forum discussion #31

Unearthing Ancient Tsunamis

Brian Atwater

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Listen to our interview with Brian Atwater here.

He’s a scientist with the U.S. Geological Survey whose expertise is studying ancient earthquakes and tsunamis, and he joined us as a guest in this Science Forum discussion.

Atwater digs in the soil for evidence of natural disasters that occurred in the past — to provide clues to the risks we face today.

Atwater says the massive earthquake and tsunami that struck northeastern Japan last week had a precedent.  It occurred in the 9th century.  Based on written records from that time and sand deposits left in the ground, Japanese scientists conclude that on July 13, 869, a tsunami swept more than 4 kilometers inland in the area around the modern-day city of Sendai. Continue Reading ...

Using similar detective work, Atwater concludes that a massive tsunami struck America’s Pacific Northwest more than 300 years ago.  He and his colleagues found evidence of this tsunami in sediments along the coast of California, Oregon, Washington, and British Columbia.  They believe this is the same tsunami that was recorded striking Japan in January 1700, and that it originated on this side of the Pacific.

Atwater and his colleagues recount their detective work in The Orphan Tsunami of 1700–Japanese Clues to a Parent Earthquake in North America.

Read our conversation with Atwater below:

  • Which coasts are threatened by tsunamis?
  • What can old documents and sediments tell us about today’s tsunami hazards?

Additional Reading

  • “The 869 Jogan tsunami deposit and recurrence interval of large-scale tsunami on the Pacific coast of northeast Japan”
  • “A study on paleotsunami using hand corer in Sendai plain (Sendai City, Natori City, Iwanuma City, Watari Town, Yamamoto Town), Miyagi, Japan”
  • “Numerical simulation of the AD 869 Jogan tsunami in Ishinomaki and Sendai plains”
  • “Medieval forewarning of the 2004 Indian Ocean tsunami in Thailand”
  • “Tsunami warning and preparedness — An assessment of the U.S. tsunami program and the nation’s preparedness efforts”
  • “Where the first wave arrives in minutes — Indonesian lessons on surviving tsunamis near their sources”
  • “Earthquake Nation: The Cultural Politics of Japanese Seismicity, 1868-1930″
  • Hide
    The guest has left this discussion, but feel free to leave your thoughts.

    Your Comments

    1. Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Brian Atwater

      As a recent National Research Council report put it, “Tsunamis happen rarely enough to allow a false sense of security.” Indian Ocean shores devastated by the tsunami of December 2004 had not seen such an event in 600 years. Near me, in Seattle, hundreds of years also elapse between tsunamis spawned at the Cascadia subduction zone. Now Japan is reeling from a tsunami so rare that its immediate predecessor probably dates from the year 869. I look forward to discussing these rare — but devastating — events.

    2. Robert

      Have tsunamis ever hit the US Atlantic coast? If so, what faults were involved and how likely are they to occur in the future?

    3. Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Elsa Youngsteadt

      Hello Brian,
      What do we know about how ancient people understood tsunamis? Were they as devastating in lower-tech/ lower-density societies as they are today?

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Brian Atwater

        For a fascinating account of how the 1755 Lisbon earthquake was interpreted in Europe, and on its philosophical aftershocks, see
        “The Lisbon earthquake” by T.D. Kendrick
        (London, Methuen, 1956)

    4. Shannon Kuleto

      Hello Brian,
      Did your research find any oral traditions among the native peoples of the west coast indicating a knowledge of one of these epic quake/tsunami events in the relatively recent past??

    5. Sara Greensfelder

      I was fascinated by the story on The World. Thank you. I’m wondering if you know how far south in California the 1700 earthquake and tsunami had significant effects. It is claimed that California’s Diablo Canyon nuclear power station location (near the San Andreas fault) should not see a quake larger than 6.5, and is built to withstand a 7.5 quake. In light of what happened in Japan, and the Cascadian subduction zone, I’m not feeling very reassured. Do you have thoughts on whether or not a huge earthquake/tsunami could befall either of the nuclear power plants on the California coast?

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Brian Atwater

        The 1700 tsunami is among those built into the tsunami-inundation maps published by the California Geological Survey. Find more here

        The 1700 tsunami spread mostly perpendicular to the long side of its source, an area of seafloor displacment elongated north-south from Vancouver Island to Cape Mendocino. In the far field the waves probably hit hardest in the western Pacific (simulation, p. 74-75 in the Nakaminato chapter of “Orphan tsunami”).

        In the 1980s and early 1990s, when Cascadia’s earthquake potential was less clear than it is now, the Nuclear Regulatory Commission supported research in geophysics and geology that ended up hastening discovery of the date and size of the 1700 Cascadia earthquake.

    6. Grace

      I was wondering if this current tsunami in Japan was larger than the ones to hit Alaska in 1964. Is its destruction greater because of topography, population, or was the 64 quake more damaging overall?
      Alaskans have a recent memory and as advanced warning as any place in the US, but I believe Japan was par with it. Did they just not have the response time or not an adequate warning system.

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Brian Atwater

        The multiple tsunamis set off by the 1964 included fast-arriving ones driven by underwater slides. Those at Chenaga, Seward, Valdez, and Whittier together account for 79 of the 106 Alaskan deaths from tsunamis that the 1964 earthquake triggered.

        On a coast near the source of an earthquake-induced tsunami, the shaking itself often arrives before official guidance does. An instructive example, in which people self-evacuated from an earthquake that failed to generate a tsunami, can be found on page 8 of “Where the first wave arrives in minutes”, a UNESCO tsunami-safety booklet (link at left, above).

        Surveys in coming months may show how strong shaking, fast-arriving waves, and large populations combined to cause so many of the deaths in Japan.

    7. Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? David Baron

      Many thanks for participating in the forum.

      If I might ask a personal question, what’s it like emotionally to study these horrific events? Do you get nervous by the shore? How has it been for you — an expert on natural disasters that occurred in the deep past — to see one play out in real time?

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Brian Atwater

        The Indian Ocean tsunami taught me that the passage of time had sanitized evidence of the 1700 Cascadia tsunami. In North America the 1700 tsunami overran fishing camps, but I had seen only a few examples. In Japan the 1700 tsunami caused flooding and damage, but anthologies of old documents tell of only two related deaths, both from a rice boat that storm waves dashed onto rocks after strong tsunami currents had held the boat offshore.

        The 2011 tsunami devastated Miyako and Otsuchi, two of the towns where the 1700 tsunami caused comparatively minor damage. I don’t know what has become of the people in those towns who treated me so kindly when I visited to learn about the waves from Cascadia.

    8. patrick kintner


      In addition to your own, what other books could you recommend for the layman to help him understand the impact of Pacific Northwest subduction zone earthquakes and their aftermaths.

    9. Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Brian Atwater

      An incomplete list, Patrick:

      “At risk: Earthquakes and tsunamis on the west coast”

      “Living with earthquakes in the Pacific Northwest”

      U.S. national earthquake hazard maps

      Tsunami-evacuation maps for Washington and Oregon

      Scenarios for several kinds of earthquakes

      An earlier scenario for Oregon

    10. karthi sundararajan

      Hi Brian
      I am from India. Some cities mentioned in our old Indian religious texts have disappeared under the sea. Have you done any studies on that? Were these events due to tsunamis?

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Brian Atwater

        Thanks for your patience, Karthi.

        Indian scientists have identified geological evidence for a tsunami from about 1,000 years ago that may correspond to legends about flooding from the sea. An initial report on this evidence:

        The investigators engaged in follow-up studies include CP Rajendran and Seshachalam Srinivasalu .

    11. Eliana Franco

      Hi Brian.
      Greetings from Quito, Ecuador. Are you still looking for funding to organise an educational campaign in our Pacific Coast, about how the people should be prepared to run away form a possible tsumami? Pehaps our government is now better organized and interested in funding!
      Eliana (Adriana´s sister)

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Brian Atwater

        Hola Eliana,

        Have researchers in Ecuador gathered documentary records of tsunamis? Especially of tsunamis earlier than those in the official catalog:

        UNESCO’s Intergovernmental Oceanographic Commission is finalizing a Spanish-language version of the Indonesian tsunami-preparedness booklet, “Where the first waves arrive in minutes” (link on this page at left under Additional Reading). Such a booklet could be customized for use in Ecuador by addition of material about Ecuadorian tsunami history and hazards.

        An excellent contact on tsunamis in Ecuador: Patricia Arreaga Vargas of the Instituto Oceanografico de la Armada (INOCAR).

    12. Patrik C

      Brian, I live in NW Oregon and just read this local news article from a couple of your colleagues regarding the estimated average recurrence of ruptures in the CSF. They are lowering it too about half of what has been stated in the past.

      How do you and the USGS view this new data?
      Also, is there a different rate of subduction for the JDF plate, Gorda plate and the Pacific plate or are they all basically the same?
      I would think if they were subducting at a different rate, there would be more activity along the fracture zones.

      Thank you for your time.

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Brian Atwater


        Most of this new evidence awaits publication in a book-length report. The new evidence may be easier to evaluate once the report becomes public.

        The Gorda plate has been interpreted as a deformed fragment of the Juan de Fuca plate. Earthquakes are common along the boundary between them, the Blanco fracture zone.

        The Pacific plate subducts beneath Japan but not beneath the western conterminous United States. New Pacific plate crust is created at the spreading ridges where, almost like a conveyor belt, it moves away from the Gorda and Juan de Fuca plates.

    13. Betty Allen Wilson

      Hi Brian,

      Amazing work. Thanks for making this scientifically complex and frightening subject so accessible and understandable to so many.

      Your friend and colleague, Betty

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Brian Atwater

        Hello classmate Betty,

        Pure happenstance that so many of the Cascadia clues would come from tidal-marsh deposits not altogether different from those of Delaware.

    14. Vicky Blakesley

      Hi Brian,
      I appreciated the article regarding 1700 Cascadia tsunami published by you and your Japanese colleagues. It is most impactful to read articles that combine and augment the interpretation of data from different disciplines. From that earthquake are there any geological and/or ecological data consistent with the tsunami waves reaching the lands around the Gulf of Alaska?

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Brian Atwater

        The reverse has been inferred, Vicky, from Alaskan tsunami deposits at several Cascadia places: Port Alberni, BC; Discovery Bay, WA; Seaside, OR; Crescent City, CA.

        The best documented of these examples is at Port Alberni, a fjord head where the 1964 Alaska tsunami ran as much as 7 m deep (doi:10.1006/ecss.1994.1028). The tsunami deposit consists of sand mostly 1-2 cm thick. It was dated by the abundance of cesium-137, a byproduct of atmospheric nuclear testing.

        The trans-oceanic 1964 Alaska tsunami originated from a source about 800 km long. The waves went mainly in directions perpendicular to this source. Those directions were largely toward the Pacific coast of Washington, Oregon, and California.

        The trans-oceanic part of the 1700 Cascadia tsunami, though aimed mainly toward the western Pacific, also spread toward the Gulf of Alaska. Its simulated flooding there can be seen on tsunami-inundation maps for Kodiak.

    15. Denis DuBay

      Are there nuclear plants along the coast of the Northwest U.S. that are at risk from a tsunami generated by the Juan De Fuca plate subducting under the North American plate?

    16. Brian. Intense interest in your work from Kiket Island and friends all over Skagit Delta. Puget Trough faults trend east/west, while the Cascadia Subduction Zone (CSZ) fault trends north/south. Could CSZ event trigger near simultaneous release along Trough faults, and produce tsunami events from two directions along inner Sound shores? Considering extended winter saturation of Delta soils and slopes, why have previous quakes NOT liquified and dumped same into the Sound? Finally with a CSZ tsunami impacting the WA coast, is the surge diminished by travel down Juan de Fuca Straits, spread within the Sound, and around many islands. To the point, what are shoreside risks of inner Sound and Skagit Delta (tulips and taters) from CSZ event. Thanks for the refs above.

    17. Alfredo Borunda

      Hi Brian, thanks for participating in the forum and helping us learn more about tsunamis. A few years ago I heard about the fear that a mega-tsunami would devastate the East Coast of the United States if the Cumbre Vieja volcano in the Canary Islands caved in. I even read a novel that had this as a premise for attack on the US! In the ensuing time I’ve read that the risk of this happening is overblown, so I am no longer sure what is the consensus in the scientific community about this. Could you throw some light? Thanks!

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Brian Atwater


        The idea was stated this way in 2001: “Waves generated by the run-out of a 500 km³ (150 km³) slide block at 100 m/s could transit the entire Atlantic Basin and arrive on the coasts of the Americas with 10–25 m (3–8 m) height.” doi: 10.1029/2001GL013110

        Points of contention include how often the volcano collapses — the intervals between collapses are thought to average tens of thousands of years or more — and how readily the sliding would generate a tsunami that is large on distant coasts. Recent discussions include these papers (cited by doi number):


    18. Susmitha Srinivasalu

      Hi Brian. Greetings from India.
      Are the nuclear power plants on the South Indian coast safe?? In what way are ancient tsunami sediments helpful for tsunami risk reduction?? Were these studies useful during the recent tsunami in japan??
      I dont agree with my father (Seshachalam Srinivasalu) who says these ancient tsunami sediments indicate that we are living in a tsunami prone area…

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Brian Atwater

        Thanks, Susmitha.

        An official site identifies one place on India’s east coast, facing the Sunda subduction zone, as having an operating nuclear power facility:

        On how this place fared in 2004:

        Sedimentary records of tsunamis on Indian Ocean shores could have provided a long-term advisory of the 2004 tsunami had those records been found beforehand:

        Similar sediments were noted a decade ago near Sendai (Jogan link). Follow-up studies (hand-corer link) were checking the length of coast involved — a clue to earthquake size.

        In western North America, clues to Cascadia’s giant-earthquake threat include sediments like those your father studies.

    19. Nancy Partlow


      How many miles is Olympia from the Cascadian Subduction Zone? How strong would the shaking be in Olympia during a subduction zone earthquake?

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Brian Atwater


        If a Cascadia fault rupture extends as far east as the Pacific coast near Grays Harbor, Washington, Olympia would be roughly 60 miles from the nearest part of that rupture.

        A recent paper gives ground motions on firm ground in Seattle in the range of one-tenth to two-tenths of the acceleration due to gravity (0.1-0.2 g), for shaking in the range of one to four cycles per second (1-4 Hz).

        Stronger shaking near Olympia is depicted on maps that depict the combined hazard from many different faults, weighted by probability of occurrence. In this example there is an estimated two percent chance that Olympia would have ground motion in excess of 0.45 g in a fifty-year period:

    20. Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Brian Atwater

      Thanks to those who joined in this discussion and to all who stopped by. It can be hoped that the disaster of March 11 ends up helping people worldwide to live more safely with earthquakes and tsunamis.

    21. John Lasher

      Dr. Atwater,
      Thank you for all the work you have done to educate people to the hazards we face from our dynamic Earth. I am from Ellensburg, WA and have been following your work since you spoke at CWU. I am curious about linkage of the Westside Faults in WA to our own Kittitas valley faults and the Yakima Fold Belt. Can you speak to this in any way? Thanks again.

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Rhitu Chatterjee

        Hi John,

        Thanks for your question. I’m the science reporter here at The World, and I moderate these online science discussions. Unfortunately, Dr. Atwater has left the discussion. (our guests stay in the discussions between one and two weeks only)

        I hope you’ll come back and join other future discussions.


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