Interpreting cross-correlations of one-bit filtered seismic noise

Shravan Hanasoge, Michał Branicki

Research output: Contribution to journalArticle

Abstract

Seismic noise, generated by oceanic microseisms and other sources, illuminates the crust in a manner different from tectonic sources, and therefore provides independent information. The primary measurable is the two-point cross-correlation, evaluated using traces recorded at a pair of seismometers over a finite-time interval. However, raw seismic traces contain intermittent large-amplitude perturbations arising from tectonic activity and instrumental errors, which may corrupt the estimated cross-correlations of microseismic fluctuations. To diminish the impact of these perturbations, the recorded traces are filtered using the non-linear one-bit digitizer, which replaces the measurement by its sign. Previous theory shows that for stationary Gaussian-distributed seismic noise fluctuations one-bit and raw correlation functions are related by a simple invertible transformation. Here we extend this to show that the simple correspondence between these two correlation techniques remains valid for non-stationary Gaussian and a very broad range of non-Gaussian processes as well. For a limited range of stationary and non-stationary Gaussian fluctuations, we find that one-bit filtering performs at least as well as spectral whitening. We therefore recommend using one-bit filtering when processing terrestrial seismic noise, with the substantial benefit that the measurements are fully compatible with current theoretical interpretation (e.g. adjoint theory). Given that seismic records are non-stationary and comprise small-amplitude fluctuations and intermittent, large-amplitude tectonic/other perturbations, we outline an algorithm to accurately retrieve the correlation function of the small-amplitude signals.

Original languageEnglish (US)
Pages (from-to)1811-1830
Number of pages20
JournalGeophysical Journal International
Volume195
Issue number3
DOIs
StatePublished - Dec 1 2013

Fingerprint

seismic noise
cross correlation
Tectonics
tectonics
perturbation
microseisms
Seismographs
seismographs
analog to digital converters
crusts
seismograph
intervals
crust
Processing

Keywords

  • Theoretical seismology
  • Wave propagation
  • Wave scattering and diffraction

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

Cite this

Interpreting cross-correlations of one-bit filtered seismic noise. / Hanasoge, Shravan; Branicki, Michał.

In: Geophysical Journal International, Vol. 195, No. 3, 01.12.2013, p. 1811-1830.

Research output: Contribution to journalArticle

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