So on Monday, we were able to finally meet Oscar for the first time. He was in Germany on vacation until then. Jon and I were very excited to meet him and get started with actual work. The first day with Oscar was spent getting a tour of where we will be working and him explaining the basics of the science equipment that we are working with. He discussed with us the physics behind the gravimeter and the GNSS receiever. In essence, a gravimeter works because there is a zero length spring that holds up a mass on a beam. A zero length spring is special in that if the length of the spring is truly zero, then the force exerted is zero. This yields a linear relationship between force and linear length where the line passes through the origin. When the mass is unlocked, it starts dropping down slightly on the beam. By adjusting the dial, we are moving a micrometer that adjusts the height of the mass. We are aiming to orient the mass to directly horizontal to the beam. Because we can measure the force on the spring, we can calculate the relative differences in gravity in mGal. All gravimeters are unique in that they are calibrated to separate values and behave uniquely.
I thoroughly enjoyed talking about the physics behind the geophysics equipment because that was the first time that someone has gone to lengths to fully break down the geology equipment. It was familiar to how I was taught throughout college during my physics major.
The next day, Oscar taught us how to use QGIS to make basic maps using topographical and bathymetric data. We were then able to overlay the information that we received from previous gravity fieldwork onto the map that we created. This was useful in seeing what the region we explored looked like in comparison to the topography of the rest of Costa Rica.
I am excited to get started with our research project. Jon and I will be creating a program to perform Earth tide corrections and topographic corrections of gravity data we collect in the field. The current way to calculate gravity corrections assumes that we are on a infinitely long stone plate of homogenous density when we are at higher elevations. This is obviously a strange assumption to make, so we will be creating a program that allows us to factor in the topography around us instead to perform gravity corrections.