Seismic and infrasound networks to study the volcano Oldoinyo Lengai (SEISVOL)
Final Report Abstract
Volcanoes pose a significant threat to society. Studying their dynamics as well as subsurface structure is crucial in building a profound understanding of magmatic systems which may lead to better prediction capabilities in the future. Oldoinyo Lengai volcano, located in the North Tanzanian Divergence (NTD), is the only currently active carbonatite volcano worldwide and presents an important endmember magmatic system in a young rift segment of the East African Rift System (EARS). This volcano typically experiences long-duration episodes of natrocarbonatitic effusions with intermittent short-duration explosive eruptions. These changes may be driven by stress interactions between different magma networks beneath Oldoinyo Lengai and neighboring rift volcanoes or caused by a complex differentiation process in which, driven by CO2, natrocarbonatitic magma is exsolved from one magma chamber. To better understand the role of the stress interactions and magma plumbing on the eruptions dynamics, this research project aimed to constrain the subsurface magmatic architecture of Oldoinyo Lengai, and a zone of ongoing seismicity and intrusive activity below the extinct 1 Ma-old Gelai shield volcano and active Naibor Soito monogenetic cone field. We installed a dense seismic network, a seismic array and infrasound sensors closely situated around the active Oldoinyo Lengai edifice. Given the near absence of anthropogenic noise, this network significantly reduced the detection threshold of volcano-tectonic events and volcanic tremor. This enabled us to locate over 10 000 volcano-tectonic events between March 2019 and June 2020, which we used, together with focal mechanisms, to map a highly interconnected plumbing system which acts as an accommodation zone between and old and new rift segment. Using the located earthquakes, we further imaged a magmatic body and a fluid-filled border fault using scattering and absorption imaging. These results suggested that Oldoinyo Lengai may be sourced by different melt pathways and that the production and transport of carbonatites may be facilitated by the border fault while the other 95% of eruption products which are not carbonatite may be hosted in the magmatic body. Finally, we used one year of seismo-acoustic tremor aided by thermal observations from space to observe temporal changes in the magmatic system. We were able to study the evolution of the crater morphology and relate different seismo-acoustic episodes to different eruption processes. Our results suggest that 12 years after the last explosive eruption, which were followed by a period of quiescence, the volcano is transitioning to a more active phase.
Publications
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SEISVOL - Seismic and Infrasound Networks to Study theVolcano Oldoinyo Lengai. GFZ Data Services.
Reiss, M.C. & Rümpker, G.
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The Impact of Complex Volcanic Plumbing on the Nature of Seismicity in the Developing Magmatic Natron Rift, Tanzania. Frontiers in Earth Science, 8.
Reiss, Miriam Christina; Muirhead, James D.; Laizer, Amani S.; Link, Frederik; Kazimoto, Emmanuel O.; Ebinger, Cynthia J. & Rümpker, Georg
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The Interconnected Magmatic Plumbing System of the Natron Rift. Geophysical Research Letters, 49(15).
Reiss, M. C.; De Siena, L. & Muirhead, J. D.
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Overview of seismo-acoustic tremor at Oldoinyo Lengai, Tanzania: Shallow storage and eruptions of carbonatite melt. Journal of Volcanology and Geothermal Research, 442, 107898.
Reiss, Miriam Christina; Massimetti, Francesco; Laizer, Amani S.; Campus, Adele; Rümpker, Georg & Kazimoto, Emmanuel O.
