【摘要】 高频假设下的地震射线理论、以及相应的地震成像理论,使得传统射线成像方法不可能具有较高的成像分辨率.相反,基于有限频的射线理论则更符合实际地震的传播规律,即地震波的走时不仅与中心射线(传统的几何射线)上的速度分布有关,而且与中心射线一定范围(称其为第一菲涅尔体)内的速度异常分布有关.鉴于此,本文提出了计算多震相菲涅耳体有限频地震射线的方法,同时给出了利用多震相菲涅耳体有限频射线进行速度和反射界面同时反演成像的迭代公式.利用多震相走时资料,分别使用传统射线走时层析成像方法和菲涅尔体有限频射线走时层析成像方法进行速度和界面的同时反演成像,结果表明:当射线密度较稀疏时,无论是对速度模型的重建还是对反射界面几何形状的更新,菲涅尔体有限频射线层析成像方法均优于传统的射线走时层析成像方法,而变频菲涅尔体有限频射线层析成像方法又优于单一频率的菲涅尔体有限频射线层析成像方法.更多还原

【Abstract】 Traditional ray tomography method based on high frequency assumption is unable to obtain a high resolution tomographic picture.In contrast,the finite-frequency ray theory is more suitable for real seismic propagation law,that is to say that the travel time is dependent not only on the velocity distribution along a central ray(or traditional geometric ray),but also on the velocity anomaly within a region(referred as first Fresnel Volume),which embrace the central ray.In this paper we first put forward an algorithm to calculate the multiphase Fresnel Volume finite-frequency ray,and then give a inversion method to simultaneous invert both velocity and reflector geometry by using these multi-phase arrival time information.In synthetic example,both the traditional ray tomographic and finite-frequency ray tomographic methods are used to simultaneously update both velocity field and reflector geometry with multi-phase arrival times,the results show that the finite-frequency ray tomographic method is advantageous over the traditional ray tomographic method in terms of velocity reconstruction and reflector geometry updating when the ray density is relatively low.The finite-frequency ray tomographic method with varying frequency is again better than the finitefrequency ray tomographic method with single frequency.更多还原