Vertical Seismic Profiling at the Chinese Continental Scientific Drilling Site

Abstract

AbstractThe research on the Sulu ultra‐high‐pressure metamorphic belt has great significance for understanding the continental geodynamic processes that occurred in the deep mantle. In recent years, Chinese continental scientific drilling and detailed comprehensive geophysical investigation including deep seismic reflection have been carried out. These offered rare basic data for the research of ultrahigh‐pressure metamorphic belt, the earth's crust and upper mantle fabrics. The drill‐hole cores offered the direct data of composition, texture, and structure of deep rocks, in which the characteristic scale is merely a few centimeters. However, drill‐hole and well‐logging can only survey in one dimension. Therefore three dimensional seismic data should be calibrated with both spatial and time sampling scales for comparing drill‐core and well‐logging data. The survey of offset and non‐offset vertical seismic profile serves to provide good links between the cores and well‐logging data with seismic reflection events, show their geological attributes, and imaging structural details of around‐hole rocks. In addition, the VSP data provide S‐wave velocity profile along the hole that is the primary source for building the S‐wave velocity structure. Besides, as a result of using digital three‐component geophones, various information of structure and rock properties in drilling area was obtained, such as shear wave velocity model in the scientific drilling area, which is a prerequisite for data processing of multi‐wave exploration. In conclusion, this work suggests VSP investigation be carried out in continental scientific drilling project in crystalline rock areas, it seems possible and feasible.