Tsunami warning in French Polynesia :

development and organization

PSI-2009

2 March 2009

Dominique ReymondCEA/DASE/LDG_Pamatai

Tsunami warning : What are the essential information for Civil Defense and the emergency plan ?

• The Tsunami Warning Centre (TWC) must be able to provide:

• 1) Information on the earthquake itself :– Location (routinely) – Focal depth (not trivial)– Magnitude (not trivial for slow and giant earthquakes)

•• 2) Information on the potential tsunami

– hour of tsunami arrival (routinely)– Importance of the tsunami (i.e estimation of amplitude of the

tsunami)

• 3) Seriousness of the warning– Evaluation of the danger : major, ocean wide, moderate, local effects

only, ..etc.

During the first tens of minutes …

• Only seismic data are generally available for the TWC in charge of warning.

• So, before receiving any tsunami data, what kind of information a TWC can extract from seismic data about a potential tsunami ? (then be able to push the red button to Civil Defense)

During the first tens of minutes …

Seismic data

Origin time

Lat, Lon (Epicenter)

Depth, H (Hypocenter)

Magnitudes (mB, ml, Md, Ms, MwP, Mm)

Scalar moment Mo ->Mw

Moment tensor : (φ, δ, λ, Mo, H)

Tsunami simulations : pre-computed amplitudes

Source duration τ, slowness Θ

Slip distribution (source function, Mo)

During the first tens of minutes …

The criteria of warning from seismic data:

If we get the 3 conditions:1. Epicenter is under-sea

2. Hypocenter is shallow (less than 60 km)3. Moment,Mo, is big : greater than # 1020 N.m

(i.e. large magnitude > 7.3 )

Definition: Mo = µ S D , whereS is fault areaD is displacement along the fault, µ is bulk modulus

Lack of warning system + lack of education

Tsunamis : Sumatera 26 dec. 2004

Tsunamis:Sumatera

Rupture zone of big Sumatra event (26 dec. 2004)

After-shocks distribution (CSEM): ~ surface of the rupture zone:~ 1000 km, ~ 200 km width, slip: ~ 20 m in the southern part~ 8 minutes of rupture duration (vr ~ 2.5 km/s)

Subduction of Indo-Australian plate under Indonesian plate.

Some statistics

Rate seismicity in the world :

• magnitude 6 : # 1 / 3 days• magnitude 7 : # 10 / year• magnitude 8 : # 1 / 2 year• magnitude 9 : # 3-4 / century

– (Sumatera 2004 was 9.3)

Dangerous earthquakes for Polynesia in XX cent.

May 1960, M 9.5,6 m, Mrq

30 Jul 1995, 8.0,3-4 m Mrq

Peru, 7.3Feb. 1996, 2-3 m Mrq

Mexico, 8.1Oct. 1995, 1m Mrq

Peru, 8.4jun. 2001, 0.9 m Mrq

Alaska, 9.2Mar 1964, 2 m Mrq

Aleutian, 8.51 avr 1946

Aleutian, 8.7Mar 1957, 2-4 m Mrq

Kamchatka, 8.3Nov 1952, 2-4 m .

Kuril, 8.2oct. 1994, 1 m Mrq

Tonga, 8.0apr 1919, 1 m Haw

Ecuador, Fev. 1996, 2-3 m Mrq

Chile, 11 nov 1922, 8.34 m Mrq

Chile, Aug 1906, 8.53.5 m Haw

undocumented Big in Marquesas Big in Polynesia and documented

Hiva Oa et Nuku Hiva: run-up for tsunami 1er April 1946

Tahiti : 4 – 6 m East shore< 1 m west shore

ISLV :# 0.70 mRurutu : 3 – 4 mTuamotu < 1 m

CEA/DASE/LDG_Tahiti

Some observations of tsunamis:Aleutian, 9 March 1957, et Aleutian 1er April 1946 in Hawaï

9 mars 1957 – Oahu - Hawaii 1 Avril 1946 – Hilo - Hawaii

CEA/DASE/LDG_Tahiti Some observations of tsunamis:top: tsunami of Chili, 30 jul. 1995 (mag. 8.0) Hiva Oa, Marquesasbottom: tsunami of Perou, 21 Feb 1996 (mag. 7.5) Hiva Oa

21 feb. 1996 – Hiva Oa - Marquises

30 jul. 1995 – Hiva Oa, Marquises

Amplitude Papeete:20 cm en 199507 cm en 1996

Warning system in the Pacific:26 states members of ITSU

Australia,Canada,Chile,China,Colombia,Cook Islands,Costa Rica,Democratic People’s Republic of Korea,Ecuador, El Salvador,Fiji,France,Guatemala,Indonesia,Japan,Mexico,New Zealand,Nicaragua,Peru,Philippines,Republic of Korea,Samoa,Singapore,Thailand, Russian FederationUnited States of America.

PTWC

JMA

ATWC

CPPT

SHOA

IGNS

28

CATW

TSUNAMI WARNING IN THE PACIFIC

PTWC(Pacific Tsunami Warning Center)

Warning to Countries (TELEX, GTS, Emails,Fax)

WARNING in French Polynesia

+ TREMORS system

+ CIVIL DEFENSE Transmission to Civil Defense

PSS_Tsunami

High-Authorities

Geophysicist on duty

Evacuation of populations

TWC, Focal points

LEVEL 3

LEVEL 2

LEVEL 4

HC HC HC HC ---- DPCDPCDPCDPC

Flow-chart of present warning to populations

The warning could start at any level in function of available delays

LDGLaboGeo

Territorial administrator

TV, radio

Mayors

Populations

Polynesian geophysical network

CEA/DASE/LDG

Real-time link

# 35 seismic stations received in real time:via SEEDLINK protocol over Internet

TAOE

DZMG

PPT

TREMORS : Overview of the automatic seismic warning system

Data acquisition

3 components seismic dataof a single station

Realtime analysis of seismic databy a PC computer

LocationDetection Magnitude, Mo

Warning from a given threshold on magnitude 7.0

Seismologist24h/24h on duty

Warning to Civil Defense

CEA/DASE/LDG

IN CASE OF WARNING

• 1 - Evaluation of 3 tsunamigenic criteria:• location• Focal depth• Energy (Mo)

2- Exchanges of data with other organisms (PTWC, CSEM): • Magnitude, seismic moment, focal depth

3 - If the earthquake has a potential tsunami risk :• Call CIVIL DEFENSE• Waiting for the first tsunami measures : tide-gauge, sea_level

stations to confirm/cancel a warning

CEA/DASE/LDG_Tahiti

Sea-level stations received in near real-time via GTS

KAUM

HivaNuku

RIKIEAST

PAPE

PENR

NIUE

KANT

POHN

KAPI

NKFA

FONG

VITI

CABO

ACAP

SANT

ARICVANU

JUAN

SANF

CALD

ANTO

VALP, SANO

SPED

TALC

ANCUD

COQU

Observed peak-peak tsunami amplitude in Papeete har bour (1946 - 2006)normalized at 90° of distance

0.00

0.01

0.10

1.00

10.00

1.0E+20 1.0E+21 1.0E+22 1.0E+23 1.0E+24

Seismic moment Mo (N.m)

Pea

k-pe

ak a

mpl

itude

(m

)

Aleutian 1 avril 1946

Alaska 1964

Chili 1960

Aleutian 1965

Tonga 1982

Peru 2001

Hokaido 2003

Tonga 2006

Kuril 15 Nov 2006

Example of tsunami warning bulletin sent to Civil Defense , for Kuril 15 Nov 2006

TSUNAMI WARNING - bulletin 3

Preliminary information on big earthquake located in Kuril, on 15 Nov 2006 :origin time : 11h14 T.U.Lat 46.7 NLon 153 E Prof :30 kmRegion :Kuril isl.Magnitude : 8.3 MwLevel of risk : REDConcerned regions of Polynesia : MARQUESAS Islands ONLY• Estimated Tsunami height : [30 - 90 cm] in NUKU_HIVA• Estimated tsunami height : [05 - 30 cm] in Papeete harbour• Estimated tsunami height : [05 - 30 cm] for RIKITEA It is not a major tsunami, but taking into account large amplification

effects of some bays in Marquesas, strong currents and vortexes should be observed …..

END

Thank you for your attention

The case of slow earthquakes

• Nicaragua Sept. 1992: mB = 5.3, Mw = 7.6• Java 2 June 1994: mB =5.5, Mw = 7.8• Peru 21 Feb 1996 : mB = 5.8, Mw = 7.5• Java 17 Jul 2006: mB = 5.5, Mw = 7.7

•Must use Mo (or Mw) instead of classical magnitude mb, Ms; Why ?

•For slow and/or giant earthquake, classical magnitudes are largely underestimated:

•Large sources with long duration, act like a natural low-pass filter