4.1

Question 1

An earthquake is a phenomenon caused by the sudden and rapid movement of large volumes
of rock along fractures on the surface of the earth called faults.

Question 2

The outermost shell of the
earth, which includes the crust and the uppermost mantle, consists of tectonic plates. These
are massive and irregularly shaped slabs of rock.

Question 3

Due to their roughness, the edges of these
plates get stuck while the plates continue moving. Eventually, when the plates move far
enough to overcome the friction of the fault and separate; the energy stored in the rocks is
released in the form of seismic waves.

Question 4

are seismic waves that travel through the interior of the earth

Answer 4

Body waves

Question 5

are the first waves that reach the surface of the earth and make the ground shake.

They move the ground back and forth along the direction they are travelin

The shaking is light or sometimes not felt

Answer 5

Primary (P) waves

Question 6

are body waves that vibrate perpendicular to their propagation direction.
They produce an up and down motion.
They move slower but shake the ground more strongly than P waves.

Answer 6

Secondary (S) waves