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The Seismogenic Zone Of Subduction Thrust Faults

The Seismogenic Zone of Subduction Thrust Faults PDF

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Author: Timothy H. Dixon
Publisher: Columbia University Press
ISBN: 0231512015
Size: 68.64 MB
Format: PDF, ePub
Category : Science
Languages : en
Pages : 692
View: 1271

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.


The Seismogenic Zone Of Subduction Thrust Faults

The Seismogenic Zone of Subduction Thrust Faults PDF

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Author: Timothy Dixon, PH D
Publisher: Columbia University Press
ISBN: 9780231138666
Size: 15.62 MB
Format: PDF, ePub, Docs
Category : Science
Languages : en
Pages : 680
View: 4554

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.


The Mechanics Of Slip At The Updip Limit Of The Seismogenic Zone

The Mechanics of Slip at the Updip Limit of the Seismogenic Zone PDF

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Author: Noah Phillips
Publisher:
ISBN:
Size: 50.69 MB
Format: PDF, Kindle
Category :
Languages : en
Pages :
View: 1900

Book Description: "The world’s largest earthquakes occur within the seismogenic zones of subduction thrusts, which lock between large magnitude earthquakes. At the updip limit of seismogenic zones, a transitional zone occurs if the subduction interface is not locked to the trench. Within this transitional zone a range of slip behaviors including seismic slip events propagating to the trench, slow slip events (SSEs), tremor, low frequency events (LFEs) and very low frequency events (VLFEs) are observed using geodetic and seismological data sets. Slip in transitional zones is believed to load the seismogenic zone, and may precede large magnitude earthquakes. Understanding the mechanics of slip in transitional zones is therefore important for characterizing the earthquake cycle.Exhumed subduction zone fault rocks preserve information about the composition, structure, and behavior of subduction zones. This thesis examines deformation structures from an exhumed, shallow (T = 190°C), subduction mélange (the Mugi Mélange, Japan) to provide insights into the mechanics of deformation in shallow transitional zones. Mapping, microstructural observations, experiments, and models are used to characterize the distribution of slip surfaces, and relate the observed surfaces to geophysical observations. Localized slip in subduction zones is expected to occur in velocity-weakening materials; however, most subducting materials (gabbro, basalt, calcite, and shale) have previously been shown to be velocity-strengthening at the updip limit of seismogenic zones. Field mapping in this study of basaltic blocks and slabs (embedded within a shale matrix) demonstrates that unstable slip occurred along their altered margins, where we document well-developed cataclasites and slip surfaces. We report the first documented occurrence of pseudotachylyte (quenched frictional melt) in a basaltic host, identified through microstructural criteria along the upper altered contact of a basaltic slab. Deformation in altered basalt is shown to have occurred through cataclasis and frictional sliding, while the surrounding shale matrix deformed through distributed pressure solution accommodated processes.Triaxial friction experiments were performed on crushed natural altered basalt and shale samples from the Mugi Mélange, at the in situ conditions of deformation, to characterize their frictional strengths and rate-and-state friction parameters. The shale is frictionally weaker ([mu] = 0.4) than altered basalt ([mu] = 0.6). and exhibits velocity-strengthening (a-b = ~0.01) behavior. Altered basalt exhibits velocity weakening behavior (a-b = ~-0.005), indicating that unstable slip may nucleate and propagate along altered basaltic margins. Numerical models of stress and strain-rates around basaltic blocks embedded in a shale matrix demonstrate that the stress threshold required for frictional failure in altered basalt is reached before the shale with increasing slip-rate. Experimental results are used to calculate critical nucleation lengths for dynamic slip in basaltic blocks with altered margins. At the conditions required to produce LFEs and VLFEs, basaltic blocks on the m- to 10’s of m-scale are required to produce dynamic failure. Blocks sitting close to this threshold are hypothesized to produce LFEs and VLFEs.Altered basalt is a ubiquitous lithology in subduction zones, and may provide a source of velocity-weakening material along which earthquakes can preferentially nucleate and propagate. Incorporation of velocity weakening altered basalt into a velocity strengthening matrix may provide a source for LFEs and VLFEs at near lithostatic pore fluid pressure conditions. Incorporation of blocks into the surrounding matrix may occur more readily around subducted seamounts and ridges"--


Geology And Tectonics Of Subduction Zones A Tribute To Gaku Kimura

Geology and Tectonics of Subduction Zones  A Tribute to Gaku Kimura PDF

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Author: Timothy Byrne
Publisher: Geological Society of America
ISBN: 0813725348
Size: 66.18 MB
Format: PDF, Kindle
Category : Science
Languages : en
Pages : 215
View: 2648

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.


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Author:
Publisher:
ISBN:
Size: 26.90 MB
Format: PDF
Category : Earthquakes
Languages : en
Pages :
View: 1375

Book Description:


Gps Studies Of Crustal Deformation In The Northern Cascadia Subduction Zone

GPS Studies of Crustal Deformation in the Northern Cascadia Subduction Zone PDF

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Author: Joseph Alan Henton
Publisher:
ISBN:
Size: 55.46 MB
Format: PDF, Kindle
Category :
Languages : en
Pages :
View: 6158

Book Description: Vancouver Island, located in southwestern coastal British Columbia, overlies the northern portion of the Cascadia Subduction Zone. This region is characterized by extensive seismicity which includes M ∼ 7 crustal earthquakes and less frequent M ∼ 9 megathrust events. Crustal deformation measurements have been carried out in this region since 1978 using various geodetic field techniques: levelling, tide gauge studies, precise gravity, laser ranging, and most recently, GPS. Earlier survey data provided key constraints to elastic slip-dislocation models for estimating the size and location of the rupture area for the next subduction-thrust earthquake. Recent estimates of crustal motions within the North Cascadia Margin based on both campaign GPS network surveys and up to 6.5 years of data from continuous GPS sites are consistent with the strain accumulation expected from a locked subduction fault. The deformation vectors are in the direction of plate convergence within the uncertainty of plate motion models. The observed strain rate across Vancouver Island is, however, smaller (by approximately a factor of 1.5) than the dislocation model prediction, suggesting the presence of visco-elastic effects. Crustal deformation measurements for central Vancouver Island fail to resolve motions that could be associated with the occurrence of large crustal earthquakes, and also suggest that the extent of the seismogenic subduction thrust zone north of the Nootka Fault Zone is extremely limited.


Encyclopedia Of Solid Earth Geophysics

Encyclopedia of Solid Earth Geophysics PDF

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Author: Harsh Gupta
Publisher: Springer Science & Business Media
ISBN: 904818701X
Size: 13.62 MB
Format: PDF, ePub, Mobi
Category : Science
Languages : en
Pages : 1539
View: 3061

Book Description: The past few decades have witnessed the growth of the Earth Sciences in the pursuit of knowledge and understanding of the planet that we live on. This development addresses the challenging endeavor to enrich human lives with the bounties of Nature as well as to preserve the planet for the generations to come. Solid Earth Geophysics aspires to define and quantify the internal structure and processes of the Earth in terms of the principles of physics and forms the intrinsic framework, which other allied disciplines utilize for more specific investigations. The first edition of the Encyclopedia of Solid Earth Geophysics was published in 1989 by Van Nostrand Reinhold publishing company. More than two decades later, this new volume, edited by Prof. Harsh K. Gupta, represents a thoroughly revised and expanded reference work. It brings together more than 200 articles covering established and new concepts of Geophysics across the various sub-disciplines such as Gravity, Geodesy, Geomagnetism, Seismology, Seismics, Deep Earth Processes, Plate Tectonics, Thermal Domains, Computational Methods, etc. in a systematic and consistent format and standard. It is an authoritative and current reference source with extraordinary width of scope. It draws its unique strength from the expert contributions of editors and authors across the globe. It is designed to serve as a valuable and cherished source of information for current and future generations of professionals.