Causal phenomena

Slippage of crustal rock along a fault or area of strain and rebound to new alignment.

General characteristics and effects

Shaking of earth caused by waves on and below the earth’s surface causing:

Surface faulting
Aftershocks
Tsunamis
Tremors, vibrations
Liquefaction
Landslides

Predictability

Probability of occurrence can be determined but not exact timing. Forecasting is based on monitoring of seismic activity, historical incidence, and observations.

Factors contributing to vulnerability

Location of settlements in seismic areas.
Structures which are not resistant to ground motion.
Dense collections of buildings with high occupancy.
Lack of access to information about earthquake risks.

Typical adverse effects

Physical damage - Damage or loss of structures or infrastructure. Fires, dam failures, landslides, flooding may occur.
Casualties - Often high, particularly near epicenter or in highly populated areas or where buildings not resistant.
Public health - Fracture injuries most widespread problem. Secondary threats due to flooding, contaminated water supply, or breakdown in sanitary conditions.
Water supply - Severe problems likely due to damage of water systems, pollution of open wells and changes in water table.

Possible risk reduction measures

Hazard mapping
Public awareness programs and training
Assessing and reducing structural vulnerability
Land use control or zoning, building codes
Insurance

Specific preparedness measures

Earthquake warning and preparedness programs

Typical post-disaster needs

Search and rescue
Emergency medical assistance
Damage needs and assessment survey
Relief assistance
Repair and reconstruction
Economic recovery

Impact assessment tools

Earthquake scales (Modified Mercalli, MSK), earthquake damage and usability forms.