Invisible earthquakes are revealing a hidden tectonic puzzle beneath California’s most dangerous fault zone.

A hidden chunk of an ancient tectonic plate is stuck to the Pacific Ocean floor and sliding under North America, complicating ...

By tracking swarms of very small earthquakes, seismologists are getting a new picture of the complex region where the San ...

Yet much about the landscape under the ice has been uncertain, because ground and air surveys are difficult in the region.