Typhoons trigger slow earthquakes

Teleseismic waves generated by large earthquakes are known to trigger other earthquakes, even at a great distance, and seasonal atmospheric pressure variations have been shown to modulate microearthquake activity. ChiChing Liu et al. now report an unexpected geological phenomenon: earthquakes triggered by weather conditions. Data from borehole strain-meters in eastern Taiwan show that slow earthquakes — seismic events spanning hours and minutes rather than minutes and seconds — can be triggered by typhoons. Numerical models suggest that low pressure associated with the typhoon results in a very small unclamping of the fault, which must be highly stressed and close to failure. Eastern Taiwan experiences very high compressional deformation, but few large earthquakes. Repeated slow earthquakes in the region may act to segment the stressed area and inhibit large earthquakes that require a long continuous seismic rupture.