Implications of differences in thermodynamic conditions for the seismic process

Variations in characteristics of the seismic process are considered under various thermodynamic conditions. In addition to the usual parameters, differences between hypocenter depths obtained from seismic moment solutions and ordinary hypocentral determinations are considered. Two different tendencies are shown to prevail in source parameter variations for events that occur above and below 80–100 km. The first tendency apparently corresponds to variations in the parameters of ordinary crustal earthquakes with increasing pressure. The second tendency is supposedly associated with the prevalence of specific deep mechanisms of seismogenesis. Distinctions in the dynamics of earthquakes developing downward and toward the surface are examined and accounted for by a low density fluid phase present in earthquake sources. The localization of deep earthquakes at certain depths and specific features of deep seismogenesis are discussed. Such features are related to the role of transformations in the material of subducting plates in the occurrence of deep earthquakes. The problem of genesis of deep earthquakes is discussed.