Subduction of the Indian and Australian plates from the Andaman Islands to the Sunda Strait has recently generated a sequence of great earthquakes; only 400km or so of this 2500km plate boundary remains unbroken in just 4 years. It is widely believed that this sequence might continue and many studies suggest that there is a high probability of the occurrence of another M8+ event there in the near future. The potential for associated tsunamis is clear. The Sumatran margin also has a high density of volcanic centres, which might be reactivated in response to seismic activity. Decades of data collection in western Sumatra, including before, during and after the recent earthquake sequence, presents an unprecedented opportunity to advance our understanding of the complex interplay between seismic and aseismic deformation, structure and rheology in the evolution of subduction zones and their associated seismic, volcanic and tsunami hazards. Our session calls together scientists working on all aspects of the geology and geophysics of the region. We particularly invite those studying the seismology, paleoseismology, geodesy, volcanology, stress evolution/interaction and structural geology of Sumatra and welcome presentations on earthquake, tsunami and volcanic hazards including studies of mitigation and preparedness.