On 8 October 2005, a devastating magnitude-7.6 earthquake struck the Kashmir region in the Himalaya. It killed more than 80,000 people, injured more than 100,000, and left 3 million homeless.
One of the worst natural disasters in South Asia, the earthquake caused thousands of landslides that buried entire villages. Muzaffarabad and Balakot were two of the hardest hit towns in Pakistan. The epicentre of the earthquake was just northeast of Muzaffarabad, which lost about half of its structures. Balakot was almost completely wiped out — the shaking and landslides destroyed 90 per cent of the town’s buildings.
The 2005 Kashmir earthquake was the result of millions of years of tectonic activity. Around 225 million years ago, India was a continent, but about 50 million years ago, it collided into Asia. This collision is responsible for the Himalaya, the tallest mountain range in the world. As the two plates squeeze together, they push the crust upward and sideways, making craggy peaks. The Himalaya are still growing, as India moves toward Eurasia at the rate of 30-50 millimetres each year.
Kashmir sits on the western-most section of where the Indian plate meets the Eurasian plate. Because of its location, it is one of the most earthquake-prone regions in the world. The plate movement causes massive amounts of stress to build up along faults. Once in a while, a large earthquake ruptures, releasing the built-up stress.
The Kashmir earthquake was devastating for a number of reasons. For example, unlike the recent 2015 earthquake in Nepal, the 2005 Kashmir quake broke all the way to the Earth’s surface. Huge scars ran along the surface of the fault for 75 kilometres (km) and, in some places, the ground moved more than 7 metres. The earthquake was shallow, and therefore produced more focused, intense damage. The less distance seismic waves travel, the less energy they lose.
This particular earthquake was a surprise to researchers, because it ruptured along the Balakot-Bagh fault and not on the more active boundary between the Indian and Eurasian plates. After the 2005 earthquake, geologists began to look at other faults in Kashmir to see if they have accumulated strain. They found that similar stress has built up on the nearby Riasi fault in Indian Kashmir, although previously the Riasi fault was considered a less active fault.
According to Assistant Professor Judith Hubbard, Principal Investigator and Team Leader of the Structural Geology group at the Earth Observatory of Singapore, understanding how shortening across a plate boundary is partitioned onto different faults is important. “In geology, the past is the key to the present,” Asst. Prof Hubbard explained. “Geologists look for the record of past earthquakes by examining the surface traces of faults, and try to reconstruct what has happened: when earthquakes happened, how large they were, and how they changed the ground surface. If we don’t study the right faults, we will construct an incomplete record, and may underestimate earthquake hazard.
“In regions like the Himalaya, seismic hazard estimates are critical,” she added. “People are vulnerable not just to ground shaking, but also to secondary hazards like landslides and dam ruptures. A place like Kashmir will never be safe from earthquakes, but hopefully through careful scientific work, geologists can provide information to engineers and governments that will help reduce the loss of life and property in the next large earthquake.”
By studying earthquakes like the 2005 Kashmir quake, we can find out more about what kind of tectonics we can expect in Kashmir, in Nepal, in the Indian Ocean, and beyond. Painting a complete picture of what happened will provide more accurate hazard maps and protect more people when the next earthquake strikes.