The 2011 Japan Earthquake and Tsunami caused unprecedented damage and loss of lives in Japan. This large earthquake created long-duration ground shaking followed by giant tsunami inundation. Post-event reconnaissance teams have reported that damage to buildings and infrastructure was often exacerbated or caused by soil instability. Understanding how combined earthquake and tsunami events affect soil instability is crucial to prepare for similar impending earthquake-tsunami events that have affected coastal areas of the United States in the past. During an earthquake, soil instability is primarily caused by liquefaction; that is, the soil acts like a liquid, and the potential for the soil to support overlying buildings and infrastructure is severely reduced. Liquefaction can also occur during the tsunami inundation in addition to scouring at the surface caused by the water current. This research will advance the understanding of soil instability caused by the combined effects of earthquakes and tsunamis. Effective strategies for designing resilient critical buildings and infrastructure will be developed. As part of this program, a graduate student will be educated in the fundamentals of geo-and-fluid mechanics, which will prepare her to become an interdisciplinary multi-natural hazards researcher. A series of education videos will be created for the purpose of encouraging college and high school students to pursue careers in science and engineering.
With regards to the 2011 Event, it is suspected that soil instability was first triggered by the earthquake, presumably via residual liquefaction and fluidization, and then further promoted by the ensuing tsunami, presumably via momentary liquefaction and scour. This hypothesis produces the questions: (1) How does earthquake-induced soil instability interact with tsunami-induced soil instability? (2) How does the elapsed time between the earthquake and tsunami affect this interaction? (3) Is enhanced scour around coastal structures worsened by the combined earthquake-tsunami multi-hazard? To answer these questions, laboratory experiments will be performed using the UC Davis Centrifuge Facility. The centrifuge is the only experimental apparatus capable of imposing successive earthquake-tsunami loading on prototypical soil-fluid-structure systems. The centrifuge experiments will aim to reveal fundamental mechanisms of soil instability caused by successive earthquake-tsunami loads and in turn, discover how this loading scenario affects soil-fluid-structure systems. The high quality and unique data obtained from the precisely controlled experiments will be invaluable for benchmarking and validating analytical and numerical prediction models.
