Seismic Noise Characterization in Proximity to Strong Microseism Sources in the Northeast Atlantic

Abstract

In this study, we present microseism data measured in Ireland with a dense network of broadband seismometers. Ireland is exposed to one of the most active ocean‐wave climates in the world and consequently enjoys relatively high levels of microseism activity, providing an excellent opportunity to study the generating sources close up. The main goal of this paper is to quantify the noise field in close proximity to its sources and to consider its characteristics in the context of current microseism generation models. An additional goal is to provide a baseline noise model for Ireland to which current and future seismic station data can be compared, helping to evaluate and improve station (and hence network) quality. We calculate seismic power spectral densities and power density functions to obtain frequency‐dependent statistics of the noise field. This leads us to present an Irish noise model that we compare with the global Peterson new high‐ and low‐noise models and the results of other published regional studies. We investigate the geographical variation of microseisms in Ireland by producing annual noise maps and time‐lapse noise maps for a two‐day storm period in April 2012. The time‐lapse maps present the seismic noise field alongside ocean‐wave parameters and provide instructive illustrations of the relationship between ocean waves and seismic noise measured on land. The recorded noise fields are in agreement with current source models of primary and secondary microseism generation. We observe prominent very‐short‐period microseisms in the 0.5–1 s period range. This observation could find practical application in the areas of marine renewable energies and flood defense systems. Online Material: Table of data of the Ireland mode low‐noise model (IMLNM) and the Ireland mode high‐noise model (IMHNM).