The overview of the joint research project for the paleo-tsunami deposits in Sri Lanka A.V. P. Vijitha, N. P. Ratnayake, K. Goto and T. Haraguchi Yala National Park
Impact of the 2004 Indian Ocean tsunami to Sri Lanka Clarifying the tsunami recurrence interval is one of the important issue for future disaster plan in Sri Lanka Insert pictures of tsunami damage at Sri Lanka
Impact of the 2004 Indian Ocean tsunami to Sri Lanka Clarifying the tsunami recurrence interval is one of the important issue for future disaster plan in Sri Lanka Insert pictures of tsunami damage at Sri Lanka
Impact of the 2004 Indian Ocean tsunami to Sri Lanka Clarifying the tsunami recurrence interval is one of the important issue for future disaster plan in Sri Lanka Insert pictures of tsunami damage at Sri Lanka
Impact of the 2004 Indian Ocean tsunami to Sri Lanka Clarifying the tsunami recurrence interval is one of the important issue for future disaster plan in Sri Lanka Insert pictures of tsunami damage at Sri Lanka
Impact of the 2004 Indian Ocean tsunami to Sri Lanka Clarifying the tsunami recurrence interval is one of the important issue for future disaster plan in Sri Lanka Insert pictures of tsunami damage at Sri Lanka
Impact of the 2004 Indian Ocean tsunami to Sri Lanka Clarifying the tsunami recurrence interval is one of the important issue for future disaster plan in Sri Lanka Insert pictures of tsunami damage at Sri Lanka
A A mythical account of the possible paleo-tsunami in Sri Lanka mythical account of the possible paleo-tsunami in Sri Lanka Mahawanse, a Sri Lankan history book: It has over 2500 yrs of recorded history of Sri Lanka, indicates possible tsunami-like event during the rule of King Kelanithissa approximately 2100-2300 yrs B.P; has resulted setting afloat his daughter, Princess ViharaMahadeviinto the sea to appease the gods. Is this true story? At this moment, no scientific evidence supports this historical account. Objective of our study This account is only one that described the possible paleo-tsunami event in the Indian Ocean countries. In order to find the geological evidence of this account, we organized Sri Lanka-Japan joint research team.
Sri Lanka suits to investigate transoceanic tsunami records No subduction zone exists around Sri Lanka. Thus, only transoceanic tsunami such as the 2004 Indian Ocean tsunami could have attacked to Sri Lanka in the past.
Sri Lanka suits to investigate transoceanic tsunami records The wave height and inundation area of the 2004 Indian Ocean tsunami have been studied well. These information are very useful to make decision of the drilling points for paleo-tsunami study. Wijetunge (2006)
Sri Lanka suits to investigate transoceanic tsunami records 1. Many lagoons and lowlands exist along the coast. 2. No strong cyclones have attacked to Sri Lanka. 3. Monsoongenerated waves are sometimes strong, but the waves never inundate far inland as like the tsunami. Sand dune lagoon
Preliminary survey and instruments 1.We firstly selected possible drilling sites (within the 2004 tsunami inundation area but not close to the river) using topographic map. 2.Approx. 40 sites were selected for preliminary survey. Circles: possible drilling points Flags: tsunami inundation area GPS navigation system using laptop.
Preliminary survey by the peat sampler Up to 5 m core sample can be easily obtained.
Preliminary survey by the peat sampler 2 2004 Indian Ocean tsunami
We selected following 3 locations for full-scale drilling Dikwella (marsh) HambantotaKirind a Dikwella sand dune marsh
Full-scale drilling at Dikwella Detail results will be provided by Dr. Goto. Radiocarbon age (ka yrbp) 0 1 2 3 4 5 6 7 8
Sub-bottom acoustic profiling at Karagan Lagoon, Hambantota
Sub-bottom acoustic profiling at Karagan Lagoon, Hambantota Bottom of the lagoon Possible sand layers
Sub-bottom acoustic profiling at Karagan Lagoon, Hambantota 2004 tsunami deposit Wijetungeet al. (2008) KR 1 KR 2 KR 3 1. Our drilling points are within the inundation area of the 2004 tsunami according to the numerical modeling by Wijetunge et al. (2008). KR 4 2. 2004 tsunami deposit is observed only in the KR-4 core.
Columnar section and radiocarbon ages at Hambantota 1.The radiocarbon age of the sample from approximately 30 cm subbottomdepth is 3530 year B. P., whereas the age of the sediments at the bottom of the core (8.3 m in subbottomdepth) is approximately 7320 year B.P. 2.The erosion by the 2004 tsunami can t explain the absence of younger sediments. We tentatively interpreted that the sedimentation rate after3500 year B. P. at southern Sri Lankan coast was remarkably slow. KR-3 core
Columnar section and radiocarbon ages at Hambantota Kirinda (marsh) sand dune marsh Kirinda is a place where Princess ViharaMahadeviarrived approximately 2100-2300 yrs B.P. We took drilling core samples at the marsh and found several sand layers. However, the sedimentation rate seems remarkably low and the age of the sample from approximately 70 cm subbottomdepth is 6000 year B. P.
Conclusion 1. In order to find the geological evidence of the account in Mahawanse, we organized Sri Lanka-Japan joint research team. 2. We conducted preliminary field survey at approx. 40 site, and selected 3 sites (Dikwella, Hambamtota, and Kirinda) for full scale drilling. We took totally 20 cores at these sites. 3. We conducted radiocarbon age dating for these cores. However, we could not find the sediments younger than 3500 year B. P. We tentatively interpreted that the sedimentation rate after 3500 year B. P. at southern Sri Lankan coast was remarkably slow. 4.We still need to explore the younger sediments from the Sri Lankan coast to investigate the validity of the historical account. With special thanks to Mr. Iwasaki and Mr. Rohan for their kind cooperation.