ERTH 2415 Lecture Notes - Lecture 8: Phase Velocity, Types Of Volcanic Eruptions, Subduction
26 Apr 2016
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Document Summary
Tsunami can also be fuelled by gravity and impact energy. Causes of tsunami: often created by underwater disturbances of the seafloor. Mostly triggered by large earthquakes (magnitude 7. 5) Less commonly by volcanic eruptions, mass movements, impacts with space bodies. Earthquake caused tsunami- trigger is a linear source (fault on seafloor) Vertical motion of rock blocks on the seafloor. Pacific ocean surrounded by active volcanoes and subduction zones. 80% of the world"s earthquakes around pacific ocean. Attenuation: loss in amplitude as the wave propagates away from its source. Period t [s]: time between two successive crests (or troughs) Frequency f [hz]: number of occurrences of the wave within 1 s. Wavelength l [m]: distance between two successive crests (or troughs) Characteristics common to all waves propagating in the open ocean. Shoaling causes waves to interact with the seafloor. Interaction starts when depth < l/2 friction slows wave down wavelength decreases: energy is concentrated in a shorter length.
