Trenching the Thousand Springs Fault
in Central Oregon
In July 2019, Graduate Student Elizabeth Curtiss trenched the Thousand Springs Fault, a west-dipping normal fault, in Summer Lake, Oregon, located in the northwestern Basin and Range. Other faults in the basin show evidence of large (>M7) earthquakes, but the Thousand Springs fault was only recently mapped and has no documented earthquake history.
The Thousand Springs Fault cuts through an area of the basin with low sedimentation rates and numerous tephras (material ejected from volcanic eruptions - the gray layers in the photos) from the past ~250,000 years, in the northeastern part of Summer Lake. Its setting is very similar to the Ana River fault which is in the northwestern side of Summer Lake and due to these factors has a well-documented earthquake history. The tephras represent an instant in time which can then be correlated across the fault and their offset can be measured. By doing this, Elizabeth will reconstruct the earthquake history of the Thousand Springs Fault and use the data to aid in Basin and Range Fault Models, in addition to completing her M.Sc. Degree.