Thin lithosphere beneath the central Appalachian Mountains: Constraints from seismic attenuation beneath the MAGIC array
Thin lithosphere beneath the central Appalachian Mountains: Constraints from seismic attenuation beneath the MAGIC array
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DOI：
10.1016/j.epsl.2019.04.045
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发表时间：
2019-08
影响因子：
5.3
通讯作者：
J. Byrnes;M. Bezada;M. Long;M. Benoit
中科院分区：
文献类型：
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作者：
J. Byrnes;M. Bezada;M. Long;M. Benoit
众所周知，美国东海岸的被动边缘在地质上是活跃的，最近恢复了地貌，板内地震活动，以及始新世时期的火山活动。这项研究使用中大西洋地球物理综合协作(MAGIC)实验的地震数据来限制阿巴拉契亚山脉中部下方遥震P波衰减的横向变化，以揭示这一“活跃”被动边缘的上地幔的结构和动力学。我们使用蒙特卡罗方法来估计衰减随数据和模型不确定性的变化。在阿巴拉契亚山脉中部西侧不到50公里的距离内，上地幔的品质因数急剧下降，以前曾在那里推断过低速异常。在有限差分波形模拟实验的基础上，拒绝将散射或聚焦等外部因素作为对观测的解释。阿巴拉契亚山脉山顶下的衰减峰值要求近至超固相线条件发生在上地幔，并与始新世时期的火山活动共处一处。我们倾向的解释是，这种衰减反映了地幔岩石圈通过山下的拆离以及随后持续的小规模对流而被移除。
The passive margin of the eastern coast of the United States is known to be geologically active, with recently rejuvenated topography, intraplate seismicity, and volcanism of Eocene age. This study uses seismic data from the Mid-Atlantic Geophysical Integrative Collaboration (MAGIC) experiment to constrain lateral variations in the attenuation of teleseismicPwaves beneath the central Appalachian Mountains to shed light on the structure and dynamics of the upper mantle at this “active” passive margin. We use a Monte Carlo approach to estimate variations in attenuation along with both data and model uncertainties. The quality factor of the upper mantle dramatically decreases over a distance of less than 50 km on the western side of the central Appalachian Mountains, where a low-velocity anomaly has been previously inferred. Extrinsic factors such as scattering or focusing are rejected as explanations for the observations on the basis of finite-difference waveform modeling experiments. The peak in attenuation beneath the crest of the Appalachian Mountains requires that near- to super-solidus conditions occur in the upper mantle and is co-located with volcanism of Eocene age. Our preferred interpretation is that the attenuation reflects the removal of the mantle lithosphere via delamination beneath the mountains, followed by ongoing small-scale convection.