Footnote
a A seismograph is a device that measures and records the motion of the ground during an earthquake. The first one was developed in 1890. Today, more than 4,000 seismograph stations are operating worldwide.
a A seismograph is a device that measures and records the motion of the ground during an earthquake. The first one was developed in 1890. Today, more than 4,000 seismograph stations are operating worldwide.