Mehetia Volcano - John Seach


(Meetia or Meketia)

Society Islands, French Polynesia

17.87 S, 148.07 W
summit elevation 435 m

Mehetia Island is the summit of a volcano which rises 4000 m from the sea floor. The volcano is located 113 km east of Tahiti and forms a 1.5 km wide island. The summit contains a 150 m wide and 80 m deep crater.

There are no historic eruptions at Mehetia Island despite young volcanic landforms such as a well-preserved crater and lava flows. There is no fumarolic activity on the island, but the volcano is considered active with undersea eruptions occurring at a depth of 600 m.

1981 Earthquake swarms
Between 6th March and December 1981 Mehetia Island experienced 3500 earthquakes over magnitude 1.4. The earthquakes occurred in two swarms.

The first swarm, which was volcanic, occurred in the first two months, and was linked to underwater eruptions at a depth of about 1600 m on the southeast flank of the island.

The second earthquake swarm was mostly tectonic and consisted of a smaller number of higher-magnitude earthquakes (up to magnitude 4.3). These were geographically dispersed and probably associated with underground resetting.

6-8 March 1981
Earthquakes abruptly start, and average more than 240 per day. Magnitude of earthquakes were less than 3.3 and were located 6 km southeast of the island.

9-25 March 1981
Earthquakes decrease to 27 per day on average. The two largest events in the swarm ccurred on 15th March (Magnitude 4.3) and 25th March (Magnitude 4.0).

26 March-30 May 1981
Earthquakes decreased to an average of 13 per day.

Mehetia Volcano Eruptions

Undersea eruptions occurred in 1981 at a depth of 1600 m.
Eruptions occurred in the past 2000 years on the island.