Ocean bottom seismometer data from the MD 156/Sumatra-OBS cruise (2006) During the Sumatra-OBS cruise (R/V Marion Dufresne, July–August 2006) 56 ocean bottom seismometers from the British OBIC pool, the French INSU pool, the University of Brest and Ifremer were deployed along the above mentioned SW–NE oriented Sumatra-AB profile just north of Simeulue Island, in the epicentral area. The profile is 252 km long, resulting in a 4.6 km instrument spacing. All instruments were successfully recovered. A total of 2090 shots were fired on the profile by a 8260 in3 air gun array tuned to single-bubble mode to enhance the low frequencies and allow deep penetration [Avedik et al., 1993]. Preprocessing of the OBS data included calculation of the clock-drift corrections to adjust the clock in each instrument to the GPS base time.