'Wonder and Fear of the Power of Tsunamis'
The third of as many as seven ASCE reconnaissance teams is in Japan studying the impact on infrastructure caused by the 9.0 magnitude earthquake and tsunami on March 11. Following teams sponsored by the Structural Engineering Institute and the Geo-Institute, the third team is sponsored by the Coasts, Oceans, Ports, and Rivers Institute, and as such will be focused on damage to port structures. It is being led by Marc Percher, P.E., M.ASCE, a senior engineer with Halcrow Group in Oakland, Calif. He is a structural analyst and designer specializing in marine oil terminals and refinery structures. Percher and/or his teammates will be discussing their findings and experiences in regular posts.
Read each day's entries:
Introduction | Day 1 | Day 2 | Day 3 | Day 4 | Day 5 | Day 6
Day 3 -- Friday, May 13
Team A: By Marc Percher
As I’m coming to understand, there is no way that we will ever truly understand the extent of the damage to Japan. Unlike Chile, the Japanese coast is highly populated, and the Sendai region is relatively flat, which leads to tsunami damages being so widespread that there is way too much ground for our small group to cover. Thus, today we broke into two three-person teams -- myself, Bill Rudolph and Yoshi Oritatsu heading to Matsushima and Ishinomaki, while Bill Bruin, Martin Eskijian, and Alex Augustin headed to the Tagajo oil terminals and to Onagawa (their report follows ours below). What we found both shocked and surprised us, but that seems to be the theme for this trip.
Matsushima is the jewel of the Tohoku region. Deep within the bay, it is close to a series of barrier islands which grow out of the water like tree-topped tan mushrooms. As it turns out, the key to Matsushima’s beauty is also key to its safety. Dr. Arikawa, who has graciously joined the team from PARI, took a side trip away from us to investigate the islands and found that on the outside there was inundation of four to eight meters, while at the town there was inundation of only 1.5 meters. Clearly, the islands played a key role in decreasing the energy of the incoming wave and saving the lovely town.
Unfortunately, the town of Ishinomaki was not as fortunate, being on the coast and without the comforts of the barrier islands. Here we saw many gravity caisson structures (read: big blocks o' concrete laying on top of each other and filled in with mud) with small movements that resulted in some displacement of the fill behind. This was not terribly surprising as there is a history of this type of performance seen in the Kobe quake as well as elsewhere in the world. The surprising thing was that the freeboard (height of the structure above the water) was almost nil, and in some places the deck was now underwater. The picture below shows one such case at a major new port facility which extends well into the bay. This will prove to be an incredible challenge for the Japanese, as they must now figure out a way to raise the deck level several meters while decreasing the likelihood of repeating this performance.
We also stumbled upon a marine oil terminal with similar sinking issues. As seen in the photo at the top of this post, the wharf where the ship would normally pull up is now at least one meter below water. While piping and equipment can be replaced, this type of failure will take some very creative thinking and a whole lotta work. At the same facility, the tsunami lifted up several tanks which were about one-third full, and we arrived just in time to see them being torn asunder with a backhoe, something I’m sure I’ll never see again (turns out it’s not too hard to do, and I’m sure kinda fun).
At another location we saw a similar tank floating response, however this one had its amazing scale "turned up to 11." Long before the trip I saw in the satellite images a large diameter tank which totally disappeared from its original location, and another that reappeared several hundred feet away, sitting on top of a breakwater. Surely this could not be the same tank -- well, of course it is. While we’ve seen several floated tanks in the region, this one blew my mind as the tank had jumped its two-meter-tall containment wall (without even obviously causing any damage). This to me may be one of the most mind-blowing things I’ve seen, but I’m sure that will change tomorrow. As I said, I’ll never understand everything, but what I do get a chance to understand only fills me with more wonder and fear of the power of tsunamis.
Team B: By Martin Eskijian and Bill Bruin
Today was the first day that our team was split. After grabbing breakfast at a local supermarket, trying out different Japanese breakfast treats (there are so many to choose from), we headed to the Sendai refinery, which has been closed since the disaster. This is a significant facility supplying refined fuels and liquid petroleum gas to northeastern Japan. From other sites in Tagajo and Sendai, we had seen flaring activity at the refinery and we figured the facility was up and running. After arriving, we were met with the nationwide federal inspection team for refineries (one or two individuals per perfecture), and we joined in for a walk through the refinery and its adjacent seven marine oil terminals. What we saw we could record, but were not permitted to take pictures. The site PGA was reported at 0.43g’s until the accelerometers stopped working, either due to a lack of power or some other reason.
Right on schedule (the Japanese custom), we started our walk through the refinery and saw things that one could only imagine the horror of seeing in real time. For our interests, the oil terminals that we visited performed very well, and there was no indication of any inertial damage. The marine structures were steel plumb and batter piles with steel X bracing and a light concrete deck with curbing. No evidence of any damage was seen and even the loading arms looked intact. This was in contrast with the Soma bunker terminal, where the topside equipment suffered heavy damage.
Damage at the refinery was predominately due to the tsunami, and was almost beyond our comprehension. Pipelines were everywhere; to be described as spaghetti would be an understatement, and repairs will be monumental. Estimates are a year or more to completely recover and return the entire refinery to operation; however, some pass-through operations have already resumed. Empty large diameter tanks (20-40 meters) had floated like rubber ducks, and landed on top of concrete containment walls or hit other stationary objects. There was no evidence of elephant’s foot failures or any sloshing type damage. The largest tanks had horizontal hoop stiffeners near the top and performed well. Most of the large diameter tanks were not anchored, and many had moved off of their ring walls. Scour was evident everywhere. Pits as deep as three meters were observed, in some cases undermining the foundations of containment structures and pipeways. We also learned that the flare fire was due to the liquid petroleum gas tank evaporation. Because they can no longer control the pressure of the storage sphere, as the compressors are no longer functional, excess pressure is being vented to the atmosphere for safety.
We also observed evidence of a catastrophic post-tsunami fire at the plant. The tanker truck rack was completely burned, along with many adjacent large diameter tanks, as well as the railcar loading area. It was reported the debris from the refinery was pushed into this area, further onshore, and the resulting impacts initiated a fire involving sulphur, asphalt, liquid petroleum gas, and gasoline. The aftermath was horrific, like a vision from Dante’s Inferno. There were ghostly twisted shapes of burned-out tanker trucks jammed into the loading rack structure. Large masses of burned twisted steel, the remains of the loading frames, were in grotesque poses, bent by the combination of blast and heat. Large storage tanks of various sizes were charred or bent into menacing positions.
Elsewhere, luckily spared of the heat and flame, liquid petroleum gas railcars, about 15 to 20 or so, were scattered like matchsticks across a wide area. The associated tracks were either buried or pushed hundreds of meters from their original position. We also observed one oil barge, overturned and leaned against the pipe rack structure more than 100 meters from the ship channel.
From the refinery, we headed east towards the Pacific. We drove by several coastal villages along Matsushima Bay, one of Japan's three most beautiful bays. Living up to claims, the bay was beautiful, filled with a series of small sand stone islands, sculpted in many fascinating shapes, and topped by a pine forest. We were all captivated by the beauty and the observation that these islands may have absorbed a significant amount of the tsunami’s fury. It was reported that many of the outer islands were overtopped completely, but from where we were near the shoreline, there were very few obvious signs of the tsunami run-up.
We then enjoyed a really good Japanese lunch of beef tongue. One of the group was very reluctant to try this famous Japanese fare, but after he was told it tasted like filet mignon (which it really does!) and some minor peer pressure, he tried it and found it to be outstanding. We washed down this great meal with some very tasty soft serve ice cream and continued the expedition.
After driving through beautiful rolling hills, pine trees and lagoons, we arrived at the coastal village of Onagawa, a site that looked unlike anything we had ever seen. The tsunami damage focused on this small seaside village was staggering, with a wave of more than 20 meters crashing through this small valley community. Cars were on top of five-story buildings, while a few three-story buildings had overturned completely, with piles broken and/or extending from the foundation. It was reported that as much as 80 percent of the village population was killed. The devastation was widespread, with the wave reaching deep into the valley. The aftermath was sobering. A complete village, almost completely swept away, with only a few of the most sturdy structures still standing. This site gave us all something to think about.
Introduction | Day 1 | Day 2 | Day 3 | Day 4 | Day 5 | Day 6