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Seismic Activities and Earthquake Resistant Techniques in Hasty Himalayas

Seismic Activities and Earthquake Resistant Techniques in Hasty Himalayas
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Nine year old Lobsang Gyaltsen was playing with his older brother when a 7.5 magnitude earthquake came with dusk on February 6, 1973 and instantly knocked down his house, burying him under the debris. Fortunately, his mother had pulled him out alive from the wreckage. However, the image and memories of what he witnessed afterwards remained forever in his mind. “After I was pulled out, I noticed everything was flat,” recalls Lobsang, who is now 49 and lives in South India as a Geshe. During that year of 1973, the town of Drago collapsed and caught fire, killing atleast 2175 people. He saw the body of his best friend’s mother smashed into many pieces. Such destructive earthquakes were not unexpected in the region. Tibetans experienced several large earthquakes, including one of world’s ten strongest quakes. Recently during August 2013, earthquakes rambled throughout the regions in Chamdo, Ganze, and Yunnan hitting over 20 times within the span of three days in some areas. Experts say that the Himalaya region and Tibetan Plateau are some of the most seismic active zones in the world. “Himalayan region is one of the most sensitive areas in terms of acute hazard,” said Amod Dixi, the executive director of Nepal’s National Society for Earthquake Technology. “It has got a very high magnitude frequency which means it is as seismic as some of the most seismic countries, better known, something like, California or Japan.” However, the safety standard of the modern buildings in the region is far from comparison to the above mentioned places. Mr. Dixi says 97 percent of the modern buildings in some Himalayan areas are built without proper engineering. Susan Hough of US Geological Survey, who had just returned from Nepal a few days ago, said one of the issues she had found with the new buildings in many countries, including Nepal, was that the first floor of the buildings did not have enough walls to support the buildings as people used them for shops, making the venerability of buildings very high. “Any place you are building with masonry construction and if it is not reinforced or inadequately enforced, we know that has got a very high venerability,” she further added. Mark Aschheim is a Professor of Civil Engineering at Santa Clara University. He says that the walls made of stones with mud molder are especially venerable to earthquakes. At the same time, while the concrete walls with wire meshes are safer than rock-walls with mud molders, experts agree that it doesn't mean the same condition applies to the roof structure. They say the traditional mud and wooden roofs are safer than concrete roofs for single story buildings. Mr. Dixi and his organization learned from the earthquake events in Nepal, Pakistan, Bangladesh and other regions that the buildings were most venerable to earthquakes if they were built within the past fifty years. He says the houses that were built prior to that time have more quake resistant ability. Giving Nepal’s Bhaktapur city as an example, he said hundreds of houses in the city are over 300 years old and they survived from three major earthquakes and are still being used as residences or temples. However, it is not to say that the modern buildings using right engineering and proper building codes aren’t earthquake resistant, according to the experts. Hough said not all old buildings are safer. Some old buildings, she said, were built with rocks with weak molders. Therefore changing building structure or making shears around the old walls are critical, she said. “In Chili, for example, after the great earthquake in 1960, they moved more towards requiring shear walls,” Hough says. In Drago, Tibetans changed their building materials from mud to wooden walls after the deadly earthquake they had experienced forty years ago. In Drago, Tibetans changed their building materials from mud to wooden walls after the deadly earthquake they had experienced forty years ago.