How Does a Tsunami Occur?
HOW TSUNAMIS OCCUR
1 As one plate subducts below another, pressure builds after many years, resulting in a section of the mega-thrust giving away
2 As this section gives way, it ruptures the ocean floor, resulting in a massive displacement of water, causing a tsunami
3 Tsunamis are barely felt as a ripple on the ocean surface, but as the wave reaches land, they increase in size as the water becomes shallower
1 Slow distortion; Pressure builds
2 Rupture displaces water
Plate’s forward pressure causes it to be pushed below another
Water crest grows as it reaches land due to shallowing water
Wave in ocean
Tectonic plates around Japan
200 km
North American Plate
Quake epicenter
Sendai
Eurasian Plate
Tokyo
Pacific Plate
JAPAN
Philippine Plate
Fault lines
EARTHQUAKE DEFORMATION
1 North American plate
Pacific Ocean Pacific plate
2 Deformation causing stress
Direction of force
3 High stress
4 Earthquake occurs as plate snaps back Tsunami
TSUNAMI OCCURS
NO TSUNAMI
1 High stress zone at plate boundary
2 No surface deformation means no tsunami HOW TSUNAMIS OCCUR Tectonic plates around Japan 200 km As one plate subducts below another, pres- sure builds after many years, resulting in a section of the mega- thrust giving away As this section gives way, it ruptures the ocean floor, resulting in a massive displacement of water, causing a tsunami Tsunamis are barely felt as a ripple on the ocean surface, but as the wave reaches land, they increase in size as the water becomes shal- lower North American Plate Quake Wave epicentre Rupture displaces in ocean water Sendai O Eurasian Plate Tokyo O Slow distortion; Pressure builds Pacific Plate JAPAN Plate's forward Wave crest pressure causes it to be pushed below another grows as it reaches land due to shallowing water Philippine Plate Fault lines EARTHQUAKE DEFORMATION TSUNAMI OCCURS 1 NO TSUNAMI Deformation causing stress Earthquake occurs as plate snaps back High stress zone at plate boundary High stress No surface deformation means no tsunami North American Tsunami plate Pacific Pacific Ocean Direction of force plate Earthquake Occurs Sources: University of Melbourne, ES&S, Geology Magazine, www.gsi.go.jp/neic.usgs.gov; Credit: Reuters graphic.is
How Does a Tsunami Occur?
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