Idealized Body Modeling of a Methane Hydrate, Methane Chimney and Basement High System Based off Gravity Observations in the Central Aleutian Basin

In this study, I modeled a known methane hydrate deposit and methane chimney in the Central Aleutian Basin which has an associated basaltic basement high that protrudes 3000 meters into the overlying sedimentary strata. The net gravity anomaly in area is negative due to the methane hydrate and free methane gas displacing seawater in the sediment pore space. Modeling was achieved by approximating individual layers with an infinite vertical cylinder at the top of the layer and subtracting from it an infinite vertical cylinder at the base to produce the total effect on the gravitational acceleration from each layer. Idealized source gravity equations were applied to each of these vertical cylinders in MATLAB and summed to produce a gravity signal over the area. A free-air gravity anomaly map was created in a geophysical software program and a profile was taken over the surface of the study area. This profile was plotted vs. distance and a linear trend was fit to the data, then subtracted from each gravity observation point to yield the residual gravity. The observed residual gravity data was plotted against the MATLAB generated theoretical gravity for the infinite vertical cylinders. While the approximations were not perfect, it was successful in producing a signal that was only a few milligals off from the observed data. With some refinement to the code this approach to modeling is a cheap and effective method to reinforce seismic or magnetic data to produce a complete picture of the subsurface.No embarg