A Model for Lg Propagation in the Gulf Coastal Plain of the Southern United States
A Model for Lg Propagation in the Gulf Coastal Plain of the Southern United States
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DOI：
10.1785/0120150197
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发表时间：
2016-04-01
影响因子：
3
通讯作者：
Conn, Ariel
中科院分区：
文献类型：
--
作者：
Chapman, Martin;Conn, Ariel
美国南部在墨西哥湾中生代早期发育期间经历了伸展构造运动，随后积累了长达 12 公里的海洋沉积物。很少有地震台在墨西哥湾沿岸平原长期运行，并且用于约束地面运动预测模型的数据也很少。先前的研究发现，该地区的 Lg 衰减与北美东部其他地区不同。 2010 年至 2012 年，Earthscope 可移动阵列位于美国中南部，当时地震活动频繁。这种情况为研究 Lg 传播提供了数据。俄克拉荷马州、阿肯色州和得克萨斯州发生了 16 次震级为 3.2-5.6 级的地震，记录距离为 1000 公里。与位于沃希托造山带和克拉通台地北部的台站相比，德克萨斯州、阿肯色州、路易斯安那州和密西西比州沿海平原的台站表现出Lg相的强烈衰减。与墨西哥湾沿岸平原下方的地壳波导相关的 Q 值估计为 Q = 365f(0.62)。然而，由于地壳减薄和由于数公里沉积物的存在而造成的滞弹性衰减，Lg 堵塞发生在墨西哥湾沿岸附近。北纬 33 度以南的平均 kappa(0) 值为 96 +/- 10 毫秒。衰减参数 kappa(0) 与研究区域后侏罗纪沉积物的厚度之间存在显着的线性相关性，例如德克萨斯州、路易斯安那州和密西西比州海岸附近的站点，覆盖了大约 12 公里的沉积物，其 kappa(0) 值类似于 160 毫秒。这种衰减的强烈空间依赖性具有重要意义，应使用此处建议的方法将其纳入地面运动预测模型的开发中。
The southern United States experienced extensional tectonics during the early Mesozoic development of the Gulf of Mexico and subsequent accumulation of up to 12 km of marine sediment. Few seismic stations have operated in the Gulf Coastal Plain for extended periods of time, and data for constraining ground-motion prediction models are sparse. Previous studies found that the region differs from other parts of eastern North America in terms of Lg attenuation. The Earthscope Transportable Array was in the south-central United States in 2010-2012, during a time of increased seismicity. That circumstance provided data for investigating Lg propagation. Sixteen earthquakes with magnitudes in the 3.2-5.6 range occurred in Oklahoma, Arkansas, and Texas and were recorded to distances of 1000 km. Stations in the coastal plain of Texas, Arkansas, Louisiana, and Mississippi exhibit strong attenuation of the Lg phase, compared with stations located to the north in the Ouachita orogenic belt and cratonic platform. Q associated with the crustal waveguide underlying the Gulf Coastal Plain was estimated as Q = 365f(0.62). However, Lg blockage due to crustal thinning and anelastic attenuation due to the presence of several kilometers of sedimentary deposits occurs near the Gulf Coast. The average kappa(0) value south of latitude 33 degrees N is 96 +/- 10 ms. A remarkable linear correlation exists between the attenuation parameter kappa(0) and the thickness of post-Jurassic sediments in the study region, such that stations near the coast of Texas, Louisiana, and Mississippi, which overlie similar to 12 km of sediments, exhibit values of kappa(0) similar to 160 ms. This strong spatial dependence of attenuation has important implications and should be incorporated in the development of ground-motion prediction models using the approach suggested here.