Understanding the Blind (Thrust Fault, That Is)

Larger imageSCEC Field Notes: Trevor Thomas Photo 1

The goal of our research is to learn more about blind-thrust faults underneath Los Angeles. These faults may pose a unique seismic threat to the LA metropolitan area. If one of these fault segments, namely the Los Angeles segment, was to rupture, the epicenter of the following earthquake could be very near the downtown area of Los Angeles.

In our research, we have used data from seismic reflection profiles gathered by the energy industry and data from boreholes we have drilled into fault-related stratigraphic folds. By studying the geometries of the folds and dating certain layers, we can determine the frequency at which these blind-thrust faults have ruptured in the past. In addition to bolstering our understanding about blind-thrusts, this knowledge also holds strong implications for seismic-hazard analysis in the Los Angeles region.

Larger imageSCEC Field Notes: Trevor Thomas Photo 2

One of the issues we face in this task is identifying layers from one borehole to the next. I am currently working on a new technique for correlating layers of sand and clay that uses their paleomagnetic properties as opposed to using their physical composition alone. This approach may give us the potential to depict fold geometries more accurately than we ever have before, which will in turn make measurements of fault slip-rates more accurate as well.

We are also working with the LA County division of Parks and Recreation and the Metropolitan Transportation Authority to get permission to dig a trench into the upper-reaches of folded strata above the Compton blind-thrust fault. This trench will allow visual inspection of strata that has been folded as a result of the most recent earthquakes along the Compton. After all, there is no better way to see a fold than with your very own eyes!

View field notes from other SURE Interns:   Select an intern... Alex Wilk Alexandra Millar Christina Velasquez Hannah Waterhouse Joshua Soble Lauren Steinberg Melissa Nunley Nathan Williams Patrick Dooling Tyanna Schlom