MBARI Geologists Investigate Seismic Threats

Geologists from the Monterey Bay Aquarium Research (MBARI) center used autonomous underwater vehicles (AUV) to investigate faults off the California coast in an effort ascertain any risks associated with them. For this study, the team focused on the coast of Southern California, in a region called the California Borderland. The ultra-high-resolution image of the seafloor was collected with the help of MBARI's autonomous underwater vehicles (AUVs). With the aid of these images, they measured the rate at which two crust pieces slide past each other, known as 'slip rate'. These are located within a region of the Borderland called the San Diego Trough Fault Zone that runs from the Mexican border northward toward Catalina Island. This was the first slip rate that has ever been recorded for an offshore fault within California Borderland. By using data from MBARI's seafloor-mapping AUV, they calculated the slip rate of the fault and measured the distance the fault had shifted. For this study, they focused on the ancient and inactive underwater channel and noticed a shift of 18 meters. Autonomous underwater vehicles (AUVs) are programmed at the surface then released to travel through the water, collecting data as they go. MBARI has designed and built several modular AUVs. One (the "CTD AUV") collects information about water chemistry, temperature, microscopic marine algae, and microscopic organisms that glow in the dark, and can also collect water samples for later analysis in the lab. The "mapping AUV" is used to create detailed bathymetric maps and can also show layers of sediment below the seafloor. The findings are reported in the December 2012 Bulletin of the Seismological Society of America.