Earthquake Damage

Earthquake damages stem from many factors, including the movement of seismic waves through the surface, the type of rock buildings are built on, and the type of building. First, let's look at seismic waves. Damages from seismic waves

P-waves are the 1st to arrive. They produce a rapid up-and-down motion.
S-waves arrive next. They produce a pronounced back-and-forth motion. This motion is usually much stronger than P-waves. S-waves cause extensive damage.
Surface waves lag behind S-waves. Love waves are the first to follow. Ground writhes like a snake
R-waves are the last to arrive. The land surface behaves like ripples in a pond. These waves may last longer than others. Causes extensive damage.

Earthquake Hazards - Ground Shaking

The severity of ground shaking depends on:

• Total energy released
• Distance from the source
• Acceleration
• Nature of the ground material
• Total time of shaking

Results:

• Liquefaction
• Landslides
• Ground Subsidence
• Building Collapse

Building Collapse

Whether or not a building will collapse during an earthquake is dependent upon many factors, including:

• Intensity of the earthquake
• Duration of the vibrations
• Nature of the material upon which the structure rests
• The design of the structure

How does a building or other structure collapse? That depends upon the construction techniques used.

Slabs disconnect
Facades delaminate
Bridges topple
Bridges come apart.

Buildings collide.
Masonry disintegrates
Slopes collapse

Lateral failures – Due to weak ground floors or lack of bracing. Think of a Deck of Cards House: Individual cards stacked to form a house are loose, and easy to fail (unbraced). However, when the cards are taped together, the house is stronger (braced)

How the ground moves is also a factor.

Oscillations – Ground shaking typically has frequencies of 0.1 to 30 oscillations / sec.

Resonance occurs when the natural oscillation of a building is the same as that of the ground shaking