Report on Niijima (Japan) — March 1993
Bulletin of the Global Volcanism Network, vol. 18, no. 3 (March 1993)
Managing Editor: Edward Venzke.
Niijima (Japan) Earthquake swarm on 23 March; no surface anomalies
Please cite this report as:
Global Volcanism Program, 1993. Report on Niijima (Japan) (Venzke, E., ed.). Bulletin of the Global Volcanism Network, 18:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199303-284020.
34.397°N, 139.27°E; summit elev. 432 m
All times are local (unless otherwise noted)
A weak earthquake swarm occurred 23 March in the N part of Nii-jima island. The earthquakes, M 1.9 maximum, were located both onshore and offshore. . . . No surface anomalies, onshore or offshore, 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.