Mehetia

Photo of this volcano
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 17.874°S
  • 148.068°W

  • 389 m
    1276 ft

  • 333040
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

Most Recent Bulletin Report: March 1982 (SEAN 07:03) Citation IconCite this Report


Seismic activity stops

Seismic activity that began in March 1981 ceased in December. Only a few low-energy events per month have been recorded since. Bathymetric reconnaissance around the island found evidence of an elliptical opening at 1,700 m below sea level on the SE flank, in the same location as the initial events of the earthquake swarm. RSP scientists interpreted the opening as a possible crater and the activity as a magmatic intrusion or eruption.

Information Contacts: J.M. Talandier, Lab. de Géophysique, Tahiti.

The Global Volcanism Program has no Weekly Reports available for Mehetia.

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.

10/1981 (SEAN 06:10) Several months of increased seismicity

03/1982 (SEAN 07:03) Seismic activity stops




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


October 1981 (SEAN 06:10) Citation IconCite this Report


Several months of increased seismicity

A swarm of earthquakes centered beneath Mehetia began suddenly on 6 March and was continuing in late October. After the first two days of the swarm, characterized by numerous weak events, seismographs began to record occasional larger shocks (figure 1). The seismic energy released during the first week of the swarm greatly exceeded the previous total energy release detected by the Tahitian seismic net since the first stations were installed in 1962-63. Both the number of earthquakes (figure 2) and energy release (figure 3) varied considerably, with periods of increased activity separated by brief lulls. Epicenters were about 10 km SE of the crater. There were several groups of foci, which may indicate vertical migration, but it was impossible to compute depths of focus for most of the events. A temporary seismic station operated on Mehetia 25-30 March recorded local earthquakes at about 13 km depth.

Figure (see Caption) Figure 1. Log plot of number of events vs. magnitude at intervals of ML 0.2 recorded from Mehetia, 6 March-15 December 1981. The b value (slope) of the regression line is 1.13 ± 0.03 for the entire swarm. For the first two days of the swarm, characterized by numerous weak events, b = 1.63. Courtesy of J. Talandier.
Figure (see Caption) Figure 2. Number of recorded earthquakes (ML 0.9 or greater) per day (3-day means) at Mehetia, 6 March-early December 1981 (293 days). The total number of such events during this interval was 3,536. The Tahitian seismic net records most local events of ML 1.1 or greater, but fluctuating levels of microseismic noise prevent consistent recording of weaker events. Courtesy of J. Talandier.
Figure (see Caption) Figure 3. Seismic energy released by the Mehetia swarm (3-day intervals), 6 March-early December 1981. Courtesy of J. Talandier.

By late October, more than 3,000 local events of magnitude 0.9 (ML) or stronger had been recorded. Of these, about 30 were stronger than ML 3.0, including magnitude 4.0 and 4.3 shocks. Because of the detection limits (usually about ML 1.1, but weaker seismicity is sometimes recorded during periods of lesser microseismic noise) for events in the Mehetia area (~140 km from the nearest Tahitian net station), harmonic tremor, if any, would probably not be recorded. Talandier's extrapolation of the well-defined frequency-magnitude relationship indicates that about 50,000 events stronger than ML 0.1 have probably occurred during the swarm. Talandier also notes that the Mehetia swarm and seismicity associated with Hawaiian volcanoes showed similarities in number and magnitude of events and seismogram characteristics, as well as the detection of long-period waves that could be generated by events occurring beneath a magma chamber. No surface volcanic activity has been reported at Mehetia. The island is uninhabited, working conditions there are difficult, and no geologist has visited the area recently.

Mehetia is a well-defined cone about 1,500 m in diameter and 435 m high, with a 200-m-diameter crater at the summit. No historic eruptions have been reported, but the limited erosion of the crater and flanks, lack of vegetation at the summit, and Tahitian legends of "big fires" all indicate that eruptions probably took place less than 2,000 years ago.

Information Contacts: J.M. Talandier, Lab. de Géophysique, Tahiti.


March 1982 (SEAN 07:03) Citation IconCite this Report


Seismic activity stops

Seismic activity that began in March 1981 ceased in December. Only a few low-energy events per month have been recorded since. Bathymetric reconnaissance around the island found evidence of an elliptical opening at 1,700 m below sea level on the SE flank, in the same location as the initial events of the earthquake swarm. RSP scientists interpreted the opening as a possible crater and the activity as a magmatic intrusion or eruption.

Information Contacts: J.M. Talandier, Lab. de Géophysique, Tahiti.

Eruptive History


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


Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
[ 1981 Mar 5 ] [ 1981 Dec ] Uncertain 0   SE of Mehetia (-1700 m?)

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


The 1.5-km-wide, steep-sided island of Mehetia, seen here from the south, is the youngest and SE-most of the Society Islands. The 435-m-high island is the summit of a large volcano that rises 4000 m from the sea floor. Wave erosion has truncated lava flows of an older edifice, leaving steep cliffs that overlie coral reefs seen at the peninsula in the left foreground. The summit of the island is fomed by a younger edifice that may have been the source of apparent eruptive events mentioned in Polynesian legends.

Photo by Jacky Vedraine (http://www.polynesiepassion.net).
See title for photo information.

Smithsonian Sample Collections Database


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

Affiliated Sites