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Center for Astrophysics Research and Technologies Seminar Series Information

 

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Imaging Subsurface Rock using Gravity Measurements

Thursday September 7, 2017
2:00 pm


 Presenter:  Megan Lewis (UNM)
 Series:  Center for Astrophysics Research and Technologies Seminar Series
 Abstract:  Understanding changes in subsurface density structure could be a useful tool in predicting volcanic eruptions. Preceding an eruption the motion of magma can both fill and create voids changing the underground distribution of mass. We created several static models of the density of a mesa in Los Alamos, NM to test the effectiveness of different experimental setups and modeling techniques, so that these techniques can later be applied to data taken over days and give rise to a method of eruption prediction. We acquired two datasets: the muon cosmic ray flux within a tunnel beneath the mesa, as well as data from a gravity survey of the mesa and tunnel. This talk will focus on the gravity data and the two modeling techniques implemented to fit that data: forward and inverse. Through forward modeling we found that our two-pronged data set (gravity above and below our target rock) helped combat the non-uniqueness problem that gravity data is prey to. The model ruled out certain density configurations, such as a uniform density model, that mesa data alone would not have been able to rule out. Overall however, the forward model was extremely constraining, which lead to an unreasonably large tilt in the layers of our best-fit model. Our inverse model converged on a physically reasonable density structure that matched both our observations and those of other studies in the area, even without good a priori information. The success of the inverse model can be further improved upon by performing a joint-inversion of the gravity and muon data.
 Host:  Gregory Taylor
 Location:  Room 190, Physics & Astronomy

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