Anisotropic effects on the near surface seismic imaging

作者：Zhang Lina; Zhang Wei^*; Zhang Jie

来源：Near Surface Geophysics, 2015, 13(5): 485-493.

DOI：10.3997/1873-0604.2015035

Anisotropic effects have been widely considered in seismic subsurface imaging but rarely for the near-surface area. The near-surface area is often assumed isotropic. Seismic refraction methods are often applied to infer a shallow velocity model, either for making static corrections or for building the top portion of a pre-stack depth migration velocity model. To study the anisotropic effects on the refractions and the near-surface imaging results, we design numerical models with horizontal-transverse-isotropy anisotropic parameters assigned in the shallow layers and perform three-dimensional seismic ray-tracing with the consideration of horizontal-transverse-isotropy anisotropy to calculate the first-arrival travel times. Then, we assume the near-surface area "isotropic" and invert a near-surface velocity model using isotropic travel-time tomography. Through these tests, we have identified that the footprints of the recording geometry could be mapped into the velocity model, and high-velocity anomalies are produced right above the refractor if the horizontal-transverse-isotropy anisotropy is ignored. By applying the azimuth-dependent travel-time tomography, we could account for anisotropic effects and infer the fast and slow velocity models to determine the direction of the symmetry axis. With the same approach, we process a three-dimensional real data set, and the results are consistent with the local geology.

• 出版日期2015-10
• 单位中国科学技术大学