Rupture Directivity in 3D Inferred From Acoustic Emissions Events in a Mine-Scale Hydraulic Fracturing Experiment

Abstract

Rupture directivity, implying a predominant earthquake rupture propagation direction, is typically inferred upon the identification of 2D azimuthal patterns of seismic observations for weak to large earthquakes using surface-monitoring networks. However, the recent increase of 3D monitoring networks deployed in the shallow subsurface and underground laboratories toward the monitoring of microseismicity allows to extend the directivity analysis to 3D modeling, beyond the usual range of magnitudes. The high-quality full waveforms recorded for the largest, decimeter-scale acoustic emission (AE) events during a meter-scale hydraulic fracturing experiment in granites at ∼410 m depth allow us to resolve the apparent durations observed at each AE sensor to analyze 3D-directivity effects. Unilateral and (asymmetric) bilateral ruptures are then characterized by the introduction of a parameter κ, representing the angle between the directivity vector and the station vector. While the cloud of AE activity indicates the planes of the hydrofractures, the resolved directivity vectors show off-plane orientations, indicating that rupture planes of microfractures on a scale of centimeters have different geometries. Our results reveal a general alignment of the rupture directivity with the orientation of the minimum horizontal stress, implying that not only the slip direction but also the fracture growth produced by the fluid injections is controlled by the local stress conditions.

Monitoring Fracture Saturation With Internal Seismic Sources and Twin Neural Networks

“…Conversely, a moving source was used to simulate induced seismicity along a fracture plane which may occur during hydraulic fracturing or geothermal stimulation (Eaton et al., 2018; Fehler et al., 2001; Holtzman et al., 2018; Lopez‐Comino et al., 2021; Rodriguez‐Pradilla & Eaton, 2020; Rowe et al., 2002). For the case of the moving source, a dust grain was released in F2 and fell through the fracture under gravity.…”

Failure characteristics of thick hard roof stratum under hydraulic pre-splitting and its application in a coal mine, Dongsheng mining area

“…Influenced by the bedding planes, the branching hydraulic fracture would have three typical propagating behaviors of crossing, offsetting and diverting along the bedding planes, on the other hand, it is rather than controlled by bedding planes. The microfracture trajectory network is determined by μ-CT and acoustic emission (Cai et al, 2023;López-Comino et al, 2021).…”

Mining-Induced Stress Control by Advanced Hydraulic Fracking under a Thick Hard Roof for Top Coal Caving Method: A Case Study in the Shendong Mining Area, China

“…The existence of the fracture surface reduces the integrity of the hard roof. Under the action of mining stress, the weak surface around the fracture surface further develops and expands, weakening the strength of the rock and the energy release level of its fracture instability [31][32][33][34][35][36][37]. The Kelpperl well in Hugoton, Kansas, reported the first successful hydraulic fracturing in 1947.…”