Seismic Velocity and Q Structure of the Middle Eastern Crust and Upper Mantle from Surface-wave Dispersion and Attenuation
Seismic Velocity and Q Structure of the Middle Eastern Crust and Upper Mantle from Surface-wave Dispersion and Attenuation
复制标题
DOI：
10.1007/s000240050206
复制
发表时间：
1998-12
影响因子：
2
通讯作者：
L. Cong;B. Mitchell
中科院分区：
文献类型：
--
作者：
L. Cong;B. Mitchell
用双站法反演了中东地区7-82秒周期范围内的基模瑞利波的观测速度和衰减，得到了剪切波速度和剪切波结构。通过研究基模和高模瑞利波的振幅谱，获得了关于每个区域内Q结构变化的附加信息。我们获得了土耳其和伊朗高原（区域1），黑海和里海周围地区（区域2）和阿拉伯半岛（区域3）的模型。在区域2中，大陆-海洋边界和混合路径的影响可能导致在那里获得的模型中的不切实际的特征。在下地壳和上地幔深度，剪切速度在所有三个区域是相似的。在地壳上10 km处，剪切波速度变化很大，1区、2区和3区的剪切波速度分别为3.21、2.85和3.39 km/s.根据台间衰减资料反演得到的Q值模型表明，地壳剪切波Q值在3区最高，在1区最低.和201分别用于区域1、2和3。这三个区域在30公里深度的CrustalQ分别为51、71和134。下地壳Q值与剪切波Q值可能达到1000或更高的稳定大陆区域的结果形成鲜明对比。这些低值可能表明流体存在于下地壳的断层、裂缝和渗透性岩石中，以及由于中东地壳所有深度的会聚和强烈变形而导致的上地壳深度。
Observed velocities and attenuation of fundamental-mode Rayleigh waves in the period range 7–82 sec were inverted for shear-wave velocity and shear-waveQstructure in the Middle East using a two-station method. Additional information onQstructure variation within each region was obtained by studying amplitude spectra of fundamental-mode and higher-mode Rayleigh waves. We obtained models for the Turkish and Iranian Plateaus (Region 1), areas surrounding and including the Black and Caspian Seas (Region 2), and the Arabian Peninsula (Region 3). The effect of continent-ocean boundaries and mixed paths in Region 2 may lead to unrealistic features in the models obtained there. At lower crustal and upper-mantle depths, shear velocities are similar in all three regions. Shear velocities vary significantly in the uppermost 10 km of the crust, being 3.21, 2.85, and 3.39 km/s for Regions 1, 2, and 3, respectively.Qmodels obtained from an inversion of interstation attenuation data show that crustal shear-waveQis highest in Region 3 and lowest in Region 1.Q’s for the upper 10 km of the crust are 63, 71, and 201 for Regions 1, 2, and 3, respectively. CrustalQ’s at 30 km depth for the three regions are about 51, 71, and 134. The lower crustalQvalues contrast sharply with results from stable continental regions where shear-waveQmay reach one thousand or more. These low values may indicate that fluids reside in faults, cracks, and permeable rock at lower crustal, as well as upper crustal depths due to convergence and intense deformation at all depths in the Middle Eastern crust.