Seismicity increasing at Shinmoedake volcano, alert level raised

The Japan Meteorological Agency (JMA) has raised the alert level for the Shinmoedake volcano, part of the Kirishimayama volcanic group in Kyushu, Japan, from 1 to 2 on October 5, 2017.

The increase in volcanic earthquakes under the volcano was first detected on September 23, 2017, and further increased on October 4.

On October 5, JMA conducted a field survey and observed fumarolic activity and weak thermal anomalies.

Over the past 24 hours, seismic network detected 87 volcanic earthquakes, JMA said 23:55 JST and raised the alert level to 2, restricting entry to areas near the crater. There are no crustal deformations associated with the increase of earthquakes, it added.

Shinmoedake – volcanic earthquakes – September/October 2017. Credit: WeatherNews.jp

The agency said there is a possibility of a small eruption in the future and warned locals and tourists to be alert as rocks could be ejected within 1 km (0.62 miles) from the crater.

The last eruption of this volcano took place on September 7, 2011.

Geological summary

Kirishimayama is a large group of more than 20 Quaternary volcanoes located north of Kagoshima Bay. The late-Pleistocene to Holocene dominantly andesitic group consists of stratovolcanoes, pyroclastic cones, maars, and underlying shield volcanoes located over an area of 20 x 30 km (12.4 – 18.6 miles). The larger stratovolcanoes are scattered throughout the field, with the centrally located, 1700-m-high (5 577 feet) Karakunidake being the highest.

Onamiike and Miike, the two largest maars, are located SW of Karakunidake and at its far eastern end, respectively. Holocene eruptions have been concentrated along an E-W line of vents from Miike to Ohachi, and at Shinmoedake to the NE. Frequent small-to-moderate explosive eruptions have been recorded since the 8^th century. (GVP)

Featured image: Kirishima in smoke after Shinmoedake eruption on January 23, 2011. Credit: Ray_go