Report on Niijima (Japan) — September 1992
Bulletin of the Global Volcanism Network, vol. 17, no. 9 (September 1992)
Managing Editor: Lindsay McClelland.
Niijima (Japan) Two weak seismic swarms
Please cite this report as:
Global Volcanism Program, 1992. Report on Niijima (Japan) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 17:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199209-284020.
34.397°N, 139.27°E; summit elev. 432 m
All times are local (unless otherwise noted)
Two weak earthquake swarms occurred 5 km WSW and NW of the island on 16 and 22 September. Maximum magnitudes were 3.5 and 3.1, respectively. No ocean-surface anomalies were observed.
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: JMA.