Detection of microseismic compressional (P) body waves aided by numerical modeling of oceanic noise sources

Abstract

[1] Among the different types of waves embedded in seismic noise, body waves present appealing properties but are still challenging to extract. Here we first validate recent improvements in numerical modeling of microseismic compressional (P) body waves and then show how this tool allows fast detection and location of their sources. We compute sources at~0.2 Hz within typical P teleseismic distances (30-90°) from the Southern California Seismic Network and analyze the most significant discrete sources. The locations and relative strengths of the computed sources are validated by the good agreement with beam-forming analysis. These 54 noise sources exhibit a highly heterogeneous distribution, and cluster along the usual storm tracks in the Pacific and Atlantic oceans. They are mostly induced in the open ocean, at or near water depths of 2800 and 5600 km, most likely within storms or where ocean waves propagating as swell meet another swell or wind sea. We then emphasize two particularly strong storms to describe how they generate noise sources in their wake. We also use these two specific noise bursts to illustrate the differences between microseismic body and surface waves in terms of source distribution and resulting recordable ground motion. The different patterns between body and surface waves result from distinctive amplification of ocean wave-induced pressure perturbation and different seismic attenuation. Our study demonstrates the potential of numerical modeling to provide fast and accurate constraints on where and when to expect microseismic body waves, with implications for seismic imaging and climate studies.Citation: Obrebski, M., F. Ardhuin, E. Stutzmann, and M. Schimmel (2013), Detection of microseismic compressional (P) body waves aided by numerical modeling of oceanic noise sources,

Observation of continuous microseismic P waves in Asia

“…The P projection of the FK result of the KSRS is in good agreement with the triangulation of back azimuths, based on the polarization analysis at single seismic stations and some of the source locations of Obrebski et al []. The ocean significant wave height (Figure c) indicates that the source region is located between the P projection and the P P projection.…”

“…However, microseismic body waves are not easily observed because Rayleigh waves usually dominate the seismic records [ Koper and Burlacu , ]. Therefore, most studies on microseismic body waves have been based on beamforming or frequency‐wave number (FK) analysis of dense local seismic networks or seismic arrays [e.g., Gerstoft et al , ; Landes et al , ; Zhang et al , ; Koper et al , ; Obrebski et al , ; Pyle et al , ].…”

Source locations of teleseismic P, SV, and SH waves observed in microseisms recorded by a large aperture seismic array in China

“…Behm and Snieder (2013) observed strong Love waves at periods of 0.20-0.67 s in the ambient noise recorded by a small aperture array in southwestern Wyoming. Using a global network of small-to-medium aperture seismic arrays, Koper et al (2010) found that the dominant component of ambient seismic energy at periods of 0.25-2.5 s was L g -a regional distance surface wave that is prominently observed on transverse components of motions (Press and Ewing, 1952). Using short-period (1-5 s) ambient noise correlation with data from arrays in South Africa and Canada, Zhan et al (2010) observed strong S wave Moho reflections (SmS), a phase which is thought to be an important contributor to L g (Cormier and Anderson, 2004).…”

On the shaping factors of the secondary microseismic wavefield

“…The amplitude of land‐recorded seismic noise in relation with the source location and efficiency to transmit seismic energy from the ocean to the continent is still under debate. Evidence of dominant offshore noise sources located in deep ocean environments has been documented by Webb and Constable [], Cessaro [], Stehly et al [], Kedar et al [], and Obrebski et al [] for noise Rayleigh waves and by Gerstoft et al [], Koper and de Foy [], Koper et al [, ], Zhang et al [], Obrebski et al [], and Gualtieri et al [] for noise body waves. Evidence of noise sources associated with coastal reflection in shallow water has been documented by Darbyshire [], Bromirski et al [], Bromirski [], Bromirski and Duennebier [], Bromirski et al [], Essen et al [], Schulte‐Pelkum et al [], Gerstoft and Tanimoto [], Tanimoto [], Yang and Ritzwoller [], and Ardhuin et al [].…”