A lot of people wonder what exactly it is I do each day, and I figure a post detailing just that would constitute a perfect opening post for my blog.
First, in general, geophysics is concerned with remotely imaging the interior of the earth. There are a number of different methods of approaching this, differing by what exactly you are looking for. A gravimetric survey measures changes in the earth’s gravitational field and can indicate changes in the density of the earth’s crust. Seismic surveys record the propagation of sound waves in the crust and provide indications of changes in stratigraphy and potentially any buried structures.
The survey I am currently taking part in is induced polarization (IP). Simply, a voltage is induced in the ground, and the decay is measured at several intervals from the source. IP’s strength is the ability to detect dispersed sources of conductive material, as gold often is. The nature of the decay provides information about the quantity and quality of the material.
An IP survey is organized around an array of electrodes which are moved down a series of lines, forming a grid. The array can vary in configuration, but will include at least one electrode for current, and any number of electrodes to measure the changes due to the current. We are using nine electrodes (forming eight dipoles) in this survey; as the dipole moves from the source of current, the depth which is measured increases as well.
The configuration of our crew then is one person on transmitter, increasing or decreasing the current as needed and recording any field observations. One person moves the current electrode (metal rods hammered into the ground and connected to the transmitter), three people move the pots (special electrodes used to perform the actual measurements, and one person on receiver, performing the actual measurements.
My work station each day is slightly more scenic than your average cubicle
I am on transmitter, which means that I spend most days in the exact same spot. Somehow you would expect this to become monotonous, but I don’t find it overly so. Time passes surprisingly quickly and there is actually a lot more going on when running the transmitter than it sounds from my description.
Suffice to say, I do enjoy this work. I love being outside all day and I have been very fortunate so far in the things I have been able to see since starting this work. I definitely consider myself lucky.
