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What is an earthquake?
The earth’s surface is made up from plates, called tectonic plates – like a gigantic jigsaw puzzle. These plates are constantly moving, which leads to a build-up of energy inside the earth’s crust. When this energy is suddenly released, the ground trembles and can cause things to fall, like televisions and shelves or even cause damage to buildings and bridges. We call this natural phenomenon, which may only last a few seconds, an earthquake. Very often the first tremors are followed by others, which are called after shocks.

Can we predict earthquakes?
No-one can predict where and when an earthquake will happen, nor how big it will be. Earthquakes come without warning and can occur at any time, on any day or in any period of the year.
Why do we have earthquakes in Lisbon?
The city of Lisbon sits on a zone of the earth’s crust which can be affected by strong earthquakes, separated by long periods of calm, during which there are only very light tremors

Are there some parts of Lisbon which are more dangerous than others in the event of an earthquake?
Yes, because the make-up of the ground varies from zone to zone in the city, meaning some places will stand up better to an earthquake. It is more dangerous in the zones near to the river due to the probability of there being a tsunami (sea-quake) and in places where the buildings are more run-down or were not built according to anti-seismic standards
What happened in the earthquake of 1755?
On the 1st of November, 1755 Lisbon suffered one of the worst earthquakes ever. After a number of tremors which left the city in ruins, gigantic waves flooded the lower areas of the city. This destruction was accompanied by a large fire which lasted for 5 to 6 days. It is calculated that many thousands of people died, with a significant number of buildings collapsing.
lisboa 1755lisboa 1755
How do we measure an earthquake?
The size of an earthquake can be measures in two ways:
By its , through the amplitude of the seismic waves recorded by a seismograph, which is related with the quantity of energy released at the centre. This is a quantitative method of measuring an earthquake.
The scale which is most used is the Richter Scale, which uses nine levels. Each level of this scale corresponds to an increase in energy of around thirty times in relation to the previous level.
By its (intensity), by evaluating the effects produced in terms of damage to building structures and in the way in which the vibrations are felt by the population. The effects are ordered into levels according to a scale of intensities of a qualitative nature.
The best known scale is the Modified Mercalli Intensity Scale which has twelve degrees. Other scales may also be used.

What is a tsunami?
The term tsunami is used to define a series of waves caused by a sudden disturbance at the bottom of the sea, normally caused by an earthquake, volcanic eruption or landslide.
As opposed to waves caused by the wind, which only disturbs the surface of the sea, the energy of a tsunami’s waves involves the whole mass of water, from the surface to the sea bottom. These waves, which can reach huge dimensions and travel from the ocean basins with only a small loss of energy, can reach speeds of between 500 and 1000 kilometres per hour on the high sea.
The speed and height of the waves depend and vary according to the depth of the water. On the high sea, waves which do not normally reach 1 m in height can surge to over 10 metres near the coast. The destruction caused directly by tsunamis, especially in coastal zones which are only a few metres above sea level, results from various factors: from flooding, from the impact of the waves (due to their enormous energy), from objects transported by the water and from the erosion caused by the strong currents.

The distance between successive waves in the open sea is quite large, although this reduces substantially near to the coast. The time it takes for a tsunami to reach land, with few exceptions, varies between a few minutes to 1 hour. The waves are able to come inland much further than with normal waves, spreading well beyond the coastal areas.

If I am near to the sea and there is an earthquake what should I do?
If you are near to the coast and the feel an earthquake there is a possibility that there may be a tsunami, and so you should follow these recommendations:
Look for a high spot, far from the coast, to take shelter. A sudden change in the sea level is an indication of a tsunami, be alert and protect yourself in a safe place;
Get away from beaches and river banks;
Switch on the radio to get more detailed information;
Prepare for a possible evacuation;
Find out about the safest locations and what roads or highways you should use;
If you are advised to evacuate the area, notify your parents and evacuate immediately;
If you are on a boat, inform the adults that they should head out to sea. The devastating effect of a tsunami is next to the coastline, where the water is shallower;
Do not approach high risk areas until the local authorities say that these are safe. Remember that the danger has not past after the first wave, a tsunami is formed by a series of waves which may get bigger as they progress;
Follow the instructions of the authorities.
an earthquake what should we do ?
In the event of an earthquake, following some very simple rules could be decisive in helping to avoid injuries and reduce material damage.
Find out about the causes and possible effects of an earthquake in your area.
Speak about the matter, calmly and serenely, with your family and friends.
Together with your family, draw up an emergency plan.
Check that everyone knows what to do in the event of an earthquake.
Agree beforehand on a meeting place, if you are separated from the other members of your family during an earthquake.
Work together and prepare your home in order to facilitate movement, freeing up corridors and passage ways, tidying away items of furniture and toys.
Identify the safest spots: interior doorways, corners of main walls, under tables and beds.
Keep a safe distance from objects which might fall or shatter.
Warn your parents about the need to fix shelving, vases and flower pots to the walls of the house and to place heavy or large objects on the floor or on the lower shelves.
Learn to switch off the electricity and to cut off the water and gas.
Put up the telephone numbers of the emergency services in a clearly visible place.

How should I organise my emergency kit?
Together with your parents, collect a torch, a portable radio and spare batteries for both, as well as a fire extinguisher, a first aid bag and essential medicine for the family. Also store water in plastic containers and canned food for two or three days.
Include something warm to wrap up in as well as resistant footwear in the kit.
(Attention: you should check the “best before” dates for some of these).

In the event of an earthquake, which places are the most dangerous inside a house?
Near to windows, mirrors, lighting and furniture and other objects which might fall.

an earthquake, if I am inside the house or any other building, what should I do?
If you are on one of the upper floors, do not run to the stairs and never use the lifts or elevators. Take shelter under the arch of an inside door, in the corners of the rooms or under a table or bed. Keep away from windows and mirrors and be very careful with falling lights, furniture or other objects.
an earthquake, if I am outside what should I do?
Very calmly head for an open space, far from the sea, rivers or steams. Do not run or wander around the streets. Keep away from buildings (especially the more run-down, tall or isolated ones) from electricity pylons and other objects which might fall. Move away from embankments, walls, chimneys and verandas.
an earthquake, what should I do if I am in a place where there are lots of people?
Stay inside the building until the earthquake stops, then leave calmly, paying attention to the walls, chimneys, electric cables, lighting and other objects which might fall. During the earthquake, do not run towards the exits. Stairs and doors are places which easily fill up with debris and might be blocked by people who are trying to leave the building.
what should I do an earthquake?
Stay calm and count on the possibility of after shocks.
Do not rush to stairs or exits. Never use elevators or lifts.
Do not light matches or lighters as there may be a gas leak.
Cut off the water and gas and switch off the electricity.
Use battery-operated torches.
Switch on the radio and follow the recommendations given out.
Avoid going by places where there are loose electric cables.
Do not use the telephone, except in extreme emergencies (serious injury, gas leaks or fires).
Do not wander around the streets to see what happened. Free them up for emergency vehicles.


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