Slate magazine is highlighting maps published shortly after the 1906 San Francisco Earthquake that attempted to detail the intensity of the devastating seismic event.
The maps come from an atlas that accompanied the 1908 scientific report attempting to explain the causes and effects of the S.F. Earthquake, titled The California Earthquake of April 18, 1906: Report of the State Earthquake Investigation Committee, according to Slate.
The maps use the data that the commission collected to represent the earthquake’s intensity geographically, with one focusing on San Francisco and another on all of California and parts of Nevada and Oregon.
Susan Elizabeth Hough, a seismologist with the U.S. Geological Survey, points out that while government officials approved funding for the commission, they refused to pay for the publication of this report.
Susan Elizabeth Hough, a seismologist with the U.S. Geological Survey suggested to Slate that the dominant political climate in the years after the quake, in which local businessmen and politicians tried hard to minimize reports of damage done, may have been to blame.
That climate was one of the main reasons that for many decades after the catastrophic event the quake’s death toll was reported at around 500, rather than the 3,000-plus who actually died, the figure that’s been generally accepted in recent years.
In the end, the Carnegie Institution provided financing for the report’s printing.
Besides reports on intensity of the quake, the committee included surveys of the effects on plants and animals, illustrations of damage inflicted and a map detailing the extensive fire damage that followed the quake.
“The commission used the Rossi-Forel scale, a now-outmoded measurement of earthquake intensity that incorporated seismograph readings (where available), human reports, and observed physical damage,” according to Slate. “Each map here refers to ‘apparent intensity’ of the effects – a term meant to remind the reader that the Rossi-Forel measurements had some degree of subjectivity to them.”
The Richter Scale, which is the best known of the measuring devices used to quantify earthquakes today, wasn’t created until the mid-1930s.