Identification of palaeotsunamis using ground penetrating radar, sedimentological and micropaleontological techniques : implications for Sri Lankan tsunami risk
Premasiri, Ranjith H. M.
MetadataShow full item record
One of the most catastrophic natural hazards which can devastate coastal zone communities isthe tsunami. The risk of tsunami devastation can be mitigated by reconstruction andquantification of past tsunamis, but this requires identification and analysis of past tsunamimagnitudes and dates even from historical times. The interpretation of geological records oftsunamigenic deposits is the core theme explored in this thesis for the characterisation ofpalaeotsunamis. Three key elements: identification of palaeotsunamites, dating theirdeposition and determination of magnitude are needed for reconstruction and quantification ofpalaeotsunamis. While several studies have described criteria for identification oftsunamigenic sediments, much less research has been carried out on reconstruction ofpalaeotsunamis.Sediment characteristics, their depositional configuration and extent of the inundation area onthe coast give infOlmation on hydrodynamic conditions of tsunami waves. This study hasdeveloped a method to estimate tsunami risk by reconstructing and quantifyingpalaeotsunamis from tsunamigenic sediments on the Sri Lankan coast rising sedimentologicaland paleontological characteristics, Ground Penetrating Radar (GPR), and optically stimulatedluminescence (OSL) dating techniques. The 2004 tsunami records were used as a control forthe study. Distinctive tsunamigenic sediment signatures were recognised. Threepalaeotsunami events were identified and dated at ISO (Krakatua), 2550±190 and 3170±320years BP and correlated with historical and archaeological records. The recurrence interval ofc 600 years postulated for the Indian Ocean was confirmed by this study and the oldest eventrecorded to date in the Indian Ocean was recognised at 3170±320BP. The method developedhere based on reconstruction of palaeotsunamis using sedimentological records, GPR andOSL techniques enables estimation of inundation distance, recurrence interval andconsequently the wave characteristics of palaeotsunamis which can be used to estimatetsunami risk for any coast.