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Publication date: 14 January 2020

Sanjeewa Wickramaratne, S. Chan Wirasinghe and Janaka Ruwanpura

Based on the existing provisions/operations of tsunami warning in the Indian Ocean, authors observed that detection as well as arrival time estimations of regional tsunami service…

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Abstract

Purpose

Based on the existing provisions/operations of tsunami warning in the Indian Ocean, authors observed that detection as well as arrival time estimations of regional tsunami service providers (RTSPs) could be improved. In particular, the detection mechanisms have been eccentrically focussed on Sunda and Makran tsunamis, although tsunamis from Carlsberg ridge and Chagos archipelago could generate devastating tsunamis for which inadequate provisions exist for detection and arrival time/wave height estimation. RTSPs resort to assess estimated arrival time/wave heights from a scenario-based, pre-simulated database. These estimations in terms of Sri Lanka have been found inconsistent. In addition, current warning mechanism poorly manages non-seismic tsunamis. Thus, the purpose of this study is to investigate these drawbacks and attempt to carve out a series of suggestions to improve them.

Design/methodology/approach

The work initiated with data retrieved from global earthquake and tsunami databases, followed by an estimation of probabilities of tsunamis in the Indian Ocean with particular emphasis on Carlsberg and Chagos tsunamis. Second, probabilities of tsunami detection in each sub-region have been estimated with the use of available tide gauge and tsunami buoy data. Third, the difficulties in tsunami detection in the Indian Ocean are critically assessed with case studies, followed by recommendations to improve the detection and warning.

Findings

Probabilistic estimates show that given the occurrence of a significant earthquake, both Makran and Carlsberg/Chagos regions possess higher probabilities to harbour a tsunami than the Sunda subduction zone. Meanwhile, reliability figures of tsunami buoys have been declined from 79-92 to 68-91 per cent over the past eight years. In addition, a Chagos tsunami is left to be detected by only one tide gauge prior to it reaching Sri Lankan coasts.

Research limitations/implications

The study uses an averaged tsunami speed of 882 km/h based on 2004 Asian tsunami. However, using exact bathymetric data, Tsunamis could be simulated to derive speeds and arrival times more accurately. Yet, such refinements do not change the main derivations and conclusions of this study.

Practical implications

Tsunami detection and warning in the Indian Ocean region have shown room for improvement, based on the inadequate detection levels for Carlesberg and Chagos tsunamis, and inconsistent warnings of regional tsunami service providers. The authors attempted to remedy these drawbacks by proposing a series of suggestions, including a deployment of a new tsunami buoy south of Maldives, revival of offline buoys, real-time tsunami simulations and a strategy to deal with landslide tsunamis, etc.

Social implications

Indian Ocean is prone to mega tsunamis as witnessed in 2004. However, more than 50 per cent of people in the Indian Ocean rim countries dwell near the coast. This is verified with deaths of 227,898 people in 14 countries during the 2004 tsunami event. Thus, it is of paramount importance that sufficient detection levels are maintained throughout the Indian Ocean without being overly biased towards Sunda tsunamis. With respect to Sri Lanka, Makran, Carlesberg or Chagos tsunamis could directly hit the most populated west coast and bring about far worse repercussions than a Sunda tsunami.

Originality/value

This is the first instance where the threats from Carlesberg and Chagos tsunamis to Sri Lanka are discussed, probabilities of tsunamis are quantified and their detection levels assessed. In addition, reliability levels of tsunami buoys and tide gauges in the Indian Ocean are recomputed after eight years to discover that there is a drop in reliability of the buoy data. The work also proposes a unique approach to handle inconsistencies in the bulletins of regional tsunami service providers, and to uphold and improve dwindling interest on tsunami buoys.

Details

International Journal of Disaster Resilience in the Built Environment, vol. 11 no. 2
Type: Research Article
ISSN: 1759-5908

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Article
Publication date: 13 July 2012

Sanjeewa Wickramaratne, Janaka Ruwanpura, Upul Ranasinghe, Samanthi Walawe‐Durage, Varuna Adikariwattage and S.C. Wirasinghe

The purpose of this paper is to propose a methodology for a priori classification of natural disasters that occur in Sri Lanka, through the development of a set of weighted…

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Abstract

Purpose

The purpose of this paper is to propose a methodology for a priori classification of natural disasters that occur in Sri Lanka, through the development of a set of weighted parameters based on the product of the disaster impact and the affected area, in order to prepare mitigation plans.

Design/methodology/approach

Experts' opinions were used for developing the parameters. Through a facilitated workshop, the weights of the disasters were obtained from experts involved in disaster mitigation at the local, regional and national levels in Sri Lanka. A correlation analysis was used to determine the most appropriate independent measures of disaster impact and affected area, the product of which was used to rank the identified disasters for further action.

Findings

For the pre‐selection of major disasters, the study showcases four weighted parameters, one of which is identified as the best. In total, five disasters have been singled out for further consideration in Sri Lanka. The product of the affected area factor, based on administrative area classification, and the impact factor, out of the two considered, that places a higher weight on minor disasters, is shown to be the best criterion.

Research limitations/implications

The geographical distribution of the participants (experts) does influence the results, and those available for the workshop were not fully representative of all Sri Lanka's provinces.

Originality/value

The paper emphasizes the importance of the consideration of the area impacted rather than the classification, which is based solely on the severity of the impact. The categorization of disasters based on experts' opinions and the related analysis revealed a priority order for planning for certain identified disasters.

Details

International Journal of Disaster Resilience in the Built Environment, vol. 3 no. 2
Type: Research Article
ISSN: 1759-5908

Keywords

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