The lithosphere-asthenosphere boundary unveiled through trans-dimensional Bayesian inversion of geomagnetic satellite data

Abstract

The lithosphere-asthenosphere boundary, distinguishing the rigid lid from the weak mantle, intricately regulates the exchange of energy and materials between the overlaying moving plates and the convecting asthenosphere across geological timescales. This pivotal boundary not only controls the formation of mountains and deep oceans but also governs natural hazards such as volcanic eruptions and earthquakes. Moreover, it plays a fundamental role in exerting influence over global climate changes and creating the hydrosphere that sustains life on Earth. Recognizing its paramount significance in cultivating a habitable environment, extensive seismic, magnetotelluric, heat flow, and viscosity measurements have been employed to scrutinize its depth variations and transitions in chemical and physical properties. Nevertheless, the precise location of the transition between the strong lid and the weak mantle, as well as the exact mechanism controlling the thickening of the lithosphere and the weakening of the upper mantle, remains a subject of ongoing debate. Tidally-induced magnetic field data, measured by geomagnetic satellites and generated through galvanic coupling between ocean sedimentary layers and the underlying conductive rocks, provide a unique opportunity to remotely sense the lithosphere-asthenosphere boundary. This study develops a new inversion algorithm to image the globally averaged conductivity profile beneath the Earth’s surface and utilizes extracted tidally-induced magnetic field data from geomagnetic satellites to focus on the lithosphere-asthenosphere boundary. Employing the trans-dimensional Bayesian concept and a three-dimensional integral equation solver that accounts for heterogeneous surface continents and oceans, this approach holds the potential to provide a significant statistical probability of the imaged lithosphere-asthenosphere boundary and other sub-lithosphere discontinuities, along with associated conductivity values. These conductivity discontinuities and values are then used to infer potential water content and partial melt in the weak mantle, crucial for unraveling the hidden mechanism behind lithosphere thickening. Keywords: lithosphere-asthenosphere boundary; tidally-induced magnetic field; trans-dimensional Bayesian; Geomagnetic satellites