Signs of earthquake damage at Hindu temples in northern India are helping scientists calculate the danger of future disasters in the same region. Who says science and religion can't work together? In this case, though, the news they have collaborated to produce isn't good.
Tectonic fault lines are most dangerous when they haven't shifted for a while. Instead of being released in a series of small- or medium-sized quakes, pressure builds up until something really big happens, with devastating consequences. With only a few decades of detailed monitoring, however, seismologists often struggle to know when past earthquakes occurred, and how much pressure was released – essential information for predicting the future.
Mayank Joshi of the Wadia Institute of Himalayan Geology has turned to Hindu temples to learn about one of Earth's most anxiety-inducing stretches of fault line, an area known as the Kashmir "seismic gap". A large earthquake struck this region in 1555, but details are sketchy and there is debate as to how much subsequent earthquakes, including four major events since 1905 along the same fault line, impacted the gap.
The possibility of a major earthquake here, perhaps as large as magnitude 9.0 and with the potential to affect millions of people, has aroused alarm. Joshi looked at the damage done to a number of temples to see what quakes they have survived. Most of the temples were built between the 7th and 10th centuries, presumably with straight walls and flat floors.
Establishing the timing of subsequent damage is a challenge, but Joshi said in a statement that when all the harm happened at once, the results “have some consistency in their pattern and orientation.” Things look far more confusing when several earthquakes have affected the same building.
The tilting of this pillar outside Lakshi Narayan temple is consistent with it being affected by the 1555 earthquake. Mayank Joshi
In Seismological Research Letters, Joshi and his colleagues report on the direction and inclination of tilt in the structures within temples around Chamba, a town famous for its ancient religious buildings. Crack lines and distortions in stone floors were also studied.
The 1555 earthquake was centered on the Srinagar Valley, but Joshi concluded that the Chamba temples, 200 kilometers (124 miles) to the southwest, were affected. However, he found no evidence that more recent events, such as the 1905 Kangra earthquake, affected this region. Local newspapers from the early 20th century suggest there was no additional damage to the Chamba temples when nearby towns were hit. “This further implies that the eastern Kashmir Himalaya segment between Srinagar and Chamba has not been struck by a major earthquake for the last 451 years," Joshi said.
If pressure in the region has been building up for such a long time, the next earthquake could be a big one. Joshi isn't speculating about a magnitude of 9.0, the size of the Tohoku earthquake whose tsunami destroyed Fukushima. However, he fears of “an earthquake of similar magnitude to that of the 2005 Kashmir earthquake that devastated the eastern Kashmir." This magnitude 7.6 event struck to the south-east of the gap, killing at least 80,000 people and leaving 4 million homeless.
Kangra fort was tilted in the 1905 earthquake, but the same quake didn't reach Chamba. Mayank Joshi