Analysis of VSP Data from the Cajon Deep Borehole

该项目包括对Cajon Pass（1800米- 3500米）第二阶段钻井期间收集的垂直地震剖面（VSP）数据进行分析。二期资料分析预计：1)确定3500米范围内的地震衰减和横波极化测量；2)确定第二阶段钻穿的主要裂缝段的地震阻抗和空间范围；3)将地壳反射率定义为6 ~ 10 km；4)确定井南（正断层）沉积剖面至基底的深度；5)在井南半井深范围内寻找与大型走滑断层有关的构造。Cajon Pass钻孔提供了最全面的结晶岩剖面之一，用于研究地震波在基岩中传播的基本特性。VSP数据将从钻井岩心和井筒地球物理测井中获得的地壳微结构和微观结构信息与大体积、长波长、长行程路径的地壳地震观测相结合。通过测量地面地震接收器无法获得的地震衰减、反射率和横波偏振的详细信息，VSP数据可以更深入地了解这些现象，就像在更广泛的地面观测中观察到的那样。

This project involves the analysis of Vertical Seismic Profiling (VSP) data collected during Phase II drilling at Cajon Pass (1800 meters - 3500 meters). Analysis of the Phase II data is expected to: 1) determine the seismic attenuation and shear wave polarization measurements to 3500 meters; 2) define the seismic impedance and spatial extent of the major fracture- interval that was drilled through during Phase II; 3) define crustal reflectivity to 6-10 km.; 4) establish the depth to basement of the (normal faulted?) sedimentary section south of the well; and 5) explore the structure associated with a large strike-slip fault within one half well depth of the hole to the south. The Cajon Pass drillhole provides one of the most comprehensively logged crystalline rock sections in which to investigate fundamental properties of seismic wave propagation in basement rock. VSP data connect crustal microfabric and microstructure information obtained from drilling core and wellbore geophysical logs to large volume, long wavelength, long travel path seismic crustal observations. By measuring in-situ seismic attenuation, reflectivity, and shear wave polarization at a level of detail unattainable with surface seismic receivers, VSP data permit a firmer understanding of these phenomena as observed in the wider domain of surface observations.