InSAR data shows that the Karakoram and Altyn Tagh
faults are moving much more slowly than predicted by conventional plate tectonics modelling.
India is moving northwards, colliding with Asia at a rate of around five centimetres a year. There are two major faults within Western Tibet: the Altyn Tagh and the Karakoram.
Following the rules of plate tectonics, models of the collision of India and Asia predict that these two faults are slipping rapidly – at two to three centimetres a year – causing a rigid chunk of Tibet to be ‘pushed out’ to the East.
A team led by Dr Tim Wright of Oxford University used a technique called Interferometric Synthetic Aperture Radar (InSAR), which can measure movement in the Earth’s surface with a precision of millimetres. Using InSAR data from the European Remote Sensing satellites gathered between 1992 and 1999, the team measured surface motion across a 500 kilometre long stretch of Western Tibet. They found barely any movement along the two faults: at most Karakoram was slipping at seven millimetres per year and Altyn Tagh by less than 15 millimetres per year.