Ancient ruins in the Himalayas reveal historic details of some the region’s biggest earthquakes, according to a new study.
Mayank Joshi and V C Thakur, archaeoseismologists at the Wadia Institute of Himalayan Geology in India, studied intricate damage signs on temples in two towns in the Himachal Pradesh district, within the Kashmir “seismic gap” of the Northwest Himalayan range. They found the way the buildings’ deformations painted a picture of seismological activity in the area and may help predict earthquakes down the track.
The work was published in Seismological Research Letters.
Calculating the strength of earthquakes that struck before modern measuring techniques can be a tricky business. Much must be inferred from rock deformations or anecdotes.
But there’s another handy archive of ground movements: stone buildings, such as temples. Earthquakes big enough to shake them, but not so strong as to knock them over, leave tell-tale signs such as tilted pillars and cracked steps.
Natural ageing, on the other hand, doesn’t produce the same consistent patterns.
To get a handle on the magnitude of earthquakes that struck the Northwest Himalaya range, Joshi and Thakur studied temples, between three and six metres tall, located in the towns of Bharmour and Chamba along the Ravi River. They were built for kings as far back as the seventh century.
To assess earthquake activity, the pair measured the angle of tilting in the pillars, the size of cracks in stone and the amount of movement of roofs and canopies.
They found damage evident on temples in Chamba may have been sustained during an earthquake in the year 1555, while the temples at Bharmour were likely damaged during an event in 1905.
Such detailed information can not only help experts understand the magnitude of past quakes, but also help predict future events.
For instance, the 1555 earthquake is thought to have centred around the Srinagar Valley, about 200 kilometres northwest of Chamba. Joshi says that if the effects of the quake extended all the way to Chamba, the region “between Srinagar and Chamba has not been struck by a major earthquake for the last 451 years”.
The tension that’s since built in the fault today, Joshi adds, could result in an earthquake of similar clout to the 2005 Kashmir event – a 7.6-magnitude earthquake that killed more than 85,000 people.