The biggest earthquake ever recorded was a magnitude 9.5 in Chile in 1960.
It was so powerful it slightly shortened the length of a day and nudged the Earth on its axis.
About 90% of the world’s earthquakes happen around the Pacific "Ring of Fire".
The same horseshoe-shaped belt is home to roughly three-quarters of the planet’s active volcanoes.
Around 500,000 earthquakes are detected worldwide every year.
About 100,000 of them can be felt, and only around 100 cause damage.
The vast majority of earthquakes are too small for anyone to feel.
Most are below magnitude 2 and are only picked up by sensitive instruments.
Nobody can predict exactly when and where a big earthquake will strike.
But early-warning systems can give you seconds to a minute of notice once one has started - enough to drop, cover and hold on.
Each step up the magnitude scale releases about 32 times more energy.
A magnitude 9 quake unleashes roughly 1,000 times the energy of a magnitude 7.
The 2011 Japan earthquake shifted the country’s main island about 2.4 m east.
The magnitude 9.0 Tohoku quake also dropped parts of the coastline by up to a meter.
The deadliest known earthquake hit Shaanxi, China, in 1556.
An estimated 830,000 people died, many in collapsing cave homes carved into soft rock.
California’s San Andreas Fault creeps about 5 cm a year - the speed your fingernails grow.
Over millions of years that adds up to hundreds of kilometers of movement.
Earthquake shaking arrives in waves: fast P-waves first, then the destructive S-waves.
Early-warning systems detect the harmless P-waves and race out an alert before the strong shaking hits.
Earth isn’t the only world that shakes - there are moonquakes and marsquakes too.
Apollo astronauts left seismometers on the Moon, and NASA’s InSight lander recorded thousands of quakes on Mars.
Aftershocks can rumble on for days, months, or even years after a big quake.
Occasionally what looked like the main quake turns out to be a foreshock of something larger.
Humans can trigger earthquakes too.
Filling large reservoirs and injecting wastewater deep underground have both set off quakes.
A single undersea earthquake can send a tsunami racing across an entire ocean.
In deep water the waves can travel as fast as a jet airliner.
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