The magnitude of an earthquake is a measured value of the earthquake size.
The intensity of an earthquake is a measure of the shaking created by the earthquake, and this value does vary with location.
The average rate of motion across the San Andreas Fault Zone during the past 3 million years is 56 mm/yr (2 in/yr).
The East African Rift System is a 50-60 km (31-37 miles) wide zone of active volcanics and faulting that extends north-south in eastern Africa for more than 3000 km (1864 miles) from Ethiopia in the north to Zambezi in the south.
The first "pendulum seismoscope" to measure the shaking of the ground during an earthquake was developed in 1751, and it wasn't until 1855 that faults were recognized as the source of earthquakes.
In 1769 was when the earliest reported earthquake in California was felt.
It is estimated that there are 500,000 earthquakes that are detected in the world each year.
100,000 earthquakes can be felt each year.
100 earthquakes cause damage each year.
A Richter scale is a formula and not an actual object.
There is about 1 earthquake every 30 seconds.
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 1556 in central China.
Florida and North Dakota have the smallest number of earthquakes in the United States.
A tsunami is a sea wave caused by an underwater earthquake or landslide (usually triggered by an earthquake) displacing the ocean water.
The hypocenter of an earthquake is the location beneath the earth's surface where the rupture of the fault begins.
The epicenter of an earthquake is the location directly above the hypocenter on the surface of the earth.
Pacific Basin
The greatest mountain range is the Mid-Ocean Ridge, extending 64,374 km (40,000 mi) from the Arctic Ocean to the Atlantic Ocean, around Africa, Asia, and Australia, and under the Pacific Ocean to the west coast of North America.
The world's greatest land mountain range is the Himalaya-Karakoram.
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.
It is thought that more damage was done by the resulting fire after the 1906 San Francisco earthquake than by the earthquake itself.
A seiche (pronounced SAYSH) is what happens in the swimming pools of Californians during and after an earthquake.
The southern California area has around 10,000 earthquakes each year.
Most earthquakes occur at depths of 50 miles from the earths surface.
North Dakota and Florida have the smallest number of earthquakes in the U.S.
The Wasatch Range, with its outstanding ski areas, runs North-South through Utah, and like all mountain ranges it was produced by a series of earthquakes.
There is no such thing as "earthquake weather".
From 1975-1995 there were only four states that did not have any earthquakes. They were: Florida, Iowa, North Dakota, and Wisconsin.
The swimming pool at the University of Arizona in Tucson lost water from sloshing (seiche) caused by the 1985 M8.1 Michoacan, Mexico earthquake 2000 km (1240 miles) away.
The most deadliest earthquake happened on Jan. 23, 1556 in Shansi, China with an estiment of about 830,000 deaths.
The largest earthquake the U.S. was a 9.2 on March 28,1964 in Prince William Sound, Alaska.
The larges earthquake ever was on May 22,1960 in Chile at 9.5.
The deepest earthquakes typically occur at plate boundaries where the Earth's crust is being subducted into the Earth's mantle. These occur as deep as 750 km (400 miles) below the surface.
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.
The majority of the earthquakes and volcanic eruptions occur along plate boundaries such as the boundary between the Pacific Plate and the North American plate.
The earliest recorded evidence of an earthquake has been traced back to 1831 BC in the Shandong province of China, but there is a fairly complete record starting in 780 BC during the Zhou Dynasty in China.
It was recognized as early as 350 BC by the Greek scientist Aristotle that soft ground shakes more than hard rock in an earthquake.
The largest recorded earthquake in the world was a magnitude 9.5 (Mw) in Chile on May 22, 1960.
California
The earliest reported earthquake in California was felt in 1769 by the exploring expedition of Gaspar de Portola while the group was camping about 48 kilometers (30 miles) southeast of Los Angeles.
Before electronics allowed recordings of large earthquakes, scientists built large spring-pendulum seismometers in an attempt to record the long-period motion produced by such quakes.
The core of the earth was the first internal structural element to be identified.
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.
Although both are sea waves, a tsunami and a tidal wave are two different unrelated phenomenona. A tidal wave is a shallow water wave caused by the gravitational interactions between the Sun, Moon, and Earth.
The cause of earthquakes 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".
In 1663 the European settlers experienced their first earthquake in America.
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.
When the Chilean earthquake occurred in 1960, seismographs recorded seismic waves that traveled all around the Earth.
The San Andreas Fault was named in 1895 by geologist A.C. Lawson.
The interior of Antarctica has icequakes which, although they are much smaller, are perhaps more frequent than earthquakes in Antarctica.
The largest recorded earthquake in the United States was a magnitude 9.2 that struck Prince William Sound, Alaska on Good Friday, March 28, 1964 UTC.
