LAKE BONNEVILLE AND THE WASATCH FAULT - NEW INSIGHTS YIELD NEW QUESTIONS ON SEISMIC RISK IN THE REGION

This is a follow-on to a 2020 GSA presentation: Evidence of Earthquake-Induced Surging in Pleistocene Lake Bonneville (Session T166). That presentation presented evidence in the Salt Lake Valley of earthquake induced surging immediately preceding the level drop of the Bonneville Flood and challenged well-accepted theories related to Wasatch Fault features.

In this work additional evidence is presented including data supporting a flood date of 17.4 ka. Features at the Zenda dam are correlated with this theory.

Evidence is also presented that this surging occurred at regular intervals in the lake, and that several previously identified climate oscillations were instead the result of multi-segment slips on the Wasatch Fault.

The potential for a present-day multi-segment failure on the Wasatch Fault is addressed, but while the author will offer an opinion, he believes this is an important issue related to current earthquake hazards in the region which warrants broader study in light of this new information.