Abstract
ABSTRACTGlacial seismicity provides important insights into glacier dynamic processes. We study the temporal distribution of cryogenic seismic signals (icequakes) at Holtedahlfonna, Svalbard, between April and August 2016 using a single three-component sensor. We investigate sources of observed icequakes using polarization analysis and waveform modeling. Processes responsible for five icequake categories are suggested, incorporating observations of previous studies into our interpretation. We infer that the most dominant icequake type is generated by surface crevasse opening through hydrofracturing. Secondly, bursts of high-frequency signals are presumably caused by repeated near-surface crevassing due to high strain rates during glacier fast-flow episodes. Furthermore, signals related to resonance in water-filled cracks, fracturing or settling events in dry firn or snow before the melt season, and processes at the glacier bed are observed. Amplitude of seismic background noise is clearly related to glacier runoff. We process ambient seismic noise to invert horizontal-to-vertical spectral ratios for a sub-surface seismic velocity model used to model icequake signals. Our study shows that a single seismic sensor provides useful information about seasonal ice dynamics in case deployment of a network is not feasible.
Highlights
Cryo-seismology has become a popular approach to study glacier dynamics
We study the temporal distribution of cryogenic seismic signals at Holtedahlfonna, Svalbard, between April and August 2016 using a single three-component sensor
Our study shows that a single seismic sensor provides useful information about seasonal ice dynamics in case deployment of a network is not feasible
Summary
Cryo-seismology has become a popular approach to study glacier dynamics (see reviews of Podolskiy and Walter, 2016; Aster and Winberry, 2017, and references therein). While strong cryogenic seismic signals, such as those generated by iceberg calving at glaciers and icestreams, are observed at ranges up to regional and even teleseismic distances (e.g. Ekström and others, 2003; O’Neel and others, 2010; Köhler and others, 2015), local glacier microseismicity, mainly related to brittle ice failure (crevasse opening) and basal processes (e.g., stick–slip), is best monitored with stations installed on the ice surface or in shallow boreholes (e.g. West and others, 2010; Walter and others, 2013; Röösli and others, 2014; Helmstetter and others, 2015b). The aim of this study is to show how the analysis of glacier seismicity from a single station (Helmstetter and others, 2015a; Gajek and others, 2017) can generate insight into related glacier surface and dynamic processes, as a cost-effective preparation for larger deployments or in remote areas where a network deployment is not feasible for logistical reasons
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