2009 Vanuatu earthquakes

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2009 Vanuatu earthquakes
2009 Vanuatu earthquakes is located in Oceania
2009 Vanuatu earthquakes
UTC time2009-10-07 22:03:14
 2009-10-07 22:18:51
 2009-10-07 23:13:48
USGS-ANSSComCat
 ComCat
 ComCat
Local dateOctober 7, 2009 (2009-10-07)
Local time06:41:25
 08:28:31
Magnitude7.7 Mw
 7.8 Mw
 7.4 Mw
Depth45.0 km (28 mi)
 35.0 km (22 mi)
 31.1 km (19.3 mi)
Epicenter12°31′01″S 166°22′55″E / 12.517°S 166.382°E / -12.517; 166.382Coordinates: 12°31′01″S 166°22′55″E / 12.517°S 166.382°E / -12.517; 166.382
Areas affected Vanuatu
 Solomon Islands
Max. intensityVII (Very strong)[1]
TsunamiYes (62 cm (24 in)) in Port-Vila, Vanuatu[2]
AftershocksYes, strongest being Mw 7.4[3]
Casualties0

The 2009 Vanuatu earthquakes were three earthquakes with magnitudes of 7.7, 7.8 and 7.4, constituting some of the largest earthquakes in Vanuatu's history.

Tectonic Setting[]

The Vanuatu earthquakes of October 7, 2009: M 7.7, Vanuatu, 22:03:14; M 7.8 Santa Cruz Islands, 22:18:51 UTC; and M 7.4, Vanuatu, 23:13:48; all occurred as a result of shallow reverse faulting on or near the plate boundary interface between the Indo-Australian Plate and Pacific Plates. In the region of these earthquakes, the Indo-Australian plate moves to the east-northeast with respect to the Pacific plate at a velocity of about 91 mm/yr. The Indo-Australian plate thrusts under the Pacific plate at the New Hebrides Trench and dips to the east-northeast. The locations, depths, and focal mechanism solutions for the October 7th events are all consistent with them resulting from reverse faulting associated with subduction along the Australia-Pacific plate boundary.

The 7.8 Mw  earthquake of October 7, 2009 (22:18 UTC), occurred about 60 km north, and 15 minutes after, a slightly smaller earthquake with a 7.7 Mw  of the same date Occurred (22:03 UTC). A third, smaller event at 7.4 Mw  occurred at 23:13 UTC, 15 km to the southeast of the first event. All three events are likely related; while the first two similarly sized events may be considered a doublet earthquake, preliminary analysis suggests that the 7.4 Mw  earthquake is likely a large aftershock of one of the events.[4]

Earthquake[]

More than a dozen earthquakes above 5.0 magnitude shook the country within two days of the earthquake sequence,[5] The largest earthquake of the sequence (7.8 Mw) struck 294 km (183 mi) northwest of the island of Santo,[6] and is the second largest earthquake of 2009, behind the 8.1 Mw 2009 Samoa earthquake Which occurred 8 days earlier nearby. None of these tremors caused any casualties,[7] but the largest event did trigger tsunami waves as high as 62 cm (2.03 ft).

Aftershocks and other events[]

About 15 Minutes prior, a 7.7 Mw earthquake struck the same area, because of their magnitudes being too similar to be considered aftershocks, both events are considered a doublet event.[8] About an Hour after that event, a magnitude 7.4 earthquake struck the same area, it is considered an aftershock to one of the events,[9] At least 9 aftershocks of magnitude 6 or higher were recorded by the USGS,[10] With some located in the Solomon Islands, such as a 6.1 Mw about 3 days after the Mainshock,[11] the largest earthquake of the aftershock sequence behind the 7.4 event was a 6.8 Mw on October 8,[12] on June 3 2009, an unrelated Mw 6.3 earthquake Struck 38 km west of the capital of Port-Vila, injuring 4, damaging a few buildings and triggering landslides.[13]

Tsunami[]

A tsunami was observed all over the Pacific Ocean, generating waves as high as 62 cm (2.03 ft) in Port-Vila, Vanuatu, 30 cm (0.98 ft) in Santa Monica, California, and 16 cm (0.52 ft) in Atka, Alaska.[14]

See also[]

References[]

  1. ^ "7.8 Magnitude earthquake in Vanuatu". 7 October 2009.
  2. ^ "M 7.8, Sola, Vanuatu". 7 October 2009.
  3. ^ "7.4 Magnitude Aftershock in Vanuatu". 7 October 2009.
  4. ^ "M 7.4, Vanuatu". 7 October 2009.
  5. ^ "Dozens of Tremors Rock Vanuatu". Earthquake Observatory. 9 October 2009.
  6. ^ "3 Earthquakes Strike Vanuatu, No Casualties Reported". 7 October 2009.
  7. ^ "7.8 Magnitude earthquake Rocks Vanuatu". 7 October 2009.
  8. ^ "M 7.7, Vanuatu". 7 October 2009.
  9. ^ "M 7.4 - Vanuatu". 7 October 2009.
  10. ^ "lists, maps and statistics - 2009". 31 December 2009.
  11. ^ "M 6.1 - 59 km S of Lata, Solomon Islands". 10 October 2009.
  12. ^ "M 6.8 - 188 km NW of Sola, Vanuatu". 8 October 2009.
  13. ^ "M 6.3 - 38 km W of Port-Vila, Vanuatu". 3 June 2009.
  14. ^ "The Vanuatu earthquakes and Tsunami of 2009". 7 October 2009.
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