I’m going to be examining the mid-Lithosphere discontinuity (MLD) in the south-eastern US by using a new receiver function stacking technique. This will provide estimates of the depth of the MLD, how sharp the MLD is, and the Phi-Power. In combination with magnetotelluric data and mineral physics, this will help determine the mechanism by which, at least in the south-eastern US, the MLD is produced by and hopefully narrow the proposed mechanisms.
This week marks the halfway point of my summer research, and in celebration (and convenient timing) Liam, I, and a grad student in our lab all went and had a blast in Toronto over this last weekend. Notably, we stayed in Greektown and ate tons of Greek food, we went to the Art Gallery of Ontario (Free for those under 25 woo), and just ate lots of good food at various restaurants throughout Chinatown and Koreatown. Another highlight was bird kingdom at Niagara Falls, which was awesome. I got to feed some lorikeets as well as hold a macaw.
Here is a picture of us at a park!
We have finally gotten a receiver function from our code, albeit with a lot of help from Tolu. There are a few issues with the code we are still ironing out, as our receiver functions appear to have completely reversed polarity?? We’ve tried a few things and looked at a few parts of the code we thought were suspect, but still no luck! Anyway, the picture below this is a receiver function for one of my above average stations within the region I care about. Note that there is more than likely something subtly wrong or just plain wrong with it! The colors show positive or negative polarity. At about 4 seconds, there is a red band that is probably representative of the moho!
One paper that my research sort of piggybacks on is a Magnetotelluric study done in the South Eastern US. Once we have results, we will be comparing it to the data within this paper. This paper attempts to couple the seemingly contradictory seismic data and magnetotelluric data, as both show different depths to the lithosphere-asthenosphere boundary. However, this paper shows that when accounting for anelasticity (finite grain size), velocity as a function of temperature is slower, even reasonable grain sizes (1 mm to 1 cm). This allows them to infer cooler mantle temperatures with the seismic results, and thus make the two different results compatible. They then argue that the modern thermal lithosphere in the Southeastern US formed in association with the Central Atlantic Magmatic Province.
Right now though, we mainly care about their depths to the lithosphere-asthenosphere boundary though! Later on we will use this paper and a few others to start interpreting geology.
Right now, one of my main challenges is working with the supercomputer they have here at the University or Rochester. It’s a little annoying to work with, because you must make sure it has all the directories of functions and programs you are using, and that you tell it where to read and write different files. You also have to be careful about the amount of cores you request for whatever job you want it to carry out because that can be a little finicky as well. Figuring out that entire system was definitely a little frustrating and took a few days of playing with it.
I already posted a picture of my field area using Matlab’s mapping toolbox, but I’ll just post another one! I also have a much more interesting polar plot of where earthquakes are coming from for the best station in my area of study (US GOGA, hence GOGAlocks zone, I'm sorry). You can see the outline of some plate boundaries on it, which is so cool! I am studying the Southeastern US because there is already a large swath of data (some seismic studies and a magnetotelluric study) I can check this new method I’m using with, and also a large portion of my area has higher P-wave velocities, which helps with the method we are using (a receiver function stacking technique).
Making this polar histogram was neat, I basically just looped through all the earthquakes I was able to match with a corresponding signal-to-noise ratio event picked up by the station and created bins for each bucket of back azimuth and epicentral distance. To match the earthquake with something the station picked up, I added in the travel time for a P-wave to get to whatever station I was checking (I used TauP) to recorded earthquake start time, and if they matched within a specified tolerance, we saved the earthquake data and station data. Oh, I also added a pretty cool feature where you could easily change the resolution of this plot, which may not sound very exciting, but it is a cool feature!
This is the polar histogram!
This is the map of the stations in my region.
As part of this internship, we are given some assignments to do concurrently with our summer research. This week’s assignment was to draft and start practicing an elevator pitch of our research. Now, I spent about 15 minutes drafting an elevator pitch and spent a few tries saying it to myself. I think this assignment wasn’t too bad in terms of difficulty, because as part of the elevator pitch, you mainly explain the broader aspects of your research, rather than the gritty details. And in terms of actually saying it, I found that I was a little inconsistent in what I would be saying, because sometimes I ended up explaining things or emphasizing things a little differently. I could probably quell this if I practiced it more, but I feel like being fluid with your explanations, especially depending on the audience, is important to a good pitch.
This speech would be important for explaining to people what I do as a scientist, as there is often a gap between scientists and the everyone else. Much of science is funded by people who don’t know many of the specific details of what they are funding, so that is another area where bridging the gap and explaining the important aspects of your research without loads of jargon would be important. Thinking about this assignment, being able to explain things, and describe the main aspects of something while maintaining a simple explanation, is probably just a good skill to have in general, as it comes up in a lot of different aspects of life.
For the past several days, I've been downloading a lot of station data from IRIS, as well as data from seismic events that are within the lifespan of these stations. The data we are interested in are all from the Southeastern US in an area of about one million km2. So far, I've been mainly trying to assess the quality of the data and how good of coverage we have (in terms of back azimuth, ray parameter, and simply ground coverage). I've been looking at signal to noise ratio events picked up at stations and cross checking them with catalogued earthquakes by adding a predicted travel time. I’m starting this event processing from the ground up with some help from Tolu. He’s going to help with writing some of the more difficult code. Next week I’m going to finally start looking at waveforms and start my receiver function stacking! Below I'm attaching a very preliminary view (and pretty ugly) of our station coverage and the number of events picked up at each station with a signal to noise ratio of greater than 2.
On the skills sheet we were given at the orientation, there was one skill that really struck me. It was the "Communicate knowledgeably about your research area and discuss
concepts in a scholarly way with academic colleagues (e.g. defend an argument when asked questions, and explain your project to people outside)" skill. As I've always kinda struggled with putting my thoughts into words (especially verbally!), because often it seems like I grasp some concept or some other idea or something, but when I'm suddenly on the spot to explain what I'm thinking I just sit there like a deer in the headlights before regaining my train of thought. Hopefully, as the summer progresses, being in that situation more and more will make it easier for me to explain myself! In fact, this Monday I am giving a small presentation on the work that I've done so far to our research group.
I’ve been having a great time in Rochester so far. I’ve gone to a beach on Lake Ontario. They had some limestone boulders with some cool little nodules of calcite. I’ve met everyone our lab group and they all seem super cool and are incredibly helpful and nice! I’ve also made a friend, we played some smash bros. This last weekend, I went with a group of people to the Rochester Science Museum, where they had a pretty sweet photonics exhibit (also a small area on seismology!).
Anyway, in terms of what I want to accomplish here at my internship this summer, I have quite a few goals. I’ll be breaking them up into thirds, corresponding with each third of the summer.
First third goals:
Second third goals:
Final third goals:
Many of these goals are more of a gradual shift than a sudden one, so they might be difficult at first glance to figure out if I’ve accomplished them or not. However, I’ll be keeping a journal which if I look back on should help me figure out how much I’ve improved. Some other goals will be pretty clear once I’ve completed them.