A road broken by an earthquake.
earthquake Primary and secondary waves radiate from an earthquake's focus and move through the Earth's interior. As they encounter a boundary, like that between the lower mantle and the liquid outer core, they are reflected and refracted. Secondary waves
- A seismometer is used to record and measure the strength of an earthquake.
- The Mercalli scale is used to measure the earthquake. Anything seven or above is considered extremely dangerous.
- Earthquakes usually occur along fault lines, or cracks that occur within the Earth’s crust.
- Japan, New Zealand, Alaska are all located on one side of a horseshoe-shaped fault line called the "Ring of Fire" that circles the Pacific Ocean and is responsible for frequent earthquakes and frequently erupting volcanos.
- The "Ring of Fire" zone was responsible for the devastating earthquakes in Indonesia in 2004, in New Zealand in early 2011 as well as a 9.0+ quake and a series of offshore earthquakes in Japan in early 2011 which also resulted in a tsunami.
- The San Andreas Fault is a fault line discovered in 1895 that stretches about one thousand and three hundred kilometers through California in the United States, and through Baja California in Mexico.
- The San Andreas fault has been the cause behind a number of significant earthquakes, such as the San Francisco Earthquake in 1906, and the Loma Prieta Earthquake in 1989.
The definition of an earthquake is the release of sudden and extreme energy that is caused by shifting in the Earth's crust.
Facts About Earthquakes
A shaking in San Francisco that measures 3.2 on the Richter scale is an example of an earthquake.
See Note at fault
- The city was almost totally destroyed by an earthquake in 1766, and again in 1797.
- The earthquake grew more intense.
- Palo Alto suffered severely in the earthquake of 1906.
- In 1894 the town suffered from an earthquake, though less severely than in 1783.
- It was totally destroyed, however, by the great earthquake of December 1908; in the centre of the town about 35,000 out of 40,000 persons perished.