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Titolo:
SEISMIC-WAVE SLOWNESS-VECTOR ESTIMATION FROM BROAD-BAND ARRAY DATA
Autore:
CHIOU SJ; BOLT BA;
Indirizzi:
UNIV CALIF BERKELEY,DEPT GEOL & GEOPHYS,SEISMOG STN BERKELEY CA 94720
Titolo Testata:
Geophysical journal international
fascicolo: 2, volume: 114, anno: 1993,
pagine: 234 - 248
SICI:
0956-540X(1993)114:2<234:SSEFBA>2.0.ZU;2-C
Fonte:
ISI
Lingua:
ENG
Soggetto:
SIGNALS; ARRIVAL; LASA;
Keywords:
FREQUENCY-WAVE-NUMBER SPECTRA; HIGH RESOLUTION; SEISMIC ARRAY ANALYSIS; SLOWNESS ESTIMATION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
33
Recensione:
Indirizzi per estratti:
Citazione:
S.J. Chiou e B.A. Bolt, "SEISMIC-WAVE SLOWNESS-VECTOR ESTIMATION FROM BROAD-BAND ARRAY DATA", Geophysical journal international, 114(2), 1993, pp. 234-248

Abstract

In this paper, a new procedure, called the coherent-signal-subspace method (CSS), for broad-band multiple-signal detection and slowness-vector estimation is discussed and applied to a surface seismographic array. The major improvements in estimation accuracy and resolution givenby the CSS method, which was developed in the fields of radar and sonar, result from the use of extended-frequency components within the data bandwidth and a high-resolution algorithm. The former is made possible through a frequency focusing transformation that for each frequency component corrects for the phase-delay difference between that frequency and a reference frequency omega0. The result is the condensation of a broad frequency band into a narrow band at omega0. The high resolution algorithm used in the CSS method is the MUSIC (multiple signal characterization; Schmidt 1986) algorithm, which is based on the eigen property of the data cross-covariance matrix that the signal phase-delay vectors lie within the subspace spanned by the signal eigenvectors. The frequency transformation improves the singularity of the estimated cross-covariance matrix and the accuracy of the estimated signal eigenvectors at omega0, which are often serious problems in seismic arrayanalysis. Combination of these two features in CSS ensures a superiorarray performance over the widely used beam steering and minimum-variance (Capon 1969) methods. Approximate methods to estimate the mean and variance of the estimated slowness vector are also presented in thispaper. The estimation biases introduced by deterministic arrival-timedeviations of array data from a plane wavefront are derived for the single signal case. It is shown that, in the case of a single signal, significant reduction in the estimation bias may be achieved if a largeenough reference frequency is used in the CSS method. Finally, with observed and synthetic ground motions, tests are performed to illustrate the utility of CSS in resolving two closely separated signals. In both cases, CSS successfully resolved two separate peaks at almost the correct slowness vectors, while the conventional beam steering and minimum variance estimation methods either failed to resolve the two signals or gave an incorrect slowness estimate.

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Documento generato il 01/12/20 alle ore 19:33:32