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Titolo:
ESTIMATES OF UPPER-CRUSTAL HETEROGENEITY IN THE BALTIC SHIELD FROM SEISMIC SCATTERING AND BOREHOLE LOGS
Autore:
LINE CER; HOBBS RW; SNYDER DB;
Indirizzi:
BIRPS,BULLARD LABS,MADINGLEY RISE CAMBRIDGE CB3 0EZ ENGLAND BIRPS,BULLABBULLARD LABS CAMBRIDGE CB3 0EZ ENGLAND MOBIL N SEA LTD LONDON WC2A 2EB ENGLAND
Titolo Testata:
Tectonophysics
fascicolo: 1-4, volume: 286, anno: 1998,
pagine: 171 - 183
SICI:
0040-1951(1998)286:1-4<171:EOUHIT>2.0.ZU;2-D
Fonte:
ISI
Lingua:
ENG
Soggetto:
UPPER MANTLE; P-WAVES; LASA; FLUCTUATIONS; ATTENUATION; EARTHQUAKE; NORSAR; TIME;
Keywords:
CORRELATION DISTANCE; HETEROGENEITY; SCATTERING; STOCHASTIC;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
36
Recensione:
Indirizzi per estratti:
Citazione:
C.E.R. Line et al., "ESTIMATES OF UPPER-CRUSTAL HETEROGENEITY IN THE BALTIC SHIELD FROM SEISMIC SCATTERING AND BOREHOLE LOGS", Tectonophysics, 286(1-4), 1998, pp. 171-183

Abstract

Constraints on small-scale heterogeneity in the upper crust of the Baltic Shield were obtained from stochastic modelling of a variety of seismic data from the BABEL and Siljan Ring surveys. A non-linear least-squares inversion scheme was applied to wavefield fluctuations in seismic reflections to obtain statistical parameters of the medium throughwhich the wave energy propagated. The reflections are from dolerite sills intruded at depths of 6-12 km into the Palaeoproterozoic upper crust of the central Baltic Shield. Analysis of the BABEL data set reveals that the upper crust is a weakly scattering stochastic medium, withvelocities characterised by an exponential autocorrelation function with a correlation length of 150 +/- 50 m and rms velocity perturbationof 1.5 +/- 0.5%. Further inversions show that most of the scattering occurs within the upper few kilometres of the crust. Analysis of the Siljan seismic data set reveals heterogeneity with length scales of 210+/- 50 m and a velocity perturbation of about 1.0%. The autocovariance and power spectrum of the sonic log, and studies of frequency-dependent Q in VSP data, from the Gravberg-1 borehole, give consistent estimates of basement heterogeneity. The upper crust in this region is characterised by a correlation distance of 35 +/- 5 m and rms velocity perturbation of 4-6% in the uppermost 1-2 km of crust, associated with near-surface fracturing, and a correlation distance of 140 +/- 50 m and rms velocity perturbation of 1.5 +/- 0.5% in the uppermost 6-8 km, associated with compositional heterogeneity. (C) 1998 Elsevier Science B.V. All rights reserved.

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Documento generato il 01/12/20 alle ore 19:46:28