Report on Niijima (Japan) — July 1996
Bulletin of the Global Volcanism Network, vol. 21, no. 7 (July 1996)
Managing Editor: Richard Wunderman.
Niijima (Japan) Seismic activity increases
Please cite this report as:
Global Volcanism Program, 1996. Report on Niijima (Japan). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 21:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199607-284020.
34.397°N, 139.27°E; summit elev. 432 m
All times are local (unless otherwise noted)
High seismicity around the island was recorded on 17 and 24-26 July. The largest earthquakes (M 4.0) were detected at 1250 and 1321 on 17 July.
Geologic Background. The elongated island of Niijima, SSW of Oshima, is 11 km long and only 2.5 km wide. It is comprised of eight low rhyolitic lava domes that are clustered in two groups at the northern and southern ends of the island, separated by a low, flat isthmus. The flat-topped domes give the island the appearance of two large plateaus bounded by steep cliffs. The Mukaiyama complex at the southern end of the island and Achiyama lava dome at the northern end were formed during Niijima's only historical eruptions in the 9th century CE. Shikineyama and Zinaito domes form small islands immediately to the SW and west, respectively, during earlier stages of volcanism. Earthquake swarms occurred during the 20th century.
Information Contacts: Volcanological Division, Japan Meteorological Agency, 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan