Regional body-wave magnitude scalings are essential for quantification of small and moderate-size earthquakes that are observed only up to regional distances. Crustally-guided shear waves, Lg, develop stably at regional distances in continental crusts and are minimally influenced by the source radiation patterns. Lg body-wave magnitude scalings, m b(Lg); are widely used for assessment of sizes of regional crustal events. The m b(Lg) scaling has rarely been tested in continental margins where Lg waves are significantly attenuated due to abrupt lateral variation of crustal structures. We test the applicability of m b(Lg) scaling to the eastern margin of the Eurasian plate around the Korean Peninsula and Japanese islands. Both third-peak and root-mean-square (rms) amplitudes of Lg vary significantly according to the crustal structures along raypaths, causing apparent underestimation of m b(Lg): Implementation of raypath-dependent quality factors (Q) allows accurate estimation of m b(Lg); retaining the transportability of m b(Lg) in the continental margin around Korea and Japan. The calibration constants for an rms-amplitude-based m b(Lg) scaling are not determined to vary by region in the continental margin due to complicated crustal structures. The calibration constants are determined to be distance-dependent. Both the third-peak-amplitude-based and rms-amplitude-based m b(Lg) scalings yield accurate magnitude estimates when raypath-dependent quality factors are implemented.
Bibliographical noteFunding Information:
We are grateful to the Korea Meteorological Administration (KMA), the Korea Institute of Geoscience and Mineral Resources (KIGAM), the Incorporated Research Institutions for Seismology (IRIS) and the National Research Institute for Earth Science and Disaster Prevention (NIED) in Japan for making seismic data available. We thank four anonymous reviewers and Professor Brian Mitchell for fruitful review comments. This work was supported by the Korea Meteorological Administration Research and Development Program under Grant CATER 2007-5111.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology