Very-Long-Period Seismic Signals and Caldera Formation at Miyake Island, Japan

• DOI: 10.1126/science.1062136
• Publication Date: 2006-03-28T18:37:53Z
• Authors: Hiroyuki Kumagai; Takao Ohminato; Masaru Nakano; Masahiro Ooi; Atsuki Kubo; Hiroshi Inoue; Jun Oikawa
• Keywords: Caldera; Magma chamber; Piston (optics); Outflow

Over a period of roughly 40 days, starting on 8 July 2000, caldera structure 1.7 kilometers in diameter developed by means gradual depression and expansion the summit crater at Miyake Island, Japan. At same time, very-long-period (VLP) seismic signals were observed once or twice day. Source mechanism analyses VLP show that moment tensor solutions are smooth step functions over time scale 50 seconds, with dominant volumetric change components. We model to explain signals, which vertical piston solid materials conduit is intermittently sucked into magma chamber lateral outflow. This offers potential for making quantitative estimations characteristic physical properties systems.