Seismic study of subduction zones, rifted margins and mid-ocean ridges

俯冲带、裂谷边缘和洋中脊的地震研究

• 批准号: RGPIN-2014-05809
• 负责人: Nedimovic, Mladen
• 金额: $ 3.79万
• 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: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=660761
• 关键词: Seismic; study; subduction; zones; rifted

The proposed research program is focused on three of the Earth's major boundaries: subduction zones, rifted margins and mid-ocean ridges, all of which form as part of the Earth's plate tectonic cycle. Subduction zones are places where oceanic and continental plates converge, and where the thinner but denser oceanic plate "ducks" under the continental plate to eventually become recycled into the Earth's mantle. Rifted continental margins form by extension and breakup of the continental lithosphere, a process that opens up new ocean basins. Mid-ocean ridges are a divergent plate tectonic boundary where new oceanic crust is being continuously generated. They make up the most extensive mountain system and the longest chain of volcanoes on planet Earth. The proposed research program relies on applying an innovative combination of state-of-the-art data analysis methods to new multichannel seismic and ocean bottom seismometer data. The goal is to image the targeted subsurface structures at unprecedented resolution in order to test leading scientific hypothesis and questions that have the potential to transform the fields of study this program focuses on. The selected study areas are: Alaska subduction zone, Juan de Fuca plate and Cascadia subduction zone, rifted margins of eastern Canada, and Southwest Indian ridge. The study areas and problems to be addressed by this program are chosen based on their suitability for achieving my short- and long-term science goals, the potential for high-impact discoveries, and interest to a broad group of earth scientists and general public. Volcanic eruptions and earthquakes at the Cascadia and Alaska subduction zones pose significant risk in the heavily populated areas of northwestern United States and southwestern Canada. How oceanic crust evolves from ridge to trench is important from the perspectives of both basic science (e.g., energy and mass exchange between the Earth's solid interior and the oceans) and societal impacts (subduction earthquake hazards). An expected outcome of this program are improved constraints on the downdip limit of maximum coseismic slip during subduction earthquakes or, in other words, better understanding of how close to the coastal cities can these large offshore earthquakes occur. Another outcome of this research program is more detailed information on lateral variations in subduction thrust (megathrust) coupling or, in simpler terms, which sections of subduction zones are strongly jammed and therefore likely to release most of the destructive seismic energy during subduction earthquakes. This knowledge will lead to advances in accuracy of probabilistic seismic hazards maps for megathrust events and improved building codes, our primary means used to mitigate against these damaging earthquakes. Better understanding of the inner workings of active magmatic systems, which are the least challenging to investigate at mid-ocean ridges because of the thin crust and relatively simple tectonic setting, will lead to better prediction of future undersea eruptions and to improved understanding of volcanoes in general. New constraints on the deep structures at rifted margins, that are also the site of major sedimentary basins that host the largest recently drilled hydrocarbon deposits, will help guide future petroleum exploration to new discoveries. All of the projects that comprise the proposed research program are high-profile international collaborations because investigations of structures deep below the seabed, which is one of the Earth's last frontiers, require major resources, both human and material.

拟议的研究计划集中在地球的三个主要边界上：俯冲带，裂痕边缘和中海脊，所有这些都是地球板块构造循环的一部分。俯冲带是海洋和大陆板汇聚的地方，在大陆板下面较薄但更密集的海洋板“鸭子”，最终被回收到地球的地幔中。大陆岩石圈的延伸和破裂形成了裂痕的大陆边缘，这一过程开辟了新的海洋盆地。海洋中脊是一个不同的板块构造边界，在该边界中正在连续产生新的海洋壳。它们构成了地球上最广泛的山系统和最长的火山链。拟议的研究计划依赖于将最先进的数据分析方法的创新组合应用于新的多通道地震和海洋底部地震仪数据。目的是以前所未有的分辨率对目标地下结构进行图像，以检验主要的科学假设和有可能改变研究领域的问题的问题。选定的研究区域是：阿拉斯加俯冲带，胡安·德福卡板和卡斯卡迪亚俯冲带，加拿大东部的裂痕和西南印度山脊。该计划要解决的研究领域和问题是根据其适合实现我的短期和长期科学目标的适用性，高影响力发现的潜力以及广泛的地球科学家和一般公众的兴趣的。卡斯卡迪亚和阿拉斯加俯冲区的火山喷发和地震在美国西北部和加拿大西南部人口稠密地区构成了巨大的风险。从基础科学的角度（例如，地球固体内部和海洋之间的能量和质量交换）和社会影响（俯冲地震危害），海洋壳从山脊变成沟渠的发展至关重要。该计划的预期结果是对俯冲地震期间最大抗震动滑移的下倒数限制的限制得到了改善，或者换句话说，更好地理解这些大型海上地震的距离如何靠近沿海城市。该研究计划的另一个结果是有关俯冲推力（Megathrust）耦合的横向变化的更详细信息，或者以更简单的术语，俯冲带的部分受到了强烈困扰，因此很可能在俯冲地震期间释放大多数破坏性的锯齿状能量。这些知识将导致概率地震危害图的准确性提高，并改善了建筑法规，这是我们用于减轻这些破坏性地震的主要手段。更好地了解主动岩浆系统的内部运作，这是在中山脊上调查的最不具有挑战性的，这是由于薄层和相对简单的构造环境，将导致更好地预测未来的底海喷发，并改善对火山的一般​​理解。对裂谷边缘的深层结构的新约束，这些结构也是主要沉积盆地的所在地，该盆地是最近钻孔碳氢化合物矿床的最大底层，将有助于指导未来的石油勘探到新发现。构成拟议研究计划的所有项目都是备受瞩目的国际合作，因为对海床深处的结构的调查（这是地球最后的前沿之一）需要大量资源，包括人类和物质。