Fiber-optic cables that constitute a world undersea telecommunications network may one-day help scientists research offshore earthquakes and the geologic structures hidden deep underneath the ocean floor.
In a paper coming this week in the journal Science, researchers from the University of California, Berkeley, Lawrence Berkeley National Laboratory, Monterey Bay Aquarium Research Institute (MBARI) and Rice University represent an experiment that turned 20 kilometers of the undersea fiber-optic cable into the match of 10,000 seismic stations along the ocean surface. During their four-day trial in Monterey Bay, they recorded a 3.5 magnitude earthquake and seismic scattering from underwater lapse zones.
Their technique, which they had previously examined with fiber-optic cables on land, might provide much-needed data on earthquakes that occur under the ocean, where few seismic stations exist, leaving 70% of Earth’s floor without earthquake detectors.
Lindsey and Jonathan Ajo-Franklin, a geophysics educator at Rice University in Houston and a visiting faculty scientist at Berkeley Lab, led the study with the help of Craig Dawe of MBARI, which owns the fiber-optic cable. The cable stretches 52 kilometers offshore to the first seismic point ever positioned on the floor of the Pacific Ocean, put there 17 years ago by MBARI and Barbara Romanowicz, a UC Berkeley Educator of the Graduate School in the Division of Earth and Planetary Science. A permanent cable to the Monterey Accelerated Research System node was laid back in 2009, 20 kilometers of which were used in this test while off-line for annual maintenance in March last year.
The ultimate aim of the researchers’ efforts is to make use of the dense fiber-optic networks all over the world—probably over 10 million kilometers in all, on land as well as under the ocean—as sensitive measures of Earth’s movement, allowing earthquake monitoring in areas that do not have expensive floor stations like those that do at much of earthquake-prone California and the Pacific.