U.S. geologists, for the first time, have extracted intact rock samples from 2 miles beneath the surface of the San Andreas Fault
The actively moving tectonic plate runs 800 miles along the length of California and is responsible for some of the planet’s most damaging earthquakes. The scientists said the extraction of the intact rocks marks the first time samples have been obtained from deep inside a moving tectonic plate.
The 135 feet of 4-inch diameter rock cores were taken to the surface through a research borehole drilled more than 2.5 miles into the Earth.
Now we can hold the San Andreas Fault in our hands, said Stanford University Professor Mark Zoback. We know what it’s made of. We can study how it works.
Zoback is one of three co-principal investigators of the San Andreas Fault Observatory at Depth project — the world’s first underground earthquake observatory.
The science team — including William Ellsworth and Steve Hickman of the U.S. Geological Survey — plans to install an array of seismic instruments in the 2.5-mile-long borehole that runs from the Pacific plate on the west side of the fault into the North American plate on the east.