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1. Internal geological processes
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5.4.
Seismic and volcanic prevention
Although we cannot stop earthquakes or volcanic eruptions, it is possible to take
decisions that reduce the risk or take measures that lessen the damage caused. The
risk formula doesn’t include the reduction of the danger but it does include the
reduction of vulnerability. For example, we can lessen seismic risk by not constructing
buildings on poorly consolidated sediments, or by reinforcing them with iron or
reinforced concrete for better resistance to the movement of the ground.
The first step is to determine the seismic or volcanic risk in the area and make maps
showing the danger. Then, prevention is worked with in three areas in order to
reduce the vulnerability or exposure to that phenomenon:
❚❚
Territorial planning
by consulting seismic hazard maps and avoiding, for
example, building in areas of high risk, especially buildings such as hospitals,
power plants and schools.
❚❚
Earthquake resistant design
used in buildings and infrastructures and the
reinforcement of existing structures to reduces seismic risk.
❚❚
Planning
before emergencies increases the capacity of the population to respond
and the methods of self-protection against earthquakes and volcanic eruptions.
In the case of volcanoes, the most adequate measure is to plan evacuation of risk
zones before the eruption. For this, there are three levels of alert, represented in
the form of a traffic light.
Key concepts
❚❚
Geological risks are threats
that come from geological
processes that cause loss
of human lives and their
belongings and buildings.
❚❚
Although these processes
cannot be prevented and are
difficult to predict, the risk
can be reducedwith adequate
preventative measures.
Prevention
is defined as the combination of the measures adopted to reduce
the risks of earthquakes and volcanic eruptions.
high
risk
low
risk
probability
Evacuation is initiated.
Follow the emergency
plan. Proceed to the
meeting points.
Pay attention to the
announcements made
by the authorities.
Return to normal
activities.
Volcanic hazard map based on lava streams in Tenerife
Volcanic traffic light
Analyse
44.
The earthquake that hit India in 1993, of magnitude 6.4 on the Richter
scale, caused 30000 deaths. A year later, another earthquake of the same
magnitude occurred in California, but only caused 63 deaths, although it
also affected a densely populated area. Howcan you explain this difference?
45.
Make a table to compare the different damage associated with both
earthquakes and volcanic eruptions.
46.
Why is it so important in the prediction and prevention of earthquakes to
know in detail the history of earthquakes on a fault line?
47.
Discuss the reasons why earthquakes have been a much more destructive
geological phenomenon than volcanic eruptions.
satellite
tsunami
warning
centre
transmitter buoy
pressure
centre
Tsunami warning system
