Complex sentence: Simeulue earthquake, and the September 2007 Mentawai earthquakes with aftershocks as large as M7,9 produced the largest release of elastic strain energy since the 1957/1964 series of shocks on the Aleautian/Alaska trench.
Split into simpler sentences: Simeulue earthquake, and the September 2007 Mentawai earthquakes. This series of events produced the largest release of elastic strain energy since the 1957/1964 series of shocks on the Aleautian/Alaska trench.