学　术

　　由资源与环境学院主办的“资环论坛”第81期特别邀请赵杨博士主讲，欢迎广大师生参加，具体安排如下：

　　报告题目：各向异性弹性逆时偏移与4维地震监测的虚拟源技术

　　报告人：赵杨　博士

　　时  间：2019年5月24日（周五）上午10:00

　　地  点：清水河校区　创新中心D518

　　报告摘要：

　　1.Anisotropic elastic reverse time migration

　　Separating compressional and shear wavefields is an important step in elastic reverse-time migration, which can remove wave-mode crosstalk artifacts and improve imaging quality. In vertical (VTI) and titled (TTI) transversely isotropic media, the state-of-art techniques for wavefield separation are based on either non-stationary filter or low-rank approximation. They both require intensive Fourier transforms for models with strong heterogeneity. Based on the eigenform analysis, we develop an efficient pseudo-Helmholtz decomposition method for VTI and TTI media, which produces vector P- and S-wavefields with the same amplitudes, phases and physical units as the input elastic wavefields. The separated vector wavefields are used to produce PP and PS images by applying a dot-product imaging condition. Several numerical examples demonstrate the feasibility and applicability of the proposed methods.

　　2.Virtual source for 4D land monitoring

　　Interferometric virtual source (VS) redatuming converts surface-triggered source records into the equivalent records as if they originated from buried receiver locations by crosscorrelating downgoing waves with the corresponding upgoing waves. However, in the presence of a complex near surface, an intricate shallow structure and highly variable weathering layers can severely distort the raypath, such that it produces uneven angle coverage to the buried VS. We address these issues explicitly by spatially filtering the potentially contaminated direct wavefields using a zero-phase matched filter, such that the filtered wavefield is consistent with a model-based ideal direct P-wavefield observed at common receiver locations. The new VS approach provides significantly improved image quality and repeatability based on a pilot field of 13 time-lapse surveys, which solved a significant repeatability problem across a 17 month survey gap.

　　报告人简介：

　　赵杨博士，2006年北京大学本科毕业，2013年初获美国加州大学伯克利分校博士学位。曾先后在斯伦贝谢、壳牌、道达尔和康菲石油进行研究工作，现就职于沙特阿美国家石油公司休斯顿研发中心，任资深地球物理勘探师，拥有7年在美国石油公司的工业界经验。发表与接收国际会议和期刊论文30余篇，申请美国专利6个。主要研究方向为：地震干涉，四维地震处理，声波与弹性波逆时偏移成像。