GEOL105 Lecture Notes - Lecture 3: Oceanic Basin, Pacific Tsunami Warning Center, Epicenter
Document Summary
A long wave that moves the entire depth of the ocean. Experienced on shore as a series of rapid surges flowing for many minutes. Cause: any disturbance on the sea floor that displaces a large water mass: incorrectly called tidal waves. Need to have vertical motion along a fault on the seafloor. Most tsunamis generated by subduction zone earthquakes. Most generated by earthquake or fault movement on seafloor. A few tsunamis are generated by volcanic processes. Quake triggered landslides can cause huge megatsunami in confined waterways. Wind waves: energy: mainly on surface, periods: typically 10 seconds, wavelengths: typically 150m (500 ft, height: typically 1-3 meters (3-10 ft) In shallow waters: water piles up at wave front, speed slows to 72 km/h (45 mph, long wavelength = onshore flow for several minutes. Hilo, hawaii is very susceptible to tsunami: shape of island and seafloor focuses tsunami on hilo, destructive tsunami in 1946 and 1960. 159 people, including many school children, killed.
