On Jan. 6 and 7, Puerto Rico was struck by two major earthquakes that left one person dead and thousands without power or running water. But as anyone who has been through a major quake knows, they aren’t a single event – they typically generate numerous aftershocks, and some, like Puerto Rico’s, are preceded by foreshocks.

As Colorado State University geophysicist Rick Aster explains, it’s almost impossible to predict the precise timing, location or size of a quake in advance. But once one occurs, scientists can make forecasts about whether more are likely to follow. Puerto Ricans can expect dozens more aftershocks large enough to feel before this event finally ends – a challenging start to 2020 for an island still recovering from past disasters.

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The Immaculate Conception Catholic Church lies in ruins after a magnitude 6.4 earthquake in Guayanilla, Puerto Rico, Jan. 7, 2020. AP Photo/Carlos Giusti

Earthquake forecast for Puerto Rico: Dozens more large aftershocks are likely

Richard Aster, Colorado State University

Puerto Rico's January earthquakes came after many foreshocks and have been followed by numerous aftershocks. Scientists are studying these sequences to improve earthquake forecasting.

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