Lateral Variation of Crustal Lg Attenuation in Eastern North America.
Lateral Variation of Crustal Lg Attenuation in Eastern North America.
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北美东部地壳Lg衰减的横向变化
DOI：
10.1038/s41598-018-25649-5
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发表时间：
2018-05-08
影响因子：
4.6
通讯作者：
Mousavi SM
中科院分区：
文献类型：
--
作者：
Zhao LF;Mousavi SM
我们对北美东北部进行 QLg 断层扫描。对302个台站记录的473次地壳地震的垂直宽带地震图进行处理，提取Lg振幅谱。层析反演以 58 个离散频率独立进行，这些频率均匀分布在 0.1 至 20.0 Hz 之间的对数空间中。这个相对较大的数据集具有良好的射线覆盖范围，使我们能够对该区域地壳衰减的横向变化进行成像。获得的宽带和单独频率的 QLg 地图为该地区的地壳衰减及其与该地区地质结构和过去构造活动的关系提供了新的见解。与较老、较冷、较干燥的加拿大地盾相比，QLg 显示出更统一的值，而较年轻的边缘的变化较大。结果证实了该地区大尺度变化与地壳地质特征的相关性。低速异常、厚沉积物、火山岩和薄洋壳的存在是观测到异常的潜在来源。平均 Q 值与主要地质省份的平均热流/发电量呈负相关。
We perform QLg tomography for the northeastern part of North America. Vertical broadband seismograms of 473 crustal earthquakes recorded by 302 stations are processed to extract the Lg amplitude spectra. Tomographic inversions are independently conducted at 58 discrete frequencies distributed evenly in log space between 0.1 and 20.0 Hz. This relatively large dataset with good ray coverage allows us to image lateral variation of the crustal attenuation over the region. Obtained QLg maps at broadband and individual frequencies provide new insights into the crustal attenuation of the region and its relationship to geological structures and past tectonic activity in the area. The QLg shows more uniform values over the older, colder, and drier Canadian Shield, in contrast to higher variations in the younger margins. Results confirm the correlation of large-scale variations with crustal geological features in the area. Existence of low-velocity anomalies, thick sediments, volcanic rocks, and thin oceanic crust are potential sources of observed anomalies. The mean Q values are inversely correlated with average heat flow/generation for main geological provinces.
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