EARTHQUAKE OR EXPLOSION.

Refinements to seismological instrumentation and the application of new processing techniques to well-known principles are outlined. Particularly, principles involved in the detection of small disturbances, the identification of earthquakes from other disruptions, and the estimation of the depth of events are reviewed. Seismic records of some explosions and earthquakes are discussed, and the future and usefulness of seismological arrays are examined. (D.C.W.)