Observations and origin of Rayleigh-wave amplitude anomalies

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14 Scopus citations

Abstract

This is a report of observations of amplitude anomalies of fundamental-mode Rayleigh waves (R1) between periods of 17 and 100 s. The anomalies are with respect to amplitudes predicted by Rayleigh-wave excitation for a reference earth model and catalogued centroid earthquake source parameters, such as are used in large-scale waveform inversions. The observations indicate that the amplitude anomalies are consistent for nearby recordings of the same event, while there is no obvious relation between the observed anomalies and the paths travelled by the waves. This is in contrast to Rayleigh-wave phase anomalies, which are consistent for similar propagation paths, and hence form the input in many inversions for along-path structure. The observations in this paper show that a similar inversion of intermediate-period amplitude anomalies for along- and near-path structure is not warranted without eliminating source effects, since the amplitude anomalies are dominated by scattering off near-source earth structure and by possible uncertainties in the source parameters. Sensitivity kernels that take the coupling between the moment tensor and displacement field into account demonstrate that Rayleigh-wave amplitude sensitivity is largest near the source. This report argues that the interaction between source-radiated Rayleigh waves and near-source earth structure may not be ignored in amplitude inversion procedures.

Original languageEnglish (US)
Pages (from-to)691-699
Number of pages9
JournalGeophysical Journal International
Volume135
Issue number2
DOIs
StatePublished - 1998

Keywords

  • Amplitude
  • Amplitude anomalies
  • Near field
  • Northridge
  • Propagation corridors
  • Rayleigh wave
  • Rayleigh waves
  • Seismic method
  • Source mechanism

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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