Collaborative Research: The Burma Arc from Collision Kinematics to Subduction Tectonics as Observed from a Passive seismic experiment (BACKSTOP)

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When two tectonic plates collide, one may slide underneath the other. This process, called subduction, often occurs when an oceanic plate meets a continental plate. The subducting oceanic plate, or subducting slab, sinks into the Earth's mantle affecting the regional mantle flow. This often generates mountain building and volcanic activity on land, like in Cascadia and Andean mountains. The volcanos may form along a curved chain called an arc. Colliding continental plates also build mountain ranges, like the Alps and the Himalayas. These processes are responsible for large earthquakes and volcanic eruptions threatening human lives and activity. Here, the researchers study a plate boundary coupling subduction with continental collision. Subduction of the Indian oceanic plate occurs along the Indo-Burma arc. It transitions to collision along the Himalayan Mountains. The scientists leverage on an international collaboration between five countries and the U.S. They use seismology, the study of seismic waves propagating through the Earth, to image in 3D mantle and crustal structures. Deploying 24 seismic stations in key locations in Myanmar, they analyze data from these instruments and ~900 other stations in surrounding India, Bangladesh and China. A primary objective is to unveil the processes responsible for the growth of the southeastern Tibetan Plateau. Another one is to quantify the effect of the Indian slab geometry on the mantle flow. The project improves the understanding of the regional tectonics. Its outcomes have strong implications for seismic and volcanic hazard assessment in Myanmar; a region which faces large dramatic events. The project provides support for two graduate students in Missouri and New Mexico, as well as the development of scientific collaborations in Myanmar. The three-year award was co-funded by NSF Prediction of and Resilience against Extreme Events (PREEVENTS) program. Here, the team investigates the role of the Indian slab beneath Burma as a "backstop" to the mantle flow around the eastern Himalayas. They also study how this impacts the growth of the southeastern Tibetan Plateau. The project consists of two components: (1) data collection from a temporary seismic array that links large arrays in India/Bangladesh and China; (2) the synthesis of data from a large number of existing stations across the region. The data acquisition component consists of 24 temporary broad-band stations deployed in key regions lacking any seismic instruments. The second component is a collaborative effort with scientists from Myanmar, India, Singapore, China, and Germany. The combined seismic network of over 900 stations spans an area of 1800 km by 2000 km. It completely covers the entire Indo-Burma Arc. The scientists use 3-D seismic tomography and anisotropic surface wave tomography to image the Indian slab beneath the Indo-Burma subduction zone. This enables them to compare flow and lithospheric deformation around eastern Himalayas and in the Indo-Burma back-arc. The project outcomes constrain the dynamics of the deformation associated with the Indian collision and subduction, and how the transition from subduction to continental collision occurs. The gained insight into the regional tectonics, as well as crustal attenuation, is key to improve seismic and volcanic hazard forecasting in Myanmar and surrounding regions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.