Lecture 6: Tsunamis Our Hazardous Environment GEOG 1110 Dr. Thieme

Tsunami Japanese for "large harbor wave" catastrophic impacts occur thousands of kilometers from geologic source Four possible causes –earthquake (along subduction zone) –underwater landslide –collapse of a volcano –asteroid impact

Subduction Zone

Indonesian Tsunami Indian and Australian plates eastward subduction beneath Eurasian plate "stick-slip" of subducting plates M 9.1 Earthquake on December 26, 2004

Banda Aceh provincial capital on northern Sumatra shaking by earthquake pummeling waves flooding after land subsided

Distant vs. Local water depth varies as wave departs epicenter wave splits into "local" tsunami along adjacent coast "distant" tsunami in deep water

Local Tsunami 1993 in Sea of Japan m waves struck Okushiri Island arrived only 2-5 minutes after earthquake 120 people killed

Tsunami Warning System "buoys in the ocean" depth gauges water pressure recorder on sea bottom also need PUBLIC EDUCATION ! !

Tsunami Runup Map

Tsunami Hazard Map indicates possible areas of wave impact based upon elevation slope of sea bottom orientation of coast