Would you believe that giant snakes, turtles, catfish, or spiders live underneath the ground, and it is their movements that create earthquakes? Maybe you wouldn't, but your ancestors did. Ancient peoples had many fanciful explanations for earthquakes, usually involving something large and restless living beneath the earth's surface.

Aristotle was one of the first to attempt an explanation of earthquakes based on natural phenomena. He postulated that winds within the earth whipped up the occasional shaking of the earth's surface.

Empirical observations of the effects of earthquakes were rare, however, until 1750, when England was uncharacteristically rocked by a series of five strong earthquakes. These earthquakes were followed on Sunday, November 1, 1755, by a cataclysmic shock and tsunami that killed an estimated 70,000 people, leveling the city of Lisbon, Portugal, while many of its residents were in church. This event marks the beginning of the modern era of seismology, prompting numerous studies into the effects, locations, and timing of earthquakes.

Prior to the Lisbon earthquake, scholars had looked almost exclusively to Aristotle, Pliny, and other ancient classical sources for explanations of earthquakes. Following the Lisbon earthquake, this attitude was jettisoned for one that stressed ideas based on modern observations. Cataloging of the times and locations of earthquakes and studying the physical effects of earthquakes began in earnest, led by such people as John Michell in England and Elie Bertrand in Switzerland.

The hundred or so years following the Lisbon earthquake saw sporadic but increasing studies of earthquake phenomena. These efforts were often spurred on by earthquake catastrophes, such as the 1783 Calabrian earthquakes that killed 35,000 people in the southern toe of Italy.