E Earthquake: shaking or trembling of the earth that accompanies rock movements extending anywhere from the crust to 680 km below the Earth's surface. Elastic Limit: the point at which any additional force to an object will permanently deform its shape. Elastic Properties: the measure of an objects ability to change shape when a force is applied to it, and return to its original shape when the force on it is released. Elastic Rebound: an objects ability to return to its original shape after being broken apart. Electric Current: movement of positive or negative particles accompanied by effects such as heat, a magnetic field, or a chemical transformation. Epicenter: the point on the Earth's surface directly above the focus of an earthquake. Explosion Earthquakes: earthquakes which are the result of the detonation of nuclear and chemical devices.