A Synoptic View of the Formation, Evolution, and Shallow Subduction of the Juan de Fuca and Gorda Plates

卡斯卡迪亚计划安装了大量海底和陆地地震仪，为胡安·德富卡和戈尔达板块提供了前所未有的覆盖范围，包括海上，以及卡斯卡迪亚的陆上。该阵列使得研究海洋板块的结构和过程成为可能，从它在扩张中心的形成，到它的演化，再到最终在大陆之下的俯冲。科学目标是绘制胡安·德·富卡和戈尔达扩散中心下方岩浆产生区域的图像，了解海洋板块的热演化，并确定板块如何随时间变形。在板块俯冲开始时开始向下弯曲的区域，将特别注意将下行板块与上覆板块分开的主断层的锁定带和过渡带。即将出现的新的3-D模型将涵盖大部分在卡斯卡迪亚大地震中失败的锁定带，这可能对美国构成最大的地震危险。这项研究的重点是根据最大观测周期的不同，建立深度在60公里到100公里之间的地壳和上地幔的三维模型。该模型将包括各向同性结构以及径向（或极化）和方位各向异性的剪切速度。这项工作将主要基于来自环境噪声和地震的瑞利波和洛夫波频散数据，这些数据将在贝叶斯蒙特卡罗反演的框架内进行解释，以产生可接受模型的分布，并从中估计不确定性。在实际情况下，将在反演中吸收接收函数和瑞利波水平/垂直振幅比。地震模型和用于构建模型的数据将被存档，并与更广泛的地球科学团体共享。高水平的数据产品，如色散图、3-D模型、接收函数、其他表面波观测数据（如H/V比）和研究代码，通过动态更新的、可访问互联网的数据库提供。该提案还将支持一名研究生。

The installation of a large array of ocean bottom and land seismometers for the Cascadia Initiative provides unprecedented coverage of the Juan de Fuca and Gorda plates, offshore, and in Cascadia, onshore. The array makes it possible to study the structure and processes of an oceanic plate from its formation at the spreading center, through its evolution, and ultimate subduction beneath the continent. The scientific goals are to image the magma producing regions beneath the Juan de Fuca and Gorda spreading centers, to understand the thermal evolution of an oceanic plates and to determine how the plate deforms over time. In the region where the plate begins to bend downward at the onset of subduction, special attention will devoted to the Locked and Transition Zones of the major fault separating the downgoing plate from the over-riding plate. The new 3-D model that will emerge will encompass much of the locked zone that fails in major earthquakes across Cascadia, which pose perhaps the greatest seismic hazard to the US.This study focuses on the development of a 3D model of the crust and uppermost mantle to a depth of between 60 km and 100 km, depending on the maximum period of observation. The model will encompass isotropic structures as well as the radial (or polarization) and azimuthal anisotropy of shear velocities. The work will be based primarily on Rayleigh and Love wave dispersion data derived from ambient noise and earthquakes, which will be interpreted within the framework of a Bayesian Monte Carlo inversion to generate a distribution of accepted models from which uncertainties will be estimated. Receiver functions and Rayleigh wave horizontal/vertical amplitude ratios will be assimilated in the inversion wherever practical. The seismological models, and the data used to construct them, will be archived and shared with the broader geoscience community. High level data products such as dispersion maps, 3-D models, receiver functions, other surface wave observables like H/V ratios, and research codes are delivered through dynamically updated, internet-accessible databases. The proposal will also support one graduate student.