Pn wave geometrical spreading and attenuation in Northeast China and the Korean Peninsula constrained by observations from North Korean nuclear explosions

Abstract

AbstractWe investigate the geometric spreading and attenuation of seismic Pn waves in Northeast China and the Korean Peninsula. A high‐quality broadband Pn wave data set generated by North Korean nuclear tests is used to constrain the parameters of a frequency‐dependent log‐quadratic geometric spreading function and a power law Pn Q model. The geometric spreading function and apparent Pn wave Q are obtained for Northeast China and the Korean Peninsula between 2.0 and 10.0 Hz. Using the two‐station amplitude ratios of the Pn spectra and correcting them with the known spreading function, we remove the contributions of the source and crust from the apparent Pn Q and retrieve the P wave attenuation information along the pure upper mantle path. We then use both Pn amplitudes and amplitude ratios in a tomographic approach to obtain the upper mantle P wave attenuation in the studied area. The Pn wave spectra observed in China are compared with those recorded in Japan, and the result reveals that the high‐frequency Pn signal across the oceanic path attenuated faster compared with those through the continental path.