2012年5月
Geophysical Observation and Monitoring for Eruptive Activity of Shinmoe-dake, Kirishima Geopark
5th International UNESCO Conference on Geoparks, 1-P-11
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- 開催年月日
- 2012年5月12日 - 2012年5月15日
- 記述言語
- 英語
- 会議種別
- 開催地
- Shimabara City, Nagasaki Pref.
- 国・地域
- 日本
Shinmoe-dake volcano is located in the Kirishima volcanic group (Kirishima Geopark) in Kyushu, Japan. Major eruptions for Shinmoe-dake occurred in 1716 -1717: fall out deposits, pyroclastic flows and mudflows were widely dispersed around the volcano [Imura and Kobayashi (1991)]. Recently, on January 19th, 2011, Shinmoe-dake began a first magmatic eruption in about 300 years, in which eruption type changed to Vulcanian after three sub-Plinian events in January 26-27th, 2011, and volcanic activity is still continuing.
For the volcanic disaster-prevention, it is very important for monitoring the volcanic activity to detect movement of magma from the chamber to the active crater in real time. However there were a few on-line observation stations (e.g., seismometer, tiltmeter, infrasound microphone) in the Kirishima area. Therefore, we installed two temporal on-line observation stations: Shinyu (KU.KRSY , 3km WSW from the crater) with a broadband seismometer and an infrasound microphone, Onami-ike Tozanguchi (KU.KRON, 4km WNW) with a broadband seismometer and a tiltmeter. These data has been transmitted to SEVO, Kyushu University using a mobile phone data terminal since January 28th, 2011. In addition, these data has been also transmitted to Japan Meteorological Agency for monitoring the volcanic activity.
During observation, many explosive eruptions and volcanic tremors were occurred at the volcano. These events were recorded clearly by our observation network. From the end of January to February 2011, harmonic tremors were recorded several times by broadband seismometers and infrasonic microphone with almost similar waveform. The lag times of two waveforms were approximately 6-7 seconds. Considering the difference of velocity between P-wave and sonic wave, the source of harmonic tremor was in the very shallow part of volcano (just under the crater). It is generally difficult to detect the location of volcanic earthquake and tremor but information of these locations is very important because these events are believed to reflect the movement of magma. Our result suggests that the observation with combination of broadband seismometer and infrasound microphone is useful to detect the volcanic event occurring very shallow part of volcano and to assess the volcanic activity.
For the volcanic disaster-prevention, it is very important for monitoring the volcanic activity to detect movement of magma from the chamber to the active crater in real time. However there were a few on-line observation stations (e.g., seismometer, tiltmeter, infrasound microphone) in the Kirishima area. Therefore, we installed two temporal on-line observation stations: Shinyu (KU.KRSY , 3km WSW from the crater) with a broadband seismometer and an infrasound microphone, Onami-ike Tozanguchi (KU.KRON, 4km WNW) with a broadband seismometer and a tiltmeter. These data has been transmitted to SEVO, Kyushu University using a mobile phone data terminal since January 28th, 2011. In addition, these data has been also transmitted to Japan Meteorological Agency for monitoring the volcanic activity.
During observation, many explosive eruptions and volcanic tremors were occurred at the volcano. These events were recorded clearly by our observation network. From the end of January to February 2011, harmonic tremors were recorded several times by broadband seismometers and infrasonic microphone with almost similar waveform. The lag times of two waveforms were approximately 6-7 seconds. Considering the difference of velocity between P-wave and sonic wave, the source of harmonic tremor was in the very shallow part of volcano (just under the crater). It is generally difficult to detect the location of volcanic earthquake and tremor but information of these locations is very important because these events are believed to reflect the movement of magma. Our result suggests that the observation with combination of broadband seismometer and infrasound microphone is useful to detect the volcanic event occurring very shallow part of volcano and to assess the volcanic activity.