The Seismic Cycle

The study of the seismic cycle has many applications, from the study of faulting to the estimation of seismic hazards. It must be considered at different timescales, from that of an earthquake, the co-seismic phase (a few seconds), the post seismic phase (from months to dozens of years) and the inter-seismic phase (from dozens to hundreds of years), up to cumulative deformations due to several seismic cycles (from a few thousand to hundreds of thousands of years). The Seismic Cycle uses many different tools to approach its subject matter, from short-term geodesic, such as GPS and InSAR, and seismological observations to long-term tectonic, geomorphological, morphotectonic observations, including those related to paleoseismology. Various modeling tools such as analog experiences, experimental approaches and mechanical modeling are also examined. Different tectonic contexts are considered when engaging with the seismic cycle, from continental strike-slip faults to subduction zones such as the Chilean, Mexican and Ecuadorian zones. The interactions between the seismic cycle and magmatism in rifts and interactions with erosion in mountain chains are also discussed.

The study of the seismic cycle has many applications, from the study of faulting to the estimation of seismic hazards. It must be considered at different timescales, from that of an earthquake, the co-seismic phase (a few seconds), the post seismic phase (from months to dozens of years) and the inter-seismic phase (from dozens to hundreds of years), up to cumulative deformations due to several seismic cycles (from a few thousand to hundreds of thousands of years). The Seismic Cycle uses many different tools to approach its subject matter, from short-term geodesic, such as GPS and InSAR, and seismological observations to long-term tectonic, geomorphological, morphotectonic observations, including those related to paleoseismology. Various modeling tools such as analog experiences, experimental approaches and mechanical modeling are also examined. Different tectonic contexts are considered when engaging with the seismic cycle, from continental strike-slip faults to subduction zones such as the Chilean, Mexican and Ecuadorian zones. The interactions between the seismic cycle and magmatism in rifts and interactions with erosion in mountain chains are also discussed.

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.

Useful attributes capture and quantify key components of the seismic amplitude and texture for subsequent integration with well log, microseismic, and production data through either interactive visualization or machine learning. Although both approaches can accelerate and facilitate the interpretation process, they can by no means replace the interpreter. Interpreter “grayware” includes the incorporation and validation of depositional, diagenetic, and tectonic deformation models, the integration of rock physics systematics, and the recognition of unanticipated opportunities and hazards. This book is written to accompany and complement the 2018 SEG Distinguished Instructor Short Course that provides a rapid overview of how 3D seismic attributes provide a framework for data integration over the life of the oil and gas field. Key concepts are illustrated by example, showing modern workflows based on interactive interpretation and display as well as those aided by machine learning.

Earthquakes along large crustal scale faults are a huge hazard threatening large populations. The behavior of such faults is influenced by the fault damage zone that surrounds the fault core. Fracture damage in such fault damage zones influences each stage of the seismic cycle. The damage zone influences rupture mechanics, behaves as a fluid conduit to release pressurized fluids at depth or to give access to reactive fluids to alter the fault core, and facilitates strain during post- and interseismic periods. Also, it acts as an energy sink for earthquake energy. Here, laboratory experiments were performed to come to a better understanding of how this fracture damage is formed during coseismic transient loading, what this fracture damage can tell us about the earthquake rupture conditions along large faults, and how fracture damage is annihilated over time.First, coseismic damage generation, and specifically the formation of pulverized fault damage zone rock, is reviewed. The potential of these pulverized rocks as a coseismic marker for rupture mechanisms is discussed. Although these rocks are promising in that aspect, several open questions remain.One of these open questions is if the transient loading conditions needed for pulverization can be reduced by progressively damaging during many seismic events. The successive high strain rate loadings performed on quartz monzonites using a split Hopkinson pressure bar reveal that indeed the pulverization strain rate threshold is reduced by at least 50%.Another open question is why pulverized rocks are almost always observed in crystalline lithologies and not in more porous rock, even when crystalline and porous rocks are juxtaposed by a fault. To study this observation, high strain rate experiments were performed on porous Rothbach sandstone. The results show that pervasive pulverization below the grain scale, such as observed in crystalline rock, does not occur in the sandstone samples for the explored strain rate range (60-150 s-1). Damage is mainly occurs at a scale superior to that of the scale of the grains, with intragranular deformation occurring only in weaker regions where compaction bands are formed. The competition between inter- and intragranular damage during dynamic loading is explained with the geometric parameters of the rock in combination with two classic micromechanical models: the Hertzian contact model and the pore-emanated crack model. In conclusion, the observed microstructures can form in both quasi-static and dynamic loading regimes. Therefore caution is advised when interpreting the mechanism responsible for near-fault damage in sedimentary rock near the surface. Moreover, the results suggest that different responses of different lithologies to transient loading are responsible for sub-surface damage zone asymmetry.Finally, post-seismic annihilation of coseismic damage by calcite assisted fracture sealing has been studied in experiments, so that the coupling between strengthening and permeability of the fracture network could be studied. A sample-scale fracture network was introduced in quartz monzonite samples, followed exposure to upper crustal conditions and percolation of a fluid saturated with calcite for several months. A large recovery of up to 50% of the initial P-wave velocity drop has been observed after the sealing experiment. In contrast, the permeability remained more or less constant for the duration of the experiment. This lack of coupling between strengthening and permeability in the first stages of sealing is explained by X-ray computed micro tomography. Incipient sealing in the fracture spaces occurs downstream of flow barriers, thus in regions that do not affect the main fluid flow pathways. The decoupling of strength recovery and permeability suggests that shallow fault damage zones can remain fluid conduits for years after a seismic event, leading to significant transformations of the core and the damage zone of faults with time.

-- Science

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.

I mages of surface displacements in response to tectonic forces can provide independent, spatially dense observations that assist in understanding sub-surface processes. When considered independently or augmented with more traditional observations of active tectonics such as seismicity and ground mapping, these measurements provide constraints o n spatially and temporally variable fault behavior across the seismic cycle. Models of fault behavior inferred from these observations in turn allow us to address topics in geologic hazards assessment, the long- a nd short - term character of strain in defor ming regions, and the interactions between faults throughout the crust. In this dissertation, I use remotely sensed observations of ground displacements from interferometric synthetic aperture radar (InSAR) t o approach several problems related to earthquak e and aseismic fault slip. I establish image p rocessing and inverse methods for better detailing subsurface fault slip and apply these to the 2 010 - 2011 Canterbury, New Zealand sequence. Then, I focus on the active tectonics of the Zagros Mountains in south ern Iran. There, I show through orogen -wide InSAR time series analysis that active strain is accommodated across the width of the mountain belt. I also use a combination of InSAR, local seismicity, and structural modeling to demonstrate that strain is v ert ically partitioned within the Zagros fold-and - thrust belt, with earthquakes controlling deformation in the underlying basement while the overlying sedimentary section shortens in t ransient, earthquake- triggered aseismic slip events. In certain examples, th ese aseismic slip events directly contribute to the growth of fault -bend folds. I use these inferences to explore a p reviously noted discrepancy between observed shortening and that which is expected from k nown earthquakes. I show that the earthquakes and short - term aseismic slip cannot account f or this discrepancy, and that additional deformation mechanisms must be active.

Earthquake and Volcano Deformation is the first textbook to present the mechanical models of earthquake and volcanic processes, emphasizing earth-surface deformations that can be compared with observations from Global Positioning System (GPS) receivers, Interferometric Radar (InSAR), and borehole strain- and tiltmeters. Paul Segall provides the physical and mathematical fundamentals for the models used to interpret deformation measurements near active faults and volcanic centers. Segall highlights analytical methods of continuum mechanics applied to problems of active crustal deformation. Topics include elastic dislocation theory in homogeneous and layered half-spaces, crack models of faults and planar intrusions, elastic fields due to pressurized spherical and ellipsoidal magma chambers, time-dependent deformation resulting from faulting in an elastic layer overlying a viscoelastic half-space and related earthquake cycle models, poroelastic effects due to faulting and magma chamber inflation in a fluid-saturated crust, and the effects of gravity on deformation. He also explains changes in the gravitational field due to faulting and magmatic intrusion, effects of irregular surface topography and earth curvature, and modern concepts in rate- and state-dependent fault friction. This textbook presents sample calculations and compares model predictions against field data from seismic and volcanic settings from around the world. Earthquake and Volcano Deformation requires working knowledge of stress and strain, and advanced calculus. It is appropriate for advanced undergraduates and graduate students in geophysics, geology, and engineering. Professors: A supplementary Instructor's Manual is available for this book. It is restricted to teachers using the text in courses. For information on how to obtain a copy, refer to: http://press.princeton.edu/class_use/solutions.html