The European Infrasound Bulletin

Christoph Pilger,Sven Peter Näsholm,Constantin Ionescu,Steven J Gibbons ,E Marchetti ,E Blanc ,Läslo Evers ,Nicolas Brachet,Tereza Šindelářová ,Tormod Kværna ,Daniela Ghica,J Ole Ross,Maurizio Ripepe,Ludwik Liszka,Alexis Le Pichon,Julien Vergoz,Lars Ceranna,Pieter Smets,Johan Kero,Yochai Ben Horin,Pierrick Mialle

doi:10.1007/s00024-018-1900-3

Abstract

The European Infrasound Bulletin highlights infrasound activity produced mostly by anthropogenic sources, recorded all over Europe and collected in the course of the ARISE and ARISE2 projects (Atmospheric dynamics Research InfraStructure in Europe). Data includes high-frequency (> 0.7 Hz) infrasound detections at 24 European infrasound arrays from nine different national institutions complemented with infrasound stations of the International Monitoring System for the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Data were acquired during 16 years of operation (from 2000 to 2015) and processed to identify and locate ∼ 48,000 infrasound events within Europe. The source locations of these events were derived by combining at least two corresponding station detections per event. Comparisons with ground-truth sources, e.g., Scandinavian mining activity, are provided as well as comparisons with the CTBT Late Event Bulletin (LEB). Relocation is performed using ray-tracing methods to estimate celerity and back-azimuth corrections for source location based on meteorological wind and temperature values for each event derived from European Centre for Medium-range Weather Forecast (ECMWF) data. This study focuses on the analysis of repeating, man-made infrasound events (e.g., mining blasts and supersonic flights) and on the seasonal, weekly and diurnal variation of the infrasonic activity of sources in Europe. Drawing comparisons to previous studies shows that improvements in terms of detection, association and location are made within this study due to increasing the station density and thus the number of events and determined source regions. This improves the capability of the infrasound station network in Europe to more comprehensively estimate the activity of anthropogenic infrasound sources in Europe.

Highlights

Infrasound is low-frequency sound below the threshold of human hearing, i.e., below 20 Hz
This study focuses on anthropogenic infrasound signatures and the main interest is on high-frequency (HF) infrasound above 0.7 Hz
This study considers a total of 24 infrasound arrays in and around Europe to detect and to locate infrasound events mostly from anthropogenic sources

Summary

Introduction

Infrasound is low-frequency sound below the threshold of human hearing, i.e., below 20 Hz. Various sources either of natural or of anthropogenic origin generate sound with infrasonic frequency components (Campus and Christie 2010; Hedlin et al 2012), mostly when explosive or eruptive processes are involved. Rocket launches, military and industrial blasts, volcanic activity and meteoroid entries are among the strongest sources of infrasound (Mc Laughlin et al 2000; Stevens et al 2002; Ceranna et al 2009; Matoza et al 2011; Marchetti et al 2013; Le Pichon et al 2013; Pilger et al 2015). Sources with lower dominant frequencies, e.g., mountain waves, microbaroms, earthquakes, volcanoes and meteoroids are mostly suppressed by this choice

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