Localization of Antarctic ice breaking events by frequency dispersion of the signals received at a single hydroacoustic station in the Indian Ocean

Abstract

Transient acoustic signals from Antarctic ice cracking and breaking events, featuring significant frequency dispersion, were observed at the hydroacoustic stations deployed in the Indian Ocean as part of the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty. Based on a comparison with numerical predictions, the measured dispersion characteristics were used to estimate the range between ice events and the receiver. Combined with the bearing capability of the IMS stations, these estimates allow us to locate ice events from a single hydroacoustic station. An analysis of range estimation errors due to uncertainty of the measured time-frequency structure of signal arrivals and due to variations of the sound speed profiles was also conducted. The analysis showed that, for the typical ice events, the location accuracy from a single hydroacoustic station was of the same order, as that determined from an intersection of bearings from two remote stations. This localization method was examined by analyzing an ice event detected at both the Cape Leeuwin IMS station and a sea noise logger deployed off the Antarctic shelf.

A Two-Station Seismic Method to Localize Glacier Calving

“…Pfeffer et al, 2008;Meier et al, 2007). Calving glaciers can rapidly advance and retreat in response to minimal climate signals, which can rapidly change the sea level (Meier and Post, 1987;Nick et al, 2013). A better understanding of calving processes is vital to developing accurate predictions of sealevel rise.…”

Using hydroacoustic stations as water column seismometers

“…[4] The International Monitoring System (IMS) is a valuable source for studying a broad range of scientific problems in the oceans: monitoring acoustics of nuclear explosions [Lawrence and Grenard, 1998], estimating the rupture length of the December 2004 Great Sumatra earthquake [de Groot-Hedlin, 2005], T-wave propagation [Tolstoy and Bohnenstiehl, 2006], shipping noise [Tolstoy and Bohnenstiehl, 2002], seismo-acoustics of ice sheets [Chapp et al, 2005], and localization of Antarctic ice-breaking events [Li and Gavrilov, 2008]. These studies, however, are at frequencies above 1 Hz and are predominantly of T-waves, which are generated by earthquakes along the plate margins [Graeber and Piserchia, 2004].…”

Calving localization at Helheim Glacier using multiple local seismic stations

“…Another method to locate calving events, known as beam-forming, uses the seismic signals recorded on several array stations to determine the time delay associated with a back azimuth that aligns the signals coherently (Koubova, 2015). A more recent method for localizing calving events is the use of frequency dispersion of surface waves, which uses a regional array (100-200 km away) of hydroacoustic stations to estimate a distance between the event and detector and combines this with an azimuth (determined from the P waves) to create a unique intersection (Li and Gavrilov, 2008), as the stations are sufficiently far to separate different seismic wave components. This method has a similar precision to using intersecting azimuths from two remote stations, which is enough to identify at which glacier the calving occurred, but not enough to localize the event within the glacier.…”