Alexis Klimasewski is a student at University of Rochester currently completing her research at USGS - Menlo Park under Dr. Valerie Sahakian.
Ground Motion Prediction Equations (GMPEs) are empirical equations used to estimate ground shaking from an earthquake. GMPEs are essential for seismic hazard analysis so it is important to reduce uncertainties in the equations in order for predictions to be as accurate as possible. GMPEs include source, path, and site terms. This summer, I will investigate how the path terms correlate with t*, a seismic attenuation parameter which measures how much high frequency energy decays over the path. The goal is to see if incorporating a t* term into the GMPEs reduces the error.
I can't believe I've been at the USGS for over a month! I've learned so much in the past few weeks not only about the specifics of my project, but about the research process in general. My project is going very well. Of course there are some things that I think I should get done faster, but it's all part of the learning process!
My biggest challenge and success so far go hand in hand. Originally, my mentors were planning on having me run a Fortran spectral inversion code to get spectra for our data and then do an inversion to decompose each record spectra into source and site spectra. However, there was a lot of work needed to run the Fortran 77 codes on my computer which doesn't have compiliers to support Fortran 77! So we decided that I should write my own inversion code in python. It has taken longer than running someone else's code would take, but it's been a great learning experience, and I now understand the inversion process a lot better than I did before. I've finally got a prelimary version of my code running, and it's really exciting to see some output!
Whew- Writting and elevator speech is difficult! I've had a variety of people ask me about my research project this summer, from people I'm working with at the USGS to my nonscientist family and friends. I know that I can't give the same speech to my friends as I can give to a Seismologist who knows more about my project than I do! My approach to the 60 second elevator speech was to start out simple and free of jargon, and then if the person I'm talking to has questions or wants to know more, I can add on more information. Here is what I have so far:
When engineers design new buildings, they use Ground Motion Prediction Equations (GMPEs) to calculate the maxiumum ground shaking at thier site. Accurate GMPEs are important for seismic hazard analysis especially when building structures like nuclear facilities, dams, and bridges. GMPEs use data about the earthquake source, path, and building site to make shaking predictions. The goal of my project is to find out if t*, a measure of how seismic energy is attenuated over the path, correlates with the path uncertainties, and if adding a t* term to GMPEs could make predicutions more accurate.
This summer, I'm using data from the ANZA network. It's a network run by UCSD and made up of strong motion and broadband sensors. Below is a map showing the active stations! All of the data is available online. I'm going to be looking at certain events at specific stations so the data files for each day need to be cut into event files and then filtered and instrument response removed. Luckily, some of the people I'm working with are helping me with the event files! And right now I'm writing scripts to process the data!
Working on the scripts has caused me to think about one of the skills I want to work on this summer: maintaining a clear log of my research activities. I'm working on making clear comments in my code and updating a latex notes file with what I do everyday. I hope to keep all my notes organized and easy to read this summer so that when I look back a few weeks from now, it's easy to understand what I was thinking about and how my scripts run.
My first week as the USGS was amazing! I've learned so many new things about seismology, and I can't wait to see what I know by the end of the summer. There are a lot of goals I hope to accomplish this summer. Some are project specific and others relate to skills I hope to gain or improve upon!
1) understand the source physics processes, computation of t*, and path effects
2) familiarize myself with the database of seismic events I'm using this summer
3) correlate calculated t* values with GMPE path terms
4) learn about the research processes and how to formulate research questions
5) think about where I want to apply to graduate school and network with professors and researchers
6) explore the bay area and all the amazing outdoor activities here!
Hi, I'm Lexie! I'm a physics & astronomy major at the University of Rochester in Western New York. I became interested in geophysics after I took an applied geophysics in the fall, and I like that it's a way to combine my physics background with my interest in Earth Science. I haven't taken many geology courses so I'm looking forward to learning a lot more about geology and seismology this summer!
In my free time I enjoy running and hiking. I also like to read, but it's difficult to find the time during the semester so I hope to be able to read a few books this summer!