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What Controls the Characteristics of Compressive Failure and Accelerated Seismic Release?

Description: 

Externally stressed brittle rocks fail once the stress is sufficiently high. This failure is typically preceded by a pronounced increase in the total energy of acoustic emission (AE) events, the so-called accelerated seismic release. Yet, other characteristics of approaching the failure point such as the presence or absence of variations in the AE size distribution and, similarly, whether the failure point can be interpreted as a critical point differs across experiments. Here, we show that large-scale stress heterogeneities induced by a notch --- which have already been shown to lead to significant aftershock activity during loading --- fundamentally change the characteristics of the failure point in triaxial compression experiments under a constant displacement rate on Westerly granite samples. Specifically, we observe accelerated seismic release without a critical point and no change in power-law exponent epsilon of the AE size distribution. This is in contrast to intact samples, which exhibit a significant decrease in epsilon before failure. Our findings imply that the presence or absence of large-scale heterogeneities play a significant role in our ability to predict compressive failure in rock.

Session: Earthquake Preparation Across Scales: Reconciling Geophysical Observations With Laboratory and Theory

Type: Oral

Date: 4/20/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Joern Davidsen

Student Presenter: No

Invited Presentation: 

Authors