Drivers, Modulators and Hazards of Collisional Orogens

碰撞造山带的驱动因素、调节因素和危害

• 批准号: RGPIN-2014-04297
• 负责人: Grujic, Djordje
• 金额: $ 2.19万
• 依托单位: Dalhousie University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=566426
• 关键词: Drivers; Modulators; Hazards; Collisional; Orogens

Conventional plate tectonic theory explains the formation of mountain belts by crustal deformation and thickening only at the plate margins, yet theoretical and observational studies have indicated that deformation also occurs in plate interiors. Accordingly, the connections between intraplate and plate margin deformations and the associated feedback mechanisms remain unclear. To address this, the proposed study considers several hypotheses, as follows. a) Break-up of a tectonic plate leads to changes of the forces acting at the plate margins and thus to adjustments in plate tectonics (widening or narrowing of the orogenic wedge). b) The resistance imparted by a rising mountain belt at a convergent margin exerts forces that lead to the deformation and eventual failure of the tectonic plate in question. c) Stresses released by mega-earthquakes in the plate interior may propagate slowly to the plate margins and influence local seismicity years after earthquake occurrence. These hypotheses will be tested by examining deformation within the frontal tectonic wedge of a collisional orogen at timescales of centuries to millions of years and by studying the stresses induced by intraplate deformation within the undergoing plate. Upper crustal deformation can be observed directly in active orogens, and the parameters controlling the deformation and morphology of tectonic wedges have been well established. According to records of intraplate seismicity, the Indian Ocean lithosphere is both shortening (folding) and breaking up coeval with contraction within the Himalayan orogen. The break-up process influences the amount of force transferred to the convergent plate boundary, which is expressed as the Himalaya. Therefore, we will concentrate on the present-day wedge of the Himalayan orogen. This complex dynamic system allows both qualitative and quantitative testing of the project hypotheses. The projected scientific contribution of the research program will be the development of a theory explaining the partitioning of stresses between deformation at plate margins and plate interiors. This will allow determination of the mechanisms and timescales of propagation of stress from an incipient breakup area to a convergent boundary zone, utilising the Indian plate as an example. The distribution and magnitude of stresses in the Himalayan wedge is not merely an academic question, because understanding of the deformation across the Himalaya is important for monitoring and prediction of seismic hazard. Furthermore, at a larger scale, this approach will allow investigation of the potential dynamic links between subduction mega-earthquakes and stress loading within the plate and along its margins. Therefore, it is expected that this program will increase the reliability of geohazard predictions through improvements in the understanding of the underlying causes of such seismicity. The hypotheses presented by this program and the questions arising during its implementation will be investigated through a combination of field, laboratory and numerical experimental studies. In particular, the questions will be tackled through multidisciplinary projects led by graduate students and involving the following: compilation, synthesis and interpretation of ocean floor geophysical and seismological data; calculation of the stresses along plate margins; numerical modelling of the evolution of orogenic wedges; geodynamic modelling of plate–plate margin interaction; and detailed field studies and microstructural analyses. Throughout this process, we shall seek to develop novel ways to date fault activity directly; this will be a crucial step in linking near and remote tectonic events and will be of fundamental importance for tectonic reconstructions in general.

传统的板块构造理论仅解释了板块边缘的地壳变形和增厚是山地带形成的原因，但理论和观测研究表明板块内部也发生变形，因此，板内变形和板块边缘变形之间的联系以及相关的反馈之间存在联系。为了解决这个问题，拟议的研究考虑了以下几个假设：a）构造板块的破裂导致作用在板块边缘的力发生变化，从而导致板块的调整。构造（造山楔的加宽或变窄） b) 收敛边缘的上升山脉所施加的阻力会产生导致相关构造板块变形和最终破坏的力 c) 特大地震释放的应力。板块内部的地震可能会缓慢传播到板块边缘，并在地震发生数年后影响当地的地震活动，这些假设将通过检查板块前缘构造楔内的变形来检验。碰撞造山带在数百年至数百万年的时间尺度上进行研究，并通过研究正在发生的板块内板内变形引起的应力，可以直接在活动造山带中观察到上地壳变形，并且已经建立了控制构造楔形变形和形态的参数。根据板内地震活动的记录，印度洋岩石圈与喜马拉雅造山带内的收缩同时发生着缩短（折叠）和破碎。破碎过程影响了其量。因此，我们将重点关注当今喜马拉雅造山带的楔形区域，从而可以对项目假设进行定性和定量测试。该研究计划的贡献将是发展一种解释板块边缘和板块内部变形之间应力分配的理论，这将有助于确定应力从初始破裂区域传播到收敛区域的机制和时间尺度。以印度板块为例，喜马拉雅楔中应力的分布和大小不仅仅是一个学术问题，因为了解喜马拉雅山的变形对于监测和预测地震灾害非常重要。在更大的范围内，该方法将允许调查俯冲特大地震与板块内及其边缘的应力载荷之间的潜在动态联系，因此，预计该计划将通过改进对地质灾害的理解来提高地质灾害预测的可靠性。该计划提出的假设及其实施过程中出现的问题将通过现场、实验室和数值实验研究的结合来调查，特别是，这些问题将通过研究生领导的多学科项目来解决。以及以下内容：海底地球物理和地震数据的汇编、综合和解释；沿板块边缘的应力计算；板块与板块边缘相互作用的地球动力学模型以及详细的现场研究和微观结构分析； 。在整个过程中，我们将寻求开发直接测定断层活动年代的新方法；这将是联系近处和远方构造事件的关键一步，并且对于整个构造重建具有根本重要性。