An automated approach to the location of icequakes using seismic waveform amplitudes

Abstract

AbstractWe adapt from volcano seismology an automated method of locating icequakes with poorly defined onsets and indistinguishable seismic phases, which can be tuned to either body or surface waves. The method involves (1) the calculation of the root-mean-squared amplitudes of the filtered envelope signals, (2) a coarse-grid search to locate the hypocentres of the seismic events using their amplitudes and (3) refinement of hypocentre locations using an iteratively damped least-squares approach. First, we calibrate the adapted method by application to real data, recorded using a network of six passive seismometers, in response to surface explosions in known locations on the western margin of the Greenland ice sheet. Second, we present a seismic modelling experiment simulating rapid supraglacial lake drainage driven hydrofracture through 1 km thick ice. The test reveals horizontal and vertical location uncertainties of ∼121 m and 275 m, respectively. Since seismic emissions from glaciers and ice sheets often have complex waveforms akin to those considered here, our adapted method is likely to have widespread applicability to glaciological problems.