The Global Positioning System has completely revolutionised how
geologists study the deformation of the Earth. If you leave a
GPS receiver in a fixed location for days, months and years, it
is precise enough to measure motions on the mil... The Global
Positioning System has completely revolutionised how geologists
study the deformation of the Earth. If you leave a GPS receiver
in a fixed location for days, months and years, it is precise
enough to measure motions on the millimetre scale, allowing us
to track strain building up across active faults, and even the
incremental drift of the tectonic plates themselves across the
Earth’s surface. But on the 26th December 2004, stations across
a sizeable slice of the Earth’s surface suddenly found
themselves being jerked around a bit more rapidly. The plots
below are from stations in southern India and northern Taiwan,
respectively. If you are thinking that date sounds a bit
familiar, you’d be right: that jerk is the signal of the massive
magnitude 9.3 earthquake tha