Measurement of Creep on the Central San Andreas Fault, California, with Iterative Closest Point Differencing of Structure from Motion and LiDAR Point Clouds

Authors: Logan Woolstenhulme*, Utah Valley University, Nathan Toke, Utah Valley University, Joe Phillips, Utah Valley University, Chelsea Scott, School of Earth and Space Exploration, Arizona State University, Jeremy Saldivar, Utah Valley University, Marissa Keck, Utah Valley University, Serena Smith, Utah Valley University, McKenzie Ranney, Utah Valley University, Michael P Bunds, Utah Valley University
Topics: Geomorphology, Field Methods, Hazards, Risks, and Disasters
Keywords: Fault, creep, structure from motion, drone, point cloud,
Session Type: Poster
Day: 4/13/2018
Start / End Time: 1:20 PM / 3:00 PM
Room: Napoleon Foyer/Common St. Corridor, Sheraton, 3rd Floor
Presentation File: No File Uploaded

Deformed cultural features, creepmeters, and GPS reference-stations show active aseismic creep on the NW-striking central San Andreas Fault (SAF). However, the distribution of creep across the fault is poorly known because surface displacement measurements are spatially sparse. We image creep by differencing a 2017 point cloud generated from unmanned aerial system (UAS) photographs processed with structure-from-motion (SfM) against the 2007 EarthScope Northern California LiDAR Project imagery. We constructed an SfM-based point cloud from 3533 photographs collected in October 2017 with an eBee Plus UAS flown at ~115m above-ground-level. The point cloud contains 1.3x10^9 points, covers a width of ~0.9-1.2km along ~2.8km of the SAF near Dry Lake Valley (36.469, -121.058). The point cloud was georeferenced using 30 ground control points (GCPs) and on-board GPS photograph location measurements. GCP and photograph locations were measured using carrier-phase, post-processed-kinetic GPS solutions, and a local base. 2017 positions were corrected to the IGS2000 2007.3 epoch of the 2007 LiDAR, and uniformly translated to adjust for plate motion. We calculated 3D displacements between the 2007 EarthScope LiDAR and the 2017 SfM imagery using the Iterative Closest Point algorithm with a 25m resolution. The results show ~30cm of right-lateral motion on the SAF with the majority of motion occurring within ~50m of the geomorphic fault trace, and ~2-5cm of SW side down vertical motion. These results are consistent with creepmeter data and show a more complete picture of the spatial distribution of creep along the central SAF.

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