Published by the American Geophysical Union as part of the Maurice Ewing Series, Volume 4. From May 12 to May 16, 1980, eighty-eight scientists from eleven countries attended a Symposium on Earthquake Prediction at Mohonk Mountain House, Mohonk, New York. This was the third in a biennial series honoring Maurice Ewing, first director of Lamont-Doherty Geological Observatory. The Symposium was one of several events that were held in 1980 to celebrate the 100th anniversary of the Graduate School of Arts and Sciences at Columbia University. The two earlier Ewing Symposia, on island arcs and deep sea drilling, reflected Ewing's lifelong interest in the structure and evolution of the ocean floor. In the Third Ewing Symposium we touch another area—earthquake seismology—that played an important part in Ewing's career. Work on surface waves and long-period seismology under Ewing's direction during the 1950's and 1960's, along with his exploration of the earth beneath the oceans, provided much of the framework on which current ideas on earthquake generation and plate tectonics are based.

In the last decade of the 20th century, there has been great progress in the physics of earthquake generation; that is, the introduction of laboratory-based fault constitutive laws as a basic equation governing earthquake rupture, quantitative description of tectonic loading driven by plate motion, and a microscopic approach to study fault zone processes. The fault constitutive law plays the role of an interface between microscopic processes in fault zones and macroscopic processes of a fault system, and the plate motion connects diverse crustal activities with mantle dynamics. An ambitious challenge for us is to develop realistic computer simulation models for the complete earthquake process on the basis of microphysics in fault zones and macro-dynamics in the crust-mantle system. Recent advances in high performance computer technology and numerical simulation methodology are bringing this vision within reach. The book consists of two parts and presents a cross-section of cutting-edge research in the field of computational earthquake physics. Part I includes works on microphysics of rupture and fault constitutive laws, and dynamic rupture, wave propagation and strong ground motion. Part II covers earthquake cycles, crustal deformation, plate dynamics, and seismicity change and its physical interpretation. Topics in Part II range from the 3-D simulations of earthquake generation cycles and interseismic crustal deformation associated with plate subduction to the development of new methods for analyzing geophysical and geodetical data and new simulation algorithms for large amplitude folding and mantle convection with viscoelastic/brittle lithosphere, as well as a theoretical study of accelerated seismic release on heterogeneous faults, simulation of long-range automaton models of earthquakes, and various approaches to earthquake predicition based on underlying physical and/or statistical models for seismicity change.

Fluid-rock interactions have long been recognized as crucial drivers in earthquakes and slow slip events. In the context of induced seismicity, the injection of high-pressure fluid underground during wastewater disposal, hydrothermal energy production or hydraulic fracturing operations have triggered earthquakes in geologically stable regions that previously had minimal detected seismicity. Many hypotheses about how these earthquakes were triggered have been proposed, including pore pressure diffusion, long-range poroelastic stressing, and fault loading and reactivation by aseismic slip. The injection of fluid into a fault not only alters pore pressure and triggers slip, but also changes properties of the fault zone that in turn impact fluid flow, pressure diffusion, and fault slip behavior. The most relevant properties here are porosity and permeability. Many experiments, in both the laboratory and in situ, show that dilatancy (the expansion of pores and the fluids within them) accompanies shear deformation of fault zone rocks. In the absence of fluid flow (i.e., undrained conditions), dilatancy reduces pore pressure, increasing the effective normal stress and strengthening the fault. Porosity changes also alter permeability. As pores dilate and more porous space becomes connected, permeability is enhanced. This facilitates fluid flow and enables pore pressure perturbations to reach greater distances along the fault in a shorter period of time. It is certainly evident that the evolution of porosity and permeability, while complex, can fundamentally influence fluid flow and fault slip behavior, and therefore needs to be taken into account in fault models with hydromechanical coupling. In the context of tectonic earthquakes and episodic slow slip events, rock porosity and permeability changes over the earthquake cycle also dictate the nature of the slip that occurs. During the coseismic period, rapid slip cracks open pore space and causes dilatancy, which strengthens the fault and prevents it from slipping further. Permeability is also enhanced as the porosity increases, which may act to weaken further parts of the fault as the fluid migrates. Over the interseismic period, the fault heals from mechanical compaction, and is also gradually sealed by ductile compaction mechanisms such as pressure solution, which involves dissolving minerals at stressed contact points and depositing them in pores. This closing of pores and permeability reduction increases the pore fluid pressure, which will weaken the fault and cause slip again, and this cycle continues. Understanding how the interplay of dilatancy, compaction produces and arrests fault slip is important in characterizing where and how slow slip events occur, and when that might give rise to earthquakes. In this thesis, I investigate the fault response to pore pressure changes coupled to porosity and permeability evolution using 2D numerical simulations of a strike-slip fault governed by rate-and-state friction. The first part of the thesis investigates aseismic slip triggered by fluid injection in the context of induced seismicity. The goal of this study is to evaluate the controlling factors for the initiation and propagation of aseismic slip, and to make testable predictions of potentially observable quantities like the migration rate of the aseismic slip front, as a function of prestress, permeability, injection rate, and frictional parameters. We showcase comparisons for different prestress conditions, permeability values, injection rates, initial state variables, and frictional properties, evaluating their relative importance in determining slip behavior. We also highlight how neglecting porosity and permeability evolution can drastically change the nature of fault slip, and connect our simulations with a limited set of observations to emphasize the important role of hydromechanical coupling in characterizing fault response to fluid injection. Furthermore, we calibrated our model and fit the results to InSAR observations of aseismic slip in the Delaware Basin that is caused by the injection of oilfield water. This shows the applicability of the numerical model to field data and potentially the monitoring of induced seismicity. The second part of the thesis focuses on earthquake cycle simulations in the tectonic context. We explore pore pressure, porosity and permeability evolution over the earthquake cycle and how they impact the occurrences of slow slip events and earthquake ruptures. The first model builds on the study of injection-induced aseismic slip and adds viscous compaction to porosity evolution to study slow slip events. We show that the slow slip events are driven by the interaction between pore compaction which raises fluid pressure and weakens the fault, as well as pore dilation which decreases fluid pressure and limits the slip instability. Cyclic behaviors of these events can range from long-term events lasting from a few months to years to very rapid short-term events lasting for only a few days. The accumulated slip for each event is on the order of centimeters, and the stress drop is generally less than 10 MPa. The second model ignores porosity evolution and only considers permeability evolution that is coupled to effective normal stress, fault slip and a characteristic healing time over which the fault heals interseismically. We demonstrate the viability of fault valving in an earthquake sequence model that accounts for permeability evolution and fault zone fluid transport. Predicted changes in fault strength from cyclic variations in pore pressure are substantial ($\sim$10-20 MPa) and perhaps even larger than those from changes in friction coefficient. We also show how fluids facilitate the propagation of aseismic slip fronts and transmission of pore pressure changes at relatively fast rates. The modeling framework we introduce here can be applied to a wide range of problems, including tectonic earthquake sequences, slow slip and creep transients, earthquake swarms, and induced seismicity.

Fluids in the Earth's Crust explores the generation and migration of fluids in the crust and their influence on the structure. This book also deals with the collection and concentration of these fluids into commercially possible reservoirs or their fossil trace formed as ore bodies. Chapter one of this book discusses fluid motion and geochemical and tectonic processes. It then defines fluid, discusses the rocks in the surface environment, and provides evidence of the changes of a rock's position and the motion of fluids. This book also explores the chemistry of natural fluids, including the composition of ocean water; pore water and deep-drill fluids; metamorphic fluids; fluid inclusions; and magmatic fluids. Volatile species in minerals, such as water, carbon and carbon dioxide, chlorine, fluorine, sulfur, oxygen, and nitrogen and other inert gases, are presented in this book. Other chapters in this book cover the solubility of minerals and physical chemistry of their solutions; the metamorphic reactions and processes; buffer systems; rock deformation; crustal conditions; dewatering of crust; and diapirism. The last part of the book discusses fluids, tectonics, and chemical transport. This book will be of great value to mining and oil geologists, as well as to pure geologists.

Our understanding of earthquakes and faulting processes has developed significantly since publication of the successful first edition of this book in 1990. This revised edition, first published in 2002, was therefore thoroughly up-dated whilst maintaining and developing the two major themes of the first edition. The first of these themes is the connection between fault and earthquake mechanics, including fault scaling laws, the nature of fault populations, and how these result from the processes of fault growth and interaction. The second major theme is the central role of the rate-state friction laws in earthquake mechanics, which provide a unifying framework within which a wide range of faulting phenomena can be interpreted. With the inclusion of two chapters explaining brittle fracture and rock friction from first principles, this book is written at a level which will appeal to graduate students and research scientists in the fields of seismology, physics, geology, geodesy and rock mechanics.

Understanding Faults: Detecting, Dating, and Modeling offers a single resource for analyzing faults for a variety of applications, from hazard detection and earthquake processes, to geophysical exploration. The book presents the latest research, including fault dating using new mineral growth, fault reactivation, and fault modeling, and also helps bridge the gap between geologists and geophysicists working across fault-related disciplines. Using diagrams, formulae, and worldwide case studies to illustrate concepts, the book provides geoscientists and industry experts in oil and gas with a valuable reference for detecting, modeling, analyzing and dating faults. - Presents cutting-edge information relating to fault analysis, including mechanical, geometrical and numerical models, theory and methodologies - Includes calculations of fault sealing capabilities - Describes how faults are detected, what fault models predict, and techniques for dating fault movement - Utilizes worldwide case studies throughout the book to concretely illustrate key concepts