Using LiDAR to unravel the mystery behind neo-tectonics

The San Andreas fault (SAF), a ~1000 mile long right lateral strike-slip fault system, accommodates > 50% of the North American-Pacific plate boundary strain. In 1989, the 7.1 Mw Loma Prieta earthquake (LPEQ occurred along a bend in the SAF and shook the entire San Francisco Bay area. The earthquake was responsible for 63 deaths, 12,000 homeless and more than $6 billion in damages. Mapping surface features, such as fault rupture traces, allows geologists to constrain the amount and recurrence of fault slip events. The Loma Prieta earthquake produced no such ruptures making it difficult to accurately quantify the amount of strain released in the LPEQ event or a probable recurrence interval for this portion of the fault. Our approach to this problem is to use new, light detection and ranging (LiDAR), technology, that utilizes airborne laser altimetry to produce high resolution maps of surface features “stripped” of vegetation. My research is focused on a ~20 mile, strike-parallel transect along the SAF that stretches from central Santa Cruz mountains southeast to the Gabilan Range.Through digitization and comparison of mapping of fault related features done pre- and post LPEQ, overlain on LiDAR digital elevation models, I was able to detect and quantify neo-tectonic features such as growing landslides, offset streams, sag ponds, and benches that will aid future seismic hazard plans for this portion of the San Andreas fault system.