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)

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/

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

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

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.

Tsunami-Spawning Earthquake in a Subduction Zone

Current situation

Post rupture the coast can subside

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.

Evidence of

Tsunami Inundation

From Clague, J (1997)

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.

West Coast Tsunami Warning Center

http://wcatwc.arh.noaa.gov/eventmap.html

Tsunami Modeling Elliot Bay Inundation

http://www.dnr.wa.gov/geology/pdf/ofr03-14.pdf

http://www.dnr.wa.gov/geology/pdf/ofr03-14.pdf

7.3 magnitude earthquake on Seattle fault

Tsunami Modeling Elliot Bay Inundation

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.

Model of Maximum Current Speeds

Tsunami Modeling Kilauea Flank Collapse

Ward, 2002

Tsunami Modeling Cumbre Vieja Flank Collapse

Florida could receive waves of about 165 feet. Kirby, 2001

La Palma and Cumbre Vieja

Cumbre Vieja

Cumbre Vieja

Monterey Bay

Modeledtsunami in the event

of a submarine landslide

U.S. West Coast Continental Shelf

U.S. East Coast Continental Shelf