Report on Niijima (Japan) — January 1992
Bulletin of the Global Volcanism Network, vol. 17, no. 1 (January 1992)
Managing Editor: Lindsay McClelland.
Niijima (Japan) Earthquake swarm but no surface changes
Please cite this report as:
Global Volcanism Program, 1992. Report on Niijima (Japan) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 17:1. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199201-284020.
34.397°N, 139.27°E; summit elev. 432 m
All times are local (unless otherwise noted)
An earthquake swarm was recorded on 3-4 January, centered 10 km SW of Nii-jima near Shikine-jima, a dome of the Nii-jima complex (figure 1). The largest shock, M 3.1, occurred at 0657 on 3 January. No surface anomalies were observed at the volcano or on the surrounding sea. Three weeks later, a swarm was recorded near Kozu-shima, 20 km SSW (figure 2).
|Figure 2. Epicenter map (top) and space/time diagram (bottom) showing seismicity around Kozu-shima and Nii-jima volcanoes, January 1991-June 1992. Courtesy of JMA.|
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.