identify focal mechanisms in the outer rise and within the subducting slab from the Global CMT Catalog and use mathematical inversion techniques to get a sense of the stress fields. I'm starting my research in South America, but I hope to expand this method to other subduction zones around the world.
In this internship so far, I have been introduced to a wide variety of tools, but there is none I use so often as the Generic Mapping Tools. It's tricky maintaing a love-hate relationship with a computer program, but it's necessary when there is work to be done!
GMT, simply put, is a suite of programs used to generate maps. Given a light understanding of computer programming languages and constant access to the online GMT Cookbook, anything is possible. Here's a sample of some of the maps and plots I've created this past week alone:
The top graph is a map of the area around the Chimbote earthquake. The quake's rupture zone is shown in red, the blue lines are a very rough estimate of which events are downdip and associated with the earthquake, and the colored events are the ones that are chosen for processing. The middle graph is a distance-along-trench vs. time plot, which shows the focal mechanisms' orientations to a "straightened-out" trench, and the bottom plot is a cumulative count of events. The blue line represents the occurrence of the Chimbote event. The significance of these plots will be explored in a future update.
Okay, maybe these plots aren't the most complicated or impressive thing to be seen in these blogs, but they represent the culmination hours of completing tutorials, fiddling, tweaking and poking the program to see the display I want. I feel like whenever you learn a new skill, there's a tipping point. It's when you feel you're not working but instead you're playing! Manipulating the code and debugging the syntax isn't as much of a chore anymore.
As for the relation to my project, GMT gives the most freedom to customize your maps EXACTLY the way you want them! I used to complain about GMT's need for specificity, but it's a strength instead of a weakness. I came in with a preference for ArcGIS, but it's clear that when it comes to modeling seismic data and focal mechanisms, GMT is the way to go.
GMT also gives so much flexibility with automating the process. The series of graphs you see above represents the Chimbote megathrust earthquake, but with quick command in Unix I can generate the same graphs for any and all large earthquakes in South America! Knowing the power of Unix and Awk is important too, but the heavy lifting is done within GMT.
Looking back on weeks 1 and 2 of my internship, I can see already that I've come a long way. The first few days of my internship were primarily made up of tutorials on Unix and GMT, and I'm becoming more and more familiar with these tools every time I generate a stick plot or a basemap. GMT especially looked like a foreign language, but with a lot of help from the tutorials I'm making progress. I worked on making some example maps and using the 'awk' command to sort the data for week two, and I think I've got the hang of that too. I'm really glad I took those Intro to Programming courses at Augustana when I had the chance.
During this internship I didn't expect to meet a lot of people. My assignment sounded like I would be in a computer lab for most of the day (which has turned out to be true) but I've met some really great scientists here! My fellow interns Elena and Isabella are fun coworkers, and I've met Dr. Emry and Dr. Hardebecke, two seismologists that are doing research somewhat related to mine. Erica Emry is actually an alumnus from Augustana, so we've been in contact before (she's actually the one who encouraged me to take those programming courses!). Yesterday Dr. Hardebecke called in by way of Google Hangout, and we had a great discussion on my research project and on her work at the USGS.
I really can't help but feel so privileged to be working with such a great team and support network. Linda is, of course, the best resource for when any of us have questions, but talking with the grad students Ying and Louisa gives good insight into what grad school work is like. Already more than two weeks have passed, and though it has been a blur of reading, discussing and scripting, I feel as though it is already going way too fast!
Some of my goals for this summer included meeting new people, becoming familiar with the tools and having a good relationship with my mentor, and I'm making great progress on all of those! For this first third of the internship I want to become a master of GMT, I want to have a firm understanding of what work I'm doing here, and I want to have a good working relationship with Linda and my fellow interns. For the second third I want to become a master of inversion (through the program called SATSI) and efficiently produce results related to this project. Finally, by the end of this internship I want to have an awesome poster that I can take to Augustana and to AGU and present confidently. I don't think these goals are too far out of my reach, and I look forward to see how I'll adapt to the challenges that this project has to offer!
Orientation week here at New Mexico Tech is coming to a close, and it's an understatement to say that I've learned a lot. We've covered local geology, data processing methods, UNIX commands, and earthquake basics. Together we've explored an observatory, analyzed seismograms, tangled with MatLab and climbed down a mountain! But the most interesting part of the week, for me, was learning about how this summer's project is like a test run for the future.
Throughout the week we've heard from professors, peers, industry employees and current grad students about some of the paths we can take in our future. Master's and Ph.D degree programs were covered in detail, and we got an outline of what life can be like working for a company in Houston. And all of it has been especially valuable to me. I think a lot about what I want to do in the future, and it seems like every day I have a new preference for what I want to be when I grow up. IRIS gives us the opportunity to have candid conversations with these folks, and get a taste of what each field is really like.
This summer's project will be a lot of things, including an introduction into academic research and learning how to set my own schedule for a long-term project. It will be a challenge, of course, but with the help of my mentor and the support of my fellow interns I can't wait to see what I'll be bringing to AGU this December!