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A file photo showing a U.S. tanker leaving the Miraflores locks of the Panama Canal on its way to the Pacific Ocean beside a ship carrying grain. New research suggests the canal and nearby Panama City face a significant risk of a large quake. ((Alberto Lowe/Reuters))

Two faults that run through central Panama have ruptured both independently and in unison over the past 1,400 years, suggesting that Panama City and the Panama Canal face "a significant seismic risk," new research suggests.

That conclusion followed a seismic hazard study undertaken as part of an ongoing expansion of the Panama Canal to allow for larger ships.

Researchers studied the Limon and Pedro Miguel faults and found that both are seismically active and have relatively short recurrence rates for large earthquakes. Recurrence rates are estimates of how frequently quakes are likely to hit a given area.

The Pedro Miguel fault actually runs between two of the locks on the Panama Canal. This fault last ruptured in 1621, resulting in a devastating earthquake.

"That earthquake resulted in nearly [three metres] of displacement where the fault crosses the canal," said lead author Thomas Rockwell, a geologist at San Diego State University. "Another such earthquake today could have dramatic effects."

The authors argue that the Pedro Miguel fault's location and rate of activity should be taken into account in the expansion of the Panama Canal and its new lock system.

The researchers say they found evidence that both the Pedro Miguel and Limon faults may have failed at the same time around 700 AD.

The authors say the apparent ability of these two faults to rupture in unison poses danger to the canal.

"While no fault passes though or beneath any critical structures, the area and structures would be subject to significant shaking," they wrote. 

The capital is also at risk, the study's authors say.

"As Panama City lies only a few kilometers from the Pedro Miguel fault, renewed activity on this fault could cause substantial damage to structures that were not designed for strong shaking," they write.

The research is published in Thursday's Bulletin of the Seismological Society of America.