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Tsunamis and Earthquakes

The 26 December 2004 Indian Ocean Tsunami: Initial Findings from Sumatra

Table of Contents

Survey Team
Survey and Methods
Tsunami Heights
Damage to Structures
Tsunami Sand Deposits
Coastal Response
Photo Gallery


Sumatra Tsunami Survey and Methods

The team collected information about:

  1. wave heights at the beach and inland,
  2. inundation distance (how far inland the water reached),
  3. runup elevation (the water's height relative to mean sea level at its farthest reach inland),
  4. flow directions,
  5. erosion,
  6. sediment deposition, and
  7. coastal subsidence.

Cartoon describing inundation distance, run-up elevation, and tsunami height
Some of the tsunami characteristics typically measured by survey teams (see Initial Findings on Tsunami Sand Deposits, Damage, and Inundation in Sri Lanka).

The team gathered some of its information from eyewitness accounts. Though not always reliable (commonly, eyewitnesses are running for their lives as they observe the tsunami), the eyewitness accounts collected in Sumatra provided several consistent pieces of information:

  • In Banda Aceh, the city closest to the earthquake epicenter, the tsunami arrived about 15 to 20 minutes after the earthquake was felt.
  • Many buildings in Banda Aceh withstood the earthquake shaking but were destroyed by the tsunami waves.
  • Likely because of the area's low elevation, the first tsunami wave that struck Banda Aceh did not have time to recede before the arrival of the next wave: the second tsunami wave rode over the first, and the third rode over the second.
Photo in Banda Aceh, see caption below
Survey-team members Franck Lavigne (white cap, second from right) and Alphonso (far right) collect eyewitness accounts from residents in Banda Aceh. [larger version]
Photo in Banda Aceh, see caption below.
Guy Gelfenbaum and Andy Moore of the ITST spoke with locals who provided eyewitness accounts of earthquake and tsunami. [larger version]
Photo in Banda Aceh, of Guy Gelfenbaum with locals.
Locals provided eyewitness account of earthquake and tsunami. [larger version]

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last modified 2005