Evidence for Stress Localization Caused by Lithospheric Heterogeneity From Seismic Attenuation
Evidence for Stress Localization Caused by Lithospheric Heterogeneity From Seismic Attenuation
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DOI：
10.1029/2021gc009987
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发表时间：
2021-06
期刊：
影响因子：
3.7
通讯作者：
Zhao Zhu;M. Bezada;J. Byrnes;H. Ford
中科院分区：
文献类型：
--
作者：
Zhao Zhu;M. Bezada;J. Byrnes;H. Ford
怀俄明州落基山脉在拉拉米造山运动期间经历了构造修改，这导致了一系列基底核心隆起，形成了现代落基山脉。这个山脉最东端的地表--南达科他州的黑山--被粉河盆地的南半部分与落基山脉的主要趋势分开，我们称之为雷霆盆地。地震层析成像研究揭示了一个高速异常，它延伸到盆地下方300公里的深度，可能代表岩石圈龙骨。我们约束地震衰减调查的假设，在岩石圈厚度的变化导致应力的本地化，因此变形。我们利用来自CIELO地震阵列的数据，CIELO地震阵列是一个线性阵列，从黑山东部延伸到雷霆盆地，向西延伸到猫头鹰溪山脉，以大角山脉为中心的BASE FlexArray部署，以及EarthScope可移动阵列。我们分析了来自深源地震事件的地震图，并在时域中比较了波形，以表征衰减的横向变化。贝叶斯反演结果显示，在黑山和大角山脉和低衰减的雷霆和大角盆地的高衰减。由于P波尾波振幅与衰减之间存在很强的负相关关系，散射被认为是干扰因素。结果支持的假设，岩石圈强度的横向变化，我们的地震衰减测量证明，在本地化的变形和造山作用在Laramide造山运动中发挥了重要作用。
The Wyoming Craton underwent tectonic modifications during the Laramide Orogeny, which resulted in a series of basement‐cored uplifts that built the modern‐day Rockies. The easternmost surface expression of this orogeny ‐ the Black Hills in South Dakota ‐ is separated from the main trend of the Rocky Mountains by the southern half of the Powder River Basin, which we refer to as the Thunder Basin. Seismic tomography studies reveal a high‐velocity anomaly which extends to a depth of ∼300 km below the basin and may represent a lithospheric keel. We constrain seismic attenuation to investigate the hypothesis that variations in lithospheric thickness resulted in the localization of stress and therefore deformation. We utilize data from the CIELO seismic array, a linear array that extends from east of the Black Hills across the Thunder Basin and westward into the Owl Creek Mountains, the BASE FlexArray deployment centered on the Bighorn Mountains, and the EarthScope Transportable Array. We analyze seismograms from deep teleseismic events and compare waveforms in the time‐domain to characterize lateral variations in attenuation. Bayesian inversion results reveal high attenuation in the Black Hills and Bighorn Mountains and low attenuation in the Thunder and Bighorn Basins. Scattering is rejected as a confounding factor because of a strong anticorrelation between attenuation and the amplitude of P wave codas. The results support the hypothesis that lateral variations in lithospheric strength, as evidenced by our seismic attenuation measurements, played an important role in the localization of deformation and orogenesis during the Laramide Orogeny.