Advances in Studies of Heterogeneities in the Earth's Lithosphere

heterogeneous structures, especially when the data quality is not very high. GAUTIER et al. perform tomographic inversion of local earthquake arrival times for crustal structure and earthquake locations in the actively rifting Gulf of Corinth. The velocities image the rift basin and the hypocenters image a regional-scale detachment fault. Inthe third group of papers, SNIEDER reviews theoretical concepts governing changes of coda waves due to small localized perturbations in the medium properties or source location, and describes how to estimatethe resulting meanand varianceofthe travel-time perturbations. CAMPILLO reviews theoretical results on properties of coda waves in asymptotic multiple-scattering regime, and how to construct Green functions from coda waves and ambient seismic noise. The results are illustrated with applications of imaging velocity structures in Alaska and California. WEGLER et al. use the theory of radiative transfer to model the transport of seismic energy in 2-D and 3-D acoustic random media. The theory accounts correctly for the direct wave front, envelope broadening caused by multiple forward scattering, and late coda caused by multiple wide-angle scattering. However, for very heterogeneous media the radiative transfer results di?er from those of the full wave equation. ZENG develops a set of scattered wave energy equations that include scattered surface waves and conversions of body waves to surface wave scattering. Numerical results show that scattered wave energy can be approximated well by body-wave scattering at earlier times and short distances, but at large distances scattered surface waves dominate the scattered body waves at surface stations.