A geophone wireless sensor network for investigating glacier stick-slip motion

Kirk Martinez,Jane K Hart,Philip J Basford,Graeme M Bragg,Tyler Ward,David S Young

doi:10.1016/j.cageo.2017.05.005

Kirk Martinez, Jane K Hart + Show 4 more

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https://doi.org/10.1016/j.cageo.2017.05.005

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Journal: Computers & Geosciences	Publication Date: May 10, 2017
Citations: 17	License type: cc-by

Affiliation: University of Southampton

Abstract

We have developed an innovative passive borehole geophone system, as part of a wireless environmental sensor network to investigate glacier stick-slip motion. The new geophone nodes use an ARM Cortex-M3 processor with a low power design capable of running on battery power while embedded in the ice. Only data from seismic events was stored, held temporarily on a micro-SD card until they were retrieved by systems on the glacier surface which are connected to the internet. The sampling rates, detection and filtering levels were determined from a field trial using a standard commercial passive seismic system. The new system was installed on the Skalafellsjökull glacier in Iceland and provided encouraging results. The results showed that there was a relationship between surface melt water production and seismic event (ice quakes), and these occurred on a pattern related to the glacier surface melt-water controlled velocity changes (stick-slip motion). Three types of seismic events were identified, which were interpreted to reflect a pattern of till deformation (Type A), basal sliding (Type B) and hydraulic transience (Type C) associated with stick-slip motion.

Highlights

The motion of glaciers is highly dependent on the behaviour of meltwater which can influence the rate at which glaciers move by creep (Duval, 1977), reduce friction to allow basal sliding (Weertman, 1957; Iken et al, 1983), and deform underlying sediments (Boulton and Jones, 1979)
We have developed a low power borehole geophone as part of a wireless sensor network, which can be used alongside GPS, subglacial wireless probes (Martinez et al, 2004), temperature and time lapse camera data (Young et al, 2015) to monitor a range of glacial processes
Four geophone nodes were installed within boreholes, to avoid surface seismic noise

Summary

Introduction

The motion of glaciers is highly dependent on the behaviour of meltwater (generated at the glacier surface by atmospheric melting) which can influence the rate at which glaciers move by creep (Duval, 1977), reduce friction to allow basal sliding (Weertman, 1957; Iken et al, 1983), and deform underlying sediments (Boulton and Jones, 1979). Recent studies of continuous measurements of glacier velocities by GPS have indicated that ice motion is commonly episodic and it has been proposed that this reflects stick-slip motion (Bahr and Rundle, 1996; Fischer and Clarke, 1997; Tsai and Ekstrom, 2007; Wiens et al, 2008). Such a process would generate microseismic events (ice quakes) at the glacier bed, which could be measured by seismometers (Weaver and Malone, 1979; Anandakrishnan and Bentley, 1993; Metaxian et al, 2003; Smith, 2006). These environmental sensor networks have enabled a wider range of areas to be monitored for fundamental science and hazard warnings (Szewczyk et al, 2004; Delin et al, 2005; WernerAllen et al, 2005; Hasler et al, 2008; Xu et al, 2014)

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