- The largest recorded earthquake in the US was
a magnitude 9.2 that struck Prince William
Sound, Alaska on Good Friday,
March 28, 1964.
- The largest recorded earthquake in the world was
a magnitude 9.5 (Mw) in Chile on May 22, 1960.
- The East African Rift System is a 50-60 km (31-37 miles)
wide zone of active volcanic and faulting that extends
north south in eastern Africa for more than 3000 km
(1864 miles) from Ethiopia in the north of Zambezi in
the south. It is a rare example of an active continental
rift zone, where a continental plate is attempting to
split into two plates which are moving away from
one another.
- Moonquakes ("earthquakes" on the moon) do occur;
but they happen less frequently and have smaller
magnitudes than earthquakes on the Earth. It appears they
are related to the tidal stresses associated with the
varying distance between the Earth and Moon. They
also occur at great depth, about halfway between
the surface and the center of the moon.
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are two different unrelated phenomena. A tidal wave is
a large sea wave produced by high winds, and a tsunami
is a sea wave caused by an underwater earthquake or
landslide (usually triggered by an earthquake) displacing
the ocean water.
- It is estimated that there are 500,000 detectable earthquakes
in the world each year. 100,000 of those can be felt, and
100 of them cause damage.
- Most earthquakes occur at depths of less than 80 km (50
miles) from the Earth's surface.
- The world's deadliest recorded earthquake occurred in 1557
in central China. It struck a region where most people lived in
caves carved from soft rock. These dwellings collapsed
during the earthquake, killing an estimated 830,000 people.
In 1976 another deadly earthquake struck in Tangshan, China
where more than 250,000 people were killed.
- Alaska is the most earthquake-prone state and one of the
most seismically active regions in the world. Alaska
experiences a magnitude 7 earthquake almost every year,
and a magnitude 8 or greater earthquake on average
every 14 years.
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along plate boundaries such as the boundary between the Pacific
Plate and the North American plate. One of the most active
plates boundaries where earthquakes and eruptions are frequent,
for example, is around the massive Pacific Plate commonly
referred to as Pacific Ring of Fire.
- The earliest recorded evidence of an earthquake has been
traced back to 1831 BC in the Shandong providence of China,
but there is a fairly complete record starting in 780BC during
the Zhou Dynasty in China.
- It was recognized as early as 530 BC by the Greek scientist
Aristotle that soft ground shakes more than hard rock in an
earthquake.
- The cause of earthquake was stated correctly in 1760 by
British engineer John Michell, one of the first fathers of
seismology, in a memoir where he wrote that earthquakes
and the waves of energy that they make are caused by
"shifting masses of rock miles below the surface".
- Human beings can detect sounds in the frequency range 20-
10,000 Hertz. If a P wave refracts out of the rock surface
into the air, and it has a frequency in the audible range, it
will be heard as a rumble. Most earthquake waves have
a frequency of less than 20 HZ so the waves themselves
are usually not heard. Most of the rumbling noise heard
during an earthquake is the building and its contents moving.
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