Seismotectonics of Canada's West Coast

加拿大西海岸的地震构造

• 批准号: RGPIN-2021-03039
• 负责人: Bostock, Michael
• 金额: $ 2.62万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=742343
• 关键词: Seismotectonics; Canada; West; Coast

Seismically active faults associated with plate tectonic processes endanger almost 3M people and societal infrastructure along Canada's west coast. They include "megathrust" plate boundaries offshore Vancouver Island and Haida Gwaii as well as smaller scale but comparably hazardous structures within the North American and Juan de Fuca plates in closer proximity to population centers like Vancouver and Victoria. The proposed research program improves our understanding of these structures (and so our ability to mitigate their associated hazards) through A) application of state-of-the-art automatic earthquake detection algorithms to publicly accessible seismic waveform archives, B) simultaneous recovery of Earth's velocity structure and precise earthquake relocation, and C) automation and application of a novel algorithm that we recently developed for quantifying fault parameters and the stress regime of small earthquakes. Preliminary analyses demonstrate that approximately 3 times as many earthquakes as currently exist in the Geological Survey of Canada catalogue can be detected using non-specific automatic detection algorithms, and that a factor of 10 times as many earthquakes as currently catalogued can be identified when template matching algorithms that search for waveforms similar to known events are subsequently employed. These algorithms supply accurate arrival-times, amplitudes and polarities of waveforms that will be used in two subsequent stages of analysis. First, high-precision relative arrival-times permit the resolution of detailed subsurface geology and its relation to seismogenic structures using double-difference tomography, enabling insights into dynamic processes responsible for earthquakes in different tectonic environments. Second, recent advances in moment tensor inversion by our group harness waveform amplitudes and polarities of small earthquakes. An earthquake moment tensor is a point-source representation of fault geometry and slip. The availability of multiple independent moment tensors for a given area enables calculation of the regional stress field and therefore seismic risk assessment. Since small earthquakes overwhelmingly dominate catalogues, our approach will allow detailed analysis of fine-scale, spatio-temporal variations in the stress regime characterizing the wide range of tectonic environments represented in western British Columbia. In particular, regionally targeted studies undertaken by diverse HQP will investigate the plate boundaries offshore Vancouver Isand and Haida Gwaii, crustal faults on Vancouver Island, the Nootka Fault Zone, the Queen Charlotte triple junction region, and the Coast Shear zone. Results from this program will lead to significant impacts in  a) assessment of seismic hazard, b) understanding of the physical processes leading to seismogenesis, and c) description of lithospheric structures and evolution, along Canada's west coast.

与板块构造过程相关的地震主动性缺陷危害了加拿大西海岸近300万人和社会基础设施。它们包括“超级”板板边界，距离海外岛和海达·格瓦伊（Haida Gwaii），以及较小的规模，但北美地区和危险的结构相对危险，在北美地区和胡安·德福卡板块（Juan de Fuca Plate）距离温哥华和维多利亚州（Victoria）等人口中心更加接近。 The proposed research program improves our Understanding of these structures (and so our ability to mitigate their associated hazards) through A) application of state-of-the-art automatic earthquake detection algorithms to publicly accessible seismic waveform archives, B) simple recovery of Earth's velocity structure and precise earthquake relocation, and C) automation and application of a novel algorithm that we recently developed for quantifying fault parameters and the stress regime of small地震。初步分析表明，可以使用非特异性自动检测算法检测到加拿大目录中目前存在的地震的大约3倍，而当与当前分类的算法相匹配时，可以识别出与已知事件相似的符合模板匹配的算法时，可以识别出目前分类的10倍地震。这些算法提供了准确的到达时间，波形的放大器和极性，这些算法将在随后的两个分析阶段中使用。首先，高精度的相对到达时时间允许使用双差断层扫描来解决详细的地下地质及其与地震生成结构的关系，从而使人们能够深入了解在不同构造环境中导致地震的动态过程。其次，我们的小组的瞬间张量反转的最新进展将波形振幅和小地震的极性振幅和极性。地震力矩张量是断层几何形状和滑动的点源表示。给定区域的多个独立矩张量的可用性可以计算区域应力场，从而计算地震风险评估。由于小地震绝大多数占据了目录，因此我们的方法将详细分析压力状态的高尺度，时空变化，这些变化表征了不列颠哥伦比亚省西部代表的各种构造环境。特别是，由Divers HQP进行的区域针对性研究将调查温哥华伊桑德（Isand）和海达·格瓦伊（Haida Gwaii）的板块边界，温哥华岛上的地壳断层，Nootka断层区，夏洛特皇后三重交界区域，以及海岸剪切区。该计划的结果将导致a）评估地震危害的重大影响，b）理解导致地震生成的物理过程，c）沿加拿大西海岸的岩石圈结构和进化的描述。