Relation between ocean wave activity and wavefield of the ambient noise recorded in northern Poland

Simone Lepore,Marek Grad

doi:10.1007/s10950-020-09963-y

Simone Lepore, Marek Grad

Open Access

https://doi.org/10.1007/s10950-020-09963-y

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Abstract

The temporal and spatial variations of the wavefield of ambient noise recorded at ‘13 BB star’ array located in northern Poland were related to the activity of high, long-period ocean waves generated by strong storms in the Northern Indian Ocean, the Atlantic Ocean, and the Northern Pacific Ocean between 2013 and 2016. Once pre-processed, the raw noise records in time- and frequency-domains, and spectral analysis and high-resolution three-component beamforming techniques were applied to the broadband noise data. The power spectral density was analysed to quantify the noise wavefield, observing the primary (0.04–0.1 Hz) microseism peak and the splitting of the secondary microseism into long-period (0.2–0.3 Hz) and short-period (0.3–0.8 Hz) peaks. The beam-power analysis allowed to determine the changes in the azimuth of noise sources and the velocity of surface waves. The significant wave height, obtained by combining observed data and forecast model results for wave height and period, was analysed to characterise ocean wave activity during strong storms. The comparison of wave activity and beam-power led to distinguish the sources of Rayleigh and Love waves associated to long-period microseisms, of short-period microseisms, and of primary microseisms. High, long-period ocean waves hitting the coastline were found to be the main source of noise wavefield. The source of long-period microseisms was correlated to such waves in the open sea able to reach the shore, whereas the source of primary microseisms was tied to waves interacting with the seafloor very close to the coastlines. The source of short-period microseisms was attributed to strong storms constituted of short-period waves not reaching the coast.

Highlights

The description of spatial and temporal variations of the ambient noise wavefield is fundamental for many aspects of seismology
The purpose of the present paper is to relate the temporal and spatial variations of the noise wavefield in northern Poland with the hitting on the coast of high, long-period ocean waves generated by strong storms in the Atlantic Ocean, the Northern Indian Ocean, and the Northern Pacific Ocean (Fig. 1a)
The temporal and spatial variations of the wavefield of the ambient noise, recorded at ‘13 BB star’ array located in northern Poland from July 2013 to September 2016, was related to hitting on the coast of high, long-period ocean waves generated by strong storms in the Atlantic Ocean, the Northern Indian Ocean, and the Northern Pacific Ocean

Summary

Introduction

The description of spatial and temporal variations of the ambient noise wavefield is fundamental for many aspects of seismology. 0.1 Hz, the noise, identified as the primary microseism, is produced by ocean waves interacting with the seafloor near the coastlines (swells) (Longuet-Higgins 1950; Hasselmann 1963; Bromirski and Duennebier 2002; Koper et al 2009; Kurrle and Widmer-Schnidrig 2010; Ardhuin et al 2011; Stutzmann et al 2012; Bromirski et al 2013; Sergeant et al 2013; Gualtieri et al 2015; Lepore and Grad 2018). The source amplitude and modulation, vary with frequency and bathymetry (Longuet-Higgins 1950; Sergeant et al 2013)

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