GSL - Oquirrh - Topliff Fault System

Oquirrh Fault System

The Oquirrh Fault bounds the west side of the Oquirrh Mountains, in rapidly growing Tooele County, Utah. It connects to the north with the Great Salt Lake Fault and to the south with the Topliff Hill Fault; together the faults are the second longest in Utah. In a project spanning several years and many students, we've been working to better understand segmentation on the system and the earthquake geology of the fault. It started as a class project by Andrew Fletcher in 2014, who used a DJI Phantom 2 and GoPro camera and SfM processing to successfully make a DEM of the Lake Bonneville highstand shoreline near where the fault cuts it. We expanded the mapping in Geospatial Field Methods the following year and successfully showed the bench and the younger Provo Shoreline are offset 3.1 m, in accord with a previous trenching study. Since then, I measured shoreline elevations along a ~30 km stretch of the fault and suggested the most recent surface-rupturing earthquake terminated at its south end near the south end of the city of Tooele. Charles Memmott is currently measuring scarp heights along the Northern and Southern Oquirrh Fault. His preliminary results suggest the most recent surface-rupturing earthquake propagated north into the Great Salt Lake, on the Great Salt Lake fault. He'll present this work at the 2021 Annual Meeting of the Geological Society of America in Portland, OR. As the project progresses, he's hoping to complete scarp measurements on the Southern Oquirrh Fault (a somewhat more complicated undertaking because the fault splays into multiple strands), and to better separate the isostatic rebound signal from the tectonic signal in the Lake Bonneville Shoreline elevations.

Topliff Hill Fault

I and Nathan Toke (also at UVU) have been co-leading a paleoseismology study of the Topliff Hill Fault, to the south of the Oquirrh Fault (Utah). We obtained a $10,000 grant from the UVU Office of Engaged Learning that supported the work and allowed us (under Dr. Toke's able leadership) to include the trench work in the 2019 edition of our summer Field Studies capstone course. Our trench logs and OSL dates show a more active history on the fault that we suspected, with a likely 5 to 7 events of modest displacement (ca. 1 m) events since the late Pleistocene. Preliminary results of this work were presented at AGU by our students (Sally Ward, Rachel Richards, and Brigham Whitney) and us.