Reproducibility of remote mapping of the 2019 Ridgecrest earthquake surface ruptures

Elaine K. Young, Michael E. Oskin, & Alba M. Rodriguez Padilla

In Preparation March 8, 2023, SCEC Contribution #12698

We use multiple, independently produced surface rupture maps of the 2019 Ridgecrest earthquake sequence to test the reproducibility of surface rupture map interpretation and completeness. The 4 July Mw 6.4 and 5 July Mw 7.1 earthquakes produced surface rupture zones approximately 20 km and 50 km in length, respectively. Three independent mappers with various backgrounds in active tectonics mapped the surface rupture from the post-earthquake lidar data without knowledge from post-earthquake field or geodetic observations. Visual comparisons of the three remote rupture maps show good agreement for scarps > 50 cm in height. For features with less topographic expression, interpretations of the data vary more widely between mappers. Quantitative map comparisons range from 18 to 54\% consistency between mapped lines with 1m buffers. The percent overlap increases with buffer width, reflecting variance in line placement as well as differences in fault-zone interpretation. Overall, map similarity is higher in areas where the surface rupture was simpler and had more vertical offset than in areas with complex rupture patterns or little vertical offset. In comparison to field observations, our remotely produced maps capture the principal rupture well but miss details and small features and geometric complexity. In general, field observations and airborne imagery detect more surface rupture features than airborne lidar. Lidar excels for detection and measurement of vertical offsets in the landscape, and it is deficient for detecting lateral offset with little or no vertical motion.

Citation
Young, E. K., Oskin, M. E., & Rodriguez Padilla, A. M. (2023). Reproducibility of remote mapping of the 2019 Ridgecrest earthquake surface ruptures. Seismological Research Letters, (in preparation).