Source pulse enhancement by deconvolution of an empirical Green's function

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Abstract
Observations of the earthquake source‐time function are enhanced if path, recording‐site, and instrument complexities can be removed from seismograms. Assuming that a small earthquake has a simple source, its seismogram can be treated as an empirical Green's function and deconvolved from the seismogram of a larger and/or more complex earthquake by spectral division. When the deconvolution is well posed, the quotient spectrum represents the apparent source‐time function of the larger event. This study shows that with high‐quality locally recorded earthquake data it is feasible to Fourier transform the quotient and obtain a useful result in the time domain. In practice, the deconvolution can be stabilized by one of several simple techniques.In this paper, the method is implemented and tested on high‐quality digital recordings of aftershocks of the Jan. 9, 1982 Miramichi (New Brunswick) earthquake. In particular, seismograms from a Jan. 17 aftershock (017 13:33 GMT, local mag.=3.5) exhibit path or site effects which complicate the determination of source parameters. After deconvolution, the apparent far‐field source of this event is a simple pulse in displacement with duration ≈ 0.07 second for both P and S.

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