Scientists have an idea what might be behind the constant vibrations, but the source has yet to be pinned down.
The SAFOD drilling rig, located in Parkfield California, near the San Andreas Fault. Credit: Earthscope/NSF
A map showing the site of ...
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The SAFOD drilling rig, located in Parkfield California, near the San Andreas Fault. Credit: Earthscope/NSF
A map showing the site of ...
More Information