Fine Recording in Time Direction for Seismological Observa tion

Abstract

In the routine seismological observation, the running speed of the recording paper or film is 1 mm/sec at the highest owing to operational restrictions; consequently, the time accuracy can hardly attain higher than 0.1 sec by the recorder of the conventional type.
An accuracy of 0.01 sec is required in the c ontinuous tripartite observation of natural earthquakes. To meet the requirement, an improved optical recording system has been developed; the main features are a horizontal slit in front of the galvanometer mirror and a cylinder lens in front of the recording film, which make the time resolving power of the system as high as the film grains allow. By this system, a time accuracy of 0.01 sec has been made possible even with the ordinary running speed,1 mm/sec. In designing the optical system, the effect of the diffraction has been prudently taken into account.