5. The Richter magnitude of an earthquake is determined from the XXX. A. duration of an earthquake B. intensity of an earthquake C. arrival of P waves and S waves D. measurement of the amplitude of the surface waves. 6. What is the epicenter of an earthquake? The epicenter is XXX.

A. a seismic wave that travels along the surface of the earth

B. the last place that motion in an earthquake is detected

C. the point on the earth's surface directly above the earthquake's focus

D. the location along a fault where the first motion of an earthquake occurs​