Shortly after midnight last Sept. 26, a digital seismograph tucked inside a shallow well on the Danish island of Bornholm picked up an unusual signal. The device, roughly the size and shape of a football helmet, registered a pressure wave passing through the rock beneath the island. The wave generated a stream of data points that zipped along cables to a nearby family’s garage, where a computer snipped the signals into chunks representing a few seconds apiece. That data then traveled via internet cables strung beneath the Baltic Sea to Copenhagen.
The journey took less than a second. But the information sat unexamined on the servers of the Geological Survey of Denmark and Greenland (GEUS) for more than 24 hours, until Nicolai Rinds, a tall seismologist with a shaved head, sat down at his desk with a cup of coffee and booted up software to examine the previous day’s seismic activity. Denmark is hardly noted for its volcanoes or earthquakes, so the jagged spikes from the Bornholm seismograph struck him as odd.
