DOI: 10.6084/m9.figshare.28769762
title: Infrasound records at Grey glacier, Patagonia, Chile.

description: A four-element infrasound array was deployed at Grey Glacier (Torres del Paine, Patagonia, Chile) between February 4–11, 2025. This dataset includes infrasound array data recorded by the four sensors in MiniSEED (.mseed) format, along with detection results from array processing provided in MATLAB (.mat) format.The GREY array is composed of four Item differential pressure transducers with a sensitivity of 400 mV/Pa, operating in the frequency band of 0.01–200 Hz and a full-scale pressure range of ±25 Pa. Each sensor is connected to a 24-bit Güralp Minimus digitizer, sampling at 100 Hz and synchronized with GPS time.Here the coordinates of the four sensors and the corresponding file name:Channels Latitude (S) Longitude (W) Altitude (m) FilenameCH1 50,986 73,27372 80 FI.GREY.01.HDFCH2 50,98554 73,27427 80 FI.GREY.02.HDFCH3 50,98583 73,27364 68 FI.GREY.03.HDFCH4 50,98573 73,27385 65 FI.GREY.04.HDF<br>Array processing was performed using multi-channel cross-correlation techniques in the time domain, applied to moving time windows across all array elements, with the same method of Ulivieri et al., 2011. The data were bandpass-filtered between 2 and 20 Hz and analyzed using 5-second moving windows with 90% overlap (shift = 0.5 s). The detections characterize the infrasound wavefield in terms of pressure amplitude, back-azimuth and apparent velocity. The file <i>GREY_detection.mat </i>contains the detections -the result of the array processing. This files contains two structures: <i>data</i> and <i>info</i>, which store processed infrasound detection results and associated processing parameters.Structure: <i>data</i>txx: Detection time in MATLAB datenum format (UTC).prs: Peak acoustic pressure values in the time window of analysis (Pascal).cc: Coherence values, indicating the degree of cross-correlation analysis (0-1).rs: Time Residual values from delays times (samples).Fp: Peak frequency values in the window of analysis (Hz).azz: Back-azimuth (° from North) indicating source direction.slw: Apparent velocity (m/s), related to wave propagation speed on the plane described by the array.Structure:<i> info</i>maxl: Maximum time lag in cross-correlation analysis (samples).freq: Frequency band (Hz) used for filtering the signals.win: Time window length for analysis (seconds).shift: Time step of moving time windows (seconds).minR: Minimum allowed time residual (seconds)sensors: Active sensors used for the array processing (1- active; 0-non active).The MATLAB script <i>detection_per_hour_polar_plot.m</i> visualizes infrasound detection data from the <i>Grey_Detections.mat</i> file, including basic filtering and plotting. It performs the following steps:Data Cleaning and Filtering: Removes spurious detections based on residual (&lt;20), slowness (200–500 s/km), and coherence (&gt;0.1).Applies two levels of coherence filtering: initial and stricter (&gt;0.7) for comparison.Time Series Plots: Plots pressure and back-azimuth over time, before and after filtering. Uses color and marker size to distinguish raw and filtered data.Hourly Detection Histogram: Computes and displays hourly counts of detections on a logarithmic scale.Back-Azimuth Distribution: Creates polar histograms showing the directional distribution of detections, both unfiltered and filtered by high coherence.<br>