Seismic moment tensor and b value variations over successive seismic cycles in laboratory stick‐slip experiments

Abstract

The formation of fault damage due to slip under high normal stresses can rarely be monitored under in situ conditions. To advance our understanding of microfracture processes, we investigated stick-slip events on Westerly granite samples containing the following: (1) a planar saw cut fault and (2) a fault developed from a fresh fracture surface. We examined temporal changes of seismic moment tensors and b values of acoustic emission (AE) events. During experiment on the saw cut surface, small AEs exhibiting non-double-couple components were observed continuously and strong AEs displaying double-couple components were visible only when approaching the slip onsets. Sliding on naturally fractured surfaces showed, in addition to double-couple components, significant volumetric contributions, especially during the interslip periods and immediately after stick-slip events indicating substantial shear-enhanced compaction within a relatively broad damage zone. The obtained results shed light on how differences in fault structure control the kinematics of microseismicity during different periods of the seismic cycle.

Analogue earthquakes and seismic cycles: experimental modelling across timescales

“…2d), respectively. Zang et al (1998), Kwiatek et al (2014), and Stierle et al (2016) used acoustic emissions to further constrain the source of laboratory earthquakes in loaded rock specimen by means of the seismic moment tensor and b value. Acoustic sensors usually have high sampling rates (kHz) and work for accelerations up to several g. A thorough review of the large body of literature on acoustic emission as a seismological tool in laboratory earthquake studies is given by Lei and Ma (2014).…”

HybridMT: A MATLAB/Shell Environment Package for Seismic Moment Tensor Inversion and Refinement

“…The resolved MTs are typically decomposed into volumetric and deviatoric components, using various decomposition schemes allowing for an understanding of the detailed physical kinematic source processes, regardless of the type of seismicity and event magnitude. The MT inversion has been applied to resolve the displacements in the source for large and small natural earthquakes (Vavryčuk et al, 2008;Scognamiglio et al, 2010;, induced microseismicity (Ross et al, 1996;Panza and Saraò, 2000;Šílený and Milev, 2006;Cesca et al, 2013;Guilhem et al, 2014;Johnson, 2014a,b), as well as for acoustic emission activity measured in situ (Manthei et al, 2001;Collins et al, 2002) or in laboratory experiments on rocks samples (Sellers et al, 2003;Thompson et al, 2009;Graham et al, 2010;Charalampidou et al, 2011;Kwiatek, Goebel, and Dresen, 2014). The analysis of seismic MTs sheds light on numerous issues of earthquake physics, such as rupture dynamics (McGarr and Fletcher, 2003;McGarr et al, 2010), fault complexity (McLaskey and Glaser, 2011;McGarr, 2012), the role of pore pressure in seismogenic processes (Fischer and Guest, 2011), and damage-related radiation of seismic energy (Ben-Zion and Ampuero, 2009;Castro and Ben-Zion, 2013, among others).…”

“…The increasing amount of seismic data recorded worldwide, especially in the field of induced seismicity (Ellsworth, 2013) and the huge amount of data recorded during laboratory experiments (Charalampidou et al, 2011;Davi et al, 2013;Kwiatek, Goebel, and Dresen, 2014) impose the development of an efficient, full-MT-inversion software that will be capable of automatically performing the inversion of hundreds or more seismic events, enabling statistical analysis of the derived non-DC properties. In this study, we present a software package for MT inversion and posterior MT refinement designed for MAT-LAB (see Data and Resources) and shell environments.…”

Seismic moment tensors of acoustic emissions recorded during laboratory rock deformation experiments: sensitivity to attenuation and anisotropy

“…The processing of AE data is similar to that of earthquake observations. Aside from accurate location of AE hypocentres it is possible to determine fault-plane solutions (Zang et al 2000;Charalampidou et al 2015), to construct and investigate the magnitude-frequency relation and to evaluate the b-value (Zang et al 1998), or to perform spatial and temporal analysis of waveforms (Kwiatek et al 2014a). The source processes of AEs can also be studied by moment tensors widely used in earthquake seismology.…”