Ocean wave height determined from inland seismometer data: Implications for investigating wave climate changes in the NE Pacific

Abstract

Abstract. Knowing the wave climate along the California coast is vital from the perspectives of climatological change and planning shore protection measures. Buoy data indicate that the wave climate is very similar along much of the California coast. We show that elements of the wave climate can be accurately reconstructed using near-coastal inland broadband seismometer data. Such reconstructions are possible because swell approaching the coast generates pressure fluctuations that are locally transformed into seismic waves at the seafloor that propagate inland and are detectable by land-based seismometers. Buoy and seismometer data show that most of the microseism energy recorded inland near the coast is generated from wave events at nearby coastal locations. A site-specific, empirically derived seismic-to-wave transfer function is demonstrated to be applicable to seismic data from the same location for any year. These results suggest that ocean wave heights estimated from near-coastal broadband seismometer data are sufficiently reliable for monitoring the coastal wave height when buoy data are unavailable, provided that adequate simultaneous nearby buoy measurements are available to calibrate the seismometer data. The methodology presented here provides an important tool that allows the investigation of potential wave climate changes from reconstructions using archived seismic data collected since the 1930s.

Seismic monitoring of western Pacific typhoons

“…Some studies propose that ground motions are induced in shallow water regions like continental shelves (Friedrich et al 1998;Bromirski et al 1999;Bromirski and Duennebier 2002;Bromirski 2001;Essen et al 2003;Rhie and Romanowicz 2006;Kedar and Webb 2005; Bromirski and Gerstoft 2009). Other scientists propose that the source region is under or trailing a typhoon (Cessaro 1994;Stehly et al 2006;Chevrot et al 2007;Kedar et al 2008;Gerstoft et al 2008;Koper and de Foy 2008;Landes et al 2010;Chi et al 2010).…”

Global trends in extremal microseism intensity

“…[6] Ocean wave and consequent microseism spectral amplitudes decline rapidly at periods longer than 25 s [Bromirski et al, 1999;Bromirski and Duennebier, 2002], but earthquake transients are much more broadband ( Figure S1). Earthquake-dominated and microseism-dominated spectra can thus be reliably discriminated via spectral detection.…”

“…Microseism metrics from global networks of long-running calibrated seismic stations are thus an integrative complement to other wave intensity monitors such as ocean buoys [Bromirski and Duennebier, 2002;Aster et al, 2008] and iceberg-or iceshelf-deployed seismometers [MacAyeal et al, 2006;Bromirski et al, 2010]. Because most microseism energy observed on land is coastally generated [Bromirski et al, 1999;Bromirski, 2001;Bromirski and Duennebier, 2002;Gerstoft and Tanimoto, 2007], extremes in microseism energy strongly correlate with extremes in near-shore wave energy [e.g., Aster et al, 2008].…”

“…SFMs are generated at the causative ocean swell period via direct pressure fluctuations at the ocean bottom in shallow water resulting from breaking and/or shoaling waves [Hasselmann, 1963]. The amplitude of the much stronger DFM is proportional to the square of standingwave components of the ocean wave field [Longuett-Higgins, 1950], such as where incoming swell interacts with coastal reflections [Bromirski et al, 1999]. Intense cyclonic lowpressure storm systems have steep pressure gradients that cause strong surface winds that transfer atmospheric energy into ocean swell [Pierson and Moskowitz, 1964], and subsequently into microseism energy.…”

Wave height quantification using land based seismic data with grammatical evolution

“…Both Bromirski [6] and Ardhuin et al [7] determined ocean wave heights at a buoy located off the Californian coast using seismic data from a single inland station quite successfully. Empirical methods were used [6] for this inversion which required time series information for the buoy including directional properties of the ocean wave field and microseism source location.…”