164. Episodic Tremor and Slip (2003)

Episodic Tremor and Slip 1
Episodic Tremor and Slip 2

Episodic Tremor and Slip (ETS) is a tectonic process that occurs predominantly in subduction zones where geologically young (less than about 40 million years old) tectonic plates slide (or subduct) beneath other tectonic plates. It involves repeated episodes of slow slips of a few centimetres over a period of several weeks on the deep subduction plate interface, 25 to 40 kilometres below Earth’s surface.

This slow slip is accompanied by seismic tremors that appear as prolonged ground vibrations, which lack the sharp shock waves that characterize even small earthquakes. Geological Survey of Canada scientists Herb Dragert and Garry Rogers discovered ETS in 2003 while studying the northern Cascadia Subduction Zone where they found that ETS episodes were surprisingly regular, with an average recurrence interval of 15 months.

The significance of this phenomenon for seismic hazard evaluations is yet to be fully determined, but it is known that episodes of deep-plate slip add stress to the shallower, locked portion of the subduction plate interface and could possibly trigger a megathrust earthquake.

Category: Science Advances

Decade: 2000s


Rogers, G. and Dragert, H., 2003. Episodic tremor and slip on the Cascadia subduction zone: The chatter of silent slip; Science, v. 300, p. 1942–1943. doi:10.1126/science.1084783.

GSC 175 - CGC 175