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.

常规的板块构造理论解释了仅在板边缘处的地壳变形和增厚的山带形成，但理论和观察性研究表明，板内部也发生了变形。彼此之间，板内和板缘变形与相关反馈机制之间的连接尚不清楚。为了解决这个问题，拟议的研究考虑了几种假设，如下所示。 a）构造板的破裂导致作用在板缘的力的变化，从而导致板块构造的调整（造山楔的扩大或狭窄）。 b）在收敛边缘上升的山带赋予的阻力施加了导致有关构造板的变形和最终故障的力。 c）板块内部巨大的地震释放的应力可能会缓慢地传播到板缘，并影响地震发生后几年的局部地震性。这些假设将通过检查数百年到数百万年的碰撞造山基因的额构成楔内的变形，并研究通过板块内板内变形引起的应力。可以直接观察到上皮变形在活跃的牛根中，并且已经很好地确定了控制构造楔形变形和形态的参数。根据板岩内地震性的记录，印度洋岩石圈既缩短（折叠），又与喜马拉雅造山机内的合同分解了coeval。分解过程影响了转移到收敛板边界的力量，该板板边界表示为喜马拉雅。因此，我们将集中精力于喜马拉雅造山基因的当今楔子。这个复杂的动态系统允许对项目假设进行定性和定量测试。研究计划的预计科学贡献将是发展理论的发展，该理论解释了在板缘和板内部室内变形之间的应力分配。这将允许确定从初始分裂区域到收敛边界区域的应力传播的机制和时间尺度，以印度板为例。喜马拉雅楔子中压力的分布和大小不仅是一个学术问题，因为对喜马拉雅山的变形的理解对于监测和预测地震危害很重要。此外，在较大规模的情况下，这种方法将允许研究俯冲肌的潜在动态联系与板内及其边缘内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善对这种地震性的基本原因来提高地质扎华预测的可靠性。该计划提出的假设以及实施过程中提出的问题将通过现场，实验室和数值实验研究的结合进行研究。特别是，这些问题将通过研究生领导的多学科项目解决，并涉及以下内容：汇编，合成和解释海底地球物理和地震学数据；计算沿板边缘的应力；造山楔的进化的数值建模；板 - 板边缘相互作用的地球动力模型；以及详细的现场研究和微观结构分析。通过此过程，我们将寻求开发直接日期过失活动的新颖方式。这将是链接附近和远程构造事件的关键步骤，对于一般的构造重建而言，这将是至关重要的。