Introduction to Seismographs
The earliest seismoscope was invented in 132 A.D., by Chang Hêng. Seismoscopes of limited effectiveness were used by Bina and others in the eighteenth century. The middle nineteenth century saw the invention by Palmieri of a seismoscope to record the times of small earthquakes. A successful seismograph of low sensitivity was invented by Cecchi in 1875. British scientists at the College of Engineering, Tokyo, independently built seismographs in the 1880's. The British in Japan made many observations with their instruments and must be credited with first demonstrating the value to seismology of seismographic devices.
Von Rebeur-Paschwitz obtained the first recording of a teleseism in 1889. In the next decade, investigators in Italy, Germany, and England studied the waves from distant earthquakes and constructed the first teleseismic travel-time charts. Wiechert introduced a seismometer with viscous damping in 1898.
Theory seems to have been neglected in the early development of the seismograph. Theoretical studies of forced damped harmonic-oscillator seismographs were presented by Perry and Ayrton, and Lippmann, but these had little effect on the construction of seismographs. In the 1890's, the importance of tilt was much debated. By 1900, many seismologists had become convinced that the effect of tilting on seismograph response could usually be neglected.
Instruments have been used in the study of earthquakes for over eighteen hundred years. The earliest known seismoscope was intended to record both the occurrence of earthquakes and the azimuths of their origins from the observer. In the eighteenth century, we find proposals to record the times of earthquakes and the character of the ground motion occurring in earthquakes. A most important advance was made late in the nineteenth century, with the invention of instruments which gave records representing earthquake ground motion as a continuous function of time. We will call such instruments seismographs, regardless of the accuracy of their representations of earth motion. This history will end at the beginning of the twentieth century.
- The Earliest Seismoscope
- Seismoscopes in Eighteenth Century Europe
- The "Seismometer" of James Forbes
- Further Studies with Seismoscopes
- The Invention of a Seismograph in Italy
- The Development of the Seismograph in Japan
- The Seismograph Becomes an International Instrument
- Early Studies of "Microseisms"
- The Tilt Controversy
- The Göttingen Seismographs