Characterization of segmentation and long-term vertical slip rates of the wasatch fault zone, utah

The segmentation model of the Wasatch Fault Zone (WFZ) in north-central Utah has been central to understanding normal fault systems around the world. In this study, we test the notion that the classically defined Brigham City-Weber segment boundary is a barrier to earthquake rupture. To do this, we examined the elevation change of the Bonneville and Provo highstand shorelines of Lake Bonneville along these fault segments. We measured shoreline paleoelevation using the publicly available ± 20 cm vertical accuracy light detection and ranging (lidar) dataset sponsored by the State of Utah (2013-2014) and a new ArcGIS toolbox called PaleoElev that was developed as part of this study. Elevation profiles of the Bonneville and Provo shorelines along the footwall of the fault exhibit constant elevation from the southern end of the Weber segment to the northern subsegment of the Brigham City segment. These elevation patterns suggest that the southern subsegment of the Brigham City segment is linked to the Weber segment and has commonly ruptured coseismically with the Weber segment since the late Pleistocene. The northern subsegment of the Brigham City segment exhibits little to no elevation change, and it is unclear as to whether this subsegment has been active since the late Pleistocene. Where the shorelines are displaced by the WFZ, we have calculated vertical slip rates. The vertical slip rates calculated in this study have significant uncertainty associated with the shoreline paleoelevation measurements. We can only confidently report two vertical slip rates from the Provo shoreline at the Pleasant View Salient, which correlate well to Holocene rates calculated from paleoseismic trenching data and support our interpretation that the Pleasant View Salient is not a barrier to fault rupture.