Tsunamis cause damage even after they have traveled thousands of kilometers from their sources, and much of the damage is through the generation of local strong currents. Even though wave heights of tsunamis that have traveled long distances are no greater than those of local tides or waves, tsunamis modify currents, resulting in unusually strong pulses of mixing, transport, and seiching (standing waves in enclosed water bodies). Seiching is common and is the most destructive hazard, particularly along narrow bays and harbors. In a new description of currents and sediment transport associated with a tsunami, Lacy et al. studied water height, currents, and suspended sediment concentrations in Monterey Bay, California, where a tsunami set off by a magnitude 8.8 earthquake off the coast of Chile on 27 February 2010 arrived approximately 14 hours later, causing strong seiching. Studying vertical velocity profiles of the tsunami waves reaching the inner shelf at Monterey Bay, the authors show that the friction from the shelf bed vastly affected the tsunami currents, and the bed drag coefficient varied with time. The observation is contrary to assumptions behind the common practice of using depth-averaged models to simulate tsunamis in the near-shore region.
- Pub Date:
- November 2012
- Oceanography: Physical: Currents;
- Oceanography: Physical: Nearshore processes;
- Oceanography: Physical: Sediment transport (1862);
- Oceanography: Physical: Tsunamis and storm surges (4302;