Paleo-tsunami record Paleo-tsunami record and tsunami hazard and tsunami hazard in Wallis and Futunain 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 Outline • Geodynamic and Seismology• Historical Earthquakes• Impact of Sep 2009 tsunami• Palaeo-earthquake research

Futuna

165oE 180o

10oS

20oS

Geodynamic of the SW PacificGeodynamic of the SW Pacific

NouvelleCalédonie

FijiVanuatu

Tonga

Kermadec

Futuna

SeismicitySeismicity

130 ≥M7 44 ≥M7.5 18 ≥M7.8 7 ≥Mw8,

Depth : 0 - 700 km,20% of world seismicity in SW Pacific

Samoa

One earthquake > M 5,5 every 7 years on average

date M km to Léava

1977 03 23 6.3 281986 03 27 6.0 201993 03 12 6.4 141993 03 12 5.5 41999 09 17 5.5 13

1973-2009: 16,300 EQs 5≥ M ≥ 8.1

Tsunamis since 1992

PNG, Fat. 2200

Nov. 26, 1999VanuatuMax. runup : 7 mFatalities : 5

Sep. 30, 2009SamoaFatalities : 200

April 1, 2007Solomon IslandsMax. runup: 10mFatalities: 60

Dec. 26, 2004West SumatraMax. runup: 50mFatalities: >250,000

• 260 km west of Wallis• 600 km West of Samoa• 400 km NE of Fiji

Fiji

WallisFutuna Samoa

Futuna and Alofi

Tonga

Futuna -80 km2 (18x5 km)-515 m high-4500 habsAlofi-30 km2

-No habs

12 March 1993 MW6.4 Earthquake

All 100 y.o. churches collapsed

traditional falés unaffected

Destruction of houses on piles acceleration > 1G

Mesures Pelletier, 1999

Reverse fault

Uplifted coral

(Observations B. Pelletier, 1999)

Uplift

12 March 1993 MW6.4 Earthquake

12 March 1993 MW6.4 Earthquake (MM VIII)

SMarch 1993March 1993

Modelling : 2.73 m slip

St Pierre Chanel 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).

Recurrence Recurrence : 70 yrs without aseismic slip

150 yrs based on last 2 events 50% aseismic movement

Fiji

Wallis

FutunaSamoa

Tonga

185 km ENE of Hihifo, Tonga190 km S of Apia, Samoa710 km NNE of Nuku’Alofa, Tonga2700 km NNE of Auckland

29 Sep 17:48 UTC 06:48:10 AM at epicenter 30 Sep 05:48 AM in Futuna & Fiji650 km from Futuna

2009 SouthWest Pacific (Tonga) Earthquake, MW 8.0

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.

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

Run-up heights and Inundation distances measured for the 2009

tsunami

LéavaLéava

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!”)

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

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

The Legend of FatuloliKo le fonu tu'a limulimua

Oral traditions speak of deadly events which devastated the coast, and may be tsunamis

Daniel Frimigacci, 1995 "La Tortue au dos Moussue"

Can we find evidence?Can we date it more precisely ?Can we associate it to a tsunami ?

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

Conclusion Conclusion Tsunami Hazard in FutunaTsunami Hazard in Futuna

• Paleo-tsunami (trenches & legend of Fatuloli)

• Local tsunami (March 1993)

• Submarine landslides offshore Léava

• Regional tsunami (Sep 2009)

• 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 !

What about tele-tsunami (Chile 1700) ?