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Global issues environmental
Factors affecting the impact of an earthquake
Magnitude of event- earthquake greater than 5 can have significant damage.
As magnitude increases the frequency of these higher earthquakes
Depth of focus- shallow focus earthquakes are more destructive than
deeper focused earthquakes as the further seismic waves have to travel, the
more of their energy is dissipated. Shallow earthquakes occur at a depth of
less than 70km.
Distance from epicentre- the further an area is away from the epicentre
the less damage it will experience as the seismic waves energy will be
Population density- higher population density can lead to a higher level of
damage or fatalities.
Degree of urbanisation- more buildings in areas increases the number of
Local ground conditions and variability- buildings constructed on reclaimed
land from the sea or old lake beds are more vulnerable to liquefaction
whereas buildings on solid foundations have less damage.
Time of day- greatest impact on lives lost occurs during rush hours and
lunchtimes in major cities as most travelling on roads, streets are most at
risk. There is less impact if an earthquake occurs at night as there are less
Day of week- weekend earthquakes are less damaging as people are not
concentrated in one place as much
Time of year- winter earthquakes cause more deaths as people suffer more
from exposure as there will be a lack of suitable shelter from the weather.
Degree of earthquake proof design- countries with buildings that are
designed to withstand earthquakes, and that have better quality buildings
are likely to have fewer deaths
Degree of preparedness of 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
Proximity to coast- areas that suffer from earthquakes that are located on
the coast are more at risk of a tsunami
Past history of seismic events- regions which have suffered more seismic
activity are more likely to be prepared for an earthquake