Spatial and temporal characteristics of acoustic emission activity during deformation of rock samples with inhomogeneous fault under biaxial compression

The spatial and temporal distributions of acoustic emission （AE） during the deformation of samples containing an inhomogeneous fault have been studied under biaxial compression. The results show that the fault strength and the duration from loading to failure increase and the failure mode changes from abrupt instability to gradual failure with increase of lateral stress σ2. The pre-setting fault and its heterogeneity play an important role in controlling AE spatial distribution during the deformation. The basic pattern of AE spatial distribution is controlled by the pre-setting fault, especially the parts with inhomogeneous strength and the strong segment, and the localization of fracturing starts from the positions with inhomogeneous strength, With increase of σ5, the dense AE distribution area spreads from the positions with inhomogeneous strength to the whole strong segment gradually. AE temporal sequence is significantly affected by σ2. The fault shows abrupt instability in final failure, which occurs on a background of ＂enhancement-quiescence＂ in microfracturing activity at lower σ2. At higher σ5, the fault shows gradual failure, and AE occurrence rate increases continuously and AER increase exponentially before and after the failure, The effect of σ2 on b-value is also remarkable, b-value shows precursory decrease in the weakening stage when fault behavior is abrupt instability, but it shows balanced change when fault behavior is gradual failure,

Spatial and temporal characteristics of acoustic emission activity during deformation of rock samples with inhomogeneous fault under biaxial compression

The spatial and temporal distributions of acoustic emission (AE) during the deformation of samples containing an inhomogeneous fault have been studied under biaxial compression. The results show that the fault strength and the duration from loading to failure increase and the failure mode changes from abrupt instability to gradual failure with increase of lateral stress σ ₂. The pre-setting fault and its heterogeneity play an important role in controlling AE spatial distribution during the deformation. The basic pattern of AE spatial distribution is controlled by the pre-setting fault, especially the parts with inhomogeneous strength and the strong segment, and the localization of fracturing starts from the positions with inhomogeneous strength. With increase of σ ₂, the dense AE distribution area spreads from the positions with inhomogeneous strength to the whole strong segment gradually. AE temporal sequence is significantly affected by σ ₂. The fault shows abrupt instability in final failure, which occurs on a background of “enhancement-quiescence” in microfracturing activity at lower σ ₂. At higher σ ₂, the fault shows gradual failure, and AE occurrence rate increases continuously and AER increase exponentially before and after the failure. The effect of σ ₂ on b-value is also remarkable. b-value shows precursory decrease in the weakening stage when fault behavior is abrupt instability, but it shows balanced change when fault behavior is gradual failure. Foundation item: Joint Seismological Science Foundation of China (105076) and continued sub-project “Statistic Features of Aftershock Sequences and Forecast of the Large Aftershocks” (2004BA601B01-04-02) managed by the Ministry of Science and Technology of China in the 10th five-year plan.