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

在地壳断层中，如圣安德烈亚斯断层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被解释为流体含量、孔隙压力、断层泥存在或组成以及损伤带影响的特征。然而，这些因素对可探测断裂带性质的相对贡献知之甚少。PIs将在加州Moss Beach的San Gregorio断层的Seal Cove活跃链的未风化暴露区域进行地震速度和电导率的现场和实验室联合研究。纵波和横波速度、各向异性和电导率将通过非常高分辨率的地震和电阻率调查在现场测量，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构造地质学的关系。这些结果将与现有的岩性和构造数据一起用于创建断裂带物理性质的综合模型。

Tobin 9909270 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.