Read the given paragraph and answer the following questions.

An earthquake is a sudden, brief shaking of the earth caused by disturbances deep within the earth’s crust. It is measured by a seismograph and its power is expressed in magnitudes on the Richter scale. Earthquakes with magnitudes of 2.0 or less are barely felt, while those over 5.0 can cause damage. Magnitudes of 6.0 or higher are considered very strong, and those over 7.0 are classified as major and highly destructive. The focus (hypocenter) is the point beneath the earth's surface where the earthquake starts, and the epicenter is directly above it on the surface. An earthquake with a magnitude of 6 on the Richter scale has one hundred times more destructive energy than a magnitude 4 earthquake.