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Results
ABSTRACT We study the problem of the moment tensor inversion of a double-couple microseismic source from observed S/P amplitude ratios. The emphasis of this work is on uncertainty quantification that includes the effect of the uncertain event location. We use a Bayesian approach to quantify the uncertainty of the fault plane solution. The posterior distribution is effectively calculated by sampling from the posterior distribution of the event location, and performing a moment-tensor inversion using individual samples. The uncertainty in the reconstructed moment tensor depends on the receiver geometry, signal noise, and the true moment tensor. After a suitable transformation of the input data, the problem can be reduced to a classical least-squares estimation problem. Presentation Date: Tuesday, October 18, 2016 Start Time: 8:50:00 AM Location: 144/145 Presentation Type: ORAL
Using copropagating P-waves to extract nonlinear elastic characteristics of rock
Feng, Xuan (Jilin University) | Liu, Cai (Jilin University) | Fehler, Michael (Massachusetts Institute of Technology) | Brown, Stephen (Massachusetts Institute of Technology) | Burns, Daniel (Massachusetts Institute of Technology) | Tencate, James (Los Alamos National Laboratory) | Szabo, Thomas L. (Boston University)
ABSTRACT We propose a dynamic method to detect the nonlinear elastic hysteretic characteristics of rock. The method is easily implemented and requires injecting two co-propagating longitudinal waves into the rock and receiving them. One of the waves is a high energy low-frequency longitudinal wave that loads strain in the rock, and a other is the low energy high-frequency longitudinal wave that is used to detect the elastic modulus variation induced by the loaded strain. Analyzing the relationship between elastic modulus variation and the loaded strain, we quantify the nonlinear elastic characteristics of the rock, including the nonlinear coefficients and slow dynamics, and evaluate hysteretic loops. A typical sandstone experiment is displayed and results show the nonlinear coefficients are independent of input amplitude of the longitudinal waves, but slow dynamics are a function of the input amplitude of the low fequency longitudinal waves. Presentation Date: Thursday, October 20, 2016 Start Time: 10:35:00 AM Location: 150 Presentation Type: ORAL
ABSTRACT We model P and S-wave mean square envelopes in 2-D random media by solving the Radiative Transfer Theory (RTT) equation using a Monte Carlo (MC) particle based approach. Using a source frequency in the order of kilohertz, typical of cross-well seismic sources, we find good agreement with finite differences in both effective and forward scattering regimes. We show that MC simulations is a much faster way of modeling scattering attenuation, compared to finite differences, and therefore is a suitable tool to characterize the medium heterogeneities associated, for example, with highly fracture reservoirs. Presentation Date: Wednesday, October 19, 2016 Start Time: 8:25:00 AM Location: 161 Presentation Type: ORAL