Historical Data in Application to Tsunami Hazard and Risk Assessment

1. Historical Data in Application to Tsunami Hazard and Risk Assessment V.GUSIAKOV Tsunami Laboratory Institute of Computational Mathematics and Mathematical Geophysics Siberian Division Russian Academy of Sciences Email: gvk@sscc.ru

3. Part I HISTORICAL CATALOGS AND DATABASES Part II TSUNAMI RISK ASSESSMENT

5. 7% 15% 33% 27% 4 (definite event) 18% 3 (probable event) 11% 2 (doubtful event) 2% 1 (very doubtful event) 5% 0 (false entry) Tectonic Landslide 10% Volcanic Meteorological Unknown 72% Distribution of the global tsunamigenic events over validity index Cause of Tsunami Distribution of the tsunamigenic events over the type of source

6. 4% 12% Pacific Ocean Mediterranean Sea (including the BlackSea) Atlantic Ocean(including the Northernand the Baltic Seas) 4% 9% 25% 59% Indian Ocean 10% 77% Whole historical period for XX century Distribution of the events over the main tsunamigenic regions Distribution of the events over the main tsunamigenic regions

7. Comparative length of tsunami catalogs for the main tsunamigenic regions

8. XIX XX Distribution of the Pacific tsunamigenic events over time for the last 500 years

9. ? A comparative length and completeness of regional tsunami catalogs in the Pacific

10. Table 1. List of historical trans-oceanic tsunamis*). MS – surface wave magnitude, I – tsunami intensity on the Soloviev-Imamura scale, HmaxNF – maximum reported run-up in the near field in m, HmaxFF – maximum reported run-up in the far field in m, FAT – number of reported fatalities due to tsunami. *) Selected according to some formal criteria - run-up height greater that 5 m at the distance greater then 5,000 km from the source.

11. Table 2. List of the historical tsunamis with run-up greater than 50 m, sorted in order of their Hmax value. MS – surface wave magnitude, I – tsunami intensity on the Soloviev- Imamura scale, m – tsunami magnitude on the Iida scale, Hmax – maximum reported run-up in m, CAU - cause of tsunami (T- tectonic, L – landslide, V- volcanic), FAT – number of reported fatalities due to tsunami. *) Run-up value is based on a single witness report and, therefore, is not very reliable .

12. Table 3. List of largest seismically-induced regional tsunamis. MS – surface wave magnitude, MW– moment-magnitude, I – tsunami intensity on the Soloviev-Imamura scale, Hmax – maximum reported run-up in m, CAU - cause of tsunami (T- tectonic, L – landslide), FAT – number of reported fatalities due to tsunami

13. Table 4. List of largest historical volcanic tsunamis. VEI – volcaniuc explosion index, VOL – total volume of eruptive material in km3, Hmax – maximum reported run-up, I – tsunami intensity on the Soloviev-Imamura scale, FAT_EVE – total number of fatalities, FAT_TSU – fatalities from tsunami

14. I = 3.55 Mw –27.1 (Chubarov, Gusiakov, 1985) 5 I 4 5 3 I 2 4 1 3 0 2 -1 1 -2 0 -3 -4 -1 Mw 5 6 7 8 9 10 -2 -3 -4 Ms 5 6 7 8 9 10 Dependence of tsunami intensity I on magnitudesMS andMw for the tsunamigenic earthquakes occurred in the Pacific in 1900-1999

15. m = log2Hmax Hmax I = ½ + log2Hav Hav Typical distribution of tsunami run-up heights along the coast calculated for seismic source equivalent to a magnitude 7.5 submarine earthquake for a model bottom relief typical for Island arc regions

16. I = 3.55 Mw –27.1 5 I 4 5 3 I 2 4 1 3 0 2 -1 1 -2 0 -3 -4 -1 Mw 5 6 7 8 9 10 -2 -3 -4 Ms 5 6 7 8 9 10 Dependence of tsunami intensity I on magnitudesMS andMw for the tsunamigenic earthquakes occurred in the Pacific in 1900-1999

17. 5 I 4 3 2 1 0 -1 -2 -3 -4 5 6 7 8 9 10 Mw I = 3.55 Mw –27.1 I(Mw) diagram for “red”, “green” and “blue” tsunamigenic earthquakes occurred in the Pacific in 1900-1998

18. Fat Over 84% of their fatalities occurred within the first hour of propagation time. Another 12% fatalities occured within the second hour, with the rest (4%) occurring in the remaining time (exceeding two hours).

19. Part II TSUNAMI RISK ASSESSMENT

20. General formula for calculation of tsunami risk is R = H * V * C, where R – risk, H –hazard, V – vulnerability, C- cost In this formula, the ITDB can contribute to calculation of H value, i.e. probability of exceedence of any selected run-up value for a given period of time • Basic steps involved in the tsunami hazard calculation by this approach are: • Selection of a geographical area • Retrieval of historical run-ups • Calculation of the recurrence function • Calculation of the “hazard curve”

21. Visualization of the observed tsunami wave heights in the Pacific (47 BC – 2003)

22. Tsunami Hazard Analysis – Step 1 (selection of a geographical area)

23. Tsunami Hazard Analysis - Step 2(retrieval of the historical run-up data)

24. Tsunami Hazard Analysis – Step 3 (calculation of the recurrence function)

25. Tsunami Hazard Analysis – Step 4 (calculation of probability of exceedence)

26. Map of degree of tsunami hazard for the Pacific, divided into three categories: low (blue), medium (green) and high (red)

27. Map of degree of tsunami hazard for the Atlantic

28. Map of degree of tsunami hazard for the Mediterranean

29. Map of degree of tsunami hazard for the Indian Ocean

30. Conclusion 1 The intensity of seismically induced tsunamis is mainly controlled by an earthquake magnitude and, in general, is directly proportional to it. Detailed study of historical data for the instrumental period of available observations (since 1900) shows, however, that the actual scattering of tsunami intensity for earthquakes with the same magnitude exceeds six grades on the Soloviev-Imamura scale. That means than tsunami amplitudes can differ by a factor of 60 for earthquakes of the same magnitude, that makes unreasonable an operational prediction of expected tsunami height at the coast, based solely on earthquake magnitude.

31. Conclusion 2 Of all 2250 tsunamigenic events, only 223 (10%) tsunamis resulted in any fatalities, all others were weak local events observable only in several particular areas of the nearest coast. From these 223 deadly tsunamis, 213 (95%) fall into the category of local and regional events with most damage and all fatalities limited to one-hour propagation time. In total, they are responsible for 426,000 (61%) fatalities

32. Conclusion 3 Ten trans-oceanic tsunamis that occurred in the World Ocean during the last 250 years are responsible for 274,000 (39%) fatalities. Among them, nearly 230,000 people were killed during just one event – the December 26, 2004 Indian Ocean tsunami. All other trans-oceanic tsunamis are responsible for 34,000 deaths or 5% of all tsunami-related fatalities

33. Conclusion 4 The study of the death toll for 10 most destructive trans-oceanic tsunamis occurred in the World Ocean during the last 250 years shows that although the damaging impact of large tsunamis can last up to 23-24 hours, over 84% of their fatalities occurring within the first hour of propagation time. Another 12% of fatalities occur within the second hour, with the rest of 4% occurring at the remaining time (exceeding two hours).

34. Conclusion 5 There is a persistent need for any information that predates or augments historically reported and instrumentally measured past occurrence of tsunamis. Geological data on paleotsunamis therefore should be included in tsunami catalogs. Only on the basis of integrity of all data (instrumental, historical and geological) can we study the time-space patterns of large tsunamis and evaluate their long-term occurrence rates.

36. The end