The History of Seismology

Early history on earthquakes is spotty and unreliable. Greek and Roman scholars often wrote about such events, but those writings were incomplete and often contradictory. Before 1775, European scholars looked to classical sources like Aristole and Pliny for explanations. Aristotle had theorized that winds within the earth caused earthquakes. Then, in 1775 a catastrophic quake in Lisbon Portugal eliminated all past beliefs on the cause of earthquakes, and inspired scientist to look at modern observations of geology and geography for answers.

The Beginning

In China in A.D. 132 the first invention to record earthquakes was assembled. This device was a ring of eight dragons, each with a metal ball held in its mouth, below the dragons squatted a row of toads. Strong earthquake would cause the ball to fall from the dragons mouth and into a toads mouth. Which toad caught the ball was supposed to indicate the direction the earthquake came from this, however, did not work. The device turned out to be more useful as a piece of art then as an instrument of science.

Communication

Global communication capabilities were a large help to earthquake observations and the further development of seismology. Advances in communication enabled scientist and observers to combine their efforts despite distance. For example, in 1822 in Chile, Maria Graham reported systematic elevation changes in the Chilean coastline. These reported changes were also observed by boat captain, Robert FitzRoy, of the H.M.S. Beagle, while his passenger Charles Darwin was on land studying the geology of the Andes.

European Contributions

In the mid to late 1800s four European men came to the front of the seismology movement. Alexis Perrey of France, made a quantitative analysis of catalogs of earthquakes, seeking commonalities within seasons and lunar changes. From Ireland there was Rober Mallet, and engineer who designed several of London's bridges, used gunpowder explosions to measure and study seismic wave velocity. Mallet was the first to estimate how deep an earthquake goes underground. In Italy, in 1875 Fillippo Cecchi built the first successful seismograph. Following his example Luigi Palmierie, from Italy, invented electromagnetic seismographs. These were the first seismic device able to routinely record earthquakes to small for human beings to notice.

Japanese Contributions

Late in the 1800s and early in the 1900s, in Japan, advances in seismology were made by three English professors. John Milne, Thomas Gray, and James Ewing, while working at the Imperial College of Tokyo, invented the first seismic devices with enough sensitivity to be used in scientific study. In this same time from Japanese researchers began their scientific inquiry into the earthquake phenomena. Seikei Sekiya was the first professor of his kind, when he was named a professor of seismology. Fusakichi Omori, a Japanese researcher studied the rate aftershock activity decay following sizable earthquakes, his equations are still in use today.

Scales

Two scales to measure the intensity of earthquakes have been created. The Mercalli Scale was composed in 1833 by Guiseppe Mercalli, this scale was based on subjective observational objectives and is, therefore, the less reliable scale. This scale was officially modified in both 1912 and 1931, the later version is still in use today. In 1935 a more scientific and better accepted scale was developed by Charles F. Richter. This scale determines an earthquakes magnitude by measuring its maximum ground motion and other factors. This scale set the standard and is now used globally.

References

• USCB: A Brief History of Seismology to 1910
• Fathom: A Brief History of Seismology

Resources

• A History of Seismology