Of all 2250 tsunamigenic events historically known, only 223 (about 10%) resulted in human fatalities. Geographical distribution of these events is shown in Fig.4. Less than a quarter of all the events had the number of fatalities exceeding 1000, and only in 132 cases the death tall exceeded 10,000. In all but 11 events, listed in Table 1, the resulted damage and all fatalities were limited to a nearby area within one hour propagation time. Those 11 events are the so called trans-oceanic tsunamis and they were able to transfer their energy well outside the area of origin. However, a detailed analysis given in Section 4 shows that even in trans-oceanic tsunamis a major damage and over 90% of all fatalities occur in the nearby area within one hour propagation time.

Trans-oceanic tsunamis

Trans-oceanic tsunamis, capable to transmit their energy far away of the source area, are quite rare events as compared to local and regional events, however, they are responsible for a considerable part of damage and fatalities resulted from all tsunamis. In this section, we give a brief description and calculate the TTT maps for the trans-oceanic tsunamis occurred in the World Ocean during the last 300 years

• November 1, 1755 Lisbon, Portugal
  A violent earthquake of intensity XI on the MMI scale occurred in the morning of November 1, 1755, the All Saints Day Catholic holiday, near the Gorringe Bank off the Iberian Coast near Lisbon, Portugal. The earthquake generated a destructive tsunami that affected the coast of Portugal, Spain, North Africa, and the Caribbean. The tsunami wave reached Lisbon about 40 minutes after the first destructive shock and surged up to 18 meters in some places near Lisbon. At Azores the wave height was up to 15 meters (Fig.4). In 9.3 hours the tsunami arrived to Saba, Netherland Antilles having 6.4 m in height. The total number of fatalities in Portugal is estimated to be 60,000. It is difficult to resolve what part of them was due to tsunami, but we can assume that it is at least half of the total that gives the estimated 30,000 victims. The Moroccan Atlantic coast was struck by 15-m waves at a cost of 9,000 - 11,000 lives (O'Loughlin, Lander, 2003). There is no any quantitative data on tsunami victims in the Caribbean islands, but taking into account the reported run-up height (from 6 to 8 meters) there should be at least some.

  
  Tsunami travel time chart for the 1755 Lisbon tsunami. Solid ellipse marks position of the earthquake source. Red color shows the area within 1-hour propagation time. Digits near the isochrones - propagation time in hours. Digits in bold show the reported fatalities, digits in italic - maximum reported run-up within the particular TTT interval.

• November 7, 1837 Valdivia, Chile
  A 8.5 Ms destructive earthquake hit the coast southern Chile on November 7, 1837 with epicenter near Valdivia, Coral and Ankud. The waves reached 8 meters at the nearest Chilean coast. 6-meter waves were observed in Hilo, Hawaii after almost 14 hours of propagation time (Walker, 1994). There is no quantitative data on the number of victims in Chile, but according to (Soloviev. Go, 1985) in Hawaii the 6-meter tsunami resulted in 58 fatalities.

• August 13, 1868 Arica, Chile

A destructive 9.1 Mw earthquake with epicenter near Arica, northern Chile resulted in 18-m tsunami waves that in 20-30 min after the quake hit the nearest Peruvian and Chilean coast. Data on resulted fatalities are fragmentary, but one can guess that at the nearby coast the tsunami took several thousand victims. Outside the source area, the largest waves (up to 10 meter) were observed at the Chatham Islands at the distance almost 10,000 km (DeLange and Healy, 1986). Along the east coast of New Zealand waves were of 3 to 5 meter in high. These waves turned out to be the most severe far-field tsunami observed in New Zealand during the 160-year period of available observations. DeLange and Healy (1986) list this tsunami as caused loss of life in New Zealand, however, do not give any numbers for fatalities. Five-meter waves reached Hawaii and resulted there in 47 fatalities in Hawaii, where waves reached 5 meter in high (O'Loughlin, Lander, 2003).


Tsunami travel time chart for the 1868 Arica, Chile tsunami.

• August 27, 1883 Krakatau, Indonesia
  The cataclysmic explosion of the Krakatau volcano in Indonesia in the morning of August 27, 1883 (the final one in a series of several gigantic explosions that started a day earlier) generated a 25-30 meter tsunami in the Sunda Strait with maximum reported run-up of 41 meter (Fig.7). These waves swept away many villages along the both coast of the strait and killed over 36,000 people. It also caused an atmospheric pressure wave that was globally registered by recording barographs. Atmospheric gravity waves caused disturbance of water surface that was widely recorded by the existing mareograph network at very remote locations France, England, Alaska, Hawaii. Among 38 available sea-level records, the largest wave (1.5 meter) was recorded by the tide-gauge in Galle (Ceylon). It is important to stress that despite the global manifestation of tsunami, most of damage and all the fatalities were confined to the close neighborhood of the source area and occurred within one hour propagation time.

  
  Tsunami travel time chart for the 1883 Krakatau tsunami.

• February 3, 1923 Kamchatka, Russia
  A major 8.3 Mw earthquake off the east coast of Kamchatka, Russia generated an 8-meterr tsunami that caused several fatalities and considerable damage in Kamchatka (Soloviev, 1978) and propagated all over the northern Pacific. Seven waves were observed in Hilo, Hawaii, the third wave was the larges with height up to 6.1 m (Walker, 1994). The waves caused at least 1 victim in Hawaii (O'Loughlin, Lander, 2003). The tsunami waves were observed in Japan and were recorded by tide-gauges at the Canada and US West Coast. It is worth to note that in Hawaii, at the distance over 5,000 km from the source area the waves (5-6 m) were almost as high as in Kamchatka, in the immediate proximity of the source (6-8 m).

• April 1, 1946 Unimak Island, Aleutians
  The April 1, 1946 Aleutians tsunami is unique among other trans-oceanic event in two aspects. First , this destructive tsunami was caused by an earthquake with very moderate magnitude (7.4 Ms) that led H.Kanamori to formulate his conception of a tsunami-earthquake (Kanamori, 1972). Second, it is the only example of transoceanic tsunami that caused more damage and fatalities in the far-field rather than in the source area. The maximum run-up of 42 meter was observed at the Scotch Cap Light House in the Unimak Island (Okal et al., 2003). Low number of fatalities (5 persons in Alaska) is, of course, the result of low population density of this area. In 5 hours up to 16-metrer waves flooded all the coast of the Hawaiian Island and caused there 159 fatalities. One more fatalities was reported at the US West Coast

  
  Tsunami travel time chart for the 1946 Aleutians tsunami.

• November 4, 1952 Kamchatka, Russia
  The magnitude 9.0Mw earthquake on early morning November 4, 1952 to the east of southern Kamchatka generated 18-meter waves at the nearest coast of the Paramushir Island (North Kuriles). In six hours the waves struck the Hawaiian Islands still having 6-8 meters in height (maximum wave of 9.1 meter was observed near Kaena Point of easrtern most tip of Oahu Island). Property damage from these waves in Hawaii was estimated from $800,000 to $1,000,000, but, fortunately, no lives were lost. Locally, the city of Severo-Kurilsk on the Paramushir Island was completely destroyed. Most of its inhabitants were newcomers, who arrived to the Kuriles just after the Second World War, they were not aware such disaster as tsunami and most of them died in the tsunami waves. All the fatalities resulted from this tsunami occurred at the nearest coast of the Paramushir Island and at the south-eastern coast of Kamchatka. The exact number is not known but in some recent studies the death tall is estimated to be as high as 10,000. No fatalities were reported from the far-field areas affected by this tsunami.

  
  Tsunami travel time chart for the 1952 Kamchatka tsunami.

• March 9, 1957 Aleutians Island, Alaska
  The magnitude 9.1 Mw earthquake on March 9, 1957 south of the Andreanoff Island, Central Aleutians, generated a tsunami that did a severe damage on the Adak Island. However, the maximum run-up on Aleutians (15 meters) was observed at Scotch Cap on the Unimak Island located almost 2500 km away of the source area. Possibly, this large wave was generated by the local landslide. In 4.5 hours tsunami reached Hawaii and hit the coast with up to 10-meter waves. Estimated damage turned out to be nearly $5,000,000. Fortunately, no fatalities resulted from this tsunami locally and at distant coast. There were two indirect fatalities in Hawaii, a reporter and a pilot, and injury to a photographer when their small chartered plane crashed inn the ocean near Oahu.

• May 22, 1960 Chile
  On May 22,1960 a magnitude 9.5 Mw earthquake, the largest earthquake ever instrumentally recorded, occurred in the southern Chile (Fig.10). The earthquake ravaged the vast area along nearly 1000-km of the Chilean coast. The main shock generated a destructive tsunami that hit the nearest coast with 8-10 meter waves. The maximum waves, reaching 15 meter in high, were observed along the 350-km section of the coast between Corral in the south and Conception in the north. Number of reported fatalities varies in different sources from 490 to 5,700. In the present study, 1000 fatalities was accepted as a reasonable assumption of the tsunami death tall in Chile. In 15 hours, 8-10 meter waves reached Hawaii (reported maximum was 12.1-m wave observed at Ahukini Point on the Kauai Island) and caused 61 fatalities in Hilo, despite the advance warning was given and warning sirens sounded more than 3 hours before the first wave arrived. However, several first waves were small, and many people returned to their homes only to be caught by the largest wave that had in Hilo up to 6 meter in high. In 22 hours, the waves reached east coast of Japan, still having 5-6 meter in high. More than 10,000 house were destroyed and 122 people died.

  
  Tsunami travel time chart for the 1960 Chilean tsunami.

• March 28, 1964 Alaska
  The magnitude 9.2 Mw Prince William Sound earthquake, second largest during the instrumental period of seismological observations, hit a large part of southern Alaska and neighboring areas of Yukon territory and British Columbia and resulted in large destruction of property and $84 million of damage. The main tectonic tsunami had a height of 10-15 meters along the nearest coast, however, in many places local tsunamis were triggered by submarine landslides having height up to 68 meters (Lander, 1996). 106 tsunami-related fatalities were reported in Alaska, and 17 in the US West coast. The damage in western Canada was about $10 millions and on the West Coast of US was nearly $12 million. In 5 hours tsunami reached Hawaii with 3-4 mete r waves (the maximum 4.9-m wave was reported in Waimea Bay in the north of Oahu). In Hawaii, this tsunami caused only minor damage and, fortunately, no fatalities.

  
  Tsunami travel time chart for the 1964 Alaska tsunami.

• December 26, 2004 Sumatra, Indonesia
  A devastating mega-thrust earthquake occurred on the morning of December 26, 2004 at 250 km south-west of Banda Aceh, northern Sumatra. With its Ms=9.3 value, it is the fourth-largest earthquake instrumentally recorded and the first one of that scale occurred in the Indian ocean region (Fig.11). The estimated rupture fault size is 1300 km by 100 km with average slip amount up to 15 m. The earthquake generated a destructive tsunami that made a severe damage at coast of 11 countries and took almost 280,000 lives - the largest mortality toll for a single tsunamigenic event historically known. The worst hit country in terms of fatalities was Indonesia where over 228,948 are listed as dead or missing. The remaining fatalities occurred in Sri Lanka (36,081), India (16,423), and Thailand (8,567). In addition to these four most affected countries, there were 300 reported fatalities in Somalia, 82 in the Maldives, 68 in Malaysia, 61 in Myanmar, 11 in Tanzania, 2 in Seychelles, 2 Bangladesh and 1 in Kenya. The Pacific Tsunami Warning Center (PTWC) in Ewa Beach, Hawaii has timely determined the earthquake with operational magnitude as high as 8.0 (soon upgraded to 8.5) but since its source was located well outside of the PTWC area of responsibility, the warning was not issued for the affected areas. The tsunami wave heights varied from 15 to 20 m along the large part of the nearest coast (north-western Sumatra), with the absolute run-up maximum of 34.5 m reached near Lhonga village, some 15 km east-west of Banda Aceh. In the far-field, the larges run-up (9.3 meter) was measured at the coast of Somalia

  
  Tsunami travel time chart for the 2004 Sumatra tsunami.

Regional tsunamis

All historically known tsunamis sources are located within the continental slope or the shelf at the average distance of 150-200 km of the coastline. A typical example of geographical distribution of tsunami sources can be seen in Fig.13 that shows position of tsunamigenic sources for 78 historical tsunamigenic events near Japan resulted in human fatalities. In this figure, red and green dotted lines show the limits of 20-min and 40-min tsunami propagation time areas, respectively. One can see that about 40% of all deadly tsunamis occur within 20 min of propagation time to the nearest coast, and ALL of them fall within 40-min time limit.

As an example of the TTT calculation for a regional tsunami, in Fig.14 a TTT chart for the June 15, 1896 Sanriku tsunami is shown. This was one of the largest tsunami whenever occurred in Japan. The maximum run-up height at the nearest coast reached 38.3 m. These destructive waves killed 27,122 people and 9247 were injured, 10617 houses were washed away. Despite the tsunami was observed all along the eastern coast of Japan as well as in Hawaii and the US West Coast, the main impact fell within just 200-km part of the eastern coast of the Iwate and Miyako Prefectures where all of 27122 fatalities occurred. From the TTT map in Fig.12 one can see that this part of the coast is located within just 40-min travel time zone. On this coast, a tsunami began after 20 min of a seismic shock. The largest was the second wave that caused most of the damage and almost all fatalities.

One of the most devastating recent tsunami was generated by a large Ms7.6 earthquake in the Moro Gulf in the Philippines on 16 August 1976 (Fig.15). A large tsunami with run-up height up to 5-6 meter generated by the earthquake resulted in the death of thousands of people in coastal communities in the Sulu Islands, North and South Zamboanga, North and South Lanao, North Cotabato, Maguindanao, and Sultan Kudarat, on the island of Mindanao (Pararas-Caraynnis , 1976).. Available estimates of the death toll for this tsunami vary from 3,700 (PHIVOLCS Web-page, 2006) to over 10,000 (Pararas-Caraynnis Tsunami Web-page, 2006) people. (This particular example shows how uncertain can be the data on fatalities even for the recent tsunamis.) Since the source of this earthquake was located very close to the heavily populated coast most of these people died during the first 30 min after the quake.

In the Indian ocean region, the majority (95%) of all tsunamigenic events occur within a narrow strip between the axis of the Sumatra-Java deep-water trench and south-western coast of the Sumatra and Java islands. Fig.17 shows the limits of 20-min and 40-min propagation time zones near the coast of Sumatra. Out of 46 historical tsunamis generated in this area from 1722 to 2005, 26 (61%) occurred within 20-min propagation time zone. Only for 4 (10%) events, the travel time of the leading wave exceeded 40 minutes, and for all tsunamigenic events in this area the minimum propagation time was within one hour.

Discussion

The current version of the GTDB contains nearly 2250 historical tsunamigenic events covering the period from 1628 BC to present. To the best of our present-day knowledge, only 223 (10%) of these events resulted in any fatalities, all others were weak local events observable only in several particular areas of the nearest coast. In total, the 223 deadly events are responsible for 694,000 lives lost due to tsunamis at the coast of the World Ocean during all the historical period of available observations.

Out of 223 deadly historical tsunamis, only 11 fall into a category of the so-called trans-oceanic events capable to produce a considerable damage and human fatalities well outside their area of origin. In total, these 11 trans-oceanic tsunamis are responsible for 371,670 (53%) of all fatalities. Among them, 280,000 people were killed during just one event - the December 26, 2004 Indian Ocean tsunami. Other 10 trans-oceanic tsunamis are responsible for 92,000 deaths that is only 13% of all tsunami-related fatalities

The rest of 212 events (95% of all deadly historically known tsunamis) are the local or regional events whose main damage and all fatalities are limited to a nearby area within one hour propagation time. In total, they are responsible for 322,000 (47%) fatalities. The present level of accuracy and completeness of the data available in the Global Tsunami Database does not allow studying a more detailed distribution of tsunami fatalities over the propagation time within this one-hour TTT zone (say, over 10-min intervals), but roughly we can say that out of these 212 local and regional deadly tsunamis, 60% had their sources within 30-min propagation time limit. This conclusion is based on counting the number of tsunamigenic sources located within 30-min TTT zone in several most active tsunamigenic regions like Japan, South America, Indonesia, Philippines, Kuril-Kamchatka and Aleutians.

The available data on fatalities from 11 trans-oceanic tsunamis allows one to carry out a more detailed study on their distribution over propagation time. Fig.18 shows a histogram of a number of fatalities over one-hour time intervals for 11 trans-oceanic tsunamis, listed in Table 1. It clearly shows that although a damaging impact of large trans-oceanic tsunamis can last up to 23-24 hours, over 80% of all their fatalities occur within the first hour of propagation time. Another 12% of fatalities happen within the second hour of TTT, and the rest 4% occur during the remaining time (exceeding two hours).

Conclusions

1. The current version of the Global Historical Tsunami DataBase (GTDB) covers the period from 1628 B.C. till present and contains nearly 2250 historical events with 1206 of them occurred in the Pacific, 263 in the Atlantic, 125 in the Indian ocean and 545 in the Mediterranean region. In total, these events are responsible for 694,000 lives lost in tsunami waves during all the historical period of available observations.
2. Out of the total 2250 events, only 223 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, 212 (95%) fall into the category of local and regional events with most of damage and all fatalities limited to one-hour propagation time. In total, they are responsible for 322,000 (47%) fatalities.
3. The 11 trans-oceanic tsunamis that occurred in the World Ocean during the last 250 years are responsible for 372,000 (53%) fatalities. Among them, 280,000 people were killed during just one event - the December 26, 2004 Indian Ocean tsunami. Other 10 trans-oceanic tsunamis are responsible for 92,000 deaths that is only 13% of all tsunami-related fatalities.
4. The detailed study of the death toll for 11 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 occuring within the first hour propagation time. Another 12% fatalities occur within the second hour, with the rest of 4% occurring at the remaining time (exceeding two hours).
5. The overwhelming majority of other tsunamis (99.5% of all historical cases and 95% of all damaging events) are local and regional events whose major damage and all fatalities are limited to a near-source area within one hour travel time. Among these events, more than a half (60%) had their sources within 30-min propagation time limit.
6. The above conclusions, obtained in the present study by the analysis of the most complete historical dataset available in digital domain, are important facts and should be taken into account in design and implementation of any regional or basin-wide tsunami warning system.