DAVID PARKER / SCIENCE PHOTO LIBRARY DAVID PARKER / SCIENCE PHOTO LIBRARY
Parkfield earthquake prediction experiment. Stakes planted along the surface trend of a fault act as visual markers to aid detection of ground movement. Seismologists have predicted that an earthquake of around magnitude 6 will occur on the San Andreas fault at Parkfield before 1993. Dozens of researchers have made the village the most heavily instrumented earthquake region in the world. A television camera aligned along the axis of the stakes is set up to record any ground rupture or movement which might occur. It is automatically triggered by signals from a creepmeter located at Middle Mountain, 4km away, the probable epicentre of the predicted quake.
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