Three-dimensional wavefield imaging of data from the USArray: New constraints on the geometry of the Farallon slab
Three-dimensional wavefield imaging of data from the USArray: New constraints on the geometry of the Farallon slab
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USArray 数据的三维波场成像：法拉隆板几何形状的新约束
DOI：
10.1130/ges00590.1
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发表时间：
2011
期刊：
影响因子：
2.5
通讯作者：
G. Pavlis
中科院分区：
文献类型：
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作者：
G. Pavlis
本文介绍了地球镜可移动阵列（TA）的P到S转换数据直接成像的初步结果。输入数据是来自Earthscope自动接收器功能调查（EARS）的接收器功能估计。EARS的波形首先被叠加，以产生来自60个不同震源区的复合事件，这些震源区由一个中心位于美国西部的放射状网格定义。复合波形成像的三维，叠前偏移方法，使用平面波分解和广义Radon变换逆算法，以产生估计的径向和横向分量散射潜力，从每个复合事件。由于数据不足，这一处理工作仅限于50起综合事件。通过三维可视化技术，将这50个事件的偏移结果叠加，以产生本文所研究的最终三维图像体。壳幔边界，410公里，660公里的不连续成像。一个不稳定的负转换的深度，已建议作为地震岩石圈-软流圈边界观察在这些结果中，但我避免解释这个功能，因为它可能是有偏见的干扰一阶，自由表面多次波从莫霍面。通过这种技术成像的最重要的新特征是直接在410公里不连续性上方的一系列东倾转换。这一特征是在整个美国西部过渡区上方的区域成像的，尽管它在亚利桑那州部分被我解释为污染了加州南部和格兰德河裂谷的一些台站的沉积物混响的干扰所掩盖。将这些结果与已发表的断层扫描模型叠加表明，这一特征与Juan de Fuca-Farallon板有关。我遵循这一假设，建立一个三维模型的顶部Farallon板，荣誉的新数据和结果，从公布的断层扫描模型。该模型阐明，这些浸渍功能是一致的弯曲板模型的板坯。使用一个简单的运动学模型的几何形状的板窗口链接到圣安德烈亚斯系统的扩大，我认为，相同的倾斜功能下看到的内华达州是一致的，看到的北方，这表明有一个连续的，相对平滑的板相关的边界层下的美国西部大部分地区。
This paper presents preliminary results from direct imaging of P to S conversion data from the Earthscope Transportable Array (TA). Input data are receiver function estimates from the Earthscope Automated Receiver Function Survey (EARS). The waveforms from EARS were first stacked to produce composite events from 60 different source regions defined by a radial grid with a center in the western United States (U.S.). The composite waveforms were imaged with a three-dimensional, prestack migration method using a plane wave decomposition and an inverse generalized Radon transform algorithm to yield estimates of radial and transverse component scattering potential from each composite event. Data deficiencies limited this processing to 50 of the composite events. The migrated results from these 50 events were stacked to produce a final three-dimensional image volume examined in this paper through three-dimensional visualization techniques. The crust-mantle boundary, the 410 km, and 660 km discontinuities are imaged. An erratic negative conversion at the depth that has been suggested as the seismic lithosphere-asthenosphere boundary is observed in these results, but I avoid interpreting this feature as it may be biased by interference with first-order, free-surface multiples from the Moho. The most significant new feature imaged by this technique is a series of east-dipping conversions directly above the 410 km discontinuity. This feature is imaged in the region immediately above the transition zone across the entire western U.S., although it becomes partly obscured in Arizona by interference with what I interpret as sediment reverberations that contaminate some stations in southern California and the Rio Grande Rift. Overlaying these results with published tomography models suggests that this feature is linked to the Juan de Fuca–Farallon slab. I follow this hypothesis to build a three-dimensional model of the top of the Farallon slab that honors the new data and results from published tomography models. The model clarifies that these dipping features are consistent with a bending plate model of the slab. Using a simple kinematic model of the geometry of the slab window linked to the widening of the San Andreas system, I argue that the same dipping features seen under Nevada are consistent with those seen to the north, suggesting that there is a continuous, relatively smooth slab-related boundary layer under most of the western U.S.