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只解释了板块边缘地壳变形和增厚导致的山脉带的形成，但理论和观测研究表明，变形也发生在板块内部。因此，板内和板缘变形之间的联系和相关的反馈机制仍然不清楚。为了解决这个问题，拟议的研究考虑了几个假设，如下所示。a）构造板块的断裂导致作用在板块边缘的力的变化，从而导致板块构造的调整（造山楔的加宽或缩小）。B）在会聚边缘的上升山脉带所施加的阻力，会产生导致构造板块变形和最终破坏的力。c）板块内部的大地震释放的应力可能会缓慢地传播到板块边缘，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碰撞造山带的前缘构造楔内几百年到几百万年的时间尺度的变形和通过研究正在发生的板块内的板内变形引起的应力来检验。在活动造山带中可以直接观测到上地壳变形，并已建立起控制构造楔变形和形态的参数。根据板内地震活动的记录，印度洋岩石圈在喜马拉雅造山带内同时缩短（褶皱）和破裂。破裂过程影响了传递到会聚板块边界的力的大小，这被表示为喜马拉雅。因此，我们将集中讨论喜马拉雅造山带的现今楔体。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。该研究计划的科学贡献将是发展一种理论，解释板块边缘和板块内部变形之间的应力分配。这将允许确定的机制和时间尺度的传播应力从一个初始的分裂区收敛边界区，利用印度板块作为一个例子。喜马拉雅楔体的应力分布和大小不仅仅是一个学术问题，因为了解喜马拉雅楔体的变形对监测和预测地震危险性是重要的。此外，在更大的范围内，这种方法将允许调查俯冲大地震和板块内及其沿着边缘的应力负荷之间的潜在动态联系。因此，预计这一计划将通过提高对这种地震活动的根本原因的理解，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进行调查。特别是，将通过由研究生领导的多学科项目来解决这些问题，这些项目涉及以下方面：汇编、综合和解释海底地球物理和地震数据;计算沿着板块边缘的应力;造山楔演变的数值模拟;板块边缘相互作用的地球动力学模拟;详细的实地研究和微观结构分析。在整个过程中，我们将寻求开发新的方法来直接确定断层活动的日期;这将是连接近距离和远距离构造事件的关键一步，对一般的构造重建具有根本的重要性。