During the collision of India with the Eurasian continent, the Indian plate was pushed about 500 kilometers under Tibet, reaching a depth of 250 kilometers. The result of this largest collision in Earth's history is the world's highest mountain range. But even more recently, the collision could be felt -- for example, the earthquakes that created the 2004 tsunami in the Indian Ocean.
The clash of the two continents is very complex. The Indian plate, for example, is compressed where it collides with the very rigid plate of the Tarim Basin at the northwestern edge of Tibet. On the eastern edge of Tibet, the Wenchuan earthquake in May 2008 claimed over 70,000 lives.
Scientists at the GFZ German Research Center for Geosciences report in the latest issue of the journal Science on the results of a new seismic method which was used to investigate the collision process.
In international cooperation, it was possible to follow the route of the approximately 100-kilometer-thick Indian continental plate beneath Tibet. To achieve this, a series of large seismic experiments was carried out in Tibet, during which the naturally occurring earthquakes were recorded. By evaluating weak waves that were scattered at the lower edge of the continental plate, this edge was made visible in detail. The boundary between the rigid lithosphere and the softer asthenosphere proved to be much more pronounced than was previously believed.
The entire Indian sub-continent moves continuously north over millions of years and has moved 2 meters below Tibet in the last 50 years alone. The Himalayas and the highlands of Tibet, the highest and largest plateau in the world, were formed this way. But the recurring catastrophic earthquakes in China are also caused by this collision of two continents.
Researchers hope this latest work will provide a better understanding of the processes involved in the collision of the two plates, and ultimately reduce the earthquake risk to millions of people across the entire collision zone.
- Rainer Kind and Xiaohui Yuan. Seismic Images of the Biggest Crash on Earth. Science, 2010; 329 (5998): 1479-1480 DOI: 10.1126/science.1191620
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