Suzanne's Mom's Blog

Photo: Jay Thakkar.
A worker examines a wooden beam in a traditional Indian kath kuni building. These earthquake-resistant structures lack metal and mortar, allowing them to flex as needed during a tremor.

I keep learning about ancient construction techniques that beat modern ones. Remember the post about self-healing concrete, here? That was in Rome. Today’s story explains why some buildings in Turkey and Syria withstood the earthquakes in February and points to ancient buildings in northern India.

Shoma Abhyankar writes at Nautilus, “The powerful 7.8 magnitude earthquake that struck Turkey and Syria on February 6 killed almost 50,000 people, most of whom died under rubble.

“The tragedy falls in a decades-long history of outsized death and destruction from recent earthquakes: The 1999 İzmit earthquake near Istanbul killed at least 17,000 people. … The immediate cause of the human tragedies was not the shaking ground itself, but the buildings people were in, most of which were constructed of reinforced cement concrete, a relatively quick and cheap building method.

“Earthquakes don’t have to be so deadly, say scholars who study this issue. Many traditional buildings have stood the test of time in regions that have endured high seismic activity for centuries.

“In Japan, people had long built earthquake-resistant structures mostly from wood. But a different tradition shows that even stone buildings can withstand vigorous shaking — if they are built with clever physics and architectural adaptations, honed over the centuries.

“In the mountainous region of Himachal Pradesh in India, near where the Indian Plate is colliding with the Eurasian Plate, many structures built in the kath kuni style have survived at least a century of earthquakes. In this traditional building method, the name, which translates to ‘wood corner,’ in part explains the method: Wood is laced with layers of stone, resulting in improbably sturdy multi-story buildings.

“It is one of several ancient techniques that trace fault lines across Asia. The foundations for the timber lacing system of architecture may have originally been laid in Istanbul around the fifth century. … Despite their ancient origins, this model of construction has mostly fared better over centuries than much of the contemporary building across the continent’s many active seismic zones.

“Built along the natural contours of the hills, kath kuni buildings typically get their signature corners from giant deodar cedars, which grow upward of 150 feet tall and 9 feet across in the Himalayas. These wooden beams layer between dry stones, which create walls. A single wooden ‘nail’ joins the beams where they come together.

“As the ponderous-looking structures rise vertically, usually up to two to three stories, the heavy stone masonry reduces, giving way to more wood. The overhanging roof typically has slate shingles resting on wooden beams. ‘The structure is like a body with heavy base, the projecting wooden balconies are limbs, and the heavy slate roof is like a head adding stability to the structure,’ says Jay Thakkar, a faculty member at the Centre for Environmental Planning and Technology University in Ahmedabad, India, who co-authored the book Prathaa: Kath-kuni Architecture of Himachal Pradesh. 

“The buildings stand free of any mortar or metal, which makes them more capable of shifting and flexing along with torques in the ground. This brilliance of mobility even continues underground. They are built over a trench at least a few feet deep filled with loose stone pieces that works as a flexible plinth. While a building constructed out of what seems almost like rubble to begin with might seem a strange defense against earthquake damage, it works. The gravitational force of the structure itself holds the stones in place.

“ ‘Unlike the cement brick wall, which becomes a single solid mass, the dry stone masonry is flexible,’ Thakkar says. ‘Staggered joints allow the external forces like tremors of earthquakes to be dispersed through the masonry thus preventing cracks in walls.’ He adds, ‘The wooden pin at the corner joint of two beams also allows movement. So when an earthquake hits, the structure sways and shakes but doesn’t collapse.’ ”

More at Nautilus, here. No firewall.