The Origin of Earthquakes

Mr. Sanchez ELA Period 2 Chose grade level 30 January 2018 How Earthquakes Happen? Parts of an Earthquake? Earthquakes happen when two pieces of Earth all of the sudden slip past each other. The surfaces that slip past each other are called fault line or fault plane. An earthquake starts in the hypocenter, which is located beneath Earth’s surface. Right above Earth’s surface is the epicenter. Sometimes large earthquakes have a foreshock.

Foreshocks are earthquakes that are smaller than the mainshock that happen after a bigger earthquake in the same place. The larger earthquakes are called a mainshock. Aftershocks always happen after a mainshock. Foreshocks and aftershocks are the same thing. Aftershock can last for week,months, or maybe even years depending on the mainshock. Fault Line-One fault line is the San Andreas fault line.

The San Andreas fault is a sliding boundary between the Pacific Plate and Northern America Plate. The fault line slices California in two from Cape Mendocino to the Mexican border. San Diego, Los Angeles and Big Sur are on the Pacific Plate. San Francisco, Sacramento and the Sierra Nevada are all on the North American Plate. Besides the San Francisco legendary earthquake in 1906, the San Andreas fault line does not run through the city. Desert Hot Springs, San Bernardino, Wrightwood, Palmdale, Gorman, Frazier Park, Daly City, Point Reyes Station and Bodega Bay all lie on the fault line.

The San Andreas fault is a transform fault. A transform fault is a strike-slip fault that is a boundary between two plates of earth's crust. Causes of an Earthquake Earthquakes are caused by faulting, which is a a sudden rock movement that happens along a rupture or break surface.