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Urban Paleoseismology of the Taylorsville Fault - New Data and Challenges from one of the Last Remaining Trench Sites on the West Valley Fault Zone, Utah

Description: 

The intrabasin West Valley fault zone (WVFZ) in Salt Lake Valley, Utah, comprises two subparallel main strands—the Granger fault (western strand) and Taylorsville fault (eastern strand)—and is antithetic to the Wasatch fault zone (WFZ). Both strands trend through the densely populated Salt Lake Valley, making sites suitable for fault trenching very sparse. A scarp trenched at the Airport East site on the Taylorsville fault in 2015 has now been destroyed by urban development. In 2022, we conducted a fault-trench study at the Indiana Avenue site, one of the last remaining suitable trench sites on the Taylorsville fault. This site was previously a green-waste landfill; however, a relatively undisturbed, small (1.5 m) fault scarp crosses the site. The elevation of the site (1288 m) suggests it was submerged by multiple pluvial lake cycles during the late Pleistocene and Holocene, including lakes Bonneville and Gilbert. The site is at or just below the shoreline of the early Holocene highstand of the Great Salt Lake (1288–1289 m), and below shorelines related to the Gilbert lake episode (1294–1297 m). Our trenches exposed a sand deposit likely related to the regression of Lake Bonneville, a clay-marl deposit likely related to the Gilbert episode and very similar to deposits in other WVFZ trenches, a paleo-Jordan River floodplain silty-sand deposit, and several clay-rich wetland deposits. Both trenches showed evidence of fault-related monoclinal warping, but only one trench showed evidence of discrete faulting in the footwall. Trench depth was limited due to shallow groundwater at the site. Due to these constraints, our trenches only revealed evidence for one or possibly two surface-rupturing earthquakes. Radiocarbon and optically stimulated luminescence samples provide age control on deposits and earthquake timing. These data will help us compare ages of deposits and earthquake timing to the Airport East and other WVFZ studies, and improve our understanding of the seismogenic relationship between the WVFZ and WFZ.

Session: From Faults to Fjords: Earthquake Evidence in Terrestrial and Subaqueous Environments [Poster Session]

Type: Poster

Date: 5/1/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Adam

Student Presenter: No

Invited Presentation: 

Authors