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Global issues earth hazards revision
Factors affecting the impact of an earthquake
Magnitude of event: earthquakes greater than 5 can have significant
damage. As magnitude increases the frequency of higher earthquakes
Depth of focus: shallow earthquakes are more destructive than deeper
focused earthquakes as the seismic waves have further to travel and more
of their energy is dissipated. Shallow earthquakes occur at a depth of less
Distance from epicentre: the further away an area is from the epicentre
the less damage it will have as seismic wave's energy will be less.
Population density: higher population density can lead to higher damage and
Degree of urbanisation: more buildings in areas increases the number of
Local ground conditions and variability: buildings constructed on reclaimed
land from sea or old lake beds are more vulnerable to liquefaction
compared to buildings on solid foundations.
Time of day: greater impact on lives lost if earthquake occurs in rush hours
as most people are travelling at that time, the impact is less if it occurs at
night as less people are travelling.
Day of week: weekend earthquakes are less damaging as people are not
concentrated in 1 place as much
Time of year: winter earthquakes cause more deaths as people suffer more
from exposure due to lack of suitable shelter.
Degree of preparedness of a community: countries that are prepared and
know what to do in an earthquake and have procedures in place to deal with
the aftermath of an earthquake will have fewer deaths.
Degree of earthquake proof design: countries with buildings that are
designed to be earthquake proof and that have better quality buildings will
have fewer deaths.
Proximity to coast: areas that are near the coast are at a higher risk from a
Past history of seismic events: regions which have a history of seismic
activity are more likely to be prepared for an earthquake.