Scientists Finally Solve the Mystery of “Clockwork” Earthquakes

For over 30 years, scientists have observed a puzzling pattern along the Gofar transform fault near Ecuador’s coast: magnitude 6 earthquakes striking every five to six years in nearly identical locations. The fault, part of the East Pacific Rise where the Pacific and Nazca plates slide past each other, has defied conventional earthquake models due to its precise timing and limited rupture size. A study published in *Science* by researchers from Indiana University Bloomington, Woods Hole Oceanographic Institution, and other institutions explains this behavior through hidden structural barriers. These barriers are complex zones where the fault splits into multiple strands, offset by 100 to 400 meters, creating gaps that disrupt larger ruptures. The study’s lead author, seismologist Jianhua Gong, noted these barriers had been suspected for years but lacked a clear explanation. Data from ocean-bottom seismometers deployed during two studies (2008 and 2019–2022) revealed identical pre-quake activity in the barrier zones: small earthquakes surged before major ruptures, then fell silent afterward. This pattern occurred in two separate fault segments 12 years apart, confirming a consistent physical process. Researchers also found evidence that seawater penetrates these gaps, further stabilizing the fault. The findings suggest these barriers act as natural brakes, absorbing stress and preventing catastrophic quakes. The Gofar fault’s behavior challenges assumptions about transform faults, which typically produce irregular seismic activity. By studying its unique structure, scientists hope to improve earthquake hazard assessments in similar underwater fault systems.