Scientific American - USA (2020-03)

DISPATCHES FROM THE FRONTIERS OF SCIENCE, TECHNOLOGY AND MEDICINE

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INSIDE

• White noise makes it easier
  to differentiate sounds


• Scientists sculpt tiny, hollow particles
  using light


• Bats find benefits in burned undergrowth


• Q&A: Ann Druyan imagines
  future worlds

SEISMOLOGY

Dark Fiber

Detectors

Fiber-optic cables stretching

below cities, above glaciers and

along the seafloor could record

earthquake vibrations and more

Celeste Labedz heard a sound like thunder

roll across the ice. She was standing on

Alaska’s Taku Glacier, a vast field of snow-

smothered ice between towering moun-

tains, when the icequake began: a short-

lived seismic tremor caused by the glacier’s

sudden movement. Immediately she scram-

bled for her notebook and jotted down the

time. Labedz, a graduate student at the

California Institute of Technology, would

check that time against data from a fiber-

optic cable she and her colleagues had just

de ployed to study such quakes—a promis-

ing new method that is shaking up geology

and adjacent fields.

Information travels through a fiber-optic

cable via pulses of laser light, most of which

moves directly through the hair-thin glass

threads. But inevitably a small amount hits

microscopic flaws in the cable and scatters

back toward the source. This reflection

varies when the cable stretches or bends

because of ground vibrations, such as those

from an earthquake or even a passing truck,

and scientists can monitor changes in the

backscattered light to quantify those move-

GETTY IMAGESments. First developed by the petroleum

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