Applying deep learning to teleseismic phase detection and picking: PcP and PKiKP cases

The availability of a tremendous amount of seismic data demands seismological researchers to analyze seismic phases efficiently. Recently, deep learning algorithms exhibit a powerful capability of detecting and picking on P- and S-wave phases. However, it remains a challenge to effeciently process enormous teleseismic phases, which are crucial to probe Earth's interior structures and their dynamics. In this study, we propose a scheme to detect and pick teleseismic phases, such as seismic phase that reflects off the core-mantle boundary (i.e., PcP) and that reflects off the inner-core boundary (i.e., PKiKP), from a seismic dataset in Japan. The scheme consists of three steps: 1) latent phase traces are truncated from the whole seismogram with theoretical arrival times; 2) latent phases are recognized and evaluated by convolutional neural network (CNN) models; 3) arrivals of good or fair phase are picked with another CNN models. The testing detection result on 7386 seismograms shows that the scheme recognizes 92.15% and 94.13% of PcP and PKiKP phases. The testing picking result has a mean absolute error of 0.0742 s and 0.0636 s for the PcP and PKiKP phases, respectively. These seismograms were processed in just 5 min for phase detection and picking, demonstrating the efficiency of the proposed scheme in automatic teleseismic phase analysis.