This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

Sunday, April 3, 2011

A hero in Oshima and a possible mystery about the tsunami waves

Abalone fisherman Susumu Sugawara
from the CNN.com article referenced in the text
The stories about the courage and dignity of the people of Japan keep arriving.  Here's just one example:

Susumu Sugawara is a 64 year old abalone fisherman from the island of Oshima, Japan.* (Note: I'm not sure which of the many Oshima's in Japan this island is.  One is 100 miles north of Sendai, and 45 miles from the epicenter of the March 11 earthquake. Another is south of Tokyo, and another is on Sendai.  If someone can help, please comment! I am guessing that it is the one north of Sendai based on the III Marine Expeditionary Force report cited in **, but can't be sure.)  In some areas the tsunami covered the width of the island**.  The residents of Oshima rely on two passenger ferries and two car ferries.  All four ferries and the 325 ton-concrete pier that they were moored to were relocated 400 feet inland, undamaged.

Instead of running to the hills when the tsunami warning came, Sugawara ran to one of his boats, the Sunflower.  He relates that as he passed his other boats he said goodbye to them, apologizing that he could not save them all.  An experienced fisherman, he says that he is used to seeing waves up to 5 meters tall, but that this one was four times that size. It broke repeatedly over his boat.  Sugawara and a very few others may be the only fishermen who have ridden a tsunami and survived.  He is now tirelessly using his boat to make hourly trips to the mainland to provide supplies to survivors on Oshima.

A mystery: There is every reason to believe Sugawara's estimate of a 20 m high wave. He is an experienced fisherman.  Wave heights reported by the media have generally been of the order 10 m, and this would be a mystery in terms of tsunami behavior because the waves steepen and increase in height as they approach land.  However, there are a few reports of a larger wave: In Ofunato, the wave is reported to have reached 77.4 feet in height. TEPCO, the Tokyo Electric Power Co. revised its initial estimate of the wave that hit Fukushima No. 1 power plant from 10 m to 14 meters, saying that they have found traces of the tsunami at that elevation. Hopefully detailed mapping will reveal more details about wave height.  The TEPCO plants were designed to withstand earthquakes of M8 and tsunami waves of 5.7 m at the No. 1 plant and 5.2 m at the No. 2 plant.

Note: In researching this, I discovered that there are a number of "Oshimas" in Japan. One is a small volcanic island called "Oshima-Oshima" not too far from the Oshima island discussed above.  Oshima-Oshima, which lies west of Hokkaido is uninhabited.  It was the source of a very destructive tsunami in 1741 when a portion of its flank collapsed.  Satake, Kenji, "Volcanic origin of the 1741 Oshima-Oshima tsunami in the Japan Sea, Earth Planets Space, 59, 381-390, 2007.

Note: I have continuously updated the list of videos on my earlier post.  In addition, the initial few minutes of this site show some helicopter footage of the tsunami overriding the greenhouses near Sendei.

*as reported http://www.cnn.com/2011/WORLD/asiapcf/04/03/japan.tsunami.captain/index.html?hpt=C2

**as reported in http://www.dvidshub.net/news/68196/japans-road-recovery-iii-mef-cg-visits-island-oshima. The U.S. III Marine Expeditionary Force is helping with relief efforts.

1 comment:

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