Before then, few geologists believed the Tohoku-Oki fault could release such a ferocious earthquake. But in six minutes, the quake cast decades of seismological dogma into doubt. The clues to how it did so lay within the astonishing power of the earthquake itself.
Violent temblors create heat as the planet’s rocks shatter and scrape against one another. In 2008, Brodsky and other leading geoscientists devised a plan to drill into the fault of the next big earthquake, see what it was made of, and take its temperature while it was still warm. This might explain how the quake happened—and whether other faults posed similar threats.
On May 6, 2012, an international team of researchers were putting this plan to the test for the first time. They floated above the Tohoku fault in the only scientific drilling vessel up to the task. But four miles of ocean covered the fault, and researchers had never drilled so deep at sea. Now, Brodsky’s caller was telling her it might stay that way.
The longest deep-sea drill in science had seized up. A fleeting chance to understand giant offshore earthquakes was dissipating under the waves.
The really big one
Brodsky has studied faults around the world—from China to Italy to California—for nearly two decades. Yet modern plate tectonics has existed for only about twice that time. There are still major gaps in our understanding of earthquakes. We do, however, know how they start.
Giant masses of crust grind against each other where tectonic plates meet. About 120 miles east of Japan, the plate supporting the Pacific Ocean is slowly skidding under an Asian continental plate. This strains the rigid crust, and force builds up at crustal cracks called faults. As if the moving plates were cranking a colossal jack-in-the-box, the tension eventually becomes too great and pop goes the fault. The crust lurches, sending the earth into seismic fits.
What we don’t know so well is how earthquakes stop—or why some don’t.
Rocks on either side of the fault scrape against each other, creating friction that slows and eventually stops the slippage. This friction also sparks heat, just as it does when we rub our hands together. Friction plays a pivotal role in how far—and how violently—the two sides of a fault slip, but scientists can’t suss out the specifics from the scribbles of seismometers.
If scientists measured the heat a quake churned out, however, they could determine how hard friction worked to stop the sliding earth. To do this, they would have to stick a thermometer inside the fault of a fresh earthquake—preferably a huge one with plenty of heat. Researchers had tried before, but their results were inconclusive. The faults had cooled off before scientists probed them.
Photo: Matt Davenport
UC Santa Cruz seismologist Emily Brodsky holds a temperature gauge used to measure the fading heat from an earthquake fault after it ruptures.
Brodsky estimated scientists had two years to measure a fault’s heat after a large quake. This left little time for organizing scientists or tracking down fault-drilling equipment once a quake happened. In 2008, Brodsky helped bring scientists from ten countries together in Tokyo to plan a response beforehand. They identified the resources they would need to marshal and the faults most likely to unleash the next big quake. The researchers agreed on eleven locations worldwide, including Alaska, Turkey and New Zealand. Not one site was under the ocean.
But after the Tohoku quake on March 11, 2011, Brodsky believed scientists had to go after its fault. The international committee agreed. Nearly…