Dynamic response of frequent tremors at Aso volcano to teleseismic waves from the 1999 Chi-Chi, Taiwan earthquake

Teleseismic waves from the 1999 Chi-Chi, Taiwan earthquake dynamically triggered isolated tremor and micro-earthquakes at Aso volcano, Japan, which is at a distance of 1400 km. Immediately after the arrival of the P-waves, short-period tremor (SPT) began to occur more frequently for about 2000 s, and during and after the arrival of surface waves, 2 micro-earthquakes were observed around the crater. Observations of frequent SPT are an indication of triggered isolated tremor which consists of both SPT and long-period tremor (LPT) components. For the cases of arrivals of seismic waves from other large teleseisms from March 1995 to June 2002, triggering of isolated tremor was observed during 1998–1999. During this period increased thermal supply to the crater was observed while the background activity was relatively low, and the volcanic system beneath the crater was more responsive to external stress perturbations.