Studies of Coda Generation and Tomography

摘要

About 600 observations of the oceanic seismic phases, Po and So, are examined, making careful measurements of the frequency-dependent properties of the coda. The coda properties varied systematically with both frequency and propagation distance. Of particular relevance to the study of seismic wave attenuation in the ocean basin is the fact that the Po coda decays only about half as fast as So coda. This result is consistent with the decay being caused by intrinsic attenuation in the mantle with quality factors of about Q sub p=1200, Q sub s=600 at 10 Hz. The goals of the research are to understand the partitioning of elastic energy between a main pulse and subsequent coda, including the frequency dependent apparent attenuation of the main pulse and the statistics and decay characteristics of the coda, and to develop methods for inverting tomographic data when these data are incomplete, especially when the angular distribution of rays is uneven. (JHD)