Discrimination between earthquakes and chemical explosions is a significant problem facing many regional seismic networks around the world. Both earthquakes and chemical explosions are sources of elastic waves; therefore, both are recorded by seismic networks. In this study various types of Pg/Sg amplitude phase ratios are explored as discriminants to distinguish between earthquakes and explosions. Amplitude information from 237 earthquakes (1.5mb4.9, 10∆916 km) and 247 explosions (1.4mb3.9, 6∆752 km) recorded by short period analog seismometers in Eastern Russia were used to calculate amplitude phase ratios of five different types. These ampli­tude ratios were analyzed separately in two regions: the Yakutia and Maga­dan regions of Eastern Russia. It was found a tendency of chemical explosions to have higher values than earthquakes for all types of amplitude ratios stu­died. The best earthquake-explosion discriminants found for both regions allow for the classification of 86-92% of the ratios as being either earth­quakes or explosions. This book is addressed to geoscientists, particularly seis­mologists and geophysicists interested in the field of seismic signal iden­tification.