Brantut, N;
(2018)
Time-resolved tomography using acoustic emissions in the laboratory, and application to sandstone compaction.
Geophysical Journal International
, 213
(3)
pp. 2177-2192.
10.1093/gji/ggy068.
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Abstract
Acoustic emission (AE) and active ultrasonic wave velocity monitoring are often performed during laboratory rock deformation experiments, but are typically processed separately to yield homogenized wave velocity measurements and approximate source locations. Here, I present a numerical method and its implementation in a free software to perform a joint inversion of AE locations together with the 3-D, anisotropic P-wave structure of laboratory samples. The data used are the P-wave first arrivals obtained from AEs and active ultrasonic measurements. The model parameters are the source locations and the P-wave velocity and anisotropy parameter (assuming transverse isotropy) at discrete points in the material. The forward problem is solved using the fast marching method, and the inverse problem is solved by the quasi-Newton method. The algorithms are implemented within an integrated free software package called FaATSO (Fast Marching Acoustic Emission Tomography using Standard Optimisation). The code is employed to study the formation of compaction bands in a porous sandstone. During deformation, a front of AEs progresses from one end of the sample, associated with the formation of a sequence of horizontal compaction bands. Behind the active front, only sparse AEs are observed, but the tomography reveals that the P-wave velocity has dropped by up to 15 per cent, with an increase in anisotropy of up to 20 per cent. Compaction bands in sandstones are therefore shown to produce sharp changes in seismic properties. This result highlights the potential of the methodology to image temporal variations of elastic properties in complex geomaterials, including the dramatic, localized changes associated with microcracking and damage generation.
| Type: | Article |
|---|---|
| Title: | Time-resolved tomography using acoustic emissions in the laboratory, and application to sandstone compaction |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/gji/ggy068 |
| Publisher version: | https://doi.org/10.1093/gji/ggy068 |
| Language: | English |
| Additional information: | This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ |
| Keywords: | Science & Technology, Physical Sciences, Geochemistry & Geophysics, Fracture and flow, Microstructure, Tomography, Acoustic properties, Seismic tomography, Dynamics and mechanics of faulting, HAMILTON-JACOBI EQUATIONS, FRACTURING PROCESS, POROUS SANDSTONES, ROCK, GRANITE, VELOCITY, CREEP, DEFORMATION, TRANSDUCERS, ALGORITHMS |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10052128 |
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