Ambient noise surface wave tomography of the Iberian Peninsula: Implications for shallow seismic structure

Abstract

We have obtained high resolution group velocity maps of Rayleigh waves at periods from 8 to 25 seconds across the Iberian Peninsula by cross‐correlating four months of ambient noise data recorded by 40 permanent broadband stations. Group velocity maps accurately image the main structural elements of the Iberian upper crust, including the Iberian Massif, Alpine orogens and major sedimentary basins. The Pyrenees and the Iberian Chain are imaged as relatively high group velocities, in contrast with the Betic Cordillera, which is characterized by low velocities. We explain these low velocities in the Betics by the presence of widespread intramontane basins created in an extensional episode simultaneous with north–south convergence between the African and Eurasian plates. The most prominent low velocity anomalies in the Iberian Peninsula are related to the Guadalquivir Basin, the flysch units of the Campo de Gibraltar, and the sediments of the Gulf of Cadiz.

Ambient Noise Recorded by a Dense Broadband Seismic Deployment in Western Iberia

“…In contrast, hard-rock regions like the CIM present lower noise levels. This separation between outcrops of the CIM and basins is consistent with previous studies based on seismic ambient noise (Villaseñor et al, 2007;Silveira et al, 2013). Northwest Iberia and in general the Atlantic coast are noisier than strictly expected from a geologic point of view, probably due to the stronger microseismic energy reaching coastal stations.…”

“…Current knowledge of the crustal structure under Portugal relies mainly on seismic wide-angle surveys dating back to the 1980s (Victor et al, 1980;Hirn et al, 1982;Díaz et al, 1993). In spite of recent work (Villaseñor et al, 2007;Salah et al, 2011;Monna et al, 2013;Silveira et al, 2013;Palomeras et al, 2014), the lateral extension and interrelation between shallow and deep lithospheric structures have yet to be fully characterized. The impact of tectonic convergence on the structure of the Iberian lithosphere is still unclear, especially to the west, beneath Portugal (e.g., Borges et al, 2001;Cloetingh et al, 2002).…”

Seismic interferometry and ambient noise tomography in the British Isles

“…The tomographic maps they produced agree well with the known geology and previous seismic studies in the region. Since then, surface wave tomography using interferometric Rayleigh and Love waves, commonly referred to as ambient noise tomography, has become an increasingly employed method to successfully produce subsurface velocity models on regional and continental scales in areas such as the United States (Bensen et al, 2008; Lin et al, 2008;Shapiro et al, 2005;Sabra et al, 2005b;Liang and Langston, 2008), Australia (Arroucau et al, 2010;Rawlinson et al, 2008;Saygin and Kennett, 2010), New Zealand (Lin et al, 2007;Behr et al, 2010), Antarctica (Pyle et al, 2010), Iceland (Gudmundsson et al, 2007), China (Zheng et al, 2008;Li et al, 2009;Zheng et al, 2010), South Africa , Europe (Villaseñ or et al, 2007;Yang et al, 2006), South Korea (Cho et al, 2007) the Tibetan Plateau (Yao et al, 2006(Yao et al, , 2008Li et al, 2009), and in this paper, Scotland.…”

Impulse Response of Civil Structures from Ambient Noise Analysis

“…With increases in data quantity, computer power, and disk storage, seismologists recently began analyzing large volumes of ambient noise field data to determine the structure of the Sun (Rickett and Claerbout, 1999) and the Earth (e.g., Sabra et al, 2005;Shapiro et al, 2005;Yao et al, 2006;Villaseñor et al, 2007;Zheng et al, 2008). Aki (1957) first proposed a method to study subsurface phase velocity beneath a seismic array using spatial autocorrelations.…”