Seismic attenuation in Iberia using the coda-<i>Q</i>method

Payo, G.; Badal, José; Cañas, J. A.; Corchete, V.; Pujades, L. G.; Serón, Francisco J.

doi:10.1111/j.1365-246x.1990.tb01758.x

Cited by 14 publications

(4 citation statements)

References 18 publications

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“…:.,Hercynian region \ Low coda Q values in Iberia are located in the Betic region and the Pyrenees, while high coda Q values are found in northwestern Iberia Payo et al 1990). L, attenuation studies in Iberia have established that in the Granada Basin (in the middle of the Betic region) the anelastic attenuation coefficients are about twice those for S-SE Iberia.…”

Section: Geological a N D Geophysical Settingmentioning

confidence: 98%

Improvements in the knowledge of the anelastic structure of the Iberian Peninsula from seismic data of the ILIHA project

Caselles¹,

Cañas²,

Pujades³

et al. 1997

Geophysical Journal International

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S U M M A R YAttenuation coefficients of Rayleigh waves propagating across the Iberian Peninsula, and quality factor models were obtained for different two-station great-circle paths. The data used were long-period wave trains contained in the seismograms provided by the ILIHA array installed in the peninsula in the 1980s. More than 300 seismograms were analysed to obtain 14 sets of similar paths, consisting of either paths totally included in one of the four pure tectonic regions or mixed paths crossing several regions. We used the two-station method lo determine attenuation parameters (yR) and then an inversion method to derive Qg' models. The attenuation coefficients of seismic energy in the 10-120 s range are in the range 2.8 x 10p3-0.1 x km-l, and correlate well with both previous results obtained from analogue WWSSN and most seismogeotectonic characteristics of Iberia. The Qa models obtained also agree with a few models for Iberia determined earlier, and they show significant variations from one region to another. As a general feature, the y-values are higher in the active seismotectonic regions (typical maximum of 2.6 x lop3 km-') than in the more stable ones (typical maximum of 1.4 x Moreover, the maximum of Q;' in the active regions (145 x 10-3-120 x In general, both the regionalized attenuation coefficients of Rayleigh waves and the quality factor models exhibit a good agreement with previously published L, wave attenuation and coda Q distribution patterns in Iberia.

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Section: Geological a N D Geophysical Settingmentioning

confidence: 98%

Improvements in the knowledge of the anelastic structure of the Iberian Peninsula from seismic data of the ILIHA project

Caselles¹,

Cañas²,

Pujades³

et al. 1997

Geophysical Journal International

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“…t is the lapse time from the origin time and f p is the predominant frequency. f p may be obtained both in the temporal domain from simple readings in the seismic records or in the frequency domain by taking the Fourier transform of the signal contained in a small time window centred at t (Payo et al 1990); in this case fp is the frequency having maximum energy in the analysed window. I is the instrument magnification curve and I' is its first derivative with respect to the frequency.…”

Section: Qo Distributionmentioning

confidence: 99%

Intrinsic and scattering attenuation from observed seismic codas in the Almeria Basin (southeastern Iberian Peninsula)

Pujades¹,

Ugalde²,

Cañas³

et al. 1997

Geophysical Journal International

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S U M M A R YThe anelastic attenuation in the Almeria Basin (southeastern Iberian Peninsula) is investigated by using seismic data collected during the summer of 1991. A multiple-lapse time-window analysis is applied to high-frequency seismograms corresponding to 20 shallow seismic events with low magnitudes ( m 12.5) and distances less than 71 km, recorded at six short-period seismographic stations. We have constructed corrected geometrical spreading and normalized energy-distance curves for the region over the frequency bands 1-2,2-4,4-8,8-14 and 14-20 Hz. A theoretical model for body-wave energy propagation in a randomly heterogeneous medium has been employed to interpret the observations. Two parameters describe the medium in this model: the scattering attenuation coefficient qs = kQ3 ' and the intrinsic attenuation coefficient yI = kQ, ', where k is the wavenumber and Qr1 and Q, are the intrinsic and scattering attenuation respectively. This model assumes that scattering is isotropic, including all orders of multiple scattering, and predicting the spatial and temporal energy distribution of seismic energy. A least-squares fitting procedure has been used to find the best estimates of the model parameters. The analysis of the spectral amplitude decay of coda waves has provided coda Q,' values at the same frequency bands. The results obtained show that Q, ', Q2 ' and Q, ' decrease with increasing frequency; for frequencies lower than 3 Hz scattering attenuation is stronger than intrinsic absorption and coda Q, ' takes values between intrinsic and total attenuation, being very close to Qy'. Q;' is more frequency-dependent than Q, ; for frequencies greater than 3 Hz intrinsic absorption is the dominant attenuation effect and Q, and Q3 have significant frequency dependence. In order to correlate the results obtained with the major geological and tectonic features of the region, a geotectonic framework for the area is provided and the predominant frequency decay in coda waves is analysed in order to obtain the coda Q frequency dependence following a power law Qc = Qo( f/fo)", where fo is a reference frequency. In this way we have obtained regionalized values of coda Q at 1 Hz (Qo). Finally, a first-order approach has allowed us to obtain intrinsic and scattering quality factors from the obtained QO and v values, leading us to obtain tentative distributions of Q,, Qs and QO at 1 Hz for the area. The derived intrinsic and scattering quality-factor distributions are in good agreement with the tectonic history and the main geological features of the region. Large scattering and intrinsic attenuation (Qs N 80, QI -100) are found in the sedimentary Neogene and Quaternary basin, while scattering is the dominant effect in the old Palaeozoic rocks of the mountains (Qs -200, QI -1000).Intrinsic Q shows a higher sensitivity to the geological characteristics than scattering Q.

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“…Preliminary studies concerning the anelastic structure and based on wavetrains recorded at analogical WWSSN stations can be found in CANAS et al (1988CANAS et al ( , 1991, PAYO et al (1990) and PUJADES et al (1990). More recently, CASELLES et al (1997) and LANA et al (1999) have achieved regionalised models of Q À1 b structure for the Iberian Peninsula.…”

Section: Introductionmentioning

confidence: 99%

Elastic-anelastic Regional Structures for the Iberian Peninsula Obtained from a Rayleigh Wave Tomography and a Causal Uncoupled Inversion

Martínez

Lana

Caselles

et al. 2005

Pure appl. geophys.

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The elastic and anelastic structure of the lithosphere and asthenosphere of the Iberian Peninsula is derived by means of tomographic techniques applied to local phase and group velocities and local attenuation coefficients of Rayleigh wave fundamental mode. The database consists of surface wavetrains recorded at the broadband stations located in the Iberian Peninsula on the occasion of the ILIHA project. Path-averaged phase and group velocities and attenuation coefficients were previously obtained by standard filtering techniques of surface wavetrains and, subsequently, local dispersion curves were computed according to the Yanovskaya-Ditmar formulation. First, a principal component analysis (PCA) and the average linkage (AL) clustering algorithm are applied to these local values in order to classify the Iberian Peninsula in several rather homogeneous domains from the viewpoint of the similarity of the corresponding local dispersion curves, without previous seismotectonic constraints. Second, averaged phase and group velocities and attenuation coefficients representing each homogeneous region are used to derive the respective elastic and anelastic models of the lithosphere and asthenosphere. This purpose is achieved by using the uncoupled causal inversion of phase and group velocities and attenuation coefficients. The main features of the homogeneous regions are discussed by taking as reference the Hercynic, Alpine and Neogene domains of the Iberian Peninsula, and two questions affecting the reliability of the elastic-anelastic models are revised. First, the coherence of the shear-velocity and Q À1 b models obtained by causal uncoupled inversion for each region is analysed. Second, the influence of the causal phase and group velocities on the shear-velocity models is evaluated by comparing elastic and anelastic models derived from causal uncoupled inversion with those deduced from non-causal inversion.

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Seismic attenuation in Iberia using the coda-Qmethod

Cited by 14 publications

References 18 publications

Improvements in the knowledge of the anelastic structure of the Iberian Peninsula from seismic data of the ILIHA project

Improvements in the knowledge of the anelastic structure of the Iberian Peninsula from seismic data of the ILIHA project

Intrinsic and scattering attenuation from observed seismic codas in the Almeria Basin (southeastern Iberian Peninsula)

Elastic-anelastic Regional Structures for the Iberian Peninsula Obtained from a Rayleigh Wave Tomography and a Causal Uncoupled Inversion

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