Lessons from the 2004 Sumatra earthquake and the Asian tsunami

Transcription

1 Lessons from the 2004 Sumatra earthquake and the Asian tsunami Kenji Satake National Institute of Advanced Industrial Science and Technology

2 Outline 1. The largest earthquake in the last 40 years 2. Tsunami generation and propagation 3. Past and future earthquakes 4. Tsunami warning and hazard reduction systems

3 The Sumatra earthquake and tsunami Worst tsunami disaster in history Casualties from tsunami Somalia 300 India 16,000 Thailand 8,300 Sri Lanka 35,000 Indonesia 160,000

4 Tectonic situation

5 Tectonic situation Dec.26 March 28

6 Tsunami Damage Thailand Myanmar

7 Tsunami surveys around Bengal Bay Andaman Is. < 5m Tsunami height, m Myanmar < 3 m Inferred tsunami source Thailand 5 15m Sri Lanka 5 15m Measured height (m) Indonesia Band Aceh, max 30 m Measured height (m)

8 Interplate earthquakes

9 A Flying Start, Then a Slow Slip Slow slip only Fast and slow slips Tsunami source Fast slip only May 20 issue of Science

10 Only four M9 events in 20 th century Cumulative seismic moment Harvard CMT

11 Three slip distribution models ~3 x Nm 6.5 x Nm 6.5 x Nm surface waves SH waves regional +surface waves telseismic body + regional +surface waves SH waves regional +surface waves telseismic body +regional +surface waves Ammon et al. (2005, Science)

12 Northward rupture propagation 1,300 km 2.8 km/s 8 minutes Ishii et al., 2005

13 Satellite Images April 12, 2004 January 2, 2005 submerged Gleebruk Village (South of Banda Aceh) Digital Globe s QuickBird satellite /images/tsunami June 3, 2004 December 30, 2004 emerged Sentinel Island (Andaman Is.) ENVISAT-ASAR /workpackages/20300/sentinel /new/images.html

14 Northern Andaman 1 m uplift Southeast Andaman 1m subsidence Crustal deformation near the source Coastal surveys and GPS observation detected meter-scale deformation along Sumatra to Andaman Is (~1,000 km) Source for crustal deformation AIST, Univ. Tokyo Sumatra Is. 1m shift to SW Uplift of Sentinel Island ENVISAT-ASAR June 3, 2004 December 30, 2004 Nagoya Univ.

15 Outline 1. The largest earthquake in the last 40 years 2. Tsunami generation and propagation 3. Past and future earthquakes 4. Tsunami warning and hazard reduction systems

16 Tsunami generation and propagation Tsunami = harbor waves

17 Deep and shallow water waves

18 Tsunami Travel Time

19 Seafloor deformation

20

21 Forward and inverse problems

22 Tsunami source estimated from arrival times

23 Jason-1 altimeter on NASA s satellite Observed Sea Surface Heights (SSH) 120 min Estimated tsunami source

24 Outline 1. The largest earthquake in the last 40 years 2. Tsunami generation and propagation 3. Past and future earthquakes 4. Tsunami warning and hazard reduction systems

25 Next earthquake? McCloskey et al., 2005 Nalbant et al., 2005

26 Past earthquakes along Sumatran trench

27 Past earthquakes along Sumatran trench Seih et al. (2004, AGU fall meeting) No giant earthquakes have struck the outer-arc islands of western Sumatra since the sequence of 1797, 1833 and Mw 9.0 slip 10 m uplift 2m Paleoseismic studies of coral microatolls reveal that failure of the subduction interface occurs in clusters of such earthquakes about every 230 years. Thus, the next such sequence may well be no more than a few decades away.

28 Cascadia subduction zone Comparison with 2004 eq B. Atwater (USGS)

29 1700 Cascadia earthquake (Mw~9) January 26, 1700 Satake et al., 2003 J. Geophys. Res. Japanese documents Cascadia fault Comparison of tsunami heights

30 Earthquake recurrence along Kuril Trench

31 Earthquake recurrence Earthquake occurrence Periodical Time between eqs. Random in time Poisson Process

32 Earthquake recurrence Earthquake occurrence Periodical Probability in next 30 yrs Random in time Poisson Process Time since last earthquake

33 Earthquake probability along Kuril trench 30 year probability as of March 2003 Mw % 03/09/26 M 8.0 M 8.1 ~60% M % 1843 M M 8.2 Mw % 04/11/29 M Mt Mw M Mw 8.2 Smaller eq. M % 1918 Mt Mw 8.5 Smaller eq. Mw 7.7 >90% HQ Earthq Res Prom, March 2003

34 Outline 1. The largest earthquake in the last 40 years 2. Tsunami generation and propagation 3. Past and future earthquakes 4. Tsunami warning and hazard reduction systems

35 1960 Chilean earthquake Largest eq. in 20 th century (Mw 9.5) The tsunami arrived Hawaii 15 hrs; 60 casualties Japan 23 hrs; 150 casualties Int l Tsunami Warning System Very few knowledge - No plate tectonics - No global seismic network - Ms= 8.5 Onagawa, Japan

36 Tsunami Warning System Global seismic network Sea level network DART buoys GLOSS Global Sea Level Observing System NOAA

37 Tsunami Information Bulletins from PTWC December 26, GMT Earthquake 1:14 GMT ( 1 st bulletin 15 min after the eq.) LOCATION - OFF W COAST OF NORTHERN SUMATERA MAGNITUDE : 08 GMT 2 nd bulletin 69 min after the eq.) LOCATION - OFF W COAST OF NORTHERN SUMATERA MAGNITUDE EVALUATION REVISED MAGNITUDE THERE IS THE POSSIBILITY OF A TSUNAMI NEAR THE EPICENTER.

38 Dissemination of Warning to Residents satellite Local Government s Local Meteorological Observatory Dedicated phone line Police, Fire office TV Residents JMA Japanese Government Radio etc

39 Tsunami evacuation maps Phonebooks in Hawaii

40 Effect of education Recent Examples: 1993 Japan with tsunami knowledge and experience 15% of residents die 1998 Papua New Guinea w/o tsunami knowledge 75% of residents die 1999 Vanuatu, Pentecost Island Video on PNG tsunami educates local village only 10 die (1000s homeless) Papua Geological New Guinea, Survey 1998 of Japan

41 Tsunami Warning and Hazard Reduction Tsunami Warning System Seismic Obs Sea Level Obs Hazard Mitigation Education and Awareness Tsunami Warning Message e.g., JMA, PTWC Coastal Communities Residents Evacuation

42 Conclusions 1. The 2004 Sumatra-Andaman earthquake was the largest event in the last 40 years and caused >200,000 tsunami casualties. 2. The tsunami was recorded by tide gauges, satellite altimetry and field surveys, and the data are used in real time to study the tsunami source. 3. Past tsunamis can be studied by historic and geologic data. Data from such paleoseismological studies can be used for probabilistic estimates of future earthquakes and tsunamis. 4. To prevent future disaster, tsunami warning systems, hazard assessment and preparation, and education are all necessary.