Emily Sexton is a student at Washington University in St. Louis currently completing her research at National Security Technologies (NSTec) under Dr. Cathy Snelson.
The objective of the Source Physics Experiment is to better identify low yield explosions from a regional distance using seismology among other diagnostics. This experiment will analyze how the compression and shear waves propagate through the earth to allow for a better idea of the source. Phase I is currently underway and consists of 7 shots. They discovered that the geology of the site, consisting of faults and a high water table in the granite posed difficulties in the experiment. For Phase II, they are looking to move to a new location with simpler geology. I will be assisting with a vibra-seis survey to gain a better idea of the geology at the new location so that they can make appropriate models for Phase II.
It's not perfect yet, but yes I have a CMP stack.
These past two weeks I have been processing the data from the vibroseis survey. After having installed the geometry to the data, I was having difficulties doing a CMP sort. All of my files were coming up as one, very long file instead of seperate files for each location. After much help from Cathy and Veraun as well as many emails with Dan Herald from Parallel Geoscience, we finally figured out that our difficult problem had a pretty simple solution in that some of the parameters were incorrect. After that I have been playing around with filters, an automatic gain control, tail mutes, and normal moveout velocities. I have found so far that the tail mutes are not adding much to the data. I am also working on creating an appropriate velocity function. I finally came up with a CMP stack, but am still working to come up with the best version of it. I have also completed my AGU abstract this week and am waiting for it to return from review before I can submit it for good.
Today is my last day at NSTec and I cannot believe the summer is already over! I have learned so much and have had the opportunity to be a part of some amazing field work. I am so thankful to everyone who made this such a beneficial experience for me and can't wait for AGU! I'm shipping up to Boston!
Last week we were able to complete the vibroseis survey. After having to postpone the survey two weeks ago, we discovered we had collected the data in SEG-2 format instead of SEG-Y. We had to start from the beginning last week, recording the data as SEG-Y files instead. After another popped air cushion, a leak in the vibe, and having to jumpstart the car to get AC, we were able to complete the survey. We used a 7000 lb peak force mini-vibe that was trailer mounted. The sweep frequency was 20-180 Hz and there were 4 sweeps per source point, each lasting 8 seconds. We acquired P-waves only. The line was 144 geophones long, but after the first 36 stations, we moved the first 24 geophones to the end of the line for a total of 168 geophone locations.
After the survey was complete, i uploaded the data into SPW3, was able to merge the files into one dataset with help from Cathy and applied the geometry. my understanding of SPW3 is still limited, but I am slowly moving in the right direction.
Last weekend I was able to escape the Las Vegas heat for a couple days and went to Jackson Hole, WY to visit some family. We did some awesome hiking, biking, and boating and it was great to spend some more time with my family.
As this week comes to an end, I find it hard to believe that the summer is already 2/3 of the way over. These past two weeks I have been working with sample data in SPW3 to figure out how to convert files and apply the geometry. Although my progress has been slow, and I have been finding difficulties with the program, I am moving forward and beginning to understand the system a bit more every day.
Last week, I went up to the test site with another man who works at NSTec, Ryan, and we hiked to some seismic stations to switch out their memory cards. Although it was extremely hot for our first hike, it cooled down significantly as we moved up into the mesa for some great hiking, beatiful views, and some wildlife siting.
We began the vibroseis survey this week, although we have had some setbacks. We laid out the line with 144 geophones and started with the mini-vibe 12 stations off the back of the first geophone. Each shot was 5 meters apart, inbetween the geophones. However, the cushion on the minivibe popped twice, and there was only one spare. After replacing the cushion the first time, we had no spares left for the second time it popped, so we had to call it a day. We should have more cushions in soon and will be going out at the beginning of next week to complete the survey. Although we didn't have all the data, it gave me a couple of files to play around with on SPW and start making SPS files to apply the geometry.
Las Vegas continues to surprise me. I had been told that forest fires were not a big danger out here because there is not much vegetation, yet there is currently a huge wildfire burning up 25,500 acres on Mt. Charleston, just outside of the city. It makes for some spectacular yet terrifying views but also smoky air when you walk out of the house. In addition, it poured today on my way to work, in the middle of the desert. I guess you never know what's going to happen next in Vegas!
The last week of June has been my first full week in the office at NSTec. Things have been moving slowly but surely in trying to figure out computer programs. After some difficulties in trying to get matlab and SPW installed, and immense amount of help from Bob, I now have three computer screens and two computers, one that has matlab and unix and the other that has SPW. I have been going through matlab and unix tutorials trying to learn more about the programs. Additionally, I have done some reading on SPW but have found that the interface between SPW and the version that we have here, SPW3 is quite different. Cathy gave me the manual for SPW3 and I have been trying to work my way through it but so far I am still having troubles figuring out the program.
The vibroseis survey is planned for next tuesday and wednesday, July 9-10, but hopefully we will be able to complete it in one day. As we are unable to access one of the sites, we will only be conducting the survey at the other site. We will be conducting the survey with some people from UNLV, and we will be using their equipment. Last week we went over to the university to take a look at the cables and the mini-vibe truck. I have completed surveys before at school using a betsy gun and at orientation using a weight drop, but I have never done a vibroseis before so I am very excited to see how the truck works.
Although safe from snakes inside the building, I have learned that you have to be on the lookout for cockroaches around here as they make frequent appearances. We also caught a lizard the other day that was trying to escape the heat and set him loose outside. My mom came into town this weekend so my family made a trip up to Bryce Canyon. It was a great opportunity to get some hiking in, although we did come across a rattlesnake on the trail who let us know that he didnt want us to be there. Despite the minor set back, the hike through the famous canyon was quite spectacular.
These past two weeks have been extremely busy working at the test site. Between waking up at 4 am and the 2.5 hour commute to where we are working, I have had little time for anything besides working, eating, and sleeping. Despite being exhausting, I have found the work at the site, SPE Climax, extremely interesting. Last week I was able to gather a lot more information about the experiment through reading and talking to people. Cathy and I sat down and she explained the entire experiment to me and how I will contribute to it. I was also able to sit down with a geologist at the site to learn about the geology of the area. Basically, for Phase I, the granite with multpile faults and an abormally high water table caused many problems with the experiment. For Phase II, I will help to conduct a vibra-seis to determine the subsurface geology of the new test site. Although the vibra-seis has been delayed due to challenges in choosing a location, it is looking like I might be conducting two surveys at seperate sites to better determine which site to choose. In this case, I will be helping to collect the data and therefore one of the first ones to take a look at the raw data. I will be using SPW to analyze the data. The survey itself should only take about 2 days.
While at the test site, I have been outside for most of the time, which is the environment that I love to work in. Last week, I went around to the seismic stations at the site with two other guys as they determined the problems in the stations and worked to fix them. It gave me some great first hand experience working with the equipment as well as hiking and offroading on a four-wheeler. This week, Brandon and a guy he's working with at Sandia, Kyle, came to the test site to install infrasound stations. I did not have much previous knowledge of infrasound, so this week was extremely beneficial in learning how the stations contribute to the experimenet as a whole. I also helped install some more seismic stations in circular arrays.
Although it has been long hours, I have thoroughly enjoyed the time I have spent at the test site thus far. Most people refer to the the test site as a waste land but I think it is actually quite beautiful with its vast views and mountains. I have even been able to see remnants of old gold mines and wild horses. Although I have not seen any yet, I have been told that there is turqouise where the igneous rock meets the limestone up in the mountains. It has been extremely hectic during the week so I have taken some time on the weekends to relax, play some golf with my dad and do some great hiking in red rock canyon.
As things are quickly underway at NSTec, I am learning that what I thought was a long time for my internship is going to go by very quickly. With almost two weeks down and seven left to go, I have a lot of goals to complete by the end of the summer.
1. Have the bulk of my AGU poster complete by the time I leave
2. Get a lot of field experience. (I should not have a problem with this one!)
3. I hope to not get stressed out when I don’t understand something.
4. Explore Red Rock Canyon
5. Learn how to cook without burning the house down
6. Improve on my knowledge of different computer programs, such as SPW
7. Spend some quality time with my Grandma and Dad
8. Not get too badly sunburned
9. Have a better idea of my future plans for after undergrad
As I start my second week at NSTec, I find it difficult to believe that I have only been in Las Vegas for a week. After completing all of my training at the beginning of last week, I accompanied Veraun up to NNSS to observe a project that they were working on. In this project, the group was injecting noble gases, Xenon and Argon, into the ground to better understand how the gases travel through the ground. Although the experiment was not directly in my field, after asking many questions, I gained a basic understanding of what was occurring at the site. It was extremely interesting being submerged in real field work and seeing firsthand how things work. If there's one thing I've learned it's that field work requires a lot of patience. After delays due to the generator not working, the injection took 10 hours to complete. Although it was a long time to wait, the weather turned out to be very nice and I was able to get to know some of the other people. We then spent the night at Mercury because we didn’t end with the injection until late at night. I have also been busy reading about the geology of the site to gain a better background knowledge of the work we will be completing. Today is the 1st day of 3 weeks of field work on SPE, so I will definitely be getting plenty of field work this summer.
Outside of work, I have been keeping busy with family. I'm living with my grandma and her adorable puppy, Lucy, this summer and have been spending lots of time with her as well as my aunt and uncle and cousins. My dad will also be here for the next couple of weeks.
As orientation week is almost over, I am getting very excited to start working on monday. I find it interesting that we are staying in Socorro, NM because Socorro means help or aid in spanish, and if there's anything we've received this week its been help. And a lot of food. The most beneficial part for me has been the practice with Matlab, Unix, and GMT. This week has also shown me the great support system that IRIS offers to interns, allowing us to communicate with each other throughout the summer whenever we are confused. I have also taken the opportunity to get accustomed to the hot, dry weather before I go to Las Vegas this summer and have been working on my dirt tan.
Till next time.
Peace. Love. and Trees.