Submarine Volcano NNE of Iriomotejima

Photo of this volcano
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 24.57°N
  • 123.93°E

  • -200 m
    -656 ft

  • 282010
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

Most Recent Bulletin Report: December 1992 (BGVN 17:12) Citation IconCite this Report


Strong submarine earthquake swarms but no surface changes

An earthquake swarm occurred at the W tip of the island 24-31 August, including a M 5.2 shock at 9 km depth on 24 August (figure 3). A total of 24 earthquakes was detected at Iriomote-jima Weather Station, on the NW coast of the island.

Figure (see Caption) Figure 3. Epicenters of earthquakes near Iriomote-jima (filled circles), September-November, 1992. Diagonal lines mark the area of the August 1992 swarm. Courtesy of JMA.

A second, more severe swarm began on 17 September, centered a few kilometers N of the island and about 20 km NE of the August swarm. Epicenters migrated towards the island, and by November, the source area encompassed the northern coast. Depths ranged from 0 to 10 km, concentrated at around 5 km.

Seismicity gradually declined toward the end of 1992, after a peak in mid-October when 112 earthquakes were recorded on the 14th (figure 4). The swarm's largest shock was M 5.2 on 20 October. A total of 1316 earthquakes occurred from 17 September to 31 December. A network of ten seismometers recorded no volcanic tremors, and no anomalies were observed on the land or sea surface.

Figure (see Caption) Figure 4. Daily number of earthquakes at Iriomote-jima, 1 August-31 December 1992. Courtesy of JMA.

The most recent seismic activity had occurred in the same area from January-May 1991, when 676 earthquakes were recorded, the largest M 4.3 (16:3-4).

Information Contacts: JMA.

The Global Volcanism Program has no Weekly Reports available for Submarine Volcano NNE of Iriomotejima.

Bulletin Reports - Index


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.

03/1991 (BGVN 16:03) High-frequency earthquake swarm; many felt shocks; no surface activity

04/1991 (BGVN 16:04) Strong felt seismicity but no surface changes

12/1992 (BGVN 17:12) Strong submarine earthquake swarms but no surface changes




Information is preliminary and subject to change. All times are local (unless otherwise noted)


March 1991 (BGVN 16:03) Citation IconCite this Report


High-frequency earthquake swarm; many felt shocks; no surface activity

A swarm of high-frequency earthquakes . . . began 23 January, peaked in February, and continued at high levels through mid-April. The press reported that more than 940 earthquakes had been recorded by 14 April. Epicenters were on the W coast (at shallow depth) where many shocks were felt daily. Tremor episodes were not recorded and surface activity was not observed on the island or the surrounding sea.

Information Contacts: JMA.


April 1991 (BGVN 16:04) Citation IconCite this Report


Strong felt seismicity but no surface changes

High levels of seismicity . . . suddenly declined in late April (figure 1). A total of 670 high-frequency earthquakes were felt by the end of April, including nine of JMA intensity IV, and a M 4.3 event on 31 March. The swarm was centered on the NW coast of the island (figure 2) at 0-10 km depth (the majority at ~5 km). No surface phenomena (steaming, bubbling, or water discoloration) were found despite frequent patrolling over the island and adjacent sea area by JMSA aircraft.

Figure (see Caption) Figure 1. Daily number of recorded earthquakes at Iriomote-jima island, 23 January-10 May 1991. Solid columns represent felt events. Courtesy of JMA.
Figure (see Caption) Figure 2. Epicenter map of earthquakes at Iriomote-jima island, 23 January-10 May 1991. A solid square marks the JMA weather station. Courtesy of JMA.

Information Contacts: JMA.


December 1992 (BGVN 17:12) Citation IconCite this Report


Strong submarine earthquake swarms but no surface changes

An earthquake swarm occurred at the W tip of the island 24-31 August, including a M 5.2 shock at 9 km depth on 24 August (figure 3). A total of 24 earthquakes was detected at Iriomote-jima Weather Station, on the NW coast of the island.

Figure (see Caption) Figure 3. Epicenters of earthquakes near Iriomote-jima (filled circles), September-November, 1992. Diagonal lines mark the area of the August 1992 swarm. Courtesy of JMA.

A second, more severe swarm began on 17 September, centered a few kilometers N of the island and about 20 km NE of the August swarm. Epicenters migrated towards the island, and by November, the source area encompassed the northern coast. Depths ranged from 0 to 10 km, concentrated at around 5 km.

Seismicity gradually declined toward the end of 1992, after a peak in mid-October when 112 earthquakes were recorded on the 14th (figure 4). The swarm's largest shock was M 5.2 on 20 October. A total of 1316 earthquakes occurred from 17 September to 31 December. A network of ten seismometers recorded no volcanic tremors, and no anomalies were observed on the land or sea surface.

Figure (see Caption) Figure 4. Daily number of earthquakes at Iriomote-jima, 1 August-31 December 1992. Courtesy of JMA.

The most recent seismic activity had occurred in the same area from January-May 1991, when 676 earthquakes were recorded, the largest M 4.3 (16:3-4).

Information Contacts: JMA.

Eruptive History


Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).


Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1924 Oct 31 Unknown Confirmed 5 Historical Observations

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Photo Gallery


An "X" marks the approximate location of Iriomote-jima submarine volcano, the southernmost Ryukyu Islands volcano. The submarine volcano is located north of the NE tip of 30-km-wide Iriomote-jima island (lower left) and WSW of the northern tip of the island of Ishigaki-shima (right-center). A major submarine eruption that was volumetrically one of the largest in Japan during historical time took place at this volcano on October 31, 1924. It produced pumice rafts that were carried by currents along both coasts of Japan as far north as Hokkaido.

NASA Space Shuttle image STS66-117-19, 1994 (http://eol.jsc.nasa.gov/).
See title for photo information.

Smithsonian Sample Collections Database


There are no samples for Submarine Volcano NNE of Iriomotejima in the Smithsonian's NMNH Department of Mineral Sciences Rock and Ore collection.

Affiliated Sites