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Author: Caroline Seyler Publisher: ISBN: Category : Languages : en Pages :
Book Description
"Subduction zones host the world’s largest earthquakes, but seismic slip is only one style of deformation along the subduction interface. The deformation processes above and below the seismogenic zone are equally fundamental to understanding how relative motion is accommodated during subduction. The plate interface updip from the seismogenic zone is commonly localized within seafloor sediments overlying the subducting slab. Whether or not an earthquake propagates through those sediments to the surface controls the likelihood tsunami generation, making the mechanical behavior of seafloor sediments essential to our understanding of shallow earthquake rupture. On the downdip portion below, high temperatures allow continuous sliding that progressively loads the seismogenic zone. This thesis investigates the deformation behavior of the updip and downdip subduction interface through experimental, field, and microstructural studies on the active Cascadia subduction system and an exhumed analog, the Leech River Fault.To investigate the likelihood of earthquakes rupturing to the surface, high velocity rotary shear experiments were conducted over a range of normal stresses on three samples of Ocean Drilling Program core retrieved from Cascadia input sediments and a suite of individual clay species to measure their frictional properties and fracture energy. The Cascadia input sediment cores show little variation in fracture energy between samples. Clay species were tested under wet and dry conditions, and difference between extremely low fracture energy wet gouges and moderately low fracture energy dry gouges was more significant than the differences between species. Comparing these results with a global compilation of fracture energy estimates, wet clay-rich gouges have the lowest fracture energy of all lithologies, which may enhance earthquake rupture to the trench. Yet Cascadia sediments have a fracture energy that is nearly an order of magnitude higher than input sediments from other subduction zones, possibly inhibiting shallow earthquake rupture propagation and tsunamigenesis.Field, petrological, microstructural, and geochronological data rewrite the history of the Leech River Fault (LRF) as a subduction interface shear zone. The shear zone is defined by mylonites developed along the contact between the schist and metamorphosed basalt, whose strong, steeply dipping foliation, downdip lineation, and kinematic indicators indicate sinistral-reverse motion. Garnet and amphibole chemical zoning in the schist and metabasalt, respectively, indicate prograde, syn-kinematic growth. Syn-kinematic metamorphic conditions of ~575 °C and ~800 MPa were determined from the schist mylonite, which match the qualitative P-T conditions of amphibolite facies determined from amphibole rim compositions in the metabasalt mylonite. The structural and metamorphic history of the shear zone confirm that it was active as the downdip portion of the subduction interface.The strength of the subduction interface downdip is an important parameter for understanding subduction dynamics that cannot be determined geophysically. Integrating microstructural observations of the mylonites with experimentally derived flow laws, I determined the controls on shear zone rheology and estimated bulk rock strength under in situ conditions. Multiple deformation mechanisms operating in the schist and metabasalt mylonites were required to accommodate deformation, and the available flow laws indicate that the bulk strength of these rocks was significantly reduced by hydrous phases like phyllosilicates and amphibole. These observations suggest that hydration and metamorphic reactions play an essential role in weakening rocks and allowing the plate interface to creep aseismically at low stresses. Together, these new observations place important constraints on the dynamics of deformation above and below the seismogenic zone"--
Author: Caroline Seyler Publisher: ISBN: Category : Languages : en Pages :
Book Description
"Subduction zones host the world’s largest earthquakes, but seismic slip is only one style of deformation along the subduction interface. The deformation processes above and below the seismogenic zone are equally fundamental to understanding how relative motion is accommodated during subduction. The plate interface updip from the seismogenic zone is commonly localized within seafloor sediments overlying the subducting slab. Whether or not an earthquake propagates through those sediments to the surface controls the likelihood tsunami generation, making the mechanical behavior of seafloor sediments essential to our understanding of shallow earthquake rupture. On the downdip portion below, high temperatures allow continuous sliding that progressively loads the seismogenic zone. This thesis investigates the deformation behavior of the updip and downdip subduction interface through experimental, field, and microstructural studies on the active Cascadia subduction system and an exhumed analog, the Leech River Fault.To investigate the likelihood of earthquakes rupturing to the surface, high velocity rotary shear experiments were conducted over a range of normal stresses on three samples of Ocean Drilling Program core retrieved from Cascadia input sediments and a suite of individual clay species to measure their frictional properties and fracture energy. The Cascadia input sediment cores show little variation in fracture energy between samples. Clay species were tested under wet and dry conditions, and difference between extremely low fracture energy wet gouges and moderately low fracture energy dry gouges was more significant than the differences between species. Comparing these results with a global compilation of fracture energy estimates, wet clay-rich gouges have the lowest fracture energy of all lithologies, which may enhance earthquake rupture to the trench. Yet Cascadia sediments have a fracture energy that is nearly an order of magnitude higher than input sediments from other subduction zones, possibly inhibiting shallow earthquake rupture propagation and tsunamigenesis.Field, petrological, microstructural, and geochronological data rewrite the history of the Leech River Fault (LRF) as a subduction interface shear zone. The shear zone is defined by mylonites developed along the contact between the schist and metamorphosed basalt, whose strong, steeply dipping foliation, downdip lineation, and kinematic indicators indicate sinistral-reverse motion. Garnet and amphibole chemical zoning in the schist and metabasalt, respectively, indicate prograde, syn-kinematic growth. Syn-kinematic metamorphic conditions of ~575 °C and ~800 MPa were determined from the schist mylonite, which match the qualitative P-T conditions of amphibolite facies determined from amphibole rim compositions in the metabasalt mylonite. The structural and metamorphic history of the shear zone confirm that it was active as the downdip portion of the subduction interface.The strength of the subduction interface downdip is an important parameter for understanding subduction dynamics that cannot be determined geophysically. Integrating microstructural observations of the mylonites with experimentally derived flow laws, I determined the controls on shear zone rheology and estimated bulk rock strength under in situ conditions. Multiple deformation mechanisms operating in the schist and metabasalt mylonites were required to accommodate deformation, and the available flow laws indicate that the bulk strength of these rocks was significantly reduced by hydrous phases like phyllosilicates and amphibole. These observations suggest that hydration and metamorphic reactions play an essential role in weakening rocks and allowing the plate interface to creep aseismically at low stresses. Together, these new observations place important constraints on the dynamics of deformation above and below the seismogenic zone"--
Author: Timothy H. Dixon Publisher: Columbia University Press ISBN: 0231512015 Category : Science Languages : en Pages : 691
Book Description
Subduction zones, one of the three types of plate boundaries, return Earth's surface to its deep interior. Because subduction zones are gently inclined at shallow depths and depress Earth's temperature gradient, they have the largest seismogenic area of any plate boundary. Consequently, subduction zones generate Earth's largest earthquakes and most destructive tsunamis. As tragically demonstrated by the Sumatra earthquake and tsunami of December 2004, these events often impact densely populated coastal areas and cause large numbers of fatalities. While scientists have a general understanding of the seismogenic zone, many critical details remain obscure. This volume attempts to answer such fundamental concerns as why some interplate subduction earthquakes are relatively modest in rupture length (greater than 100 km) while others, such as the great (M greater than 9) 1960 Chile, 1964 Alaska, and 2004 Sumatra events, rupture along 1000 km or more. Contributors also address why certain subduction zones are fully locked, accumulating elastic strain at essentially the full plate convergence rate, while others appear to be only partially coupled or even freely slipping; whether these locking patterns persist through the seismic cycle; and what is the role of sediments and fluids on the incoming plate. Nineteen papers written by experts in a variety of fields review the most current lab, field, and theoretical research on the origins and mechanics of subduction zone earthquakes and suggest further areas of exploration. They consider the composition of incoming plates, laboratory studies concerning sediment evolution during subduction and fault frictional properties, seismic and geodetic studies, and regional scale deformation. The forces behind subduction zone earthquakes are of increasing environmental and societal importance.
Author: Kirsty Mckenzie Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
In this dissertation I use observations of upper-plate deformation to constrain the kinematics and dynamics of tectonic processes that occur at subduction zones and within plate boundary transition zones. I combine observations that record deformation over weeks to decades (geodetic observations), tens to hundreds of thousands of years (field observations and geochronology), and millions of years (field observations and plate boundary reconstructions), with earthquake cycle modeling. This research is primarily focused on the Cascadia subduction zone, however the results are applicable across many subduction zones globally. Specific related cases that are highlighted include the Hikurangi margin (New Zealand) and the Nankai trough (SW Japan). The studies in my research range from using observations of slow slip earthquakes to constrain the plate motion direction and forces acting down-dip of the seismogenic zone, to observations of permanent upper-plate deformation to better understand the relationship between shallow mechanical locking on the plate interface and upper-plate deformation. Some key findings I present over several chapters are: (1) a model for the Cascadia subduction zone (and other obliquely-convergence subduction zones) that suggests that loading of the locked region at deep levels is down-dip and thus oblique to the loading direction at shallow levels; (2) a new coupling model for the Cascadia subduction zone that relates the variation in GPS velocities (and permanent deformation) from south to north across the margin to the locations of upper-plate strength (geologic terrane) boundaries; and (3) permanent coastal uplift is not being produced continuously, and instead observations from central Cascadia suggest uplift rates can change significantly over ~20 kyrs.
Author: J.F.v. Raumer Publisher: Springer ISBN: 9783642846427 Category : Science Languages : en Pages : 0
Book Description
The Alps are an arched mountain chain stretching 1500 km between Vienna and Graz in Austria and Genova in Italy. They resulted from the collision of the African and Laurasian plates during Mesozoic and Tertiary times. The high standard of knowledge attained over the last 30 years by the working groups on "Alpine Metamorphism" is well known and helped considerably to recognize pre-Mesozoic elements in the Alps. In Part I of this book the subdivision of the major Alpine units and pre-Mesozoic pal inspastic reconstructions are covered before discussion of the pre-Mesozoic geology in Parts II, III and IV It is understood that the Mesozoic and later events overprinted pre-existing structures veiling the earlier history and the nature of protoliths. Although the Alpine overprint does not facilitate the recognition of older struc tures, pre-Mesozoic basement units were recognized during the first beginnings of geological observations in the Alps, about 200 years ago. Fifty percent of the Alpine domain is underlain by basement units that have been unconformably covered since Permian and Mesozoic times. This basement appears today in a complex pattern among the Alpine structures. The history of their discovery and explanation, parallel with a growing sophistication of research methods, are the subject of the introductory chapter of Part II.
Author: Timothy Byrne Publisher: Geological Society of America ISBN: 0813725348 Category : Science Languages : en Pages : 215
Book Description
This volume highlights the career of Dr. Gaku Kimura, professor emeritus of geosciences at the University of Tokyo, by showing the spectrum of research required to understand these dynamic environments and the range of research he has inspired. The first three chapters provide context for the growth of accretionary prisms by examining the thermal structure of the ocean crust, and the sedimentary facies and potential fluid pathways in the Shikoku Basin. Next, two chapters look at the regional-scale structure of the plate boundary and the rheology and hysteresis of the hanging wall of the subduction zone in SW Japan. The following five chapters discuss the progressive deformation and thermal maturation of sediments along accretionary margins from Japan to New Zealand to western North America. The final two chapters look at the deformation processes near the subducting plate interface with the last chapter proposing a link between outcrop-scale observations and seismic slip.
Author: Shanshan Li Publisher: ISBN: Category : Faults (Geology) Languages : en Pages : 290
Book Description
Characterizing spatial and temporal variations of slip behavior observed along subduction faults is of great significance for understanding the dynamics of subduction zones, features of great subduction zone earthquakes and deformation patterns across the subduction plate boundary through the seismic cycle. The Alaska-Aleutian subduction zone is one of the most tectonically active margins in the world. Great earthquakes and slow slip events recorded in this area are closely related in space. An increasingly dense array of Global Positioning System (GPS) receivers measures surface deformation at sites with high accuracy and provides a perfect tool for estimating the slip distribution on the plate boundary. GPS observations show that the motion of the Earth is not entirely linear: the long-term steady motion is interrupted by events like earthquakes, slow slip events (SSEs) and deformation of volcanoes, etc. Two long-term SSEs were detected in Lower Cook Inlet, Alaska (1992.0-2004.8 and 2009.85-2011.81) by inverting the slip distributions from GPS site velocities. The occurrence of SSEs based on the estimated slip distribution patterns provides strong evidence for the transition from stick-slip behavior to episodes and continuous aseismic creep on the subduction plate interface. Coulomb stressing rate changes (CSRC) due to the two detected long-term SSEs indicate that regions in the shallow slab (30-60 km) that experience significant increase in CSRC show an increase in seismicity rate during SSE periods. The modified quantitative rate/state stress transfer model suggests that the SSEs increase stress on surrounding faults, thereby increasing the seismicity rate even though the ratio of the SSE induced stressing rate to the background stressing rate is small. The SSEs were shown to cause significant stress changes in the seismogenic zone. This highlights the importance of exploring the relationship between SSEs and earthquakes, as well as how this relationship impacts the strain accumulation in the subduction zone. A repeat survey of the existing campaign GPS sites combined with continuous GPS sites provided a > 20 year time span for estimating the interseismic velocities of the Alaska Peninsula. From this I inferred a more precise model for the location and spatial extent of the change from locked to creeping behavior across the Alaska Peninsula. Given this more detailed distribution of the slip behavior, the results suggest that slip behavior correlates with the pre-existing plate fabric on the downgoing plate, seismic behavior, the reflection character of the slab interface itself and the rupture history of past great earthquakes.
Author: Publisher: Elsevier ISBN: 0444538038 Category : Science Languages : en Pages : 5604
Book Description
Treatise on Geophysics, Second Edition, is a comprehensive and in-depth study of the physics of the Earth beyond what any geophysics text has provided previously. Thoroughly revised and updated, it provides fundamental and state-of-the-art discussion of all aspects of geophysics. A highlight of the second edition is a new volume on Near Surface Geophysics that discusses the role of geophysics in the exploitation and conservation of natural resources and the assessment of degradation of natural systems by pollution. Additional features include new material in the Planets and Moon, Mantle Dynamics, Core Dynamics, Crustal and Lithosphere Dynamics, Evolution of the Earth, and Geodesy volumes. New material is also presented on the uses of Earth gravity measurements. This title is essential for professionals, researchers, professors, and advanced undergraduate and graduate students in the fields of Geophysics and Earth system science. Comprehensive and detailed coverage of all aspects of geophysics Fundamental and state-of-the-art discussions of all research topics Integration of topics into a coherent whole
Author: Serge Lallemand Publisher: Springer Science & Business Media ISBN: 3540879749 Category : Science Languages : en Pages : 278
Book Description
Subduction is a major process that plays a first-order role in the dynamics of the Earth. The sinking of cold lithosphere into the mantle is thought by many authors to be the most important source of energy for plates driving forces. It also deeply modifies the thermal and chemical structure of the mantle, producing arc volcanism and is responsible for the release of most of the seismic energy on Earth. There has been considerable achievements done during the past decades regarding the complex interactions between the various processes acting in subduction zones. This volume contains a collection of contributions that were presented in June 2007 in Montpellier (France) during a conference that gave a state of the art panorama and discussed the perspectives about "Subduction Zone Geodynamics". The papers included in this special volume offer a unique multidisciplinary picture of the recent research on subduction zones geodynamics. They are organized into five main topics: Subduction zone geodynamics, Seismic tomography and anisotropy, Great subduction zone earthquakes, Seismogenic zone characterization, Continental and ridge subduction processes. Each of the 13 papers collected in the present volume is primarily concerned with one of these topics. However, it is important to highlight that papers always treat more than one topic so that all are related lighting on different aspects of the complex and fascinating subduction zones geodynamics.
Author: Y. Dilek Publisher: Geological Society of London ISBN: 1786204789 Category : Science Languages : en Pages : 430
Book Description
Earthquakes and tsunamis are devastating geohazards with significant societal impacts. Most recent occurrences have shown that their impact on the stability of nations–societies and the world geopolitics is immense, potentially triggering a tipping point for a major downturn in the global economy. This Special Publication presents the most current information on the causes and effects of some of the modern and historical earthquake–tsunami events, and effective practices of risk assessment–disaster management, implemented by various governments, international organizations and intergovernmental agencies. Findings reported here show that the magnitude of human casualties and property loss resulting from earthquakes–tsunamis are highly variable around the globe, and that increased community, national and global resilience is significant to empower societal preparedness for such geohazards. It is clear that all stakeholders, including scientists, policymakers, governments, media and world organizations must work together to disseminate accurate, objective and timely information on geohazards, and to develop effective legislation for risk reduction and realistic hazard mitigation–management measures in our globally connected world of today.
Author: Paul Segall Publisher: Princeton University Press ISBN: 140083385X Category : Science Languages : en Pages : 465
Book Description
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
Author: Caroline Seyler
Author: Caroline Seyler
Author: Timothy H. Dixon
Author: Kirsty Mckenzie
Author: J.F.v. Raumer
Author: Timothy Byrne
Author: Shanshan Li
Author: 
Author: Serge Lallemand
Author: Y. Dilek
Author: Paul Segall