EARTH 108 Lecture 5: Tsunami - Cause and Magnitude
14 Jun 2016
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Lecture 5: tsunami (cause, magnitude) lecture outline: the 26 dec 2004 sumatra earthquake, the 26 dec 2004 indian ocean tsunami, tsunami speed & wavelength, tsunami run-up, other causes of tsunamis. Plates are stuck together, and energy is accumulated. When energy is released, the earthquake causes a tsunami. Tsunami is caused by a sudden displacement of a large amount of water. Tsunami speed is related to the depth of the ocean, some examples: 6,000 m deep 872 km/hr, 4,000 m deep 712 km/hr, 100 m deep 113 km/hr. Tsunami wavelength compared to wind waves tsunami waves: Wavelength becomes smaller as sea shallows wind waves: Less than 1km in the open ocean. In shallow water, up to 10m, or more. Run up: most tsunami waves are long, so they often appear more as walls of water, often the water drains from the shore before it hits, time span between waves can be about 15 minutes.
