Harry Fielding Reid - Seismology

Seismology

After returning to Baltimore, Reid devoted his next 35 years to a career in research and teaching at Johns Hopkins. The Geology Department had been founded several years before and was then under the chairmanship of Charles Bullock Clark. Reid’s relationship with other members of his department is uncertain, and his professional identity was fluid as well. Geophysics was a new field at that time, and Reid could later fairly claim to be the first American scientist to practice it as a specialty. By 1911, and after a series of promotions, he would be granted the title Professor of Dynamic Geology and Geography.

In 1902, Reid began to collect seismological data for the USGS. At that time the science of seismology was extremely new, and there were only a handful of working seismographs anywhere in the world. One was installed at the Johns Hopkins geology lab, and in 1911 Reid would publish the first comprehensive treatment on the subject in English. His interest in such measuring devices may have begun in the early 1880s with his study under Henry Rowland, who was a path-breaking figure in the use of fine instruments to measure and assess nature at the atomic level. Reid’s British friend and colleague, J. J. Thomson, made use of a similar interest in measurement to prove the existence of the electron as a particle with both mass and charge.

The 1906 San Francisco earthquake offered Reid the chance to take his interest in seismology to a new level. Andrew Lawson was then chair of the geology department at the University of California at Berkeley, and Lawson had been one of the first (1888) Hopkins Ph.D.s in geology. Perhaps through his influence Reid was chosen the only non-Californian to study the great earthquake as part of a state-funded commission. Through a close examination of how different points of land along the California coast and nearby inland had moved over the course of the previous half century - here his access to USGS data was crucial - Reid was able to determine that the earthquake was a result of forces he identified as “elastic strain.” This strain had built up slowly but unequally at points along the San Andreas Fault, and it took a massive temblor to release the strain at that point along the fault where the greatest energy had accumulated.

During the previous generation European scientists had begun to wonder if faults were related to earthquakes, and vice-versa, but it was Harry Fielding Reid who established that there was a clear and dynamic relationship. He would call his new theory “Elastic Rebound,” and it remains even into the 21st century at the foundation of modern tectonic studies.