Sensitivity Analysis and Testing of Joint Inversion with Gravity and Cosmic Ray Muon Data for Prediction of Shallow Subsurface Density Variations

Session: Advances in Upper Crustal Geophysical Characterization [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Estimating subsurface density is important for imaging and monitoring many geologic structures, such as volcanic edifices, reservoirs and aquifers. Muon tomography has been used in recent years to complement traditional gravity measurements in joint inversion techniques as an effective method for probing shallow subsurface density variations. Areas of crossing muon trajectories provide a higher resolution alternative to, e.g. seismic constraints, whilst the spatial sensitivity of gravity measurements provide a way of imaging structures on larger spatial scales. When used together, they form a unique dataset that has proven to be quite powerful. In previously published work, we calibrate a joint inversion of gravity and muon data for density estimation by applying this method to image a regionally extensive, high-density layer beneath the town of Los Alamos, New Mexico, which sits atop a mesa formed by the Quaternary ash-flow tuffs on the Pajarito Plateau flanking the nearby Jemez volcano. While the study targets a static density structure, its approach may be extended to time-dependent density variations such as those associated with fluid flow. We aim to build upon this by developing a forward model for predicting time-dependent density changes and anlaysing the subsequent measurement sensitivities that would be required in the gravity and muon data in order to observe them. For this we have chosen Redondo Peak---a resurgent dome located in the Valles Caldera nearby Los Alamos, New Mexico---as our target survey region. The network of back roads and logging trails that surround it, together with its high prominence with respect to the nearby topography, make it an excellent choice for an initial case study. We aim to use these factors to optimize the theoretical field deployment of muon detectors and gravimeters to the area and model the likely inversion results so that, in future endeavours, we might best be able to observe subsurface fluid dynamics beneath the peak.

Presenting Author: Katherine S. B. Cosburn

Authors