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| Saturday, 19 February 2005 |
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Is it possible to predict a disaster? by Dr. S. Terrence Gamini de Silva, It is extremely difficult to predict any future event with certain degree of accuracy, leaving aside the forecasting of disasters. However, it is possible to study any particular event in the past and make use of such experience to forecast the nature of a future event. It was highlighted in the newspapers that certain animals were able to remain unaffected of the tsunami attack as they were able to sense this disaster beforehand and save themselves. Though we are experimenting about this, it is possible to provide at least some of the features related to future disasters with certain amount of accuracy, using the available information. Let us have an overview of the information that could be obtained in case of such disasters. Cyclones Generally, destructive cyclones originate in the Bay of Bengal. These are more frequent in the pre-monsoonal period (April to May) and the post-monsoonal period (September/October to December). Ten districts of Sri Lanka are more prone to cyclones. They include, Jaffna, Kilinochchi, Mullativu, Mannar, Vavuniya, Anuradhapura, Polonnaruwa, Trincomalee, Ampara and Batticaloa. Floods Country is prone to floods throughout the year, depending on the rainfall. However, wet zone floods are limited to the period from April to the early part of December and the dry zone floods occur from September to early part of May each year. Droughts Every year somewhere in Sri Lanka, people experience droughts of short duration. Droughts with regional or national impact do occur in every 3-4 years. The dry and arid zones are generally considered as the drought prone areas in Sri Lanka. The extreme north-west, Mannar, Kalpitiya areas and the extreme south-east, Hambantota, Yala areas are the worst affected. Landslides The occurrence of landslides have a relationship to the rainfall and therefore it is commonly seen in Ratnapura, Kegalle, Kalutara, Kandy, Kurunegala and Matale districts from May to November and in Badulla and Nuwara-Eliya districts from December to April. Volcanic eruptions Fortunately, volcanic eruptions are not seen in Sri Lanka. Earthquakes and tsunamis Despite some reports of earthquakes of lower magnitude, so far no earthquake disasters have been reported within the land area of Sri Lanka. However, the situation seems to be changing now.
Although the Sri Lankan coastal belt would have been affected by tsunamis in the past, such attacks have been only documented in historical records. Rajawaliya reports the first tsunami affecting Mannar during the reign of King Ravana and probably the second such disaster was reported to have struck Sri Lanka about two thousand seventy five years ago during the period of King Kelanitissa. It is very unfortunate that no scientific explanation on these disasters had been attempted. As a result when the tsunami struck Sri Lanka on 26th December 2004, in spite of such previous events, the people of Sri Lanka looked upon it as something new. In case if the people have had awareness about tsunami waves before, the number of deaths in this disasters would have been much less. That is why it is important to study the past and present events of this nature. The only experience in recent times we have had of tsunami is the one we faced with on 26th December. There are many lessons we could learn from this event. We now understand that tsunamis affect the coastal belt more than the deep sea and also that the magnitude of the impact caused to a greater extent depend on the elevation of the coastal belt. However, we have no idea as to when an earthquake or a tsunami could strike a country. From the 26th December experience we realised that earthquake / tsunami could strike several countries at the same time. Therefore to understand such disasters it is necessary to study similar experiences elsewhere in the world. The disasters could be analysed in various aspects. This analysis of earthquakes and tsunamis is confined to a very limited area - the relationships with full moon Poya day. The last tsunami attack was on a full moon Poya day of the month of December. Therefore it may be useful to analyse the earthquakes and tsunamis in other countries on the same basis. Such a study is attempted in order to understand disasters with reference to their date of occurrences. Since 1900, eleven earthquakes have been reported with a magnitude of more than 8.5 on the Richter scale. The following table gives the details regarding the date of occurrence. In table 1 there are 11 major earthquakes since 1900 and four of them have been on a full moon Poya day or a day close to it. Five of these earthquakes were above 9.0 in magnitude and have resulted in tsunamis. Of these five, three have happened on full moon Poya day or a day closest to a Poya. This is the main finding of this short study. However, it is difficult to provide a reasonable interpretation of the results of this work as the numbers involved are small. These facts I think are sufficient to make a hypothesis that there is a relationship with the position of the moon and earthquakes/tsunamis. It is necessary to understand that earthquakes and tsunamis do not always befall on full moon Poya days. In fact the earthquake with the highest magnitude in this table, the disaster in Chile in 1960, actually happened 12 days after the full moon Poya day. It is necessary to stress the need of further research on this association before accepting or rejecting the above hypothesis. It may be possible to unearth more information using such exercises, which may necessarily help us to understand the different aspects associated with such disasters. |
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