Earth’s mantle torn into 4 pieces under quake-prone Tibetan plateau – scientists
The model, generated from high-resolution earthquake data, offers the clearest picture yet of the mysterious geological processes that occured when the Indian and Asian tectonics plates collided some 50 million years ago, giving rise to the highest and largest plateau in the world - the Tibetan Plateau.
The collision of these continental plates is behind some of the world’s deadliest earthquakes including the 1950 Assam-Tibet quake which killed more than 1,500 people and more recently, a magnitude 6.9 earthquake which struck the Qinghai Province of China in 2010, leaving more than 2,000 dead.
This new research, carried out at the University of Illinois, found that the upper mantle layer of the Indian tectonic plate appears to be torn into four pieces that dive under Asia - each at a different angle and distance from the origin of the tear.
"The presence of these tears helps give a unified explanation as to why mantle-deep earthquakes occur in some parts of southern and central Tibet and not others," co-author of the study Xiaodong Song said.
The intact regions of crust between the tears are strong enough to acquire strain to generate earthquakes. The crustal areas above the torn regions, however, are exposed to more of the heat from the mantle and are therefore more flexible and less susceptible to earthquakes, the researchers said.
"What were previously thought of as unusual locations for some of the intercontinental earthquakes in the southern Tibetan Plateau seem to make more sense now after looking at this model," said co-author Jiangtao Li. "There is a striking correlation with the location of the earthquakes and the orientation of the fragmented Indian upper mantle."
The team gathered geophysical data from various sources to generate seismic wave tomographic images of Tibet that extend roughly 160 kilometers deep.
The results published in the Proceedings of the National Academy of Sciences could offer insight into future seismic activity in the region and help assess earthquake risk in the area.