Modelling and inversion of electromagnetic data in volcanic regions – The effect of topography

Unravelling the internal structure of volcanoes is an essential step to understand the architecture of the magmatic system and advance hazard assessment. Electromagnetic (EM) measurements are particularly suited for this task due to the high contrast in resistivity between melts and solid rock. Due to this, EM surveys of active volcanoes have gained significant attention in recent years. However, many modelling and inversion algorithms only provide a rough approximation of the significant topography of the volcanoes. Currently it is not clear to which level the topography has to be incorporated to provide reliable and robust results. We use two modern finite-element modelling algorithms for magnetotelluric data to assess the impact of different approximations. Based on the geometry of a recent survey at Mt. St Helens we will compare the results of the two algorithms with different topography approximations. We will discuss different strategies for incorporating topography and how to ensure valid calculations of magnetotelluric forward responses.
The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)