dinal waves of the earthquakes in the regional zone (QP). This method is based on analyzing the spectra of the
Pn waves that are generated by one source and recorded at two stations; it does not require calculating the spec-
trum of the source and, thus, substantially simplifies the solution of the problem. This method is applicable if
the propagation conditions of the signals between the source and each station are identical, i.e., the signal-to-
station paths lie in the structurally and compositionally similar geological environments. Using the estimates of
the QP-factor and the coefficient of seismic attenuation t*, calculated by the suggested method, we assessed the
classification of the source–station paths as pertaining to the stable (S) or tectonic (T) regions for a number of
earthquakes in Iran and South California and for the underground nuclear explosion of September 25, 2009 in
North Korea. It is shown that the source–station path classification derived in the present study on the basis of
the QP and t* parameters generally agree with the estimates derived in (Kedrov et al., 2010) from the attenuation
coefficient b
of the spectral parameters of recognition of the explosions and earthquakes. In the Appendix, it is demonstrated by the examples of several earthquakes in South California that prompt estimates of the QP
parameter can also be calculated in the time domain from the amplitudes of the Pn waves at a frequency of 3
Hz, which are provided in the Bulletin of the International Data Center in Vienna.