What Causes an Earthquake? Faults Explained
This aerial photo shows the San Andreas Fault, a large strike-slip fault in California.
We all have our faults, and that includes planet Earth. Earthquakes rattle the globe every day, big and small, most recently making news this week with temblors in Puerto Rico and southern California.
They all spring from faults deep underground, but what kind? The impact and severity of each quake depends on the answer to that question. (See video: “Earthquakes 101.”)
The Earth’s crust is made of a jigsaw puzzle of continental and oceanic plates that are constantly ramming each other, sliding past each other, or pulling apart. Along the Ring of Fire girding the Pacific Ocean, for example, the seafloor plunges beneath Asia and the Americas, building mountains, feeding volcanoes, and triggering earthquakes.
Most earthquakes arise along such fault zones. The ground first bends and then snaps—an earthquake—to release energy along faults. Here are a list of the various ways Earth can shake.
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