UGS Excavates New Fault Trench on the West Valley Fault Zone

The Utah Geological Survey (UGS) recently excavated a trench in Salt Lake City exposing a cross-sectional view of the West Valley fault zone. Due to extensive urbanization in the Salt Lake Valley, this is one of the last available sites to study the fault.

UGS staff performs investigations of past earthquake activity (paleoseismology) by excavating trenches across hazardous faults (those known to be earthquake sources) every few years in cooperation with the federal U.S. Geological Survey (USGS) to understand past earthquake behavior and timing. This data includes when an area on a specific fault last moved during an earthquake larger than about Magnitude 6.5, and the average recurrence interval of past earthquakes.

Data from these investigations are incorporated into updates to the USGS National Seismic Hazard Maps that are part of the International Building Code (IBC) and International Residential Code (IRC) that are adopted in Utah and govern building design to help prevent collapse during earthquakes. Without data from paleoseismic investigations, such as our current project in Salt Lake City, the necessary information would not be available to design buildings and other infrastructure to withstand earthquakes, leading to significant deaths, injuries and financial losses from collapsed and severely damaged infrastructure during an earthquake. More information on earthquake hazards is available at