Project Title: Waveform tomography with massive datasets: The East Asia case study
Researcher: Dr Hui Dou
The knowledge of the structure of the lithosphere and its interactions with the underlying mantle is important for understanding the evolution of Ireland, its offshore, and the broader North Atlantic region. The structural and thermal evolution of major basins and the enigmatic intraplate volcanism in and around Ireland have been driven by the dynamics of the lithosphere-asthenosphere system. The massive seismic datasets available today make possible seismic tomography at an unprecedented level of detail, provided that methodology is developed to handle the very large volumes of broadband seismic data and to solve the very large inverse problems needed to achieve the fine, regional-scale resolution. Broadband seismic imaging has already revealed strong, previously unknown variations in the lithospheric thickness beneath Ireland and surroundings, some of them formed by the Caledonian Orogeny that created the Irish landmass and others relating to the distribution and mechanisms of the Paleogene intraplate volcanism in the region. As a comparative case study, East Asia offers important additional insights into the lithospheric dynamics of orogenies and mechanisms of intraplate volcanism. This research benefits from a unique, dense regional dataset assembled in China over the last decade and is now available for use in regional tomography. East Asia is a complex region with a variety of crustal types and tectonic styles. The active collision of India and Asia, multiple earlier orogenies, and the current subduction of the Pacific and Philippe Sea plates have produced strong seismic heterogeneities in the crust and mantle beneath East Asia, preserving the record of the deep lithospheric evolution of the region. The origin of the numerous intraplate volcanoes is debated, attributed to deep mantle plumes, asthenosphere flow, or deep melting caused by subducted slabs near 600 km depth. By combining new data from permanent networks in China with large global datasets in this case study, I aim to obtain a high-resolution, 3-D, S-wave model of the crust and upper mantle beneath East Asia. It will help us to understand the tectonic and geodynamic evolution in the region and should yield new insights into the deep mechanisms of orogeny and intraplate magmatism, a major element of the evolution of Ireland as well. From the methodological perspective, the study will also test the resolution limits of regional waveform tomography, using the extremely dense data sampling of the region.