Geophysical constraints on the crustal structure of the southern Rio Grande rift
Geophysical constraints on the crustal structure of the southern Rio Grande rift
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里奥格兰德裂谷南部地壳结构的地球物理约束
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
M. Hussein
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文献类型：
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作者：
L. Thompson;A. Velasco;A. Zamora;M. Hussein
里约热内卢大裂谷（RGR）仍有地质活动的证据，包括第四纪断裂、地震活动和小速率的加宽。我们绘制了地壳厚度和地震速度比图，生成了约束地壳模型截面，突出了南部RGR （SRGR）的区域延伸。具体来说，我们计算了来自EarthScope USArray可移动阵列的147个台站的接收函数和接收函数堆栈，并使用克里格插值方案对地壳和速度结果进行了插值。我们包括一种新的优化重力反演方法，使用接收函数结果作为反演密度剖面的约束。我们建立了约束的地壳模型，将SRGR的特征描述为在SRGR区域显示较浅的莫霍线（30公里），这比之前提出的要厚。在盆地和山脉省，地壳在RGR西部呈分层状，在RGR东部向大平原方向较厚，下地壳层密度较大。我们还发现特拉华盆地显示出明显的地球物理异常，可能是由于厚厚的饱和沉积物。鉴于该地区没有其他研究确定的深部地幔异常，我们认为裂谷可能是上地幔小尺度对流的结果，我们得出结论，RGR至少是盆地和山脉省与大平原之间的边界，可能反映了平板俯冲的终点。
Abstract Evidence of geologic activity still occurring in the Rio Grande rift (RGR) includes quaternary faulting, seismicity, and widening at a small rate. We map the crustal thickness and seismic velocity ratio to generate constrained crustal model cross sections that highlight the regional extension of the southern RGR (SRGR). Specifically, we computed receiver functions and receiver function stacks for 147 stations from EarthScope USArray Transportable Array and previously collected data in the southwestern United States, and interpolated the crustal and velocity results using a kriging interpolation scheme. We include a new optimized gravity inversion approach using the receiver function results as a constraint for inverted density profiles. We produce constrained crustal models that characterize the SRGR as showing a shallower Moho (30 km) in the region of the SRGR, which is thicker than previously suggested. The crust appears to be delaminated west of the RGR in the Basin and Range Province and thicker east of the RGR toward the Great Plains with a denser lower crustal layer. We also find that the Delaware basin shows a significant geophysical anomaly, likely due to thick saturated sediments. Given that there is no deep mantle anomaly determined from other studies in this region, we suggest that rifting could be the result of small‐scale convection of the uppermost mantle, and we conclude that the RGR is at a minimum the boundary between the Basin and Range Province and the Great Plains, perhaps reflecting the terminus of flat slab subduction.