USING A VIRTUAL OUTCROP MODEL FOR FRACTURE ANALYSIS: METHODOLOGY AND ASSESSMENT

This study presents a virtual outcrop model (VOM) which was analyzed for the purposes of fracture analysis. VOMs have been shown to be useful and accurate methods for data collection in geology, however, there still remain gaps in best practice and specific use cases. This work addresses those of fracture analysis using a VOM and an initial assessment of accuracy. The outcrop used in the study is a fractured granite in the eastern Santa Monica Mountains, CA and was modelled with the software Meshroom. Fracture tracing and measurement on the VOM was performed in the software CloudCompare, which automatically generated planar features that were then filtered and manually assessed in order to avoid analysis of non-fracture entities. This highlights a current bottleneck in such remote sensing workflows because automated processes are simply unable to discern geologically relevant features. A direct comparison to field data was also done, based upon linear scanlines correlated to the VOM. Intensity measured in the field was calculated to be 22.3 m^-1, whereas using the VOM the intensity was 17.3 m^-1. Intensity differences was primarily due to the loss of resolution in the VOM for areas of homogenous color and texture, making fractures difficult to detect. This shows a potential issue with using VOMs for the purposes of fracture characterization, depending upon the desired resolution of fracture data. Future work will look to better constrain the error of VOMs by placing them in the context of multiple scales of fracture analysis.