Seismological Equipment
State-of-the-art seismological equipment was installed at the Detroit Observatory in 1909 by the Observatory's fifth director, W. J. Hussey. To pinpoint the epicenter of an earthquake, data were needed from at least three seismological stations located a distance apart. The Detroit Observatory communicated the magnitude and other characteristics of tremors detected in Ann Arbor to other scientific stations across the country.
The seismographs were located in the basement of the Observatory's 1908 addition, which was torn down in 1976. The instruments were mounted on concrete piers that were isolated from the floors and walls of the building so that human activity would not disturb them. Two seismographs recorded east-west movement, one recorded vertical movement, and one recorded both north-south and east-west movement. The instruments were mechanically operated. A clock located upstairs in the Observatory's clock room furnished the time through a wire connection. The time was recorded on all three seismographs simultaneously.
The Observatory was situated on what was, at that time, the outskirts of Ann Arbor, so vibrations from wagon traffic and streetcar lines were at a minimum. Yet, vibrations from passing trains were regularly detected by the seismographs.
Earthquake Detections
Scientists at the Detroit Observatory detected numerous significant earthquakes. Some of these earthquakes had epicenters as far away as California, Mexico and Turkestan.
Equipment Before 1909
During Mark W. Harrington's administration of the Observatory (1879-1891), two small seismoscopes were located in the basement. They were attached to the base of the pier of the meridian circle telescope for stability. Although seismographs that recorded data were invented in 1875, the seismoscopes at the Observatory prior to 1909 detected but did not record seismic data.
Ancient Seismology
The first seismoscope was invented in China around 132 A.D. The instrument consisted of a wine jar with eight dragon's head spouts pointing in each of the principal directions. Each spout held a ball. A ceramic frog sat below each spout, its open mouth ready to catch any ball dislodged by an earthquake. The direction of the tremor could be determined by which balls fell.