Dynamic Imaging of Glacier Structures at High‐Resolution Using Source Localization With a Dense Seismic Array

Abstract

Dense seismic array monitoring combined with advanced processing can help retrieve and locate a variety of seismic sources with unprecedented resolution and spatial coverage. We present a methodology that goes beyond classical localization algorithms through gathering various types of sources (impulsive or continuous) using a single scheme based on a gradient‐descent optimization and evaluating different levels of phase coherence. We apply our methodology on an Alpine glacier and demonstrate that we can retrieve the dynamics of active crevasses with a metric resolution using sources associated with high phase coherence; the presence of diffracting materials (e.g., rocks) trapped in transverse crevasses using sources with moderate phase coherence; and the two‐dimensional time evolution of the subglacial hydrology system using sources with low phase coherence. Our study highlights the strength of using an appropriate and systematic seismological approach to image a wide range of subsurface structures and phenomena in settings with complex wavefields.

Mapping Glacier Basal Sliding Applying Machine Learning

“…We extracted information from an extensive beamforming catalog which was developed using an advanced MFP localization scheme based on a gradient‐decent optimization that meets the challenging, seismically “loud” environment. A complete detailed description on the methodology and the MFP implementation can be found in (Nanni et al., 2022). We used four sub‐catalogs with center frequencies of 5, 10, 15, and 20 Hz.…”

“…Matched field processing (MFP) is the natural extension of plane wave beamforming and yields for the location of seismic noise sources in range, depth and azimuth by analyzing spherical waves in the close environment of the underlying seismic array (Bucker, 1976). The approach was originally developed in ocean acoustics (Baggeroer et al, 1993;Kuperman & Turek, 1997), but a broad spectrum of applications can be found in environmental seismology to study near-surface processes on the exploration scale (Corciulo et al, 2012;Cros et al, 2011;Umlauft & Korn, 2019;Vandemeulebrouck et al, 2010) and the rapidly emerging special research field of cryoseismology to better understand dynamics within for example, Alpine glacial ice (Nanni et al, 2021(Nanni et al, , 2022Umlauft et al, 2021;Walter et al, 2015Walter et al, , 2020.…”

Mapping glacier basal sliding with machine learning

“…Matched field processing (MFP) is the natural extension of plane wave beamforming and yields for the location of seismic noise sources in range, depth and azimuth by analysing spherical waves in the close environment of the underlying seismic array [45]. The approach was originally developed in ocean acoustics [46,47], but a broad spectrum of applications can be found in environmental seismology to study near-surface processes on the exploration scale [48,49,50,51] and the rapidly emerging special research field of cryoseismology to better understand dynamics within e.g., Alpine glacial ice [52,22,27,53,54].…”

“…We extracted information from an extensive beamforming catalog which was developed using an advanced matched field processing localization scheme based on a gradient-decent optimization that meets the challenging, seismically "loud" environment. A complete detailed description on the methodology and the MFP implementation can be found in [54]. We used four sub-catalogues with center frequencies of 5 Hz, 10 Hz, 15 Hz and 20 Hz.…”

“…The accumulation zone of temperate based glacial ice is typically less active than the ablation zone. The ablation zone, however, is characterized by a multitude of physical processes such as crevasse formation, meltwater flow or avalanches and rockfalls provoked by increasing temperatures in lower altitudes[54]. Even though the geodetic observations show coherent behavior across the network and the glacier's extent (Fig.A.13), model predictions of distant stations which were situated in the accumulation zone may be challenged due to regime differences.…”