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 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. Seismicity Depth : 0 - 700 km, 20% of world seismicity in SW Pacific
: 16,300 EQs 5≥ M ≥ 8.1
130 ≥M7
44 ≥M7.5
18 ≥M7.8
7 ≥Mw8,
Futuna
Samoa
Fiji
Vanuatu
date M km
to Léava
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 and Alofi Wallis Samoa Futuna Fiji Tonga 260 km west of Wallis
80 km2 (18x5 km)
515 m high
4500 habs
Alofi
30 km2
No habs
260 km west of Wallis
600 km West of Samoa
400 km NE of Fiji
Wallis
Futuna
Samoa
Fiji
Tonga

7. Bathymetry 0-300m not mapped
Pelletier et al., 2000

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

9. 12 March 1993 MW6.4 Earthquake Reverse fault
(Observations B. Pelletier, 1999)
Mesures Pelletier, 1999
Uplift
Uplifted coral
12 March 1993 MW6.4 Earthquake

10. ? S 12 March 1993 MW6.4 Earthquake (MM VIII)
St Pierre Chanel ( ) 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 ?

11. 2009 SouthWest Pacific (Tonga) Earthquake, MW 8.0
185 km ENE of Hihifo, Tonga
190 km S of Apia, Samoa
710 km NNE of Nuku’Alofa, Tonga
2700 km NNE of Auckland
29 Sep 17:48 UTC 06:48:10 AM at epicenter
30 Sep 05:48 AM in Futuna & Fiji
650 km from Futuna
Fiji
Wallis
Futuna
Samoa
Tonga

12. 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.

13. 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

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

16. 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!”)

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

19. Event 1 – BP
Event 2- ca. 470 BP

21. The Legend of Fatuloli Ko 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 ?

23. Futuna event chronologies and selected potential source areas.
Futuna event chronologies and selected potential source areas and chronological data discussed in the text, blue filled circles identify approximate location of sites referred to in the text Red arrowed lines are indicative of direction of approximate maximum tsunami wave energy in deep water only away from the subduction zone sources (shown as short solid black lines on the coast of South America). Lime green colour relates to the source (line adjacent to Samoa), tsunami direction (arrows), and date of inundation for Futuna and Samoa. Orange colour indicates possible TKT source for Event 1 (line and arrows adjacent to Samoa), and possible contemporaneous events in the region. Black coloured dates relate to Event 2 and indicate potential sources in South America, and Pacific island sites with potential contemporaneous event records.
direction of ~ max. wave energy in deep water away from subduction zone sources
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.

24. 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 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) ?