Fluid pressure driven by tectonic loading at marine convergent margins mediates the effective normal stress at subduction fault, affecting a wide range of processes including the aseismic-seismic transition, accretionary wedge morphology, coseismic rupture propagation, etc. The mechanical coupling between sediment frame deformation and fluid flow controls the generation of overpressure and thus is affected by both the frame rheologic behavior and sample permeability. In this study, we simulate the mechanical coupling using lab-constrained rheologic and hydraulic properties, and successfully reproduce the experimental results of both the synthetic samples and natural sediments recovered from the Nankai subduction zone. We establish a method to extract frame viscous behavior from the porosity data of a saturated uniaxial-strain creep test. A poro-visco-elastic FEM model is then presented to properly simulate the viscous behavior and evaluate the role of frame viscous strain in mitigating overpressure. Finally, with the consideration of sediment viscous deformation, we upscale the model to margin scale to infer pore pressure evolution within the Nankai accretionary prism over a geological timescale.

Frictional measurements were made on natural fault gouge at seismic slip rates using a high-speed rotary-shear apparatus to study effects of slip velocity, acceleration, displacement, normal stress, and water content. Thermal-, mechanical-, and fluid-flow-coupled FEM models and microstructure observations were implemented to analyze experimental results. Slightly sheared starting material (Unit 1) and a strongly sheared and foliated gouge (Unit 2) are produced when frictional heating is insignificant and the coefficient of sliding friction is 0.4 to 0.6. A random fabric gouge with rounded prophyroclasts (Unit 3) and an extremely-fine, microfoliated layer (Unit 4) develop when significant frictional heating occurs at greater velocity and normal stress, and the coefficient of sliding friction drops to approximately 0.2. The frictional behavior at coseismic slip can be explained by thermal pressurization and a temperature-dependent constitutive relation, in which the friction coefficient is proportional to 1/T and increases with temperature (temperature-strengthening) at low temperature conditions and decreases with temperature (temperature-weakening) at higher temperature conditions. The friction coefficient, normal stress, pore pressure, and temperature within the gouge layer vary with position (radius) and time, and they depend largely on the frictional heating rate. The critical displacement for dynamic weakening is approximately 10 m or less, and can be understood as the displacement required to form a localized slip zone and achieve a steady-state temperature condition. The temporal and spatial evolution of hydromechanical properties of recovered from the Nankai Trough (IODP NanTroSEIZE Stage 1 Expeditions) have been investigated along different stress paths, which simulate the natural conditions of loading during sedimentation, underthrusting, underplating, overthrusting, and exhumation in subduction systems. Porosity evolution is relatively independent of stress path, and the sediment porosity decreases as the yield surface expands. In contrast, permeability evolution depends on the stress path and the consolidation state, e.g., permeability reduction by shear-enhanced compaction occurs at a greater rate under triaxialcompression relative to uniaxial-strain and isotropic loading. In addition, experimental yielding of sediment is well described by Cam-Clay model of soil mechanics, which is useful to better estimate the in-situ stress, consolidation state, and strength of sediment in nature.

Accretionary prisms in convergent margins are natural laboratories for exploring initial orogenic processes and mountain building episodes. They are also an important component of continental growth both vertically and laterally. Accretionary prisms are seismically highly active and their internal deformation via megathrusting and out-of-sequence faulting are a big concern for earthquake and tsunami damage in many coastal cities around the Pacific Rim. The geometries and structures of modern accretionary prisms have been well imaged seismically and through deep drilling projects of the Ocean Drilling Program (and recently IODP) during the last 15 years. Better understanding of the spatial distribution and temporal progression of accretionary prism deformation, structural and hydrologic evolution of the décollement zone (tectonic interface between the subducting slab and the upper plate), chemical gradients and fluid flow paths within accretionary prisms, contrasting stratigraphic and deformational framework along-strike in accretionary prisms, and the distribution and ecosystems of biological communities in accretionary prism settings is most important in interpreting the evolution of ancient complex sedimentary terrains and orogenic belts in terms of subduction-related processes. This book is a collection of interdisciplinary papers documenting the geological, geophysical, geochemical, and paleontological features of modern accretionay prisms and trenches in the northwestern Pacific Ocean, based on many submersible dive cruises, ODP drilling projects, and geophysical surveys during the last 10 years. It also includes several papers presenting the results of systematic integrated studies of recent to ancient on-land accretionary prisms in comparison to modern analogues. The individual chapters are data and image rich, providing a major resource of information and knowledge from these critical components of convergent margins for researchers, faculty members, and graduate and undergraduate students. As such, the book will be a major and unique contribution in the broad fields of global tectonics, geodynamics, marine geology and geophysics, and structural geology and sedimentology.

Tectonic geomorphology is the study of the interplay between tectonic and surface processes that shape the landscape in regions of active deformation and at time scales ranging from days to millions of years. Over the past decade, recent advances in the quantification of both rates and the physical basis of tectonic and surface processes have underpinned an explosion of new research in the field of tectonic geomorphology. Modern tectonic geomorphology is an exceptionally integrative field that utilizes techniques and data derived from studies of geomorphology, seismology, geochronology, structure, geodesy, stratigraphy, meteorology and Quaternary science. While integrating new insights and highlighting controversies from the ten years of research since the 1st edition, this 2nd edition of Tectonic Geomorphology reviews the fundamentals of the subject, including the nature of faulting and folding, the creation and use of geomorphic markers for tracing deformation, chronological techniques that are used to date events and quantify rates, geodetic techniques for defining recent deformation, and paleoseismologic approaches to calibrate past deformation. Overall, this book focuses on the current understanding of the dynamic interplay between surface processes and active tectonics. As it ranges from the timescales of individual earthquakes to the growth and decay of mountain belts, this book provides a timely synthesis of modern research for upper-level undergraduate and graduate earth science students and for practicing geologists. Additional resources for this book can be found at: www.wiley.com/go/burbank/geomorphology.