Mild, 45-second volcanic tremor in June 2012

Our previous report on Bandai (also called Bandai-san) discussed a significant increase in seismicity during 14-16 August 2000 (BGVN 25:08). However, no eruption resulted and no large change in GPS data was noted. The volcano is located in Fukushima Prefecture, Japan, about 220 km N of Tokyo (figure 2). This report notes that volcanic tremor was recorded in June 2012.

Figure 2. A map of the major volcanoes of Japan. Bandai is just N of Tokyo. Courtesy of the U.S. Geological Survey.

Recent monthly reports of volcanic activity from the Japan Meteorological Agency (JMA), translated into English, resumed in October 2010; the only recent report on Bandai was in June 2012. Thus, in this report, we lack JMA reports between January 2005 and May 2012 and only summarize activity during June 2012.

According to JMA, on 25 June 2012 volcanic tremor with a duration of 45 seconds was recorded, the first since 9 June 2009. No change in volcanic earthquakes, ground deformation, or fumarolic activity was observed. Volcanic earthquakes have remained at a low level at least through September 2012. A camera located at Kengamine (~7 km N of the summit) showed that gas emissions remained low, rising less than 100 m in height.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/).

Information is preliminary and subject to change. All times are local (unless otherwise noted)

June 1987 (SEAN 12:06) Cite this Report

Earthquake swarm

An earthquake swarm began 16 June, with 155 events recorded that day by the seismograph 2 km SSE of the summit (table 1). Epicenters were mainly concentrated 10 km SW. Seismicity decreased to

Table 1. Daily number of felt earthquakes at Wakamatsu Observatory, 10 km W of the epicentral area of the Bandai swarm, June 1987.

Information Contacts: Japan Meteorological Agency (JMA).

November 1988 (SEAN 13:11) Cite this Report

Increased seismicity

Seismicity increased toward the end of November. A total of 188 events were recorded by the seismometer 1.8 km NNW of the summit, up sharply from the background level of ~20/month (figure 1).

Figure 1. Monthly number of recorded earthquakes at Bandai, 1965-88. Courtesy of JMA.

Information Contacts: JMA; AP; UPI.

August 2000 (BGVN 25:08) Cite this Report

Unprecedented increase in seismicity during 14-16 August

The last increase in seismicity at Bandai (located in the Fukushima prefecture about 20 km N of Tokyo) occurred in November 1988 (SEAN 13:11) when a total of 188 seismic events was recorded, up sharply from the background level of ~20 events/month. In contrast, at the same site up to 416 seismic events were recorded in one day when seismicity increased during 14-16 August 2000.

On the afternoon of 16 August the Japanese Meteorological Agency (JMA) issued a volcano advisory for Bandai. An abnormally high number of earthquakes, including felt earthquakes and volcanic tremor, was recorded at the A site seismometer 1.8 km SSE of the summit. The increase began on 14 August when 179 seismic events were recorded; this was the greatest seismicity to occur at the volcano since seismic monitoring began in 1965. On 14 August two of the four M 2 earthquakes that occurred were felt, and a volcanic tremor event lasted for 31 seconds. On 15 August the level of seismicity increased to 416 events, and two volcanic-tremor events lasted 40 and 55 seconds, respectively. At 2304 on 15 August a M 2.9 earthquake occurred, which was the largest event in the series. As of 1400 on 16 August there were 41 events. On 18 August a climbing ban was placed on the volcano. Due to the abnormally high level of seismicity, scientists monitored closely for signs of an impending eruption. Scientists observed no large change in GPS data or images from the monitoring camera. On 28 September officials lifted the climbing ban but warned climbers that an eruption could still occur.

Information Contacts: Volcano Research Center - Earthquake Research Institute (VRC-ERI), University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-0032 Japan (URL: http://www.eri.u-tokyo.ac.jp/VRC/index_E.html); Maki Kazuo, JMA-Sendai, 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan; The Japan Times.

September 2012 (BGVN 37:09) Cite this Report

Mild, 45-second volcanic tremor in June 2012

Our previous report on Bandai (also called Bandai-san) discussed a significant increase in seismicity during 14-16 August 2000 (BGVN 25:08). However, no eruption resulted and no large change in GPS data was noted. The volcano is located in Fukushima Prefecture, Japan, about 220 km N of Tokyo (figure 2). This report notes that volcanic tremor was recorded in June 2012.

Figure 2. A map of the major volcanoes of Japan. Bandai is just N of Tokyo. Courtesy of the U.S. Geological Survey.

Recent monthly reports of volcanic activity from the Japan Meteorological Agency (JMA), translated into English, resumed in October 2010; the only recent report on Bandai was in June 2012. Thus, in this report, we lack JMA reports between January 2005 and May 2012 and only summarize activity during June 2012.

According to JMA, on 25 June 2012 volcanic tremor with a duration of 45 seconds was recorded, the first since 9 June 2009. No change in volcanic earthquakes, ground deformation, or fumarolic activity was observed. Volcanic earthquakes have remained at a low level at least through September 2012. A camera located at Kengamine (~7 km N of the summit) showed that gas emissions remained low, rising less than 100 m in height.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/).