Report on Kozushima (Japan) — October 1995
Bulletin of the Global Volcanism Network, vol. 20, no. 10 (October 1995)
Managing Editor: Richard Wunderman.
Kozushima (Japan) Earthquake swarm ends in mid-October
Please cite this report as:
Global Volcanism Program, 1995. Report on Kozushima (Japan) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 20:10. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199510-284030.
34.219°N, 139.153°E; summit elev. 572 m
All times are local (unless otherwise noted)
As reported in BGVN 20:09, on 6 October a M 5.6 earthquake occurred adjacent to Kozu-shima and a seismic swarm followed for the next few days. After that, seismic events continued but decreased toward the end of October; in total, during October there were 246 felt earthquakes.
Geologic Background. A cluster of rhyolitic lava domes and associated pyroclastic deposits form the small 4 x 6 km island of Kozushima in the northern Izu Islands. Kozushima lies along the Zenisu Ridge, one of several en-echelon ridges oriented NE-SW, transverse to the trend of the northern Izu arc. The youngest and largest of the 18 lava domes, 574-m-high Tenjoyama, occupies the central portion of the island. Most of the older domes, some of which are Holocene in age, flank Tenjoyama to the north, although late-Pleistocene domes are also found at the southern end of the island. Only two possible historical eruptions, from the 9th century, are known. A lava flow may have reached the sea during an eruption in 832 CE. Tenjosan lava dome was formed during a major eruption in 838 CE that also produced pyroclastic flows and surges. Earthquake swarms took place during the 20th century.
Information Contacts: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan.