We analyse seismograms of the slump episodes at Stromboli on December 30, 2002. Using a simple single force model, we estimate the volume involved in the individual subevents and attempt a chronological reconstruction of the whole process. Our results indicate the occurrence of two main events that could be interpreted as a submarine slump, which caused the observed tsunami, and a subaerial slump, which did not produce destructive sea waves. A total volume of about 20 × 106 m3 results for the submarine event, which developed over about 2 minutes with several distinct detachments, the first and largest displacing a volume of 10.8 × 106 m3. The second, subaerial, slump involved at least 2.5 × 106 m3, in about 90 s. A large long period pulse is also recognizable in the seismograms of the Stromboli station. We tentatively interpret this feature as tilt caused by the water load associated with the inundation in the Ficogrande area, on the northeastern side of the island.