Lecture 6: Tsunamis Our Hazardous Environment GEOG 1110 Dr. Thieme.
Transcript of Lecture 6: Tsunamis Our Hazardous Environment GEOG 1110 Dr. Thieme.
Lecture 6:
Tsunamis
Our Hazardous Environment
GEOG 1110Dr. 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
• 15-30 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