Instruments for the Earthquake Laboratory at the Chicago Exposition

Abstract

THE first earthquake instrument ever invented, a drawing of which is shown on the wall, is in all probability that of Chōkô, dating from the year A.D. 132. The first instrument used for keeping systematic records in Japan was Palmieri's modification of the contrivance sketched out by the late Robert Mallet. Since this not only have all forms of seismographs and seismoscopes employed in Europe and America been employed, but many special forms have been designed in Japan, with the result that rather than Japan borrowing from Europe and America, these countries are using inventions which had their origin in Japan. A few of these instruments are exhibited in this laboratory. The main feature in their construction is that they all work from “steady points,” and for small earthquakes at least, we can say with confidence that the diagrams they yield are absolute measurements of the earth's motion. From diagrams written on stationary plates we know the extent and the direction of the principal vibrations in a shock, but when the movements are recorded on a moving surface, we know the period or the rapidity with which the movements follow each other. From these latter diagrams the acceleration or suddenness of movements may be calculated, and the factors given to engineers enabling them to construct to resist known forces, rather than stuiply building strongly because an earthquake is strong.