Date and Time
Bath Royal Literary and Scientific Institution, 16-18 Queen Square, Bath BA1 2HN
The 2004 magnitude 9.1 earthquake and resulting tsunami originated on the subduction zone margin offshore North Sumatra (part of the Sunda subduction zone system). The resulting tsunami killed more than 200,000 people, devastating large coastal regions around the Indian Ocean, in particular in North Sumatra (Aceh) and Thailand.
Since the earthquake, a large number of countries, in collaboration with Indonesia, have invested in collection of geological and geophysical data in order to better understand the structure of this subduction zone and its potential for large earthquakes and tsunami. The data are also important for a general understanding of these processes and of other subduction zones worldwide. The UK has played a significant role in this effort. This talk will show some of the results of data collected in projects over the last few years, including those led by UK scientists. This includes marine geophysical data that images below the seafloor to show the structure of the subduction zone and the properties of the faults that move and generate the earthquakes. Sediment cores sampling the upper few metres below the seafloor have also been collected to see where submarine sediment flows were triggered by the earthquake shaking in 2004 and in previous earthquakes.
Finally, in 2016, an expedition of the international Integrated Ocean Discovery Program (IODP: scientific ocean drilling) drilled the sediments coming into the subduction zone. These sediments, which originate from the Himalaya and Tibetan Plateau, form the tectonic plate boundary fault – their properties ultimately control the behaviour of the fault. Drilling and sampling of these sediments has now provided information about the properties of the fault zone and why it generated such a large earthquake and tsunami.
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