The research completed falls within the two broad topics of (1) Seismic source mechanisms and (2) Seismic wave propagation. The specific research tasks within each category have broad applicability to the problem of discrimination of earthquakes from underground nuclear explosions, with particular emphasis on the Asian continent. Source mechanism investigations included detailed studies of several earthquakes in eastern Turkey from the standpoint of field and teleseismic observations and of precursory phenomena (Toksoz et al., 1977, 1978; Toksoz and Arpat, 1977). Wave propagation work included studies of attenuation mechanisms in rock (Johnston et al., 1978) and the application of a technique for simultaneous inversion of surface wave attenuation and phase velocity information to data from several continental and oceanic paths (Lee, 1977; Lee and Solomon, 1978). Details of these studies are given in preprints and abstracts. A list of publications completed under the contract during the reporting period is also included.