Collaborative Research: Correlogram Migration of Scattered Teleseismic Body Waves

研究了一种利用散射远震体波相关图偏移成像地球反射率分布的新方法。应用于地震勘探的相关偏移方法正在扩展到利用远震体波对密集接收阵列下的地壳和上地幔结构进行成像。这些波包括P - SV相和P - P表面反射相，以及其他直接相和表面散射相。结果是记录阵列下每个散射波的反射率分布图像。目前使用接收函数对横向变化结构进行成像的方法主要是直接将P转换为SV到达进行地下照明。鬼反射的相关成像提供了P到SV透射波的互补分辨率。讨论了利用远震阵列数据对横向变化介质进行不同相位相关图偏移成像的实用性问题。此外，还研究了相关图偏移作为数据质量、接收器间距和所使用的远震数据类型的函数的局限性。由于实际的远震阵列构型会产生一些混叠效应，一种对这些效应不那么敏感的类波束偏移算法——波径偏移算法正在进行远震阵列数据成像试验。在Wasatch前缘使用不同的远震阵列配置对远震数据的相关图偏移进行了测试。本研究的意义在于开发了利用远震数据对横向变化结构进行成像的新方法，将接收函数成像推广到包括转换反射和鬼反射。相关图成像对密集地震台网最为有效。

A new methodology for the imaging of the earth's reflectivity distribution by correlogram migration of scattered teleseismic body waves is being investigated. The correlation migration methods developed for applications in seismic exploration are being extended to the imaging of crustal and upper mantle structure beneath a dense receiver array using teleseismic body waves. These waves include P to SV and P to P surface reflected phases, in addition to other direct and surface scattered phases. The result is an image of the reflectivity distribution beneath the recording array for each of the scattered waves. The current imaging methods using receiver functions for laterally varying structure mostly use directly converted P to SV arrivals for subsurface illumination. Correlation imaging of ghost reflections provides complementary resolution to that of P to SV transmitted waves. Questions concerning the practicality of using correlogram migration of different phases for the imaging of laterally varying media using teleseismic array data are being addressed. Also, the limitations of correlogram migration as a function of data quality, receiver spacing and type of teleseismic data used are being investigated. Since for practical teleseismic array configurations, some aliasing effects will result, a new beam-like migration algorithm, call wavepath migration, which is less sensitive to these effects, is being tested for the imaging of teleseismic array data. The correlogram migration of teleseismic data is being tested using different teleseismic array configurations across the Wasatch Front. The significance of this research is the development of new imaging methods for laterally varying structure using teleseismic data, which generalizes receiver function imaging to include converted as well as ghost reflections. Correlogram imaging is most effective for dense seismic networks.