DRRR Part 10

Disaster Readiness and Risk Reduction
10. Types of Earthquake Hazard

1. Ground shaking - is both a hazard created by earthquakes and the trigger for other hazards such as liquefaction and landslides. Most earthquake damage results are from the shaking cause by seismic waves passing beneath buildings, roads, and other structures.

2. Ground rupture - occurs when movement on a fault breaks through the surface. Rupture may occur suddenly during an earthquake or slowly in the form of fault creep. Fault rupture almost always follows preexisting faults, which are zones of weakness.

3. Liquefaction - describes a phenomenon whereby a saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress, usually earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid.

4. Ground subsidence - is defined as the lowering of the land surface. Many different factors can cause the land surface to subside. Subsidence can occur rapidly due to a sinkhole or underground mine collapse, or during a major earthquake.

5. Tsunami earthquake - can be defined as an undersea earthquake for which the surface wave magnitude (Ms) differs markedly from the momentmagnitude (Mw), because the former is calculated from surface waves with a period of 20 seconds, while the latter is a measure of the total energy release at all frequencies.

6. Landslide, earthquake and landslides are frightening and destructive natural disasters. An earthquake is the sudden, rapid shaking of the earth caused by the breaking and shifting of rock deep underground. Landslides and debris flow occur in all U. S. states. In a landslide, masses of rock, earth or debris move down a slope.

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