In this study, we use data from the SEISConn seismic experiment to calculate Sp receiver functions in order to characterize the geometry of upper-mantle structure beneath southern New England (northeastern United States). We image robust negative-velocity-gradient discontinuities beneath southern New England that we interpret as corresponding to the lithosphere-asthenosphere boundary (LAB) and identify a well-defined step of 15 km in LAB depth at a longitude of 73°W, which we interpret to be the boundary between Laurentian and Appalachian lithosphere, although the offset may be larger if the putative LAB phase is reinterpreted to be a mid-lithospheric discontinuity. We infer that the lithosphere throughout the region is substantially thinner than elsewhere in the continental interior, consistent with regional tomographic studies and previously published Sp receiver function results. The presence of thinned lithosphere suggests that the low-velocity Northern Appalachian Anomaly (NAA) in the upper mantle may extend as far south as coastal Connecticut. The presence of regionally thinned lithosphere and a step in lithospheric thickness suggests that inherited structure may be preserved in present-day lithosphere, even in the presence of more recent dynamic processes associated with the NAA.

中文翻译：

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美国东北部新英格兰南部下方岩石圈台阶和普遍岩石圈减薄的证据

在这项研究中，我们使用来自 SEISConn 地震实验的数据来计算 Sp 接收函数，以表征新英格兰南部（美国东北部）下方的上地幔结构的几何形状。我们对新英格兰南部下方的稳健负速度梯度不连续性进行了成像，我们将其解释为对应于岩石圈-软流圈边界 (LAB)，并在 73°W 的经度处确定了 LAB 深度 15 公里的明确台阶，我们将其解释为解释为劳伦斯和阿巴拉契亚岩石圈之间的边界，尽管如果将推定的 LAB 相重新解释为岩石圈中部不连续性，偏移量可能会更大。我们推断整个地区的岩石圈比大陆内部的其他地方要薄得多，与区域断层扫描研究和先前发表的 Sp 接收函数结果一致。岩石圈变薄的存在表明上地幔中的低速北阿巴拉契亚异常（NAA）可能向南延伸至康涅狄格州沿海。区域性变薄的岩石圈的存在和岩石圈厚度的一个台阶表明，即使存在与 NAA 相关的更近期的动态过程，遗传结构也可能保留在当今的岩石圈中。