Long-period tremors (LPTs) have been observed in active volcanoes since the pioneering work by Sassa (1935) on supervolcano Asosan in Japan. Since then, numerous efforts are devoted to detecting these activities and sometimes using them as a proxy of upcoming volcanic eruption. Typically, the dominant period of these LPTs can range from 1 sec to several tens of seconds and they are often considered as a diagnostic indication of fluid and gas motion inside the volcanic conduit (e.g., Kawakatsu et al, 2000; Chouet & Matoza, 2013). However, seismic expression of these LPTs remains elusive. In particular, systematic analysis of temporal variations of these LPTs in a given volcano and systematic comparisons of these LPTs activities among different active volcanoes are currently lacking.
What can long period seismic tremors and their spatiotemporal variability tell us about the state of physical-chemical processes and fluid motion inside active volcanoes (Gonnermann and Manga, 2007) ? This project aims at detection/characterization of LPTs in active Japanese volcanoes through analysis of multi-years continuous broadband seismic data, with the first focus on Asosan and Sakakuragima in Kyushu. These spatiotemporal variations in LPTs activities may be coordinated with efforts on ambient noise analysis of seismic velocity changes associated with static and dynamic stress due to environment forcing and earthquake activities.