Sedimentary and Crustal Structure of the Western United States From Joint Inversion of Multiple Passive Seismic Datasets
Sedimentary and Crustal Structure of the Western United States From Joint Inversion of Multiple Passive Seismic Datasets
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DOI：
10.1029/2021jb022384
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发表时间：
2022-01
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影响因子：
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通讯作者：
Guoliang Li;T. Bidgoli;Min Chen;Xiaodan Ma;Jiaqi Li
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文献类型：
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作者：
Guoliang Li;T. Bidgoli;Min Chen;Xiaodan Ma;Jiaqi Li
准确的地壳地震图像对于评估地震危险和阐明形成地表地貌的构造过程至关重要。尽管人们已经使用各种地震数据集和层析成像方法对加州和内华达州进行了广泛的研究，但该地区缺乏能够准确定义浅层（<8 km）和深层地壳的地震模型。我们利用最近增加的地震数据覆盖范围，建立一个新的三维横波速度模型，联合反演瑞利波椭圆率，相速度，和横波P波形。在大峡谷，新模型揭示了一个不对称的基底，在西部急剧倾斜，在东部缓慢倾斜。在它的西缘之下，在海岸山脉，我们解决了一个楔形，低速区在中上地壳，解释为方济各会复杂。我们的图像证实，西部大峡谷的隆起和沉积中心的东移是由俯冲过程中的楔合和俯冲的复杂。在整个海盆和山脉中，在北方海盆和山脉的南半部，已分解的地壳平均厚度为38公里，比邻近地区厚约5公里。增厚的地壳与中新生代熔结凝灰岩爆发的主要火山中心重叠。这种空间相关性可能表明岩浆侵入和底侵作用有助于地壳生长和增厚之前中新世盆地和山脉的扩展。总的来说，新模型与该地区的活动源研究一致，但提供了一个更全面的看法，在这个大的和构造复杂的地区的浅层和深层结构。
Accurate seismic images of the crust are essential for assessing seismic hazards and elucidating tectonic processes that shape surface landforms. Although California and Nevada have been studied extensively using various seismic datasets and tomographic methods, the region lacks a seismic model that can accurately define both the shallow (<8 km) and deeper crust. We take the advantage of recent increases in seismic data coverage to build a new 3D shear wave speed model by jointly inverting Rayleigh wave ellipticity, phase velocity, and teleseismic P waveforms. In the Great Valley, the new model reveals an asymmetric basement, steeply dipping in the west and gently dipping in the east. Beneath its western margin, in the Coast Ranges, we resolve a wedge‐shaped, low‐velocity zone in the upper‐middle crust, interpreted as Franciscan Complex. Our images confirm that uplift of the western Great Valley and an eastward shift of its depositional center are caused by wedging and underthrusting of the complex during subduction. Across the Basin and Range, the resolved crust has an average thickness of 38 km in the southern half of the northern Basin and Range, about 5 km thicker than neighboring regions. The thickened crust overlaps with major volcanic centers of the mid‐Cenozoic ignimbrite flare‐up. This spatial correlation may suggest magmatic intrusions and underplating contributed to crustal growth and thickening prior to Miocene Basin and Range extension. Overall, the new model is consistent with active source studies in the region but provides a more comprehensive view of shallow and deep structures across this large and tectonically complex region.