- 11.1: What Is an Earthquake?
- An earthquake is the shaking caused by the rupture (breaking) and subsequent displacement of rocks (one body of rock moving with respect to another) beneath Earth’s surface. A body of rock that is under stress becomes deformed. When the rock can no longer withstand the deformation, it breaks and the two sides slide past each other. Most earthquakes take place near plate boundaries, but not necessarily right on a boundary, and not necessarily even on a pre-existing fault.
- 11.3: Measuring Earthquakes
- There are two main ways to measure earthquakes. The first of these is an estimate of the energy released, and the value is referred to as magnitude. It is often referred to as “Richter magnitude,” but that is a misnomer, and it should be just “magnitude.” The other way of assessing the impact of an earthquake is to assess what people felt and how much damage was done. This is known as intensity and is assigned to locations, rather than to the earthquake, and therefore intensity can vary widely.
Thumbnail: Epicenter of the 2010 Chile earthquake with a collapsed building in Concepción. Image used with permission (CC-SA-BY; Claudio Núñez).