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Tsnuami

A simulated tsunami reaches Japan ten hours after its start along the Pacific coast of North America

One winter’s night in the year 1700, a mysterious tsunami flooded fields and washed away houses in Japan. It arrived without the warning that a nearby earthquake usually provides. Samurai, merchants, and villagers recorded the event, but nearly three centuries would pass before discoveries in North America revealed the tsunami’s source.
The Orphan Tsunami of 1700 tells this scientific detective story through clues from both sides of the Pacific. The evidence uncovered tells of a catastrophe, a century before Lewis and Clark, that now helps guide preparations for future earthquakes and tsunamis in the United States and Canada.

large_Alaska tsunamiThe risk of a deadly tsunami ravaging the United States is now leading scientists to investigate hazards posed by giant earthquakes off the Alaskan coast.

Scientists are concentrating on the Alaskan-Aleutian subduction zone, where the tectonic plate underlying the Pacific Ocean is diving underneath the continental plate underlying North America. Tsunamis can be caused by earthquakes, especially large ones, and the second-largest recorded earthquake in history was a magnitude 9.2 at this zone in 1964.

“It concerns us a lot that we might have deadly waves aimed at U.S. shores,” said Geologist David Scholl, an emeritus scientist at the U.S. Geological Survey at Menlo Park, Calif., who discussed the work in Eos, a publication from the American Geophysical Union.

Traveling tsunamis
The fear is that a tsunami caused by a major earthquake along this zone could race across the Pacific Ocean and devastate highly populated areas of the U.S. West Coast, as well as Hawaii.

“We’ve been focusing on tsunami risks since 2004, when the Banda Aceh earthquake and tsunami led to a loss of about 250,000 lives, and then the 2011 Tohoku-Oki earthquake and tsunami claimed another 20,000 or so people and caused a nuclear disaster. Tsunamis show us that you may have an earthquake in one part of the world that visits damage on areas thousands of miles away.”

For instance, a tsunami in 1946 generated by a magnitude 8.6 temblor on the Alaskan-Aleutian Islands subduction zone near Unimak Pass, Alaska, caused significant damage along the West Coast, claimed 150 lives in Hawaii, and inundated shorelines as far away as the South Pacific islands and Antarctica.AlaskaMegathrust_e_0530

“These waves can travel at 500 mph (700 kph),” Scholl said. “From the Aleutians, a tsunami could get to Hawaii in four or five hours, two or three hours to get to Washington, Oregon, British Columbia and the California coast. And they don’t lose much energy as they go. The waves aren’t horribly high as they travel over the deep ocean, only a meter (3 feet) or so, but when they get to the coast, in shallow waters they grow in height to dozens of meters, and in places like Long Beach harbor in California, they’d cause rapid currents that can tear up the harbor area.”

Next big one
It remains uncertain where the next tsunami generated along this zone might occur. It appears unlikely that a quake as large as the magnitude 9.2 event in 1964 will happen again soon — the interval for such major quakes is about 900 years.

However, the areas between the Shumagin and Fox Islands on the zone may cause trouble, Scholl said. In addition, the last time the Semidi Islands section of the zone experienced a great earthquake was in 1938, a magnitude 8.2 event, and enough time has passed for strain to build up for another major temblor. Indeed, satellite analysis of the area suggests the shallower portion of this section is accumulating strain at a high rate.

The Semidi IslandsResearch is under way to examine the ancient history of tsunamis on several of the Aleutian Islands by looking at layers of sediment there. The hope is to yield insights on how often tsunamis recur there and to link these deadly waves to specific earthquakes to better model the potential deadliness of tsunamis based on the magnitudes and locations of the earthquakes that cause them. Such research is key to building effective defenses against tsunamis. [ History’s Biggest Tsunamis ]

“When it came to the Fukushima disaster in Japan, they designed a sea wall to handle a tsunami, but they ended up lowballing how high the wave would be,” Scholl said. “You have to know how bad tsunamis have been to know what to prepare for.”

 

 

 

Related:

Tsunami & Earthquake Research at the USGS

Recent News, Events, and Research

Starting Points

Research Studies, Past Events

Tsunami Preparedness WeeknwsNational Weather

March 27, 2014, marked the 50th anniversary of the 1964 Great Alaska Earthquake and Tsunamis.

2014 Tsunami Preparedness Week Stories

To learn about tsunamis, tsunami risk, and tsunami preparedness, visit the links below.

National Oceanic and Atmospheric Administration

Federal Emergency Management Agency

U.S. Geological Survey

State/U.S. Territory Activities and Information

Alaska

Alaska Division of Homeland Security and Emergency Management: Tsunami Mitigation / Alaska Tsunami Education Program / Alaska Earthquake Information Center / Kenai Peninsula Office of Emergency Management: Earthquake and Tsunami / Anchorage Office of Emergency Management: Tsunami Preparedness

California

California Geological Survey / California Office of Emergency Services Earthquake and Tsunami Program / My Hazards: Hazard Mitigation Portal / Tsunamizone.org/ / SAFRR – Science Application for Risk Reduction: Tsunami Scenario / Del Norte County Office of Emergency Services / Prepare Del Norte / Los Angeles County Office of Emergency Management: Tsunami / City of Los Angeles Emergency Management Department Information Center / Marin County Sheriff’s Office: Tsunami / Mendocino County Office of Emergency Services / Monterey County Office of Emergency Services / Orange County: Tsunami Emergency / Redwood Coast Tsunami Work Group (Mendocino, Humboldt, Del Norte Counties) / San Diego County Office of Emergency Services: Tsunami Facts and Preparedness / San Francisco (City and County) Tsunami FAQ / San Luis Obispo County: Tsunami Information / San Mateo County Office of Emergency Services / Santa Barbara County Tsunami Inundation Maps / Santa Cruz County Office of Emergency Services: Tsunami / Sonoma County Fire and Emergency Services / Ready Ventura County

Commonwealth of the Northern Marianas Islands

Commonwealth of the Northern Marianas Islands Homeland Security and Emergency Management (You Tube Channel) / Tsunami Preparedness Decision Wheel

Guam

Guam Homeland Security and Office of Civil Defense: Tsunamis

Hawaii

Hawaii State Civil Defense / National Weather Service Honolulu Forecast Office: Hawaii Tsunami Preparedness and Safety Information / Pacific Tsunami Museum / Hawaii County Civil Defense Agency / Honolulu (City and County) Department of Emergency Management / Kauai County Civil Defense Agency / Maui County Civil Defense Agency

Maine

Maine Tsunami Awareness / Maine Geological Survey: Tsunamis in the Atlantic Ocean

North Carolina

North Carolina Department of Public Safety: Tsunamis

Oregon

Oregon Tsunami Clearinghouse / Preparing for a Cascadia Subduction Zone Tsunami:A Land Use Guide for Oregon Coastal Communities / Coos County Emergency Management / Curry County Emergency Services Department / Douglas County Emergency Management / Lincoln County Emergency Management: Earthquake & Tsunami / Tillamook County Emergency Management

U.S. Virgin Islands

Virgin Islands Territorial Emergency Management Agency: Plan and Prepare – Tsunamis

Virginia

Virginia Department of Emergency Management: Tsunamis / City of Norfolk Department of Emergency Preparedness and Response: Tsunamis

Washington

Washington Military Department Emergency Management Division / Living on the Ring of Fire and its Consequences: The 1964 Good Friday Alaskan Earthquake and Tsunami / Grays Harbor County Division of Emergency Management / Jefferson County Department of Emergency Management: Tsunami Information / Pacific County Emergency Management Agency: Tsunami

 

 

Resources:

1700 Cascadia earthquake

The Orphan Tsunami of 1700 – University of Washington

Orphan Tsunami Gets a Frightening Parent | LiveScience

Tsunamis and Earthquakes – USGS PCMSC

National Tsunami Hazard Mitigation Program – Tsunami

A great Alaska earthquake meets southern California

Department of Geology & Geophysics

Subduction zones and earthquakes

Subducting plate geology in three great earthquake ruptures

Aleutian Islands | The CELESTIAL Convergence

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