Volcanic Activity on Mt. Asama Posted on： Feb 1, 2009 Revised on： Feb 13, 2009 Earthquake Research Institute, University of Tokyo The volcanic alert levelfor Mount Asama was raised to level 3 as announced by the Japan Meteorological Agency at 1:00pm, February 1, 2009. A small eruption also occurred at 1:51am on February 2, 2009. Minor eruptions then continued intermittently from 7:46am on February 9, 2009. The report on the volcanic activity of Mount Asama will be posted on this page. Quick reports from the Volcano Research Center of ERI, the Asama Volcanic Observatory, and the Komoro Volcanic-Chemical Observatory will also be posted on this page. (Coordinated by the Outreach Office. Supervised by Professor Toshitsugu Fujii, Professor Minoru Takeo, and Professor Setsuya Nakada.) 【Updates】 A picture taken from a helicopter at 2:00pm on February 12, 2009 was posted. A picture of a minor eruption, occurring at 6:06pm on February 12, 2009 was posted. The distribution of fallen ash and the volume of erupted lava due to the eruption of February 2, 2009 was estimated. Minor eruptions continued intermittently from 7:46am on February 9, 2009 (as of February 9, 2009). Explanation of seismic activity at Mount Asama and time transition of crustal movement were posted. Pictures taken from a helicopter were posted. A reference document from the Japan Meteorological Agency was posted. Pictures of the volcanic ash, collected on February 2, 2009, were posted. A summary of fallen ash in the mountain areas due to the eruption on February 2, 2009 was posted. Waveform of seismic wave and air-shock due to the eruption was posted. A picture of volcanic smoke of Asama Volcano, captured by satellite, was posted. Pictures provided by the Asama Volcanic Observatory were posted. The observational data of crustal movements was posted. Data from a quasi-real-time seismic waveform monitor was posted. 【Pictures of Mount Asama taken from a helicopter (about 2:00pm on February 12, 2009)】 Professor Setsuya Nakada Cooperated by: The Tokyo Shimbun Pictures of Mount Asama at 2:00pm on February 12, 2009. (Click picture to see the photo album on the web.） 【A minor eruption at 6:06pm, February 12, 2009】 Etsuro Koyama, Technical Supporting Staff Picture of a minor eruption at 6:06pm on February 12, 2009. Volcanic glow due to the eruption is slightly visible. (Click the picture for a larger image.) 【Estimate of the fallen ash distribution and the volume of erupted lava due to the eruption of February 2, 2009】 Fukashi Maeno, Assistant Professor The total volume of erupted lava and ash due to the eruption of February 2, 2009 was estimated to be 20,000 tons. (Click the picture below to see more detail. Available in Japanese only.) 【Minor eruptions that continue intermittently from 7:46am on February 9, 2009】 Etsuro Koyama, Technical Supporting Staff A minor eruption occurred at 7:46am on February 9, 2009. Below is the picture of Mount Asama as of 8:26am on February 9, 2009. (Click the picture for a larger image.) 【Seismic activity and time transition of crustal movement】 Professor Minoru Takeo Yosuke Aoki, Assistant Professor Seismic activity of Mount Asama from January 1, 2004 to February 1, 2009. Change in GPS baseline length from 1996 to 2009. （Click figures for each explanation page. Available in Japanese only.） 【Observational pictures taken from a helicopter on February 2, 2009】 Etsuro Koyama, Technical Supporting Staff Pictures taken during an observation by Japan Meteorological Agency’s helicopter. （Click picture to see photo album on the web.） 【Pictures of the volcanic ash produced by the eruption on February 2, 2009】 Yuki Suzuki, Researcher at ERI Sampling place： Intersection at Sengataki Onsen, Karuizawa （Collected by Etsuro Koyama） Most of the volcanic ash are debris particles of old lava. Small amounts of magmatic substance is also included. （Click figures to see each PDF format documents. Available in Japanese only.） 【Fallen ash in the mountain area due to the eruption on February 2, 2009】 Fukashi Maeno, Assistant Professor at ERI The Advanced Industrial Science and Technology The Japan Meteorological Agency Investigation results of fallen ash due to the small eruption on February, 2009. (Click the figure below to see PDF format document. Available in Japanese only.) Reference document issued by the Japan Meteorological Agency at 5:40pm on February 4, 2009 (PDF). Available in Japanese only. 【Waveform of seismic wave and air-shock】 Takao Ohminato, Associate Professor Waveform of seismic wave and air-shock, and some other phenomenons created by the eruption. （Click the diagram to see the PDF document. Available in Japanese only.） 【Volcanic smoke captured by the satellite, MTSAT】 Takashi Kaneko, Assistant Professor Infrared image of volcanic smoke captured by the multifunctional transport satellite (MTSAT). (Click image to see PDF document. Available in Japanese only.） 【Data of the crustal movement】 Yosuke Aoki, Assistant Professor A map of GPS observation points on Mount Asama. ● represents observation points by ERI ■ represents observation point by the Japan Geographical Survey Institute KAHG：Eastern margin of the crater AVOG：ERI’s Asama Volcanic Observatory According to the observational data, the crust at Mount Asama expands north-south due to the volcanic activity. The figure below is a plot of the baseline length between KVCO and TASH. It shows that the length of the baseline has been getting longer since September 2008, indicating expansion of the volcano. 【Pictures and reports from the Asama Volcanic Observatory】 Etsuro Koyama, Technical Supporting Staff Estimated starting time of the eruption： 1:51am on February 2, 2009. Time when rumbling sound of eruption stopped： 2:11am and 30 seconds on February 2, 2009. Picture taken at 2:50am, after the rumbling sound stopped.（Volcanic glow is visible.） Fallen ash at Sengataki Onsen（left：3:33am， right：3:40am） Pictures of volcanic ash samples. 【Data from a quasi-real-time seismic waveform monitor】 Hiroshi Tsuruoka, Assistant Professor Click diagram below to see data of waveform monitor. Map of observation points. （Click map for larger image.） 【Real-time pictures of volcano】 Real-time pictures taken by monitoring camera installed at the Asama Volcano Observatory. (Click picture below to go to link.) （Mount Asama at 4:20pm on February 1, 2009） 【Eruption at 1:51am on February 2, 2009】 A small eruption occurred at 1:51am on February 2, 2009. Fallen ash was reported even in the southern part of the Kanto area. The height of the volcanic smoke due to the eruption reached 2,000m. The eruption scattered volcanic cinders about 1km northward from the crater. 【Situation up until February 1, 2009】 The full account of raising the volcanic alert level (the Japan Meteorological Agency). Short-periods of earthquakes became more frequent starting 7:00am, February 1, 2009. The earthquake focus is probably located right beneath the mountain top. The mountain started slightly swelling, probably due to magma ascent, from about 2:00am. The frequent earthquake and the mountain swellings were the main reasons to raise the alert level. Mount Asama at 11:30pm on February 1. (Click picture for a larger image.） Volcanic glow is not visible yet as of 11:00pm, February 1, 2009. （Volcanic glow： It is a phenomenon of air above the crater which makes it seem red because of the reflection of erupted magma and red-hot volcanic rocks.） 【Links of past Mount Asama volcanic activity】 A minor eruption on August, 2008 (Japanese only). A small eruption on September, 2004. History of the Mount Asama eruption (Japanese only). 【Links】 The Japan Meteorological Agency Reports of the Mount Asama eruption (Japanese Only). Reference document on volcanic activity of Mount Asama. (PDF, issued by the agency at 9:40am on February 2, 2009. Japanese only.) Reference document on volcanic activity of Mount Asama. (PDF, issued by the agency at 5:20pm on February 1, 2009. Japanese only.) 【Definition of terms】 Volcanic alert level: Volcanic forecast and warning system was introduced on December 1, 2007. 【Level 5: Evacuate】 People living in the danger area need to evacuate. 【Level 4: Prepare to Evacuate】 People living in the alert area need to prepare for evacuation. Disabled people need to evacuate. 【Level３: Do not approach the volcano】 Access to the volcano and the danger area need to be regulated. Disabled people need to prepare for evacuation, if needed. 【Level ２: Do not approach the crater】 Access to crater needs to be regulated. 【Level 1: Normal】 Access into the crater needs to be regulated. （Note： Target area for evacuation and regulation differ, depending on the condition of the area and the volcanic activity.） Volcanic earthquake and volcanic tremor There are many types of volcanic seismic activity. It is believed that the difference reflects the difference of under-ground activity. Even though there are many ways to classify volcanic seismic activity, it is roughly classified as follows: Volcanic earthquake： Caused by small destructions of the crust due to volcanic activity such as magma migration. Volcanic tremor：Tremors that are typical for volcanoes, observable using a seismometer. It is distinct from volcanic earthquakes because the waveform and the duration tend to be longer (it can be several days) than those of the other ones. In most cases, it precedes an eruption. Thus, it is one of the important elements in predicting eruptions.