Earthquake Hazard Management

In the UK, there are not many earthquakes. However, did you know there are an average of 20,000 earthquakes recorded per year? Most of them are recorded in the earthquake belts, with 80% of them happening along the rim of the pacific ocean. To constantly be in fear that large earthquakes may hit, is a reality that people in those areas have to face. Although it is impossible to prevent an earthquake from happening, it is possible to identify and assess the hazards, build safer structures, and learn about earthquake safety. Earthquake hazard management is what we will be looking at today, with some examples along the way.

Definition of earthquake hazard management

So, how do we define earthquake hazard management? Earthquake hazard management is to evaluate the hazard created when earthquakes occur and use strategies to minimise the damage caused by earthquakes. It is easy to assume that the earthquake itself is a hazard but what the earthquake can cause is also a hazard. Earthquake hazards are anything that can happen due to an earthquake that affects the normal activities of people. This can include ground shaking, landslides, fires, flooding, surface rupture, liquefaction, and tsunamis.

Fig. 1 - liquefaction caused by an earthquake, 2004

Hazards can be put into two categories depending on what causes them and when it happens. Primary hazards happen immediately and are caused by the energy released by the earthquake. Secondary hazards happen as a result of the primary hazards.

Earthquake hazard management would be to predict the possible primary and secondary hazards caused and prepare for them.

Earthquake Hazard Management prevention

Earthquake hazard management is not about trying to stop the hazards from occurring but thinking about the possible scenarios that may happen because of an earthquake and preparing for the hazard so the damage can be reduced. Earthquake hazard management uses strategies such as prediction, preparation, and protection to reduce vulnerability in earthquake-active regions.

Areas that are affected by earthquakes use building codes. There are strict guidelines that new builds have to follow and existing buildings have to adjust to so people are protected from future earthquake hazards. By creating buildings that do not collapse and are safe to live in, earthquake hazard management is able to prevent disasters.

Buildings that have rubber shock absorbers in the foundation absorb tremors. Steel frames can sway with the earth's movements when there is an earthquake. Lightweight roofs and safety glass are used to prevent injury if they are pushed out of the building during tremors. There are always outside areas near the building planned to accommodate people to assemble during evacuation.

Fig. 2 - Retrofitted building with elevated building foundation and rubber bearings

Earthquake Hazard Management assessment

Different ways of analysing and assessing earthquake hazards are used in earthquake hazard management so that preparations for the hazards can be made. Modelling different magnitudes of earthquakes in different places and envisioning how the ground would shake allow experts to assess potential earthquake hazards. Also using records of past earthquakes and geology to compare with the observations of what is happening today are ways experts used to assess potential earthquake hazards.

Predicting earthquakes can also help to assess earthquake hazards. Predicting earthquakes is not easy but monitoring the tremors of the earth with a seismometer can help with finding changes in the movement of the earth.

From this experts can understand where the earthquake may occur but it is hard to predict when it will happen.

Earthquake hazard management emergency

Even though earthquakes can be monitored and there are prediction techniques, it is hard to predict in detail what will happen. So it is important to prepare and plan what to do when there is an earthquake. Preparation can be in the form of training people through practising earthquake drills and confirming evacuation routes and where to evacuate. This can increase the chances of survival as people know how to react quickly in these situations. It is also necessary to prepare emergency kits, first aid kits, blankets, food, and water supplies.

Earthquake hazard management safety tips

Many of the strategies for earthquake hazard management are on a country or local area level, whether it be practising to evacuate or building codes for houses. However, there are also precautions that can be taken on an individual level. Safety tips are given by many sources from the government to insurance companies and are simple precautions that everyone can take when there is an earthquake.

Before an earthquake:

• Identify the potential hazards in the home. If there are tall pieces of furniture, secure them to the wall or ceiling. Don't place fragile objects made out of glass or ceramics in high places. Also, avoid putting heavy items on top of tall furniture as they can fall during tremors and cause injury.
• Prepare emergency kits, fire extinguishers, food supplies, and water.
• Plan where to evacuate and evacuation routes.

During an earthquake:

• Drop, cover, and hold on. If you feel an earthquake and you are at home, drop to the ground, find somewhere such as under a table where you can protect and cover yourself and hold onto the structure.
• If outside, move away from buildings and structures that can fall on you and go to open spaces. Be wary of windows breaking and try to cover yourself with what you have.

After an earthquake:

• Only start to move when the earthquake stops.
• Once the earthquake stops, open the doors or windows and secure an escape route. If the building starts to twist from being shaken doors may get stuck in door frames.
• Check on family members and others who may be around.
• Try to find some thick-soled shoes to walk around in as there might be glass or other sharp broken objects on the floor.
• Obtain information from battery-powered radio.
• Check for fire and turn off the gas. Turn off the electricity too.
• Evacuate to the nearest evacuation area, if you are near the sea, evacuate to a higher place in case of tsunamis.

Fig. 3 - Sign indicating evacuation route for when tsunamis occur

Earthquake Hazard Management examples

Most countries follow the strategy of prediction, preparation, and protection when it comes to earthquake hazard management. However, some countries are more regularly affected by earthquakes and prioritise earthquake hazard management. For example, we can look at the case study of earthquake hazard management when an earthquake struck Tohoku, Japan in 2011.

Case study Tohoku Japan

An earthquake of 9.0 magnitude hit Tohoku on March the 11th 2011. The earthquake lasted for 6 minutes and caused a tsunami that had a height of over 40 meters. When large earthquakes such as the Tohoku earthquake occur, it is the ultimate test to see if the earthquake hazard management work. Let's look at the earthquake hazard management that had been done by the country.

Protection

Billions of pounds are spent on making buildings resistant to earthquakes. This included types of glass that don't shatter, weights in the building to counter the sway, and absorbers in the foundation. There were also larger sea walls built along the coast to stop tsunamis from reaching inland.

Preparation

There is an earthquake and tsunami drill on the 1st of September every year for rescue and emergency services to practice how to respond. There are also drills within schools and workplaces. There is government funding and policies for preventing earthquake hazards. Emergency alerts are sent to all smartphones and are also televised.

Prediction

70 million pounds were spent on lasers that monitor the slightest movements of the ground. Japan has had a warning system for tsunamis made up of a network of seismographs since 1952.

There are buoys in the ocean which sense offshore earthquakes and can predict the areas which are at risk. Once detected the areas are notified through alerts. Tsunami prediction has been improved in Japan by the 80% to 90% accuracy and can predict the level of damage.