Khalia Payton is a student at Fort Valley State University currently completing her research at United States Geological Survey – Pasadena Field Office under Dr. Elizabeth Cochran .
The goal of this project is to effectively simulate tremor along the San Andreas Fault. Tectonic tremor is a weak vibration of the ground initially discovered in subduction zones but has subsequently been observed along transform faults like the San Andreas. Our primary area of focus is in a region known as Parkfield which is mid-way on a fault segment between locked segment to the south and a creeping segment to the north where two tectonic plates are continuously moving without major earthquakes. Due to Parkfield's rather unusual history of successive earthquakes at regular intervals, deep borehole seismometers were installed along this region and spectral signatures of motion unlike typical earthquakes were discovered. We now call this phenomenon tremor. In order to better understand what tremor actually is and whether or not it is indicative of potential earthquakes we will utilize the RSQSim to study a complex fault system. My role is to examine a suite of parameters to understand the fault properties that allow tremor to occur. I will determine the required conditions to match previous tremor observations. This cutting-edge work will yield results of which have the potential to help make communities safer from earthquake hazards.
Ok so here are a few different plots I've come up with. Top left (Time vs. Magnitude), top right (Magnitude vs. Frequency), bottom left( Magnitude vs. Events per year), and bottom right (Basicallly time between events). Here I have 8 graphs, the first four are results from my hard-stop model of a section with no tremor patches, a b-value of 0.012, and sheer stress of 1.5. The last four are also from a hard- stop case with a b-value of 0.012 and sheer stress of 6.5. I'm currently in the process of contrasting my models with no tremor patches to see how they change when a matrix of parameters are varied. Once I've come up with a conclusion on what's happening here I will then narrow down the matrix to a subset because these runs are time consuming. After all of that we add the tremor patches back into the models into a variety of ways and try to summarize those results. It's ALOT of trial and error but hey that's the name of the game.
This week I ran into a few different snags with my runs. At first I thought I was a genius beacuse I was able to come up with about 6 fault plots in one day. I later found out that I'm only 80% genius because I was deleting the runs way before they could properly write out necessary information for an accurate fault plot and over all statisic plot for the given data. So I had to delete all output files and start over. I now know that each run takes a few hours, not seconds. Now I'm in the process of contrasting my models without tremor to my models with tremor, hopefully we'll see some sort of difference.The programming is going fine I would say, navigating around with unix gets easier everyday. My living situation is beautiful I'm not sure if I mentioned it before but my apartment has the most beatiful courtyard with several flowers, palm trees and pool. It's like an oasis when I go back home.
On Tuesday 6/17 my mentor and I took a trip to UC Riverside . There was a group meeting that included a number of people working with the earthquake simulator, RSQSim. It gave me a chance to meet some of the other people working with the earthquake simulator and learn about their projects. I spoke with with Jim, Keith, and Kayla specifically about my work this summer. On Wednesday I wasn't feeling too well so I was able to work for home on tweaking my shear and normal stress parameters for the simulation. I think I'm getting the hang of creating the scripts. I'm also in the process of applying for the AWG scholarship.
This summer I will utilize the RSQSim which is used to study the effects of both small- and large-scale fault system geometry on recurrence statistics in a idealized but complex fault system. The team I work with here at the USGS and UC-Riverside is the first to simulate tremor so we utilize some seismic data results from David Shelly and Jeanne Hardebeck in order to narrow down the options for parameters we should use. In addition we use results of perameter tests examining slow slip earthquakes with the simulator from Harmony Colella. We use R to interpret our data.
So my first week has generally consisted of a lot of head scratching hair pulling as I try to teach myself Unix and R. The tutorials are helpful but oh so tedious to work through. Other than tutorials I've been reading tons of literature related to my project in order to gain some much need background knowledge on fault tremor. My mentor is super helpful and my office is deathly quiet.. it's a little scary. I'm excited to get started on my project next week, I think that will be a lot more interesting than tutorials.
Trying to get this coding down