COLLABORATIVE RESEARCH: In Situ and Laboratory Measurement of Seismic Velocity Across an Exposed Brittle Fault Gouge Zone

孔 9909376在地壳断层，如圣安德烈亚斯和俯冲带巨型逆冲断层，异常地震速度，地震反射率和电导率已被解释为流体含量，孔隙压力，断层泥的存在或成分，和损害区的影响的签名。 然而，这些因素的相对贡献，可检测的断层带属性知之甚少。 PI将在加州莫斯海滩的圣格雷戈里奥断层的活跃海豹湾链的未风化暴露区进行地震速度和电导率的现场和实验室综合研究。 将在实地通过高分辨率地震和电阻率勘测测量压缩波和剪切波速度和各向异性以及电导率，并在实验室对高压下的代表性样品进行测量。 现场测量将记录无法在实验室中取样的长尺度效应，弥合实验室和地球物理现场数据之间的差距，而实验数据将记录孔隙压力和应力在深度的影响以及物理性质与岩性和结构地质的关系。 结果将与现有的岩性和构造数据一起沿着用于创建断层带物理性质的综合模型。

Hole 9909376 In crustal faults such as the San Andreas and subduction zone megathrusts, anomalous seismic velocity, seismic reflectivity, and electrical conductivity have been interpreted as signatures of fluid content, pore pressure, fault gouge presence or composition, and damage zone effects. However, the relative contribution of these factors to detectable fault zone properties is poorly known. The PIs will conduct a combined field and laboratory study of seismic velocity and electrical conductivity across an unweathered exposure of the active Seal Cove strand of the San Gregorio Fault in Moss Beach, California. Compressional and shear wave velocity and anisotropy and electrical conductivity will be measured in the field through very high-resolution seismic and resistivity surveys, and in the laboratory on representative samples at elevated pressure. Field measurements will document long length-scale effects that cannot be sampled in the laboratory, bridging the gap between laboratory and geophysical field data, while the experimental data will document pore pressure and stress effects at depth and the relationship of physical properties to lithology and structural geology. The results will be used along with existing lithologic and structural data to create an integrated model of fault zone physical properties.