Assessment of tsunami threat to Sri Lanka from potential mega-thrust earthquakes in the Arakan subduction zone

Janaka J. Wijetunge
2010 Journal of the National Science Foundation of Sri Lanka  
This paper describes a numerical study carried out to assess the threat posed to Sri Lanka by potential tsunamigenic earthquakes in the Arakan subduction zone in the northeastern Bay of Bengal. The fault plane model adopted in the present simulations corresponds to a moment magnitude of M w = 8.8, which may be considered as a worst-case scenario. A hydrodynamic model based on linear shallow-water equations was employed to simulate tsunami propagation from the source to the shoreline around Sri
more » ... anka. The model results extracted at an average water depth of about 5 m off the coastline were processed to obtain the spatial distribution of the maximum value of the 'tsunami amplitude' (i.e., the height of the crest of the tsunami waves above mean sea level) as well as the arrival time contours for the leading wave. The numerical simulations suggest that the coastal zone of the Northern Province is at most risk from a tsunami generated in the Arakan fault plane with maximum tsunami amplitudes of the order of 10 m, whilst the maximum amplitudes along the coastal belt of the Eastern and Southern Provinces could reach up to about 5.6 m and 2.6 m, respectively. On the other hand, the coastline in the Western Province in the shadow zone of direct tsunami impact will only receive waves of small amplitude up to 0.6 m. The numerical results also indicate that the tsunami waves will first hit the east coast about 160 minutes after the earthquake, followed by the coastal belts of the Northern and Southern Provinces. The information presented in this paper relating to likely tsunami amplitudes and arrival times around the coastline of Sri Lanka would help authorities responsible for evacuation to make better judgement as to the level of threat in different areas along the coastline, and to act accordingly, if a large earthquake as to occur in the Arakan subduction zone in future.
doi:10.4038/jnsfsr.v38i2.2042 fatcat:mn36jsgsxncrljcuufimxozsye