The most energetic earthquakes occur where oceanic plates submerge beneath continental plates during plate tectonics. Quakes in these subduction zone settings commonly carry the risk of triggering severe tsunamis. But when the earth shook with a moment magnitude of 8.1 near the northern Chilean city of Iquique on 1 April 2014, the resulting tsunami was relatively small. A unique seismological data set provides a possible explanation.
