Saturday, April 30, 2011

More imagery--Minami Sanriku and beyond -- and tsunami erosion

The oblique air photo above (by "yaozy"), available on Google Earth, shows dramatic tsunami scour features in the Minami Sanriku harbor. It also gives a better sense of the area I walked around in April of 2010. Finally I can faintly see the baseball diamond near the (destroyed) river gate, and get a sense of the tsunami erosion around the large apartment building at the shoreline, a building designated for vertical evacuation. I still don't know how many people used this building for evacuation, and if so, did they successfully get onto the roof because the upper floor was flooded.

I have been readjusting to life back in Seattle, trying to finish up several manuscripts that got pushed aside by the events of 11 March. These manuscripts deal with neotectonics and tsunami history of the Kamchatka Peninsula.

The other day, we were trying to imagine "life before Google Earth." I remember life before photocopy machines, let alone word processing! I was rereading a classic, early article by Minoura on a Kamchatka tsunami deposit, and wondering if we could relocate his sites. So much of Minoura-san's materials will have been destroyed by the earthquake in Sendai. I realized his work was not only before Google Earth and GIS, but probably done without GPS.... Though we had handheld GPS in our post-tsunami survey in Nicaragua in 1992, it wasn't working very well. Funny, there were two sets of maps -- the Nicaraguans had maps prepared by the Soviet Union for the Sandinista regime, and we from the U.S. had maps prepared by the U.S. Defense Mapping Agency, which said "destroy after using." The "KGB" maps were more accurate than the "CIA" maps.... Of course, air photos are still the best for on-the-ground location, though post-tsunami, things change. And some countries are not so enthusiastic about providing/ making public their air photos. How things are changing now with so much on the web.

Meanwhile (back to the present), thanks to Paleoseismicity:

for posting some good links, such as:
The title of this panorama project should be "japan-tsunami-panoramas" though.

From Google Earth, I found a newly acquired image of the harbor of Minami Sanriku that shows clearly severe tsunami erosional features, which by their looks are mostly from the outflow -- Bre MacInnes will be interested to see these. Part of her dissertation was about tsunami erosion, particularly by the 2006 (or 2007) central Kurils tsunamis.

Here is a before image of the Minami Sanriku harbor from June 2010:

and the same view from 6 April 2011:

and my rough attempt (I did not orthorectify the images) to outline before and after shorelines, as well as the scour ponds made by the tsunami:

OK, back to my manuscripts.

Thursday, April 14, 2011

Tohoku coast -- Focus on Survivors

It's hard sometimes to think about statistics when peoples' lives are involved, but I found the data below heartening. Despite the widespread devastation in these towns, preliminary data show that really, most people survived. Early statistics used the total population of these towns, but these data attempt to count only the part of the population that was in the inundated area.

The table is ordered from most to least casualities (= dead plus missing). I added the survivors columns, which therefore are ordered from least to most survivors, top to bottom. So the bad news comes first

Preliminary table of survivors within inundated region of Iwate, Miyagi and Fukushima prefectures*
Prefecture Township Population within the inundated area (a) Dead + Missing (b) % casualites (a)/(b)x100 Survivors % survivors
Iwate Otsuchi 7839 1616 20.6 6223 79.4
Iwate Rikuzen-Takada 13547 2459 18.2 11088 81.8
Miyagi Onagawa 8816 1504 17.1 7312 82.9
Miyagi Natori 12132 1873 15.4 10259 84.6
Iwate Kamaishi 9331 1306 14.0 8025 86.0
Miyagi Shiogama 173 23 13.3 150 86.7
Fukushima Minami-Souma 13919 1474 10.6 12445 89.4
Miyagi Yamamoto 9341 788 8.4 8553 91.6
Miyagi Minami-Sanriku 13306 1090 8.2 12216 91.8
Iwate Yamada 11721 911 7.8 10810 92.2
Miyagi Kesennuma 29648 2138 7.2 27510 92.8
Fukushima Namie 2749 186 6.8 2563 93.2
Miyagi Ishinomaki 102670 5520 5.4 97150 94.6
Miyagi Higashi-Matsushima 32993 1713 5.2 31280 94.8
Fukushima Souma 9227 408 4.4 8819 95.6
Iwate Miyako 24937 1083 4.3 23854 95.7
Iwate Tanohata 1075 38 3.5 1037 96.5
Iwate Ofunato 15500 494 3.2 15006 96.8
Fukushima Futaba 1061 32 3.0 1029 97.0
Fukushima Shinchi 4258 118 2.8 4140 97.2
Miyagi Iwanuma 7310 183 2.5 7127 97.5
Fukushima Okuma 1053 24 2.3 1029 97.7
Miyagi Watari 13186 284 2.2 12902 97.8
345792 25265 7.3 320527 92.7

Average survival rate within inundated area: 92.7%

Statistics Bureau & Director-General for Policy Planning of Ministry of Internal Affairs & Communications
released "Populations and Number of families within the Expected Inundation Areas" in Japanese.

Inundation areas are estimated by aerial and satellite photos; not the survey on site.
*The table prepared by Yamamoto, Masahiro (Jody B. added survivor columns).

Tuesday, April 5, 2011

Minami-Sanriku update

See my previous blog for more background on Minami-Sanriku.
Only some survive on top of the town disaster management center
Pictures: Shinichi Sato/AP

"Chilling new photographs show people desperately clinging to a mast on a roof as the Japanese tsunami destroys the building beneath them.

In the combination of three photos, taken by Shinichi Sato amidst the March 11 disaster, survivors cling to an antenna tower and handrails on the roof of the Minamisanriku Government Disaster Readiness Center in Minamisanriku, north-eastern Japan.

About 30 people fled to the roof of the three-storey building and climbed higher as the tsunami rushed in. Only nine people survived and about 20 were swept to their deaths."

A young female official who kept delivering the evacuation message to townspeople until the last moment has not been found. Tanioka says the story of her bravery and dedication is now nationally known.

Lensman braved tsunami

Wednesday, April 6, 2011

"MINAMISANRIKU, Miyagi Pref. (Kyodo) When the municipal disaster prevention building in Minamisanriku, Miyagi Prefecture, was engulfed by the tsunami on March 11, its officials clinging to the top of the structure, a local photographer captured the drama in a series of pictures.

The photos, made available by Shinichi Sato, show the three-story building completely submerged by the wall of water except for its antenna and rooftop fence, to which Mayor Jin Sato and nine other survivors from the office clung.

(Shinichi) Sato, 45, who ran a photo studio in his home until the tsunami hit, captured the scene from an elementary school overlooking the town.

'A tsunami will come,' he thought soon after the powerful earthquake struck. He first instructed his family to evacuate, then took his camera and drove to a hilly area where he could see the town below.

As Sato continued pressing the camera shutter, he was oddly calm and didn't feel terrified, he said. Sato is now photographing the recovery effort."

From a Rapid Damage Assessment and Need Survey

The report has high-resolution images from a number of the towns including and south of Minami-Sanriku. It is about 7 Mb and was provided to me by Tom Banse of Public Radio Olympia Bureau. Support public radio!

The report has high-resolution images from a number of the towns including and south of Minami-Sanriku. It is about 7 Mb and was provided to me by Tom Banse of Public Radio Olympia Bureau. Support public radio!

Monday, March 28, 2011

Minami-Sanriku before and after

The Sanriku coast I – Minamisanriku before and after

To the right is a Google map image of the towns we visited in April 2010 to learn how they were preparing for tsunamis. This trip was led by Nobuo Shuto and Fumihiko Imamura. We were an international busload. Minami-Sanriku was our second stop, coming up from Sendai.

If you followed the tsunami news at all, you will recognize the name of this town from the references to it as “the town that disappeared.” But many people survived, and many largely due to preparedness. We visited this town in April of 2010 to see how tsunami mitigation had developed. Minami Sanriku is no stranger to tsunamis. Here is a summary of recent historical cases.

1896 Meiji Sanriku and 1933 Showa Sanriku tsunamis. The town experienced two giant local tsunamis in recent 100 years. The Meiji Great Tsunami in 1896 showed the maximum height of about 3.5 m, and the Showa Great Sanriku Tsunami that of about 2.2 m. Information: Nobuo Shuto

Chile 1960 tsunami. The tsunami from Chile in 1960, reaching heights up to 5 m, destroyed the town and killed 41 residents. Thus in the public square near the shore there is a gift monument from Chile (a replica of an Easter Island monument) in memory of those victims. It was snowing when we were there in mid-April 2010.
"One of my neighbours who ran with her three-year-old baby strapped to her back later realised that the child had fallen off and been swept away as they struggled in the water," Shiba said. "It was terrible." "I was pregnant at the time and had to hang from the edge of a wooden roof when the water and debris gushed into my house," said Shiba, adding: "The baby died just one day after she was
born." Across Japan's Pacific coast the death toll from the 1960 quake -- the strongest on record with a magnitude of 9.5 -- reached 142. -- from 1 March 2010

Chile 2010 tsunami. When in 2010 (the 50th anniversary year of Chile 1960) Chile had another great subduction-zone earthquake and tsunami, Minamisanriku residents were ready for its arrival. The river gate (see photo) came down to keep the tsunami at bay, people evacuated to higher ground, and no one died, though there was damage to aquaculture and harbor structures.

(news article of 1 March 2010) --"Japanese grandmother Matsuko Shiba rests at an evacuation shelter in Minami Sanriku Town on February 28 2010. When Chile's massive earthquake sent a tsunami racing towards Japan at the weekend, Shiba knew to head for high ground, and for good reason. Half a century ago a killer wave from the South American country destroyed the picturesque fishing town of Minami Sanriku. Another refugee in 2010, Yoshida, watching her carefree grandson, said that her town 50 years ago received a lot of help from people across Japan. Today, she said, 'we also need to help people suffering from disasters overseas. And, we, the elderly, need to talk more about what we experienced to the younger people.' " -- from 1 March 2010

Our visit in April 2010

It was a cold, wet day when we visited Minami-Sanriku on 12 April 2010. Our leaders took us to the waterfront, where a river gate was the main point of our stop, and we also walked in the park and saw the many tsunami monuments. The rain turned to wet snow. I look around at how flat is was and how close to sea level, taking pictures of an apartment building that was clearly labeled as a vertical evacuation structure for those near the waterfront. This particular piece of land was intentionally left just as a park because at high tsunami risk, and people could evacuate to the nearby tall, reinforced concrete building if there was a tsunami warning.

These gates are meant to keep tsunamis out. I suppose they may also be used for storm surges. They take time to activate and lower the gates, and on the day we visited, they could not get the gate down. In the 2010 Chile tsunami, they had plenty of advance warning, and the gate worked. They gave us a handout describing how they were trying to decrease the time to gate lowering with the possibility of using it for locally generated tsunamis.

Below is a "before" map showing the location the three features we saw on the waterfront of Minami-Sanriku in April 2010.

11 March 2011 Tohoku earthquake and tsunami hit Minami-Sanriku

You can see below in this post-tsunami image that the 4-story building stood, and what I read makes me think that people on the top of this building, which is now half-surrounded by water, survived. It also looks like the river gate is still there, but with severe erosion around the left bank. The tsunami would have significantly overtopped the gate, and in any case, I don't think there was time to bring it down. The park's trees have been washed away, from this view it's hard to see much else, but it's likely all the monuments were toppled and transported some distance, but they may be salvaged.

NHK World, 28 March: A 4-story public apartment building in the coastal area was almost completely inundated, suggesting that tsunami up to 16 meters reached the building.

The town hall was a three story building in the center of town. The mayor, Jim Sato, was one of about 8 or 10 that survived on the top of it, by clinging to things like steel railings, while about 20 others were washed off the top of the building, about 13 meters high. After the tsunami the building is a skeletal wreck--I saw images on an NHK documentary last weekend. The nearby hospital (the largest building complex in this oblique view) withstood the tsunami, with staff moving patients higher and higher, to the fifth floor; the tsunami reached the fourth floor (from NHK documentary).

16 March – town 10,000 missing:

19 March – situation terrible, some reason for hope:

Although the numbers of dead and missing are increasing, there are now about 10,000 survivors accounted for; the mayor holds out hope that many still not documented left town for other places, but the fatalities are sure to rise:

When the Observer asked mayor Sato to account for the discrepancy, he said the problem lay in the manner of counting. "At first we assumed only the 7,000 at the public shelters had survived, but we realise now that many others sought refuge with friends or left the town. That was our mistake. I still can't tell you how many are dead. We still don't know how to make an accurate estimate."

From IOC/UNESCO report of 28 March 2011

Minami-Sanriku T







7 km2 flooded of 164 total

  • Many areas are inundated
  • Tsunami ht by Waseda U. Evacuation building: 15.4 m

There are many terrible images of this fishing village post-tsunami, but I am choosing to focus on the survivors such as these children in an evacuation center at a secondary school in Minami-Sanriku.

Photograph: Stephen Morrison/EPA

Saturday, March 26, 2011

Simon Winchester in Newsweek – bad science


Besides his bad science, Winchester suggests that potential survivors should give up hope, and this is not true [see my prior blog]:

I surely hope that Mr. Winchester is not claiming any scientific background (he has an undergraduate geology degree from Ozford) in the case of this essay, in which he badly misrepresents scientific and cultural knowledge, to the point of potential harm in future events, and insult to Japanese victims and survivors.

I only hesitate to write this because it will bring further attention to this awful essay, which in turn might cause Mr. Winchester sell more books. I am speaking only to the tsunami, and related geological comments; for more about the seismicity issues, see:

Here are some excerpts from the Winchester’s essay (his quotes are in italics, with points of particular contention in red), with my comments (particular rebuttals in blue), especially with reference to the tsunami:

I. …all geological events are sudden, and all are unexpected if not necessarily entirely unanticipated….

Jody remark: The first phrase is a tautology, completely depending on the definition of “geological event.” As geologists, we recognize many “events” in the geological record that are perhaps “sudden” on a geological time scale, but not on a human time scale. If you want to sell more of your books, then this would be a good description of a “geological event.” Moreover, these events are not unexpected, they just may be hard to predict, though Winchester later contradicts himself by predicting the San Andreas fault will be the next to go (the most egregious part of the essay, see Christie Rowe’s link). A counter-example of something that has become predictable in many cases would be volcanic eruptions, though, like the 2011 Tohoku events, the scale can be beyond what was formally anticipated.

II. ….At first, the shock was merely a much stronger and longer version of the temblors to which most Japanese are well accustomed. There came a stunned silence, as there always does. But then, the difference: a few minutes later a low rumble from the east, and in a horrifying replay of the Indian Ocean tragedy of just some six years before, the imagery of which is still hauntingly in all the world’s mind, the coastal waters off the northern Honshu vanished, sucked mysteriously out to sea….

Jody remark: it was not mysterious at all to the Japanese, they are well educated for what to expect after a large earthquake, if they are on the coast. All the tsunami warnings went off, many people who had the opportunity escaped. It’s only true that this tsunami was larger than formally planned for.

III. ….The rumbling continued, people then began to spy a ragged white line on the horizon, and, with unimaginable ferocity, the line became visible as a wall of waves sweeping back inshore at immense speed and at great height. Just seconds later and these Pacific Ocean waters hit the Japanese seawalls, surmounted them with careless ease, and began to claw across the land beyond in what would become a dispassionate and detached orgy of utter destruction….

Jody remark: Well, I guess it’s fair to say that tsunamis are “dispassionate and detached.” However, by the time the tsunami approached the shore, it was not moving at immense speed (see below), and the heights until it came onshore (and in that case particularly in steep regions) are also not great. It took minutes to tens of minutes for these waves to hit the seawalls. The destruction was indeed terrible, but many reinforced concrete structures survived.

IV. ….But in this corner of northeast Japan, with its wide plains of rice meadows and ideal factory sites and conveniently flat airport locations, there may well be a great deal of inland—but there is almost no uphill….

Jody remark: Winchester has decided to focus only on the Sendai plain, whereas the majority of the affected region is not at all flat. And then his problem is, that by focusing on Sendai, the following points he makes are even more mistaken.

V. The most egregious, partly because it causes potential survivors to give up hope:

….And so the reality is this: if a monstrous wave is chasing you inland at the speed of a jetliner, and if the flat topography all around denies you any chance of sprinting to a hilltop to try to escape its wrath, then you can make no mistake—it will catch you, it will drown you, and its forces will pulverize you out of all recognition as a thing of utter insignificance, which of course, to a tsunami, all men and women and their creations necessarily must be….

Jody remark: Completely bad science about tsunami speed, and anyone who watched the tsunami cross the Sendai plain, with any experience in watching tsunami videos, would marvel at how slow and almost stately it was, albeit still terrifying. Reinforced concrete along the shore and inland (such as the airport building) survived, and many people survived here by moving quickly away from the shoreline as soon as shaking stopped. They were not ignorant of tsunami threat. And, as anyone who would care to look up “tsunami” in any reasonable reference knows, they move at the speed dependent on the square root of water depth (see footnote), hence the tsunami as it approached Sendai already was moving much more slowly than a jetliner (“jetliner” is the speed over the deep ocean, several kms deep; see footnote) and was moving even more slowly as it cross the Sendai plain. I guess on the Sendai plain you could say it was the speed of a jetliner as it taxis… not trivial to outrun, but there was advance time.

Bottom line: I agree with Mr. Winchester that the Earth can throw punches beyond the scale of local human survival, though except for asteroid impacts, these remain local events on a global scale and have not brought an end to the human species, which would be a real “geological event.”

Besides his bad science, though, Winchester suggests that potential survivors should give up hope, and this is not true [see my prior blog]:


The speeds as the tsunami crossed the plain are not trivial, but given that people had natural and human warning systems, and that they had 10s of minutes to start their escape, most would have made it.

Speed of a tsunami –example of Sendai plain


Water depth






over the deep ocean




at the edge of the shelf




"as it approaches"




beginning to be visible from ground level




at Sendai airport, max




crossing the plain, typical




Tsunami wave speed = √(gh) --this is the basic “shallow water wave equation”

= [square root of (g times h), where g is gravitational acceleration, it’s ~9.8 m/sec/sec on Earth’s surface; and h is water depth]

These speeds are calculated without consideration of viscosity, which was higher than water on the Sendai plain, because of mud and vegetation, and this would cause a lower speed.