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Earthquakes, Tsunamis, and the Oregon CoastEarthquakes, Tsunamis, and the Oregon Coast

When will the next Megaquake occur?Why are tsunamis so destructive?How much of the coast is affected?

When will the next Megaquake occur?Why are tsunamis so destructive?How much of the coast is affected?

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Tsunamis Sudden shifting of the ocean floor due to earthquakes, volcanic eruptions, and submarine slumping. open ocean: short heights, long wavelengths (>100 km), and long periods -- 400-500 mph!!!

shallow water: their length shortens and their height increases dramatically.

These are NOT tidal waves

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Tsunami AnimationTsunami Animation

http://nctr.pmel.noaa.gov/animate.html

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Sumatra 2004, >275,000 Sumatra 2004, >275,000 Dead!Dead!

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BeforeBefore

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AfterAfter

7Courtesy of Mate 3rd Class Tyler J. Clements/U.S. Navy

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Tsunami -- Sea floor deformation

Tsunami -- Sea floor deformation

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Geologic record in Coastal EstuariesGeologic record in Coastal Estuaries

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Multiple events

recorded in

coastal sediments

Multiple events

recorded in

coastal sediments

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Detective StoryDetective StoryTracking down details of the last big event

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Records of a Records of a tsunami in tsunami in Japan for Japan for

which there which there was no was no

earthquakeearthquake

Records of a Records of a tsunami in tsunami in Japan for Japan for

which there which there was no was no

earthquakeearthquake

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Stumps of drowned trees revealed by winter storms

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Tree ring dating

Tree ring datingCareful dating

of the drowned trees correlates with Japanese tsunami

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Recurrence intervalRecurrence interval

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Tsunami risk, PNWTsunami risk, PNW

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Cascadia Core Sites:

1999 = gray, 2002 = yellow

Older existing cores = white

Washington Channels defined by 8 days of multibeam survey, now classified!

Turbidite Paleoseismology:

Extending the earthquake record

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Paleoseismology can address these Paleoseismology can address these questions through development of long questions through development of long temporal and spatial histories of past temporal and spatial histories of past earthquakesearthquakes

This works better in the submarine This works better in the submarine environment than on land because of environment than on land because of continuous sedimentation.continuous sedimentation.

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Turbidites Turbidites are easy to are easy to capture, but capture, but what do they what do they mean?mean?

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(Quasi) Time predictable model?

R2 = 0.9851

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010002000300040005000600070008000900010000

Time (cal yr BP)

Cumulative proxy for event "size"

A time predictable model, over 10,000 years of record, fits the actual A time predictable model, over 10,000 years of record, fits the actual recurrence data quite well. recurrence data quite well.

This means that if this is correct, we can predict the time, but not the size This means that if this is correct, we can predict the time, but not the size of the next Cascadia great earthquake, about 200 years from now for a full of the next Cascadia great earthquake, about 200 years from now for a full

margin rupture, and overdue for a southern margin rupture.margin rupture, and overdue for a southern margin rupture.

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Know this sign and where to go!

Know this sign and where to go!

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