Guided Notes about Earthquakes and Society

Section 19.4

1) Most earthquake damage results from the prolonged shaking of the ground by surface waves.

2) The most severe damage occurs to unreinforced buildings made of stone, concrete, or other brittle building materials.

3) Wooden structures are remarkably resilient and generally sustain significantly less damage during an earthquake.

4) Some buildings in earthquake-prone areas even rest on large rubber structures that absorb most of the vibrations generated during a quake.

5) Two Major Types of Structural Failure

The supporting walls on the ground floor fail and cause the upper floors to fall and collapse as they hit the ground (pancaking)

If the vibrations of the ground have the same frequency as the natural sway of the building, then they will sway violently

6) How do earthquakes trigger landslides?

In areas with fluid-saturated sand, seismic vibrations may cause subsurface materials to liquefy and behave like quicksand, which generates landslides in areas with a slope.

7) Why are earthquake waves amplified in areas with soft soil?

Because soft materials have little resistance to deformation, seismic waves are amplified and can cause more damage.

8) What is a fault scarp?

Fault scarp occurs in areas of great vertical offset where the fault intersects the ground surface.

9) What is a tsunami? How large can they be in shallow areas?

A tsunami is a large ocean wave generated by vertical motions of the seafloor during an earthquake. These motions displace a column of water, creating a wave which can become 30 meters tall in shallow areas.

10) Two factors used to determine the probability of earthquakes

The history of earthquakes occurring in an area

The rate at which strain builds up in the rocks

11) What is a seismic gap?

A seismic gap is the sections of active faults that haven’t experienced significant earthquakes for a long period of time.