Crustal Composition and Moho Variations of the Central and Eastern United States: Improving Resolution and Geologic Interpretation of EarthScope USArray Seismic Images Using Gravity
Crustal Composition and Moho Variations of the Central and Eastern United States: Improving Resolution and Geologic Interpretation of EarthScope USArray Seismic Images Using Gravity
复制标题
DOI：
10.1029/2019jb018537
复制
发表时间：
2020-03
期刊：
影响因子：
--
通讯作者：
H. L. Zhang-H. L.-Zhang-2128667979;D. Ravat;A. Lowry
中科院分区：
文献类型：
--
作者：
H. L. Zhang-H. L.-Zhang-2128667979;D. Ravat;A. Lowry
在解释波长小于可移动阵列站距的地质特征方面，EarthScope的USArray可移动阵列存在不足，但可以通过使用更高空间分辨率的重力数据来克服这些缺点。在这项研究中，我们利用US阵接收函数来减少重力异常解释中的不唯一性。我们根据沉积盆地以前的密度变化、地壳的Vp/Vs变化、莫霍面变化和由面波层析成像得到的体波成像的上地幔密度变化模拟重力异常，以估计Vp/Vs。虽然可以得出这些地震变化的平均密度和密度对比，但由它们模拟的重力异常并不能解释美国观测到的整个重力异常场。我们使用未建模的重力异常(残差)来重建与地质来源相关的地壳密度的局部变化。该方法使用速度-密度关系，不同于假定均衡补偿的密度计算。这些地壳内密度确定了没有被US阵列站间距采样的地质源，在某些情况下，还被US阵列站间距混叠。我们在美国中部密苏里州布卢姆菲尔德普卢顿附近展示了一个这种改善的例子。
EarthScope's USArray Transportable Array has shortcomings for the purpose of interpreting geologic features of wavelengths less than the Transportable Array station spacing, but these can be overcome by using higher spatial resolution gravity data. In this study, we exploit USArray receiver functions to reduce nonuniqueness in the interpretation of gravity anomalies. We model gravity anomalies from previously derived density variations of sedimentary basins, crustal Vp/Vs variation, Moho variation, and upper mantle density variation derived from body wave imaging informed by surface wave tomography to estimate Vp/Vs. Although average densities and density contrasts for these seismic variations can be derived, the gravity anomalies modeled from them do not explain the entire observed gravity anomaly field in the United States. We use the unmodeled gravity anomalies (residuals) to reconstruct local variations in densities of the crust associated with geologic sources. The approach uses velocity‐density relationships and differs from density computations that assume isostatic compensation. These intracrustal densities identify geologic sources not sampled by and, in some cases, aliased by the USArray station spacing. We show an example of this improvement in the vicinity of the Bloomfield Pluton, north of the bootheel of Missouri, in the central United States.