Challenges in volcano magma chamber imaging: A numerical study

Volcanic eruption is a continuous threat to many places in the world. Despite recent advances in volcano monitoring techniques and developments in monitoring networks, eruption forecasting remains a challenging task, partly because an accurate description of the current state of a volcano is missing. Such a description requires knowledge about the time varying internal structures of the volcano. An ultimate goal is, therefore, to obtain snapshots of the volcano structures across multi scales. However, due to limitations in imaging techniques in highly heterogeneous volcanic environments, e.g., strong velocity gradient near surface and rich in small-scale scatterers throughout the volcano, only relatively large-scale structures are normally recovered. This is relevant to imaging all important magma chambers, which have often been illusive. Recent studies reveal that magma chambers can have large aspect ratio, i.e., a thin body that extends laterally more than a few times its thickness. This extreme geometry adds to the complexity of the imaging problem. In this research, we present a systematic study of how different factors affect the ability to recover a clear image of a magma body and their relative importance in the imaging problem. Classes of synthetic models with different weights of these factors are generated. The models are then used to generate synthetic seismograms using numerical simulations of full wavefield seismic wave propagation. The seismograms are used as the input to various image techniques for recovering images of the synthetic models. Our preliminary results show that even in a non-scattering environment, imaging a magma chamber can be challenging due to, e.g., weak velocity contrast between the magma body and the surrounding rock materials. The imaging problem is compounded by strong scattering. The aim of the work is to understand the limitations of current imaging and acquisition approaches, and to better understand what we can “expect to see”.