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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.
The theory of seismic ray under the assumption of high frequency and the corresponding theory of seismic imaging make it impossible for the traditional radiography method to have higher imaging resolution. On the contrary, the ray theory based on finite frequency is more in line with the propagation law of actual earthquakes, Is not only related to the velocity distribution in the central ray (the traditional geometric ray) but also to the velocity anomaly distribution in the central ray (referred to as the first Fresnel body). In view of this, The method of using the finite frequency ray of the Fresnel body of multifrequency facies to reconstruct the velocity and reflection interface simultaneously is given.According to the multiphase seismic data, The results show that when the ray density is sparse, it is not only the reconstruction of the velocity model but also the reflection of the reflection of the velocity model The renewal of the interface geometry and Fresnel body finite-frequency radiographic tomography method are superior to the traditional method of radiographic traveltime tomography, Nirvana finite-frequency radiographic tomography is superior to Fresnel finite-radiomere tomography at a single frequency.