The water will be affected when something slides into the water or if there is a large vertical slip strike under the water.

During the 1812 earthquake, the river flowed north for 3 days. That occurred because the area, now known as "Reelfoot Lake", suddenly sank, and it took the river 3 days to fill what is now the lake.

The Tsunami of 2004 was caused by a massive vertical slip strike under the Indian Ocean.
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QMC, USCG (Ret)
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