Quality Control Metrics for Cepstral Analysis with Homomorphic Deconvolution

In this study we describe an improved cepstral method that can be used for estimating the depth (<2 km) of very shallow earthquakes and explosions. Knowing the depth is important, especially for explosions, for which the best depth indicator, the seismic depth phase (pP) is often not easily discernible from the first arrival (P). Unlike the previous cepstral studies, our method utilizes the power and complex complex cepstrum, and homomorphic deconvolution (HD). The use of quality control metrics increases analyst confidence that a plausible signal–echo delay pair was identified. The metrics quantify liftering adequacy and success of the HD. The most important criteria for successful HD shows good signal–echo delay lag recovery, and a plausible deconvolved signal and echo with similar shape to the initial waveform. The successful application of the method to a few near-ideal cases of high signal-to-noise ratio events warrants testing the proposed metrics on a larger number of well-located events.