• tsunami;
  • megathrust;
  • deep seismic;
  • earthquake

The Sumatra subduction zone is the most seismically active region on Earth. In the past 5 years, it has been the site of three great earthquakes, including the 26 December 2004 Sumatra-Andaman earthquake. That event produced a devastating tsunami around the Indian Ocean that claimed approximately 230,000 lives and caused terrible damage and destruction.

Part of the subduction zone still is locked and is likely to break in the next decade or so. To study the seismic and tsunami risk in this locked region, a deep seismic reflection survey, the Tsunami Investigation—Deep Evaluation Seismic (TIDES) project, was carried out in May 2009 using a CGGVeritas vessel towing a 15-kilometer-long streamer, the longest ever used during a seismic survey. The survey should provide the first ever seismic images of the locked zone from the seafloor down to a depth of 50 kilometers.