Earthquakes and Tsunamis
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Transcript of Earthquakes and Tsunamis
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Earthquakes and Tsunamis
• According to long-term records (since about 1900), we can expect about 18 major earthquakes (7.0 - 7.9 on the Richter scale) and one great earthquake (8.0 or above) in any given year
• The number of earthquakes and tsunamis resulting in fatalities has increased approximately in proportion to global populations
• The growth of giant urban cities near regions of known seismic hazard is a new experiment for life on the Earth
• Tsunamis are a threat to life and property for all coastal residents
Sources: NEIC 2003; USGS 2004; UNEP 2005 (GEO 2004/2005)
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Tsunami Animationshttp://ffden-2.phys.uaf.edu/645fall2003_web.dir/elena_suleimani/runup4.mov
http://es.ucsc.edu/~ward/indo.mov
http://iri.columbia.edu/~lareef/tsunami/#Tsunami_Animation:_National_Institute_of
And Videos… http://www.asiantsunamivideos.com/
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Sumatra Tsunami -
Aceh Province in
Sumatra
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TSUNAMISTSUNAMISWhat and What and HowHow
MOST GENERATED BY SHALLOWEARTHQUAKESSudden displacement of seawaterAlso submarine landslides, volcanic eruptions
Most Tsunami Generated Here
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TSUNAMISTSUNAMISGENERATEDGENERATED
BYBYEARTHQUAK ESEARTHQUAK ES
Large EQ (>8.5-9.0)Shallow EQ – at or near the seafloor (< 50 km)Subduction zones
Sudden displacementmoves overlying columnof water generating wave
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TSUNAMISTSUNAMISWhat and HowWhat and How
SPEED DEPENDS ON WATER DEPTHFast in deep ocean (>1000 km/h)Slows near shore (30-50 km/h)
HEIGHT DEPENDS ON WATER DEPTH Small in deep ocean (few cm to 1 m)
Grows near shore (can be >30 m)
April 1, 1946 Tsunami , Hilo, HawaiiMaximum flooding 6 meters
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Tsunamis – Deep vs Shallow
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WHY IS A TSUNAMIWHY IS A TSUNAMIA HAZARD?A HAZARD?
WAVE HEIGHTS GROW IN SHALLOW WATER
Best Case: Quickly Rising Tide
Worst Case: Wall of turbulent water with rocks
and debris
Runups > 30 m
April 1, 1946Aleutian Islands earthquake
Hilo, Hawaii
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Tsunami - Lituya Bay Alaska
On July 10, 1958, an earthquake triggered a landslide, which created a wave that
wiped out trees 1,700 feet up a hillside on the opposite side of Lituya Bay, Alaska.
Within minutes a wave that had traveled 2,500 miles from the Aleutian Islands in Alaska came crashing into Hilo. It killed one hundred fifty-nine people and caused millions of dollars in damages.
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Tsunami-Spawning Earthquake in a Subduction Zone
Current situation
Post rupture the coast can subside
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Cascadia block diagram
Mw ~9 earthquake &tsunami ~300 years ago
WASeattle
Ms ~7.3 earthquake &tsunami ~1000 years ago
So--geologic evidence tells us that the coast of Washington experienced a greatearthquake and tsunami ~300 years ago, and also that theSeattle area experienced a large earthquake and tsunami ~1000 years ago.
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Evidence of
Tsunami Inundation
From Clague, J (1997)
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Willapa longer recordThis and other cores tell usthat large earthquakes and tsunamisoccur on the Washington coastevery 100-1000 years(average ~500 years).
~3500 years ago
~300 years ago
There aresimilar records in Alaska, Oregon & northern California.
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West Coast Tsunami Warning Center
http://wcatwc.arh.noaa.gov/eventmap.html
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Tsunami Modeling Elliot Bay Inundation
http://www.dnr.wa.gov/geology/pdf/ofr03-14.pdf
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http://www.dnr.wa.gov/geology/pdf/ofr03-14.pdf
7.3 magnitude earthquake on Seattle fault
Tsunami Modeling Elliot Bay Inundation
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Tsunami Inundation Depths – Bellingham
Venturato, A.J., V.V. Titov, H.O. Mofjeld, and F.I. González (2004). NOAA TIME eastern Strait of Juan de Fuca, Washington, mapping project: Procedures, data sources, and products. NOAA Tech. Memo. OAR PMEL-127 (PB2005-101207), 22 pp.
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Model of Maximum Current Speeds
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Tsunami Modeling Kilauea Flank Collapse
Ward, 2002
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Tsunami Modeling Cumbre Vieja Flank Collapse
Florida could receive waves of about 165 feet. Kirby, 2001
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La Palma and Cumbre Vieja
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Cumbre Vieja
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Cumbre Vieja
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Monterey Bay
Modeledtsunami in the event
of a submarine landslide
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U.S. West Coast Continental Shelf
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U.S. East Coast Continental Shelf