The crystalline rock includes unaltered igneous rock and mineralogically altered rock. Filtering, surface consistent deconvolution, and trace editing were used to suppress both the strong coherent source generated noisefield, and the high amplitude ambient noise field from mining operations. Velocity models for migration were constructed using ray-based inversions of the first arrivals from the reflection lines, and then incorporating travel times from transmission data. Stacks were poststack depth migrated and combined into seismic sections of the total mine depth. Combined source sections for two lines of the survey compare well with borehole data, and with the formations seen in the mine walls.
Faults are also visible acting as conduits for groundwater movement.
Imaging differences in lithology, contrasts due to mineralogic alteration, and structural faulting has potential importance for the mining operation. Locating structural features, such as those controlling groundwater flow, also has environmental applications. Traveltime inversion was employed to construct geologically reasonable models that fit the data appropriately. Several groups of seismic waves that relate to different structural elements of the margin were identified and utilized. The final models include slope sediments, the Valparaiso forearc basin, subducting sediments, a margin wedge, upper and lower continental crust, and a two-layer oceanic crust.