Scientists who drilled deeper into an undersea earthquake fault than ever before have found that the tectonic stress in Japan’s Nankai subduction zone is less than expected. The findings are a puzzle but will help scientists home in on the link between tectonic forces and the earthquake cycle and potentially lead to better earthquake forecasts, both at Nankai and other megathrust faults such as Cascadia in the Pacific Northwest. The drilling reached over two miles into the Nankai subduction zone and was conducted in 2018 with the IODP scientific drilling vessel Chikyu.