San Andreas depicts a series of earthquakes resulting from tectonic plate movement along the San Andreas Fault in California. As the film's stakes rise and the quakes become more intense, seismologists in the film track the increasing power of the quakes on numerical scales developed to measure the power of earthquakes.
Categorized as natural disasters—naturally occurring events that lead to the destruction of landscapes and infrastructure or loss of life—major earthquakes involve sudden, violent shaking of the ground. This shaking results from volcanic activity or movement within the earth's crust, which is made up of tectonic plates (composed of rock) that sit on the mantle layers of Earth. In a major earthquake, the built environment is at risk of collapsing and the topography of a region may be permanently changed. Human and animal lives are also at risk, be it from falling buildings and infrastructure, broken glass, lack of medical attention, restricted access to food and water, or displacement from shelter for extended periods.
San Andreas is named for the San Andreas Fault, a break in the earth's crust that spans the length of coastal California and demarcates the sliding boundary between the Pacific Plate and the North American Plate. Based on historical examples such as the 1906 San Francisco earthquake, the film imagines the destruction that would result if the immense built-up strain of the plate boundaries pushing against each other were released.
In the movie, the last of the earthquakes measures in at a magnitude of 9.6, a number that expresses an earthquake's size based on seismographic oscillations. A measure of 9.6 makes the fictional earthquake in the movie the most powerful in history, worse than the real-life estimated 9.5 magnitude Valdivia earthquake that struck Chile in 1960.
