The 26 December 2004 Sumatra tsunami recorded on the coast of West Africa

  • A Joseph National Institute of Oceanography, Dona Paula, Goa 403 004, India
  • JT Odametey Survey Department, PO Box 191, Accra, Ghana
  • EK Nkebi Survey Department, PO Box 191, Accra, Ghana
  • A Pereira Viterbi School of Engineering, University of Southern California, Los Angeles, California, CA 90089, USA
  • RG Prabhudesai National Institute of Oceanography, Dona Paula, Goa 403 004, India
  • P Mehra National Institute of Oceanography, Dona Paula, Goa 403 004, India
  • AB Rabinovich Institute of Ocean Sciences, Department of Fisheries and Oceans, 9860 West Saanich Road, Sidney, British Columbia V8L 4B2, Canada; PP Shirshov Institute of Oceanology, Russian Academy of Sciences, 36 Nakhimovsky Prospect, Moscow 117997, Russia
  • V Kumar National Institute of Oceanography, Dona Paula, Goa 403 004, India
  • S Prabhudesai National Institute of Oceanography, Dona Paula, Goa 403 004, India
  • P Woodworth Proudman Oceanographic Laboratory, Joseph Proudman Building, 6 Brownlow Street, Liverpool L3 5DA, UK

Abstract

Analysis of sea-level data obtained from the Atlantic Global Sea Level Observing System (GLOSS) sea-level station at Takoradi, Ghana, West Africa, clearly reveals a tsunami signal associated with the Mw = 9.3 Sumatra earthquake of 26 December 2004 in the Indian Ocean. The tsunami arrived at this location on 27 December 2004 at approximately 01:38 UTC (which is close to the expected tsunami arrival time at that site), after travelling for more than 24 hours. The first wave was negative (trough), in contrast with the South African stations where the first wave was mainly positive (crest). The dominant observed period at Takoradi was about 42 minutes. The maximum trough-to-crest wave height (41cm) was observed on 28 December at 00:15 UTC. There were two distinct tsunami ‘bursts', separated in time by about 14 hours, the larger being the second burst. A small residual lowering of the sea level (~15cm) during the tsunami and for several days afterwards, and a delayed (~4.5 days) lowering of seawater temperature (up to ~4.5°C), was observed, possibly indicating the presence of internal waves through the Gulf of Guinea associated with propagating tsunami waves. The prominent tsunami signal found in the Takoradi record suggests that tsunami waves could also be found at other sites off the West African coast.

Keywords: Atlantic Ocean, focusing, Ghana, GLOSS, Gulf of Guinea, internal wave, reflection, sea-level changes, tide gauge, tsunami wave, West Africa

African Journal of Marine Science 2006, 28(3&4): 705–712
Published
2006-12-08
Section
Articles

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eISSN: 1814-2338
print ISSN: 1814-232X