Microscopic imperfections in rock crystals deep beneath the Earth’s surface play a key role in how the ground slowly moves and resets in the aftermath of major earthquakes, says new research from the University of Cambridge.
The stresses resulting from these defects – which are small enough to disrupt the atomic building blocks of a crystal – can transform how rocks beneath Earth’s crust move and then transfer stress back to Earth’s surface, setting the stage for the next earthquake.
By understanding how these crystal defects influence rocks in the Earth’s upper mantle, scientists can better interpret measurements of ground motions following earthquakes, which indicates where stress is building up and in turn where future earthquakes occur.
The researchers’ work reveals that the way Earth’s surface settles after an earthquake, and stores stress prior to a repeat event, can be traced to tiny defects in rock crystals from the deep.
Their results show how hot rocks in the upper mantle can mysteriously change from flowing almost like syrup immediately after an earthquake to becoming thick and sluggish as time passes.
Until now it had been thought that the increase in viscosity was because of the competing push and pull of crystals against each other, rather than being caused by microscopic defects and their stress fields inside the crystals themselves.
https://phys.org/news/2021-06-crystals-deep-microscopic-clues-earthquake.html