This essential reference for graduate students and researchers provides a unified treatment of earthquakes and faulting as two aspects of brittle tectonics at different timescales. The intimate connection between the two is manifested in their scaling laws and populations, which evolve from fracture growth and interactions between fractures. The connection between faults and the seismicity generated is governed by the rate and state dependent friction laws - producing distinctive seismic styles of faulting and a gamut of earthquake phenomena including aftershocks, afterslip, earthquake triggering, and slow slip events. The third edition of this classic treatise presents a wealth of new topics and new observations. These include slow earthquake phenomena; friction of phyllosilicates, and at high sliding velocities; fault structures; relative roles of strong and seismogenic versus weak and creeping faults; dynamic triggering of earthquakes; oceanic earthquakes; megathrust earthquakes in subduction zones; deep earthquakes; and new observations of earthquake precursory phenomena.

The Mechanics of Earthquakes and Faulting

The progressive fracture of Lac du Bonnet granite

The role of acoustic emission in the study of rock fracture

Deep drilling and induced seismicity experiments at several locations worldwide indicate that, in general, the brittle crust in intraplate regions is critically stressed, pore pressures are close to hydrostatic, and in situ bulk permeability is ∼10 −17 to 10 −16 m 2 . This high permeability, three or four orders of magnitude higher than that measured on core samples, appears to be maintained by critically stressed faults and greatly facilitates fluid movement through the brittle crust. We demonstrate that such high permeabilities can maintain approximately hydrostatic fluid pressures at depths comparable to the thickness of the seismogenic crust. This leads to the counterintuitive result that faulting keeps intraplate crust inherently strong by preventing pore pressures greater than hydrostatic from persisting at depth.

How faulting keeps the crust strong

Triaxial compression experiments were conducted to investigate the inelastic and failure behavior of six sandstones with porosities ranging from 15% to 35%. A broad range of effective pressures was used so that the transition in failure mode from brittle faulting to cataclastic flow could be observed. In the brittle faulting regime, shear-induced dilation initiates in the prepeak stage at a stress level C' which increases with effective mean stress. Under elevated effective pressures, a sample fails by cataclastic flow. Strain hardening and shear-enhanced compaction initiates at a stress level C* which decreases with increasing effective mean stress. The critical stresses C' and C* were marked by surges in acoustic emission. In the stress space, C* maps out an approximately elliptical yield envelope, in accordance with the critical state and cap models. Using plasticity theory, the flow rule associated with this yield envelope was used to predict porosity changes which are comparable to experimental data. In the brittle faulting regime the associated flow rule predicts dilatancy to increase with decreasing effective pressure in qualitative agreement with the experimental observations. The data were also compared with prediction of a nonassociative model on the onset of shear localization. Experimental data suggest that a quantitative measure of brittleness is provided by the grain crushing pressure (which decreases with increasing porosity and grain size). Geologic data on tectonic faulting in siliciclastic formations (of different porosity and grain size) are consistent with the laboratory observations.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/96JB03281

The transition from brittle faulting to cataclastic flow in porous sandstones: Mechanical deformation

The failure process in a brittle granite sample can be stabilized by controlling axial stress to maintain a constant rate of acoustic emission. As a result, the post-failure stress curve can be followed quasi-statically, extending to hours the fault growth process which normally would occur violently in a fraction of a second. Using a procedure originally developed to locate earthquakes, acoustic emission arrival-time data are inverted to obtain three-dimensional locations of microseisms. These locations provide a detailed view of fracture nucleation and growth.

Quasi-static fault growth and shear fracture energy in granite

The location of acoustic emission (AE) sources during deformation of rock has proven to be a useful non-destructive analytic technique. We present experimental results,based on AE observations, that show the nucleation and growth of macroscopic fault planes in granite and sandstone samples. By controlling axial stress to maintain constant AE rate rather than more conventional loading conditions such as constant strain rate or constant stress, we have been successful in retarding the failure process in triaxial experiments. As a result, the post-failure stress curve has been followed quasistatically, extending to minutes or hours the fault growth process that normally would occur violently in a fraction of a second. In addition to this novel control system, three-dimensional locations of AE events were determined by analyzing the relative arrival times of AE pulses recorded on a network of transducers attached to the sample. In this manner, as many as 40 000 AE events were located in the course of a single experiment. While the details of fault formation varied from experiment to experiment, a number of features were consistently observed. In all three granite experiments, the fault plane nucleated abruptly at a point on the sample surface soon after reaching peak stress. Prior to fault nucleation, microcrack growth was distributed evenly throughout the granite samples. From the nucleation site, the fault plane grew across the sample, accompanied by a gradual drop in axial stress. AE locations showed that the fault propagated as a fracture front (process zone) with in-plane dimension of 10-50 mm. As the fracture front passed, the AE from a given region would drop to a low level. If allowed to progress to completion, stress eventually dropped to the frictional sliding strength. Sandstone samples showed somewhat different response. In these experiments, a diffuse damage zone appeared prior to peak strength and gradually localized into an incipient fault plane. After passing through peak stress, this plane grew, as in the granite samples, to eventually bisect the sample.

Chapter 1 Observations of Quasistatic Fault Growth from Acoustic Emissions

We have conducted constant flow-rate permeability measurements on three core samples taken from the 12-km-deep well on the Kola Peninsula, USSR. All cores are from 11.4– 2.0 km depth. Pore pressures, Pp, used in these permeability measurements ranged from 112–117 MPa. Measurements were performed at effective confining pressures (Peff=pc-Pp) ranging from 10 to 400 MPa. The resulting permeabilities varied from approximately 2.5 × 10−17 m2 (25 μDa) at a Peff of 10 MPa to 1 × 10−22 m2 (0.1 nDa) at a Peff of 300 MPa. The unusual sensitivity of permeability to Peff exhibited by these samples is most likely the result of severe stress-relief crack damage that occurred during coring and sample retrieval. This strong pressure dependence underscores the importance of measuring permeability at in situ pressures to obtain meaningful bounds on in situ matrix permeabilities in this well. In an attempt to infer closure pressure of these stress-relief cracks, and provide estimates of in situ Peff, we have analyzed the pressure dependence of permeability, resistivity and crack porosity. By applying an equivalent-channel-model analysis, these data appear consistent with either an in situ pore pressure exceeding the hydrostat by as much as 100 MPa or a hydrostatic Pp and sub-lithostatic in situ vertical stress. In either case, if this closure pressure accurately reflects the in situ confining pressure, then an upper bound on in situ matrix permeabilities would be 1 × 10−20 to 2 × 10−19 m2 for the samples studied.

Laboratory‐determined permeability of cores from the Kola Superdeep Well, USSR

An Algorithm for Adaptive Assessment in Time Series Seasonal Oscillations and Its Testing Based on the Example of Variations in the CO2 Concentration in the Atmosphere

A. Sidorin

Papers

Quasi-static fault growth and shear fracture energy in granite

Chapter 1 Observations of Quasistatic Fault Growth from Acoustic Emissions

Laboratory‐determined permeability of cores from the Kola Superdeep Well, USSR

An Algorithm for Adaptive Assessment in Time Series Seasonal Oscillations and Its Testing Based on the Example of Variations in the CO2 Concentration in the Atmosphere

Regularization of the Solution of the Inverse VES Problem by the Contrast Stabilization Method: Testing the Algorithm on Model Data