Japan’s earthquake felt around the world

Beth Hickenlooper, who works for the St. Johns River Water Management District, provided the following.

When the March 11 earthquake shook Japan, it was literally felt around the world.

The St. Johns River Water Management District, South Florida District and U.S. Geological Survey (USGS) have all reported data that shows the 8.9-magnitude earthquake was felt in Florida. Specifically, wells that are monitored by the government agencies showed disturbances between 1 and 3 a.m., East Coast time.

Tom Mirti, director of the District’s Division of Hydrologic Data Services, says it’s not unusual to register the effects of an earthquake at great distances from the source of the quake. The higher the magnitude of a quake, the higher a chance that the disturbance is felt many time zones away. Mirti remembers seeing similar well disturbances in December 2004 when an earthquake triggered a tsunami in the Indian Ocean.

The recent earthquake off Japan, registered in many of the District’s Floridan aquifer monitoring wells, was likely caused by a transient change in pressure in the confined wells as the seismic pressure waves moved past, Mirti says. Even so, the quake had no effect on Florida or the monitoring wells.

According to geology.com, earthquakes can be felt many miles away from the center of the quake because the seismic waves travel through the earth’s crust. Primary waves (known as P waves) can travel through any material and move quickly, followed by secondary waves (known as S waves). A quake’s surface wave is like a wave on water, moving slowly and for a longer duration, and is often the most destructive part of an earthquake.