Date of Degree Completion
Master of Science (MS)
Second Committee Member
Third Committee Member
The 66-km-long Winter Rim Fault (WRF) system, located in the northwestern Basin and Range Province, encompasses several Holocene fault scarps within the Summer Lake basin that include the WRF system, a normal fault divided into three segments: Slide Mountain (SMF), Winter Ridge, and Ana River (ARF), and the newly-mapped Thousand Springs fault (TSF). The current least-compressive stress field is oriented ~264° (Crider, 2001). The USGS estimates a slip rate of 0.43 mm/yr, earthquake magnitudes of 6.5-7.19, and recurrence interval of 3.1 ka (Crone et al., 2009). However, these estimates are only based upon ARF and the unfavorably slip-oriented SMF. With high-resolution LiDAR, means to calculate a more inclusive slip rate estimate is possible, with fault scarps that cut radiocarbon-dateable tufa-coated paleoshorelines from Pleistocene Pluvial Lake Chewaucan. The faults have been active since the lake receded, and paleoshorelines are offset and no longer continuous. Twenty-four shoreline tufa samples were measured and calibrated, however 17 samples were eliminated, mostly due to discordant duplicate ages and unacceptable d13C ranges. Results revealed Pluvial Lake Chewaucan’s most recent highstand at ~1,340 m is 13.4 ± 0.1 to 13.7 ± 0.5 ka BP, with an average age of 13.5 ka BP, along with an earlier and higher highstand approximately 26.2 ± 0.2 to 34.3 ± 0.3ka at ~1,380 m. Comparing fault scarp-based slip distribution data with four historical events, it is reasonable to estimate that there have been approximately three to six surface-rupturing events since the earlier higher highstand along the Winter Ridge and SMF segments, two to three events for the ARF segment since the most recent highstand, and one to two events on the TSF between 2.12-4 and 12-15 ka BP. The USGS estimated the WRF system to have a slip rate of 0.43 mm/yr. From this study, I presented slip rates that ranged between 0.18 to 0.74 mm/yr, which lie squarely in the middle of Crone et al (2009) published range. This method provided the opportunity for obtaining slip rates through means other than trenching.
Hall, Jennifer, "Surface Offset and Slip Rates for the Winter Rim Fault System in the Summer Lake Basin, Oregon" (2017). All Master's Theses. 900.