The Walker Lane is a major element of the North American-Pacific plate boundary. This northwest trending zone of discontinuous active faults and disrupted topography that sits between the Sierra Nevada on the west and the north-northeast trending faults and ranges of the Great Basin to the east is associated with a well-defined zone of northwest-directed right-lateral shear based on GPS data. The Walker Lane has been suggested to mark the future site of the primary plate boundary thus research on the zone is fundamental to gaining an understanding of how a transform fault initiates and eventually becomes organized into a through-going plate boundary. This project focuses on a portion of northern Walker Lane in western Nevada where geologic evidence of this right-lateral shear is not evident and there is a discrepancy between geologic and GPS measurements of slip rate. LiDAR, geochronologic, and paleomagnetic data collected in this study are used to resolve this mismatch, detect unrecognized faults, and test if rotation of crustal blocks accommodates shear zone motion. The societal and scientific impact of the research will be enhanced by inclusion of both high school and undergraduate science students in the proposed research. The results will aid in assessment of seismic hazards in the Reno-Carson City corridor.
This project focuses on the portion of the Walker Lane in Nevada that encompasses the Lake Tahoe, Carson, Smith, Mason, Antelope, Bridgeport and Walker Lake basins and Carson and Wabuska structural lineaments. Here, geodetic data indicate ongoing northwest directed right-lateral shear strain is accumulating at about 5 to 6 mm/year and cumulative shear displacement of 20-30 km has enigmatically resulted in the development of a set of roughly en echelon normal fault-bounded basins in the absence of any major northwest-directed strike-slip faults. This project will collect and analyze LiDAR for evidence of strike-slip along the major structures of the region, apply cosmogenic, optically stimulated luminescence, and radiocarbon dating to identified offset surfaces to better quantify the rate at which faults are slipping, and utilize gravity and paleomagnetism to clarify the long-term structural development of the basins. The project will test the hypothesis that the displacement field across the region is taken up by a combination of vertical-axis rotations, southeastward translation of crustal blocks approximately parallel to the Walker Lane, and opening of the en-echelon set of basins. The goals of the research are to: (1) locally clarify whether or not the mismatch in geodetic rates is real, (2) assess whether or not the blocks bounding the basins record rotation and, if so, related to observed basin asymmetry, (3) compare the collected observations in the framework of prior hypotheses concerning the structural development of this portion of the Walker Lane, and (4) and integrate the mode of deformation observed here to elsewhere in the Walker Lane and the San Andreas fault system with an aim toward understanding the processes associated with the structural initiation of a continental strike-slip fault system.
