Additional Reports

Reports are sometimes published that are not related to a Holocene volcano. These might include observations of a Pleistocene volcano, earthquake swarms, or floating pumice. Reports are also sometimes published in which the source of the activity is unknown or the report is determined to be false.


Acoustic Signals in 1996 from Unknown Source

western Pacific Ocean


Index of Monthly Reports

Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

01/1996 (BGVN 21:01) Acoustic signals in late January; source not locatable


Contents of Monthly Reports

All information contained in these reports is preliminary and subject to change.

01/1996 (BGVN 21:01) Acoustic signals in late January; source not locatable

The JMA Ocean Bottom Seismograph off the Boso Peninsula (E of Tokyo) detected T-phase-like signals after 22 January, and clear T-phase signals on 27 January (figure 1). According to tentative analyses of arrival times at the detectors, the signals were interpreted to have propagated from the S. As of mid-February, JMA had not determined a specific source for these signals. However, discolored seawater was observed above two submarine volcanoes in the Volcano Islands during January: Minami-Hiyoshi on 12 January, and Fukutoku-okanoba on 12, 22, and 23 January.

Figure 1. Example of T-phase signals (spikes) detected by the Ocean Bottom Seismograph off the Boso Peninsula, Japan, 27 January 1996. Courtesy of JMA.

Information Contact: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan.