Tuesday’s 7.9 magnitude earthquake in the Gulf of Alaska sent vibrations through the earth that caused water to rise and fall in wells in Florida, thousands of miles away. Sensors near Fort Lauderdale and Madison, near the Georgia border, showed a minor change in water levels after the earthquake, according to the United States Geological Survey (USGS). A water level rise from 41.59 feet to 41.77 feet was recorded at the well near Madison before it returned to normal. At the well near Fort Lauderdale, the water level fell from 1.42 feet to 1.31 feet. Why did water levels in these wells some 3,800 miles away from the earthquake’s epicenter change?
Vibrations that move through the earth called seismic waves are the culprit. Seismic waves are depicted by the upward and downward lines on seismographs used to detect earthquakes around the world. “Water levels in wells respond to the seismic-wave induced expansion and contraction of the aquifer tapped by the well, in turn causing step or oscillatory fluid-pressure changes,” the USGS says. The changes in groundwater levels are often seen hundreds, or even thousands, of miles away from an earthquake’s epicenter.