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Paleo-tsunami record and tsunami hazard in Wallis and Futuna

Paleo-tsunami record and tsunami hazard in Wallis and Futuna. Geoffroy Lamarche, NIWA, Wellington James Goff, University NSW, Sydney Bernard Pelletier, IRD, Nouméa. STAR Meeting 16-18 October 2010 Nadi, Fiji. Outline. Geodynamic and Seismology Historical Earthquakes

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Paleo-tsunami record and tsunami hazard in Wallis and Futuna

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  1. Paleo-tsunami record and tsunami hazard in Wallis and Futuna Geoffroy Lamarche, NIWA, Wellington James Goff, University NSW, Sydney Bernard Pelletier, IRD, Nouméa STAR Meeting 16-18 October 2010 Nadi, Fiji

  2. Outline • Geodynamic and Seismology • Historical Earthquakes • Impact of Sep 2009 tsunami • Palaeo-earthquake research

  3. Geodynamic of the SW Pacific Futuna 10oS 20oS 165oE 180o

  4. Depth : 0 - 700 km, • 20% of world seismicity in SW Pacific • Seismicity • 1973-2009: 16,300 EQs 5≥ M ≥ 8.1 • 130 ≥M7 • 44 ≥M7.5 • 18 ≥M7.8 • 7 ≥Mw8, date M km to Léava 1977 03 23 6.3 28 1986 03 27 6.0 20 1993 03 12 6.4 14 1993 03 12 5.5 4 1999 09 17 5.5 13 Futuna Samoa Fiji Vanuatu Tonga Nouvelle Calédonie Kermadec One earthquake > M 5,5 every 7 years on average

  5. Tsunamis since 1992 PNG, Fat. 2200 April 1, 2007 Solomon Islands Max. runup: 10m Fatalities: 60 Dec. 26, 2004 West Sumatra Max. runup: 50m Fatalities: >250,000 Nov. 26, 1999 Vanuatu Max. runup : 7 m Fatalities : 5 Sep. 30, 2009 Samoa Fatalities : 200

  6. Futuna • 80 km2 (18x5 km) • 515 m high • 4500 habs Alofi • 30 km2 • No habs Futuna and Alofi • 260 km west of Wallis • 600 km West of Samoa • 400 km NE of Fiji Wallis Samoa Futuna Fiji Tonga

  7. 12 March 1993 MW6.4 Earthquake All 100 y.o. churches collapsed Destruction of houses on piles  acceleration > 1G traditional falés unaffected

  8. Mesures Pelletier, 1999 Uplifted coral Reverse fault (Observations B. Pelletier, 1999) Uplift 12 March 1993 MW6.4 Earthquake

  9. 12 March 1993 MW6.4 Earthquake (MM VIII) S March 1993 St Pierre Chanel (1803-41)describes an EQ in 1841 similar to that of March 93 (34 h fore-shock sequences, 19 severe quakes in 24h, after-shocks for 2 months). Modelling : 2.73 m slip Recurrence : 70 yrs without aseismic slip 150 yrs based on last 2 events  50% aseismic movement ?

  10. Wallis Samoa Futuna Fiji Tonga 2009 SouthWest Pacific (Tonga) Earthquake, MW 8.0

  11. Futuna post-tsunami Survey • EQ occurred at 5:48am on 30 Sep. local time in Futuna, ~650 km west of epicentre. • PTWC issued warning at 6:04am for tsunami arrival in Wallis at 6.35am. • No warning by authorities for Wallis & Futuna • No reported tsunami on Wallis. • Tsunami hit the Futuna between 7.00 and 7.20am • The tide was approximately 3/4 out.

  12. Evidence of the 2009 tsunami • Debris on road and beaches • Rocks moved • Salt-burnt grass and leaves • Broken branches • Debris held in bushes and trees • Interviews of people • Videos • photos

  13. Run-up heights and Inundation distances measured for the 2009 tsunami

  14. Léava Is there a local effect from the topography of the bay ? River is clearly fault controlled (“the sea is travelling beneath the house, and sprouting in the Taro crops behind the village!”)

  15. Palaeo-tsunami research aims at identifying past events through geological evidence observed in trenches

  16. Event 1 – 1860-2000 BP Event 2- ca. 470 BP

  17. The Legend of FatuloliKo le fonu tu'a limulimua Daniel Frimigacci, 1995 "La Tortue au dos Moussue" Oral traditions speak of deadly events which devastated the coast, and may be tsunamis Can we find evidence? Can we date it more precisely ? Can we associate it to a tsunami ?

  18. Futuna event chronologies and selected potential source areas. A - Austral Is., CI - Chatham Is., CkI - Cook Is., F - Futuna, H - Henderson Is., h - Healy caldera, Hu - Huahine, Society Is., K - Kauai, Hawaii, Ku - Kuwae, M - Marquesas, S - Samoa, V - Vanuatu. direction of ~ max. wave energy in deep water away from subduction zone sources

  19. Conclusion Tsunami Hazard in Futuna • The 1993, 2009 events and oral tradition indicate that the tsunami hazard is high • People (density 55) living exclusively on a 50-400 m-wide coastal strip • Tide gauge will be installed in 2009 • Alarm in Futuna must be independent than that of Wallis ! • Paleo-tsunami (trenches & legend of Fatuloli) • Local tsunami (March 1993) • Submarine landslides offshore Léava • Regional tsunami (Sep 2009) What about tele-tsunami (Chile 1700) ?

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