Influence of in situ stress variations on acoustic emissions: A numerical study

Qi Zhao, Nicola Tisato, Giovanni Grasselli, Omid K. Mahabadi, Andrea Lisjak, Qinya Liu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

16 Citations (Scopus)

Abstract

The study of acoustic emissions (AEs) is of paramount importance to understand rock deformation processes. AE recorded during laboratory experiments mimics, in a controlled geometry and environment, natural and induced seismicity. However, these experiments are destructive, time consuming and require a significant amount of resources. Lately, significant progresses have been made in numerical simulations of rock failure processes, providing detailed insights into AE. We utilized the 2-D combined finite-discrete element method to simulate the deformation of Stanstead Granite under varying confining pressure (Pc) and demonstrated that the increase of confining pressure, Pc, (i) shifts failures from tensile towards shear dominated and (ii) enhance the macroscopic ductility. We quantitatively describe the AE activity associated with the fracturing process by assessing the spatial fractal dimension (D-value), the temporal distribution (AE rate) and the slope of the frequency-magnitude distribution (b-value). Based on the evaluation of D-value and AE rate, we defined two distinct deformation phases: Phase I and Phase II. The influence of Pc on the spatial distribution of AE varies according to the deformation phase: for increasing Pc, D-value decreases and increases during Phases I and II, respectively. In addition, b-value decreases with increasing Pc during the entire experiment. Our numerical results show for the first time that variations of D- and b-values as a function of in situ stress can be simulated using the combined finite-discrete element approach. We demonstrate that the examination of seismicity should be carried out carefully, taking into consideration the deformation phase and in situ stress conditions.

Original languageEnglish
Pages (from-to)1246-1252
Number of pages7
JournalGeophysical Journal International
Volume203
Issue number2
DOIs
Publication statusPublished - 2015
Externally publishedYes

Keywords

  • Earthquake source observations
  • Fractures and faults
  • Mechanics, theory, and modelling
  • Numerical solutions
  • Statistical seismology

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

Cite this