m _b(Pn) Scale for the Korean Peninsula and Site-Dependent Pn Amplification

摘要

The Korean Peninsula is located in the far-eastern Eurasian plate margin where crustal structures vary laterally, causing significant raypath-dependent modulations of crustal phases. The discriminative variations of crustal phases hinder application of conventional local magnitude scales in the continental margin. The mantle-lid phase is less affected by the crustal structures than the crustal phases, providing a better constraint to magnitude estimation. A regional body-wave magnitude scale based on the mantle-lid P wave (Pn), m _b(Pn), is developed for regional events around the Korean Peninsula. The m _b(Pn) scale is determined to be m _b(Pn) = 0. 380 (±0.299) + log A + 2.012 (±0.122) log d, where A is the peak-to-peak Pn amplitude in μm and d is the epicentral distance in km. The m _b(Pn) estimates of regional events around the Korean Peninsula are determined. The m _b(Pn) estimates are compared with other available magnitude estimates (m _b(Lg), M _L). The influence of structures beneath stations on Pn amplification is investigated from inter-station magnitude residuals. A characteristic spatial variation of inter-station magnitude residuals with strengths mostly between -6 and 6 %, but with maximum strengths of ±10 %, is observed. The inter-station magnitude residuals appears to be correlated well with geological and seismic structures in the crust.