GK12
Eric Johnson NSF Graduate Fellow
Thesis Title:
Lacustrine Response to Seismic Activity, Sawtooth Mountains, Central Idaho

Research Advisor:
Drs. Glenn Thackray and Dave Rodgers

Teacher Partner:
Kristi Wehrspann

Degree Sought:
Masters of Geology

University Department and/or Lab:
Geosciences

Description of Research:
Abstract: Seismic activity along the Sawtooth Fault is thought to have occurred within the last 10,000 years, and this activity should be recorded in sediments from lakes and marshes within the Sawtooth Valley. Seismic activity would be recorded as lake bottom slump deposits, distorted laminated sediments, microstructures disrupting lake sediment laminations, and tsunami and seiche (large lake wave) deposits in marsh sediments. I suggest that the records of this activity should be more distinctive in sediments closer to the center of the main Sawtooth Fault segment and less prominent further away. Sediments from lakes and peripheral marshes will be collected from sediment cores and analyzed using descriptive core logging, magnetic susceptibility, total carbon analysis, and grain size analysis.  Sediments will be dated by radiocarbon and luminescence dating.  Analysis of these sediments will constrain the timing and potentially the magnitude of fault motion and shaking along the Sawtooth range front, which will greatly improve understanding of regional seismic hazards, and of regional tectonic processes through estimates of fault slip rates. Stable isotope analysis as well as pollen and diatom assemblages will serve as proxies of past paleoclimates within this region. This analysis will also serve to establish a more complete record of seismic and climatic events that have occurred in the Sawtooth Valley from the late Pleistocene to the present day.

An example of how you integrate your research into your GK-12 experience:
First, we plan on bringing up the seismic aspect of my work during our section on earthquakes that is coming up in a few weeks. I will have the opportunity to explain about earthquake records and how my research is focused around determining the movement of the fault along the Sawtooth range front. Second, when we talk about the water cycle this winter, we are considering bring the students to my lab at ISU and showing them the lake sediment cores that I have collected, and how that material got into the lake and what it can tell us.


Profile date: Sept. 2008



Eric Johnson
johneric@isu.ed