Geophysics and Tectonics Seminar spring-2021

Volcanoes are notoriously difficult structures to image from a seismic perspective, owing to their often pronounced topography, complex edifices composed of ash, ice, rock, air pockets, fluids, and various melt related products, and their consequential high attenuation and low scattering mean free paths. Conventional methods relying on direct arrivals, such as P-wave tomography, thus suffer from diffuse seismic envelopes due to strong multiple scattering as well as prohibitive source-station ray coverage inherent in their geometries. In recent years, seismic interferometry has presented an intriguing way to both leverage structures that are particularly complex and expand ray coverage to include any interstation path within the medium of interest. Here, we describe an approach, from basic concepts all the way to cutting edge results, that exploits pervasive distributed icequake activity to reconstruct inter-station impulse responses on Mt Erebus, Antarctica. We subsequently reconstruct a reflectivity image for the magmatic system, all the while significantly pushing back the single scattering limit inherent in classic methodologies. This approach is applicable for any strongly scattering medium in which distributed ambient seismicity exists, and will be generalized at other glaciated North American volcanoes in the future.