Great earthquakes and tsunamis: Insight from marine geophysical studies offshore Sumatra, Indonesia
About the Event:
The Andaman Sumatra subduction system extends over 4000 km starting from the Andaman Island in the north up to Java in the south, where the Indo-Australian plate subducts beneath the Sunda plate. In the last 16 years, the Sumatra section offshore has hosted three great earthquakes with Mw>8.4, one tsunami earthquakes with Mw~7.8, and has induced two other great earthquakes (Mw>8.2) on the subducting Indo-Australian plate in the Wharton Basin. In order to understand the nature of these earthquakes and their links with tsunami generation, we have carried out 8 marine experiments, of which three were in collaboration with EOS (MegaTera, MIRAGE I and II). These results show faulting, bending and un-bending of the plate as it subducts, subducted seamounts and plateaus down to 30-60 km depth beneath the forearc. Our results also show that there is a causal link between frontal rupturing and tsunami generation. We find that the morphology of the subducting lower plate controls the position of the décollement, and influences the earthquake segmentation both along strike and along dip direction.
In the intra-plate deforming Wharton Basin, we have discovered the presence of conjugate shear zones, thick sedimentary basins along re-activated fracture zones, and propose that these re-activated fracture zones might be the sight of a nascent plate boundary between India and Australia; the occurrence of the 2012 twin earthquakes, Mw=8.6 and 8.2, supports this hypothesis. In this talk I will highlight some of these results, specifically focusing on the three joint IPGP-EOS experiments.
About the Speaker:
Singh was born and raised in Varanasi, also known as Banaras, India and did PhD in theoretical seismology at the University of Toronto, Canada, and spent a year at the University of Cambridge, England. He joined the Institut de Physique du Globe de Paris as a post-doc in 1988 and then moved to the University of Cambridge as a Researcher in 1990 where he developed a group in theoretical seismology. In 1998, he led the establishment of LITHOS Group to develop methods to jointly analyse seismic and marine EM data, but soon after that he moved to the Institut de Physique du Globe de Paris to lead the creation of the Marine Geoscience Department that he ran until 2008, while keeping his part time position at the University of Cambridge, maintaining the LITHOS Group between the two institutions. After the 2004 great Andaman Sumatra Earthquake and Tsunami, he persuaded Schlumberger to fund the acquisition and processing of long offset seismic data offshore Sumatra in 2006 and later persuaded CGG to fund a similar experiment in 2009, deploying 15 km long streamer, the longest streamer ever deployed. In 2015, he partnered again with Schlumberger to acquire ultra-deep seismic reflection data across the Atlantic Ocean to image the base the lithosphere down to 100 km depth. In 2012, he created the Paris Exploration Geophysics (GPX) Group, in collaboration with Mines ParisTech and other industry partners and started an international Master of Research in Exploration Geophysics, which has now become the International Master in Solid Earth Sciences at IPG Paris. Singh has a very broad research interests, from earthquake and tsunami to the inner core.
Singh has supervised over 85 PhD students and post-docs, published more than 180 papers in peer reviewed journals, including 14 in high impact journals such as Nature and Science. He was elected the American Geophysical Union Fellow in 2010, awarded the Grand Prix of the French Academy of Sciences in 2011, the European Research Council Advance Grantin 2013, and the Society of Exploration Geophysicists Distinguish Lecturer in 2018. He was a frequent visitor to the Scripps Oceanographic Institution, University of California, San Diego until 2012, and presently shares his time between Paris and Singapore since 2013, specially in winter.