Tokyo has been rocked again by another earthquake—one of hundreds of quakes to hit the country this year. It comes after revellers were tied up in a 7.5-magnitude quake that struck Central Japan on New Year’s Eve last year, triggering the country’s first tsunami warning since the 2011 Tōhoku ‘nuclear’ event.
Japan’s most potent earthquake for several decades toppled buildings, caused fires, and knocked out critical infrastructure in the Noto Peninsula as families celebrated New Year’s Day. However, despite a raft of earthquakes and aftershocks, Japan has fared far better than comparable examples, including Turkey’s 7.8-magnitude earthquake in February 2023, with its success largely attributed to the resilience of its buildings in the face of structural collapse.
The reason for this?
For more than a century, Japan has been at the cutting edge of seismic architecture and structural engineering, changing building codes to mitigate risks from thousands of earthquakes every year. Japan has adjusted standards for structural engineering, turning past disasters into hard lessons for the future, with timber design at the forefront of Japanese construction techniques.
In February, Wood Central spoke to Graham Sayer, director of Japanese Lumber – who from next week will be helping to guide a tour of Australian architects, engineers and developers around Japan, who said the west could lean much from the Japanese, who for centuries have been building predominately timber buildings to withstand earthquakes and other natural disasters.
“The timber culture comes down to the fact that bricks weren’t introduced here until the 1860s (by the Germans),” said Mr Sayer– a native New Zealander with deep relationships with sawmills and merchants across the country. “So it’s not a civilisation built on bricks (or stone) like many European civilisations.”
And from a policy standpoint, these changes began in 1923 when a 7.9-magnitude earthquake flattened Yokohama, killing more than 140,000 people and toppling hundreds of thousands of structures. Many of Japan’s ancient buildings, made from wood, were not equipped to handle frequent quakes. This tragedy allowed Japan to introduce the world’s strongest and most advanced seismic standards to its building codes, now known as the Building Standards Act. These standards bolstered new and existing timber—and concrete-based construction, particularly in heavily urbanised areas like downtown Tokyo.
Japan, which is among the largest consumers of timber in constriction worldwide, has now specified that “all buildings must not collapse during an earthquake of any force, despite the damage they sustain” – including detached housing, which, from 1981, must be built for “sustainable human life” during an earthquake.
Timber Engineering Research looks at Seismic Protection Technologies.
As Japan now looks to taller mass timber buildings to drive decarbonisation, seismic protection technologies (SPTS) have emerged as a hotspot in timber engineering research. This includes seismic dampers and base isolation, described as the “Cadillac of performance options when you protect buildings in high seismic locations,” according to California-based structural engineer Krista Looza, who remarked on the resilience of Japan’s timber buildings under heavy shock.
“They have almost three times as many earthquakes as we see here in California,” he said. “And California is considered a region of high seismicity. So you can imagine in Japan, people are very prepared and aware of the hazards they live in.”
According to Architecture Digest, seismic dampers are placed between the columns and beams of each building floor and employ piston heads in cylinders of silicone oil to transfer vibrations to the liquid rather than the structure during an earthquake.
Base isolations come in many forms and at many price points, from rubber pads installed at the building’s foundation to act as tremor absorbers to decoupling an entire structure from its foundation and setting it atop a flexible pad so that when the ground shakes, the architecture remains intact and stable.
“The most economical option to protect a structure from cracks and collapse is fortification, making walls, columns, and beams thicker to better handle stress during a natural disaster.”
When a building is under construction, architects can specify materials like precast concrete walls, which help absorb lateral loads, or steel moment frames to build support directly into the structure.
“Reinforced concrete and structural steel bracing are contemporary industry standards that were long thought to be better options than wood; however, engineered products like cross-laminated timber have recently been proven lateral force resistant by the US Forest Service, which has led to a building code change for approval of CLT structures in seismic areas.”
Quake Test on the World’s Tallest Full-Scale Timber Building
In June, Wood Central reported that researchers in California, also subject to high seismic activity, were using “the shake table” to test a 10-storey cross-laminated timber building at the University of California, San Diego. Previously reported by Science Blog, the experiment, known as the TallWood Project, is the tallest full-scale building ever to undergo testing on an earthquake simulator or shake table.
The shake table can recreate earthquake movements of various magnitudes on the Richter scale, ranging from 4 to 8, by mimicking seismic activity from past earthquakes, including the Northridge earthquake that hit Los Angeles in 1994.
“The combination of the largest payload capacity in the world, an outdoor setting, and the newly added six-degrees-of-freedom shaking capability makes the UC San Diego shake table a powerful and unique facility,” said Professor Joel Conte, principal of the Department of Structural Engineering at the UC San Diego Jacobs School of Engineering.
“It’s the only place where the TallWood Project tests could happen,” Conte said.
Mass timber buildings are gaining popularity as greener and faster alternatives to concrete and steel structures – including the 11-storey Port Plus building, which rose in Tokyo last year. With new building codes updated to permit more high-rise mass-timber buildings, many questions exist about how such buildings would fare in earthquakes.
“Mass timber is part of a massive trend in architecture and construction, but the seismic performance of tall buildings made with these new systems is not as well-understood as other existing building systems,” said Shiling Pei, principal investigator and associate professor of civil and environmental engineering at Colorado School of Mines.
Meanwhile, in Japan, engineers say preparedness is the best way to combat an earthquake’s potentially deadly effects. After every event, Japanese scientists inspect buildings to find where they have gone structurally wrong. This knowledge helps ensure that every subsequent tremor will be less disastrous than the last.
Please Note: Wood Central will have exclusive coverage from the Timber Development Association-organised Japanese study tour next week.
