Over the past 1,300 years, the Nankai Trough, the 500-mile-long boundary between two tectonic plates off the southwestern coast of Japan, has been one of the world’s most active tsunami hotspots. Now an international team of scientists has embarked on a multiyear project to drill four miles down into the heart of this subterranean wave machine. The Nankai Trough Seismogenic Zone Experiment, called Nantroseize, will be the first attempt to penetrate a tsunami-generating hotspot and could help scientists understand the source of the huge swells. “We can monitor the ocean all we want, but we’ll never understand why some earthquakes produce tsunamis and why others do not until we understand how faults work,” says geophysicist Nathan Bangs of the University of Texas.