Based on studies of ancient ruins like tilted pillars, cracked steps and sliding stone canopies of the 7th-century A.D. temples in northwestern India, seismologists have revealed the extent of some of the largest historic earthquakes in the region.The seismologists studied the signs of destructive earthquakes imprinted upon the ancient stone and wooden temples in Chamba and Bharmour -- towns in the Himachal Pradesh district, within the Kashmir "seismic gap" of the northwest Himalayan range. The type of damage sustained by Chamba temples suggested that they may have been affected by the 1555 earthquake, while the Bharmour temples were damaged by the 1905 quake, the seismologists said.The epicentre of the 1555 earthquake is thought to be in the Srinagar Valley, about 200 km northwest of Chamba. However, if the 1555 earthquake did extend all the way to Chamba,"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," said Mayank Joshi, seismologist at the Wadia Institute of Himalayan Geology in Dehradun in Uttarakhand.
The stress built up in this section of the fault "may be able to generate an earthquake of similar magnitude to that of the 2005 Kashmir earthquake that devastated the eastern Kashmir," Joshi added.Further at the temples, the team measured the tilt direction, the degree of inclination of pillars and the full temple structures, and cracks in building stones, among other types of damage. They then compared this damage to historic accounts of earthquakes and information about area faults to determine which earthquakes were most likely to have caused the damage."In the Chamba-area temples, there are some marked features that indicate that the body of the temple structure has suffered some internal deformation. The pillars and temple structures are tilted with respect to their original positions. The rooftop portions show tilting or displacement," Joshi explained.The researchers looked for regular kinds of deformation to a structure and damages that have some consistency in their pattern and orientation, rather than ageing and ground subsidence where there is no regular pattern of damage. Other damages uncovered by the researchers included upwarping of stone floors, cracked walls, and a precariously leaning fort wall.The findings were published online in the journal Seismological Research Letters.