DAVID R. FRAZIER / SCIENCE PHOTO LIBRARY DAVID R. FRAZIER / SCIENCE PHOTO LIBRARY
Researcher using a seismograph. This instrument is designed to detect and record the movement of the ground during an earthquake. The output is the trace seen on the roll of paper. During an earthquake, this trace oscillates in response to the shaking of the ground, and can be analysed to determine the type and strength of the learthquake. This researcher is using a ruler to measure the time interval between two events. Photographed in Volcanoes National Park, Hawaii, USA.
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