|

Urbanites urged to head up, not down, to survive tsunami

by Richard Solomon

Sitting across from me at a Naka-Meguro pizzeria, Riccardo Tossani pulled out his iPhone to check his Spyglass app. He glanced out the window to survey the adjacent taller buildings, ignoring the cherry blossoms that were in full bloom.

“The only safe way to escape a tsunami,” said Tossani, “is up.” Our restaurant, in fact, was 11 meters above sea level, or four meters shy of the minimum 15-meter clearance he believes is required to avoid an advancing tidal wave, should it resemble the Tohoku tsunami of 3/11.

Although counterintuitive, if a tsunami was to strike Tokyo, you might well be safer on the top floors of a Tokyo skyscraper than anywhere else. Tossani should know: He is an architect, master planner and urban designer who researched the actions of those who survived and perished in Tohoku last year for the newly published “Natural Disaster and Nuclear Crisis in Japan” (Routledge). He and other experts in their field authored the book, which now forms perhaps the most comprehensive analysis of Japan’s triple disaster.

Long before establishing his Tokyo-based firm, Riccardo Tossani Architecture, in 1997, Tossani had become aware of the dangers that earthquakes pose to buildings and their inhabitants. In 1993 on Guam he had experienced first-hand a massive quake measuring 8.1 on the Richter scale that caused catastrophic damage. Tossani had also lived in earthquake-prone Los Angeles for nine years, designing a variety of structures. Before that he studied the engineering of mass dampers and isolation systems used to keep tall structures standing while at Harvard and MIT. Arguably, Tossani understands the importance of architectural engineering in terms of life safety.

“Given what we have learned from Tohoku, it makes perfect sense to look strategically and defensively at what could happen to Tokyo,” said Tossani.

Indeed, the University of Tokyo’s Earthquake Research Committee predicted as of January 2012 that there is a 70 percent chance the metropolis will suffer an earthquake of magnitude 7 or higher within the next four years. Everyone living in Tokyo knows the earth is grumbling. One can debate the facts as to when, where and how large a seismic event will be, but the reality is that Tokyo is both densely populated and one of the most dangerous cities in the world in terms of seismic activity. It sits at the convergence of four tectonic plates.

Tossani’s knowledge of structural engineering as well as 25 years of experience in Japan, California and the South Pacific gives him confidence that an earthquake is going to be the least of our problems. He believes the Japanese have long understood the dynamics of constructing buildings to withstand the constant seismic activity on their islands. This is why most of the buildings in Japan’s history were made of wood, paper (shōji) and lightweight materials designed to flex.

Tossani says that many older buildings are safer than we imagine, while modern seismic engineering methods allow for developers to build higher and with reduced probability of expensive cosmetic damage.

“What modern engineering has been able to do over the last 30 to 40 years is to minimize the possibility of catastrophic damage,” Tossani explained. “Reinforced concrete and steel-frame buildings, especially built after 1981, have an extremely low chance of collapsing. Back when working with slide rulers, architects purposely over-designed and over-built to ensure safety. It is not so much that newer building techniques protect us better, but rather through modern computing we can build more efficiently for the same seismic event with less concrete and steel.”

Fire remains a hazard in any seismic event. However, Tossani points to modern fire codes that minimize the amount of flammable materials used in today’s buildings. “Electric and gas reticulation systems are designed to shut down automatically. Catastrophic damage to Tokyo and its inhabitants from an earthquake is no longer the real issue.”

The bigger concern, he believes, is that of a tsunami striking Tokyo. In Tohoku, whilst many concrete buildings remained intact, the furniture, belongings and inhabitants all got swept away. Collective memory of the tsunamis of 869, 1611, 1896 and 1933, as well as recent government planning, all failed to prevent 19,000 lives from being lost.

“What we discovered in Tohoku was that many of the maps published by the Ministry of Land, Infrastructure and Transportation distributed to local municipalities indicated areas as low risk that were in fact death zones,” said Tossani. “Because many of the municipalities had distributed maps that showed only the four-meter zones, many people made a beeline for them, only to be overwhelmed.”

Twelve evacuation sites out of 25 designated by the Onagawa government as safety zones were swept away. In Minamisanriku, also in Miyagi Prefecture, 31 of 80 sites were washed away. In total the tsunami swept away more than 100 evacuation sites along the Tohoku coast. “That contributed to the direct loss of thousands of lives,” said Tossani.

Tossani believes that, as in Tohoku, those living in Tokyo are ill-prepared for a tsunami. In the case of 3/11, 500 km of coastline were affected. When the tsunami came onshore, the energy was concentrated by the natural topography. Where the landscape included bays, hills and valleys, the concentration of the energy forced water upwards in elevation to 40 meters.

“Bays don’t dissipate the energy. They act as a funnel to concentrate it,” said Tossani.

His message echoed that of professor Yoshinobu Tsuji, formerly of the Tokyo University Earthquake Research Institute, who wrote that as tsunamis approach an ever-shallowing shoreline, the pent-up energy at the end of a V-shaped bay has nowhere to go but up.

Should, as government agencies are predicting, a major earthquake occur within 100-150 km of Tokyo Bay in the Tokai area or Ibaraki’s Oki region, Hiroshi Takagi, an associate professor of engineering at the Tokyo Institute of Technology, believes the resultant tsunami would be similar to or greater in height than the Tohoku tsunami.

“The southwestward opening of Tokyo Bay makes it particularly vulnerable to tsunami from the Tokai region,” said Takagi.

Takagi, who coauthored “Behavior of the 2011 Tohoku Earthquake Tsunami and Resultant Damage in Tokyo Bay,” reported that major quake-induced tsunami have struck Tokyo Bay in 1703, 1854, 1923 and 1960 as well as on March 11, 2011. The largest tsunami to hit Tokyo Bay is thought to have been the result of the 1703 Great Genroku Earthquake, which flooded areas of Miura 6-8 meters above sea level in the south, parts of Yokohama at 3-4 meters elevation and, as far north as Funabashi, areas at 2 meters elevation.

On the presumption that energy from a future tsunami might find its way into Tokyo Bay, Tossani is currently researching data to quantify just how many people may be exposed and to determine the areas most at risk. Millions of people in Tokyo and Yokohama, it is thought, live within 2-3 meters of sea level. As evidenced by the recent Tohoku tsunami, everyone within 5 km of the shoreline at 15 meters elevation or below is potentially at risk.

Tossani also points to the enormous amount of debris one can expect to block Tokyo streets between the buildings. In Tohoku 25 million tons of it was left onshore. It took until mid-May last year to clear just 3.5 million tons of debris. In Tokyo, as in Tohoku, such detritus will block access, preventing fire engines and other emergency vehicles from getting to affected buildings.

“All you have to do is imagine three or four high-rise apartment buildings on the shorefront of Tokyo Bay that (each) contain 400 or 500 people that have had the good sense to go up to the roof, but there is no place for a helicopter to land,” said Tossani. “What are those people going to do for the next one or two weeks that it may take to dig through the mountain of debris preventing emergency vehicles from accessing those in need?”

For this reason, Tossani advocates that Tokyo adopts similar legislation to Los Angeles’ 1974 flat-top roof law, whereby tall buildings are required to have emergency helicopter landing facilities.

Tossani’s message is clear: Don’t worry about buildings falling down. If you are in a four-story building — all made of concrete and steel these days — get up to the roof. If you are in a 50-story building, stay high or get up higher.

It’s a safety message that also has the backing of Masato Minami, senior structural engineer at international structural engineering firm Arup. “It is safer to go up a tall building to escape the flooding rather than to try to escape from that building,” he said, as heavier buildings are more resistant to lateral seismic forces, including a direct hit by a tsunami.

The challenge before administrators is to educate the public to go against their natural instincts and head up rather than down.

“The way to instill counterintuitive thinking is by education, good understanding and appropriate drills,” said Tossani. “You either teach people to march to their doom or you teach people to go to a place that is truly safe.”

Closing tip: If you want to check your elevation and don’t own an iPhone, Google Earth offers a similar service at no cost. From within the application, simply place your cursor over your place of work or residence. The approximate elevation will appear towards the bottom of your screen.

Richard Solomon posts regular Beacon Reports at www.beaconreports.net. Send your comments on this issue and story ideas to community@japantimes.co.jp