Initial indications are that Diego Garcia not affected (tsunami article)

[pinto]

interesting piece from globalsecurity.org about Diego Garcia and the effect of topography on tsunamis.

Diego Garcia
"Camp Justice"
7°20'S 72°25'E

Initial indications are that Diego Garcia was not affected by the Andaman Tsunami of 26 December 2004. It is located south of the tip of India, well with in range of what the tsunami, with a max elevation of 22 and an average elevation of only 4 feet. Civilians monitoring shortwave radio reported on rec.radio.shortwave that a female operator, in answer to a query from an aircraft after giving weather information, reported no ill effects from the earthquake.

Officials said the Diego Garcia Navy Support Facility, which houses about 1,700 military personnel and 1,500 civilian contractors, suffered no damage related to the earthquake and ensuing tsunamis. Personnel at the facility reported no unusual activity or problems over the weekend. Diego Garcia, the southernmost island in the Chagos Archipelago, sits about 1,000 miles south of India and roughly 2,000 miles from the earthquake’s epicenter. Even though an earthquake like Sunday’s will radiate destructive waves in all directions, the damage caused by the water differs greatly depending on the undersea topography.

Favorable ocean topography minimized the tsunami’s impact on the atoll. Diego Garcia is part of the Chagos Archipelago, situated on the southernmost part of the Chagos-Laccadive Ridge. To the east lies the Chagos Trench, a 400 mile long, underwater canyon that ranges in depth from less than 1,00 meters below the surface to depths that plunge to over 5,000 meters. It is one of the deepest regions of the Indian Ocean. Diego Garcia is located to the west of Chagos Trench, which runs north and south. The depth of the Chagos Trench and grade to the shores does not allow for tsunamis to build before passing the atoll. The result of the earthquake was seen as a tidal surge estimated at six feet.

Tsunami runup at the point of impact will depend on how the energy is focused, the travel path of the tsunami waves, the coastal configuration, and the offshore topography. Small islands with steep slopes usually experience little runup - wave heights there are only slightly greater than on the open ocean. This is the reason that islands with steep-sided fringing or barrier reefs are only at moderate risk from tsunamis.

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http://www.globalsecurity.org/military/facility/diego-garcia.htm