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岩石物理性质在不同方向的差异即各向异性必然导致地震波速度和衰减的各向异性。本文在实验室模拟不同的埋藏深度,用超声波沿三个方向即垂直地层层面方向(V方向)和平行地层层面的方向(h1、h2方向,相互正交)测量了露头砂岩(取自云南楚雄盆地T3)的纵横渡速度vp、vs和品质因子Qp、Qs,并计算了速度和衰减各向异性系数γv、γQ。实验结果表明:①速度vp、vs和品质因子Qp、Qs均随埋藏深度的增加而增加;②速度v和品质因子Q具有明显的方向性,垂直岩层层面方向的速度对和品质因子Q小于平行岩层层面方向的速度V和品质因子Q;③横渡衰减大于纵波衰减,即Qs>Qp;④衰减各向异性系数大于速度各向异性系数(约1个数量级),并且衰减各向异性系数随埋藏深度增加的减小率比速度各向异性系数随埋藏深度增加的减小率大,因此衰减可能是一个比速度对岩石各向异性更为敏感的地震特征参数。
The anisotropy of rock physical properties in different directions inevitably leads to the anisotropy of seismic velocity and attenuation. In this paper, we simulate different burial depths in laboratory, and outcrop sandstones (taken from Chuxiong, Yunnan Province) were measured by using ultrasonic waves along three directions (V direction) and parallel stratigraphic direction (h1 and h2 directions, The vertical and horizontal transversal velocities vp, vs and quality factors Qp, Qs of basin T3) were calculated, and the velocity and attenuation anisotropy coefficients γv and γQ were calculated. The experimental results show that: (1) The velocity vp, vs and the quality factor Qp and Qs both increase with the increase of the burial depth; (2) The velocity v and the quality factor Q have obvious directivity. The velocity in the direction of vertical strata is less than parallel to the quality factor Q The velocity V and the quality factor Q in the direction of the formation; ③ the transversal attenuation is greater than the attenuation of the longitudinal wave, ie Qs> Qp; ④ the attenuation anisotropy coefficient is larger than the velocity anisotropy coefficient (about one order of magnitude); and the attenuation anisotropy coefficient varies with burial The rate of decrease in depth increases is greater than the rate of decrease in velocity anisotropy in response to the increase in burial depth, so attenuation may be a seismic characteristic parameter that is more sensitive to rock anisotropy than velocity.