Alan Linde, Selwyn Sacks, and colleagues have made the surprising finding that typhoons trigger slow earthquakes in eastern Taiwan. The group monitored deformation in the area during 2002-2007 using three highly sensitive borehole strainmeters installed 650 to 870 feet deep. “These devices detect otherwise imperceptible movements and distortions of rock,” Sacks explained, “We also measured atmospheric pressure changes, because they usually produce proportional changes in strain, which we can then remove.”

Taiwan has frequent typhoons in the second half of each year but is typhoon-free during the first four months. During the five-year study period, the researchers identified twenty slow earthquakes that each lasted from hours to more than a day, but they did not detect any slow events during the typhoon-free season. Eleven of the twenty slow earthquakes coincided with typhoons. Those eleven were also stronger and characterized by more complex waveforms than the other slow events.

For information, see the Nature Letter or the CIW Press Release.