Kin-Yip Chun

Attenuation of 1–6 s Lg waves in Eurasia

We report our investigation of the Lg attenuation characteristics in Eurasia using digital recordings from the Incorporated Research Institutions for Seismology/Chinese Digital Seismic Network broadband stations. To maximize the utilization of the current station and source distribution in the region, we have derived a new technique known as the source pair/receiver pair (SPRP) method for Lg attenuation measurement. The procedure eliminates seismic source and site effects, leaving behind decontaminated amplitude data from which regional wave attenuation is estimated. For Lg attenuation studies the SPRP method is more flexible and of greater general applicability than its predecessor, the reversed two-station method (Chun et al., 1987). The application of the SPRP method to our time domain analysis of 33 regional and far-regional seismic events has provided stable regional average for Lg attenuation in periods of 1–6 s. Our time domain analysis, aided by a damped least squares inversion algorithm, has led to robust measurements of Lg attenuation (Q) and its frequency dependence (η) in nine subregions of tectonic significance. Regions of active tectonics and seismicity generally have lower Q0 than that in the stable continental interior. Subregional Q and η are found compatible with the published results in areas of relatively uniform geology; η values are comparatively poorly determined, suggesting that they are susceptible to the presence of crustal heterogeneities along the wave paths.