The cleverly ambiguous title of this book plays with the many uncertainties that surround our experience of earthquakes. Just who are these “observers”: are they scientists, farmers or city dwellers? In answering this question, Deborah Coen offers a wealth of information in a book that reads with the appeal of fiction. In 10 chapters, from “The human seismograph” to “A true measure of violence: California 1906-1935”, she spins a compelling yarn of how 19th- and early 20th-century scientists gathered accounts by observers of seismic events that could furnish quantifiable information.
Drawing on examples of how earthquakes were studied in Western countries, Coen considers early seismologists’ challenge in dealing with the physiological and sociological elements at play in the study of earthquakes, and in particular the impact of national identity, as well as differences in perception of risk in different countries. She details the symbiotic relationship between scientists and the common folk, as well as the impact of journalism on earthquake science and the development of information-gathering by networks of “citizen-scientists” in many central European countries that, by the early 20th century, allowed scientists to establish earthquake catalogues and accounts of their effects.
Well-researched historical quotations help to transport the reader to an era in which Alexander von Humboldt’s earthquake descriptions were seen to validate those of “natives” in South America, whom he described as having greater “presence of mind” than the Europeans prone to “hysteria” during seismic events. The book’s middle chapters detail the struggle of Swiss and Austrian scientists to develop a questionnaire that would give them the capacity to distil observers’ descriptions into a single-intensity number in the Rossi-Forel scale in use at the time to display it on maps, as a way to synthesise information: the location of maximum intensities was correlated with the earthquake’s locus and ultimately with geologic faults.
Earthquakes in North America are dealt with at the end of the book, and these accounts are useful in helping the lay reader to understand the limitations of earthquake intensity scales through the story of a visit to Alaska in 1905 by geographers Ralph Tarr and Lawrence Martin. I don’t wish to spoil the story, so I’ll just say that it underlines the inherent limitations of human seismological observations in places with scant populations. The final chapter chronicles the establishment of some of today’s best-known seismological observatories as a consequence of the large 1906 San Francisco earthquake - an event that also helped to spur the development of scientific monographs based on interdisciplinary studies. Coen also explains how data recorded by seismological observatories in California helped Charles Francis Richter develop the earthquake magnitude scale that is still in use today.
But perhaps Coen’s most surprising achievement here is that she exposes, through the lens of history, the philosophical rift between global and regional seismological studies that was initiated by the development of modern seismographs. Meanwhile, the question that continues to inspire debate among today’s “earthquake observers” is whether such events should be considered primarily as natural phenomena, or whether their study should be driven by a sense of societal responsibility. Coen’s account clearly points to the importance of both approaches. The historical context in which these stories are told here affords her the opportunity not only to acknowledge the contribution to seismology of many unsung heroes but also to expose the challenges of earthquake science.