Use GNSS to investigate the Present-day Tectonic Deformation in Western Canada

使用 GNSS 调查加拿大西部当今的构造变形

• 批准号: RGPIN-2022-04724
• 负责人: Jiang, Yan
• 金额: $ 1.89万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=750976
• 关键词: Use; GNSS; investigate; Present; day

Contrary to the well-studied Cascadia Subduction Zone, crustal deformation in the Canadian Cordillera and its relation to the earthquake is not well understood. For example, GPS observations show that Puget Sound is a zone of northward-directed crustal compression (shortening) and seismicity. However, the existing crustal motion model does not show in detail how the pattern of deformation extends north into the Fraser Lowland and Vancouver, a region of high development and population density. The current lack of understanding of the deformation adds considerable uncertainty to the hazard model in Western Canada. An improved understanding of the present-day tectonics contributes to a better seismic hazard model, which is incorporated into residential building codes and the building codes of critical infrastructure (dams, power facilities, LNG plants), which will reduce risk and increase societal resilience. We will measure and model large-scale tectonic motions in Western Canada, focusing mainly on the Southern Canadian Cordillera, covering most of British Columbia and the nearby population centers in Alberta, such as Calgary and Edmonton. This model divides the elastic lithosphere into small blocks, assuming that the blocks are bounded by block boundary faults. The observed crustal deformation rate is assumed to be the sum of the rigid block rotation rate and elastic deformation rate due to the coupling of the block boundary faults. The block motion model has been successfully applied in the Western US and Alaska to explain the observed deformation field and seismicity, considering the elastic deformation caused by slip deficit at the subducting plate, rigid rotation, and coupling on the inland faults. However, a block model covering the entire Western Canada currently does not exist due to a sparse GNSS network coverage in the past. An increased number of newly installed continuous Global Navigation Satellite System (GNSS) stations improves the data coverage in the southern Cordillera. In addition, episodic GNSS sites will be occupied to improve the density further. We will collect and process GNSS data using up-to-date hardware and software. Advanced time series processing techniques will be used to derive GNSS secular rate and the noise model for accurate velocity determination. We will combine the GNSS velocity field with geological and seismological data to define crustal blocks in Western Canada and calculate the bounding fault slip rates. The outputs will provide a unified velocity model and present-day crustal fault slip rates in Western Canada. Comparing the present-day fault slip rate with the geologically determined fault slip rate will provide insights into the tectonic history of the Cordillera. Such a GNSS-based kinematic block motion model provides critical constraints on the first-order deformation pattern and the possibility of future earthquakes on faults and improves our understanding of the crustal dynamics in the cordillera.

与经过充分研究的卡斯卡迪亚俯冲带相反，加拿大科迪勒拉山脉的地壳变形及其与地震的关系尚不清楚。例如，GPS 观测显示普吉特海湾是一个向北的地壳压缩（缩短）和地震活动区。然而，现有的地壳运动模型并没有详细显示变形模式如何向北延伸到弗雷泽低地和温哥华这个高度发展和人口密度的地区。目前对变形缺乏了解给加拿大西部的灾害模型增加了相当大的不确定性。加深对当今构造的了解有助于建立更好的地震灾害模型，该模型已纳入住宅建筑规范和关键基础设施（水坝、电力设施、液化天然气工厂）的建筑规范，这将降低风险并提高社会复原力。我们将测量和模拟加拿大西部的大规模构造运动，主要关注加拿大南部科迪勒拉山脉，覆盖不列颠哥伦比亚省的大部分地区以及阿尔伯塔省附近的人口中心，例如卡尔加里和埃德蒙顿。该模型将弹性岩石圈划分为小块，假设这些块以块边界断层为界。观测到的地壳变形速率假设为由于块体边界断层耦合而产生的刚性块体旋转速率和弹性变形速率之和。块体运动模型已在美国西部和阿拉斯加成功应用，解释了观测到的变形场和地震活动，考虑了俯冲板块滑移不足、刚性旋转和内陆断层耦合引起的弹性变形。然而，由于过去 GNSS 网络覆盖稀疏，目前不存在覆盖整个加拿大西部的区块模型。新安装的连续全球导航卫星系统（GNSS）站数量的增加改善了科迪勒拉山脉南部的数据覆盖范围。此外，还将占用间歇性GNSS站点以进一步提高密度。我们将使用最新的硬件和软件收集和处理 GNSS 数据。先进的时间序列处理技术将用于导出 GNSS 长期速率和噪声模型，以实现精确的速度确定。我们将把 GNSS 速度场与地质和地震数据结合起来，定义加拿大西部的地壳块体并计算边界断层滑动率。输出将提供统一的速度模型和当今加拿大西部的地壳断层滑动率。将当今的断层滑动率与地质确定的断层滑动率进行比较将有助于了解科迪勒拉山脉的构造历史。这种基于 GNSS 的运动块运动模型为一阶变形模式和未来断层上发生地震的可能性提供了关键约束，并提高了我们对山脉地壳动力学的理解。