JACKSONVILLE, Fla. – A powerful 7.6 magnitude earthquake struck off the northeast coast of Japan late Monday. Thereafter, a tsunami of 50 cm was measured just south of Aomori along the coast.
A 7.6 magnitude quake is near the top of the Richter scale. Keep in mind the scale is logarithmic, meaning as you go up in magnitude, the strength increases substantially.
Japan is in the hot spot for earthquake activity as the country lies on many fault lines. It’s in a region called the “Ring of Fire”. This area extends from Japan to the west coast of the United States.
This zone is the most active seismically and volcanically in the world. In fact, roughly 90% of all earthquakes occur in the zone, and 75% of all active volcanoes are in the zone.
Faults are fractures in the Earth’s crust where rocks move.
A normal fault is when the block above the fault line moves downward relative to the block below. A reverse fault is when the block above the fault moves up and over the lower block. Finally, a strike-slip fault is when two blocks slide past each other. When these collisions occur, energy is released, resulting in waves of shaking. This is what we know of as an earthquake.
When this occurs over the ocean, energy travels upward and expands in all directions. This triggers a tsunami, which typically can reach up to 10 to 100 feet high.
Tsunamis can travel hundreds of miles and reach speeds over 500mph! When the wave approaches the coast, it slows down and increases in height. This is why if a Tsunami Advisory or Warning is issued, you need to move to higher ground immediately.