Teaching Field Camp Week 1 - Norman, OK

For the next 3.5 weeks I'll be a teaching assistant for the University of Oklahoma geophysics field camp.  The point of the camp is to teach senior geophysics students how field data is collected, processed, interpreted, and applied to the problem.  This is an important capstone class because prior to now students just see geophysical data as equations, numbers, and options in software and on paper.  Now they must hike in the field, observe the geology, collect the data, and finally figure out what it all means.

Week 1 was done in Norman, OK back at the school.  Monday the students listened to lecture on geophysical methods, were introduced to the equipment, and finally were tasked with using differential GPS on the North Oval of campus.  Differential GPS is much more sophisticated than the GPS in your car.  Each unit costs ~$80,000, and one is mounted on a tripod and remains stationary throughout the day.  This station is referred to as the base, and is the most crucial link in any geophysical survey.  The second station is mounted in a backpack and is the rover.  Students walk around with the rover collecting data points, then at the end of the day the base station is used to calibrate the rover data.  We know the base station doesn't move during the day, but it appears to in the data.  This is because GPS locations are highly susceptible to changes in atmospheric humidity, irregularities in the satellite orbits, and a number of other factors.  Without going into more detail, look below at the Excel plot of the oval before and after correction.  Data points are much closer (within centimeters) after correction, and those centimeters make all the difference in some survey environments.  This plot came from one of our students reports that was turned in during the week.

The next objective was to collect a seismic line over a branch of the fault system that slipped during the earthquake sequence of November 2011 in central Oklahoma.  Setting out a seismic line is a long, arduous task, so the students needed a practice day.  We setup a short (~300m) line by the school's duck pond.  Below is a time-lapse video I took of the practice session on Tuesday.

The next two days were collecting the real data in Prague, OK with Friday reserved for processing.  Without going into great detail of how we setup and collected that data I'll say that 72 geophones were deployed every 10m.  Geophones are small seismometers effectively that only measure the motion of the ground in one direction (up and down in this case).  After processing the data we get an 'image' of what's going on underground.  Are the rocks bent (folded), broken (faulted), or otherwise layered/interesting.  We expected to cross the branch of the fault responsible for some of the stronger aftershocks.

Below are some of the processed images from a student.  This is a rough processing and can be improved with more time, but that is beyond the scope of what is expected in the field.  The faults are marked by yellow lines and indicated places were the rock has broken and slipped.  Also notice the folded layers to the left of the section.  More work and interpretation is needed to obtain further geologically useful interpretations.

Expect more posts as we re-group in Cañon City, CO and begin working on gravity, magnetics, and ground penetrating radar.

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