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Numerical Modeling of Neotectonic Movements and State of Stresses in the Central Seismic Gap Region,Garhwal Himalaya

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Journal of Mountain Science 2008年第4期5卷 279-298页

作者： Ganesh Raj JOSHI daigoro hayashi Simulation Tectonics Laboratory Faculty of ScienceUniversity of the RyukyusOkinawa 903-0213Japan

This paper presents finite element modeling(FEM) to simulate the present-day stress field and crustal deformation using NE-SW structural section in the central Seismic Gap region of the Garhwal *** study deals with the effect of geometrical characteristics and rock layer parameters on the upper *** results show that two types of tectonic regimes developed in the central Seismic Gap region:the geotectonics of the northern part has been controlled by regional compression,whereas southern part is characterized by regional ***,thrust faults are induced in the northern part and normal faults are extensively developed in the southern *** evidences noticeably indicate that the compressive tectonic environment of the Himalaya becomes change into the extensional tectonic regime in its *** computed shear stress accumulation along the northern flat of Main Himalayan Thrust(MHT) implies that considerable amount of interseismic stress is building up along the MHT system in the Himalaya,which ultimately release through the possible future great Himalayan earthquake(M>8).The comparison between our modeled stress field,faulting pattern and horizontal shortening rate with the distribution of the microseismic events,focal mechanism solutions,active faulting and GPS data in the central Seismic Gap region shows good agreement.

关键词：地震变形应力分布有限元分析

Numerical modeling of the development of southeastern Red Sea continental margin

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Earthquake Science 2009年第3期22卷 239-249页

作者： Sunil Kumar Dwivedi daigoro hayashi Simulation Tectonics Laboratory Faculty of Science University of the Ryukyus

The Red Sea continental margin （RSCM） corresponds to a wide hinge zone between Red Sea and Arabian plate. This margin has been studied through geological and geophysical observations primarily in regard to the evolution of Red Sea rift. This margin is characterized by occurrence of thin sediments, significant onshore uplift, tectonic subsidence of the offshore sedimentary basin, active faulting and seismicity. Studies indicate that sedimentary sequences of the margin are deformed by faults and folds resulting from at least two phases of extension and a phase of uplift. During the two phases of extension due to regional plate stress the sequence was cut by set of extensional faults. While during the phase of uplift the sequence was deformed by folding and faulting. The present paper aims to clear the structural development of RSCM during these tectonic episodes, taken as particular tectonic event, by two-dimensional finite element modeling on plane strain condition. Elastic theology is assumed for the oceanic, continental and transitional crust along with syntectonic deposits. Stress field, shear stress and fault distribution suggests that mantle plume weakened the crust following rifting due to regional stress and developed the margin. These results are well consistent with those from present seismicity, active faulting and neotectonic studies.

关键词： Red Sea rift continental margin numerical modeling seismicity neotectonics

Development of extensional stresses in the compressional setting of the Himalayan thrust wedge: inference from numerical modelling

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Natural Science 2010年第7期2卷 667-680页

作者： Ganesh Raj Joshi daigoro hayashi 不详

The estimation of contemporary tectonic stress field and deformation in active fold-and-thrust belts are imperative in identifying active geodynamics and resulting faulting phenomenon. In this paper, we focus on contemporary extensional tectonics in the overall compressive setting of the Himalayan orogen. Here we examine the regional tectonic stress field and upper crustal deformation in the Himalayan thrust wedge using a 2D finite element technique, incorporating elastic rheology under plain strain condition. The elastic models demonstrate that the extensional tectonic stress and related nor- mal faulting is extensively developed in the southern front of the Himalaya at shallow crustal level (<10 km in depth). Our modelling shows a good consistency with the geological field evidences of active faulting, focal mechanism solutions of medium size earthquakes in the several sectors of the Himalaya. Results based on numerical simulation, tectonic analysis and taking geological and geophysical data into account, we interpret that the present-day extensional tectonic activity is not restricted in the southern Tibet but distributed in the different sectors of the Himalayan fold-and-thrust belt co-exist with compressional structures. Modelling results also indicate that the nature, distribution and orientation of the maximum compressive stress (?1) of the Himalaya are mainly controlled by the intra crustal Main Himalayan décollement (MHT). The significant amount of shear stress/strain concentration along the MHT in the western Nepal predict that the region is prone to moderate and great future earthquakes.

关键词： Extensional Stress Field Convergent Displacement Finite Element Modelling Himalayan Wedge

Finite element modelling of the pull-apart formation: implication for tectonics of Bengo Co pull-apart basin, southern Tibet

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Natural Science 2010年第6期2卷 654-666页

作者： Ganesh Raj Joshi daigoro hayashi 不详

The tectonic deformation and state of stress are significant parameters to understand the active structure, seismic phenomenon and overall ongoing geodynamic condition of any region. In this paper, we have examined the state of stress and crustal deformation during the formation of the Beng Co pull-apart basins produced by an enéchelon strike-slip fault systems using 2D Finite Element Modelling (FEM) under plane stress condition. The numerical modelling technique used for the experiments is based on FEM which enables us to analyze the static behavior of a real and continues structures. We have used three sets of models to explore how the geometry of model (fault overlap and pre-existing weak shear zone) and applied boundary conditions (pure strike-slip, transpressional and transtensional) influence the development of state of stress and deformation during the formation of pull-apart basins. Modelling results presented here are based on five parameters: 1) distribution, orienttation, and magnitude of maximum (σH max) and minimum (σH max) horizontal compressive stress 2) magnitude and orientation of displacement vectors 3) distribution and concentration of strain 4) distribution of fault type and 5) distribution and concentration of maximum shear stress (σH max) contours. The modelling results demonstrate that the deformation pattern of the en-échelon strike-slip pull-apart formation is mainly dependent on the applied boundary conditions and amount of overlap between two master strike-slip faults. When the amount of overlap of the two master strike-slip faults increases, the surface deformation gets wider and longer but when the overlap between two master strike-slip faults is zero, block rotation observed significantly, and only narrow and small surface deform ation obtained. These results imply that overlap between two master strike-slip faults is a significant factor in controlling the shape, size and morphology of the pull-apart basin formation. Results of numeric

关键词： State of Stress Deformation Regime Pull-Apart Formation Numerical Modelling Southern Tibet

Finite element modelling of the pull-apart formation: implication for tectonics of Bengo Co pull-apart basin, southern Tibet

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Development of extensional stresses in the compressional setting of the Himalayan thrust wedge: inference from numerical modelling

Natural Science 2010年第6期

作者： Ganesh Raj Joshi daigoro hayashi

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日本冲绳海槽和欧亚板块附加体二维构造应力场的有限元模拟及其构造意义初探

Natural Science 2010年第7期

作者： Ganesh Raj Joshi daigoro hayashi

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桂林工学院学报 2008年第1期28卷 1-7页

作者：卢汉堤黄俭惠林大五郎木村政昭桂林矿产地质研究院广西桂林541004 日本琉球大学理学部物质地球科学系日本冲绳903-0213

应用有限元方法模拟了日本冲绳海槽和欧亚大陆板块附加体二维构造应力场,并根据库仑-摩尔准则讨论了有限元模型中断裂构造发育与变形,定量化地研究了大陆岩石圈的扩张作用以及菲律宾海板块的俯冲作用对大陆板块边缘构造应力场及其变形... 详细信息

应用有限元方法模拟了日本冲绳海槽和欧亚大陆板块附加体二维构造应力场,并根据库仑-摩尔准则讨论了有限元模型中断裂构造发育与变形,定量化地研究了大陆岩石圈的扩张作用以及菲律宾海板块的俯冲作用对大陆板块边缘构造应力场及其变形作用的影响。数学模拟的结果表明,大陆地壳底部的扩张作用使得冲绳海槽内发育正断层,从而导致冲绳海槽这一弧后盆地的形成。菲律宾海板块的俯冲作用引起欧亚板块附加体中形成逆掩断层。有限单元模拟实验结果与研究区地震震源机制的研究结果是一致的。

关键词：冲绳海槽欧亚板块附加体构造应力场有限元方法扩张作用俯冲作用