Hazards, preparation methods, and damage control relating to earthquakes

1. Hazards, preparation methods, and damage control relating to earthquakes Edward Shin

2. Earthquake hazards • Ground shaking • Tsunami • Landslide/Liquefaction

3. Ground shaking • Earthquake’s primary destruction mechanism. • The waves travelling along earthquake shake the ground, which can cause larger damage to structures on top. • Roads, buildings, pipes, environment, lives, etc are affected. • Damage to structures depend on the composition of structure. Generally softer materials are prone to more damage. • According the Modified Mercalli Intensity, I is not felt whereas V is strong enough to wake people up. VIII causes structural damage, and XII’s damage is so large it can throw objects into air. • Naturally, higher magnitude correspond to higher intensity. • Frequency of magnitude decreases as the value of magnitude increases.

4. Tsunami • Caused by sea floor disruption. • Elevated sea level lowers itself to the equilibrium, propagating tsunami waves. • The waves can travel, and cause death and damage in seashore. • In deep ocean, tsunami waves are only about a metre high. • As tsunami waves approach shore where sea level becomes shallow, the energy that was distributed throughout the ocean depth concentrates on lesser depth, causing the waves to slow down and increase its height. • In shores, tsunami waves are 10s of metres high. • The waves have the potential to wipe out everything in its path.

5. Landslide/liquefaction • Ground movements from earthquake encourage landslide. • Water saturation in soil causes soil to have liquid like behaviour. • Manmade landfill has the highest risk of liquefaction. • Loss in soil strength results in heavier objects on top to sink. • Ground is displaced elsewhere. • Landslide block roads, pipes, and power lines. • Landslide can also alter stream paths, and generate clouds of dust.

6. Preparation methods • Prediction/detection • Earthquake insurance • Earthquake resistant designed buildings • Resource stockpiling • Everyday preparation

7. Prediction/detection • There is controversy whether we even have the technology to accurately foretell when and where the earthquake will occur at what magnitude. • In short, it is not possible to predict earthquakes in advance with confidence, but it is possible to find the probabilities of earthquakes in particular regions. • Most earthquakes occur at tectonic boundaries. • Seismologists should inform locals to move to a safer location, and locals should take on the advice in order to minimize death and injuries. • Since human activities can induce earthquakes, we should take note of what we’re doing to the environment. However, human induced earthquakes are mostly minor and do not possess significant risks. • Although foreshocks can occur before a larger earthquake, a small earthquake in itself is not enough evidence to foreshadow a larger follow up earthquake. • Tsunami can be detected because the speed of ocean wave is slower than the seismic wave.

8. Earthquake insurance • Earthquake insurance will not reduce structural and emotional damage, but it can be useful for monetary purpose. • The cost will vary depending on how much one desires to be insured, and how the building was structured. • Keep calm.

9. Earthquake resistant designed buildings • Buildings respond to acceleration transmitted from the ground. The initial inertia of the building causes the building to stay where it is, but the acceleration causes the building to move. • Stress builds up , and eventually weak structures that cannot stand up to the stress fail and break down. • Tall buildings typically amplify the movement and shake for longer duration than short buildings. • There are several ways to have earthquake resistant designed buildings. Some have strong and flexible structure while others have the entire structure behaving as a single stiff unit. • Steel frame, cross bracing, and strong foundation are keys to resist earthquakes, and they are often used.

10. Resource stockpiling • A typical person needs 4 litres of drinking water per day. • Have food that does not need to be cooked and can be stored for a long duration. • Prepare a first aid kit, flashlights, radio, batteries, clothes, cash, medications.

11. Everyday preparation • ‘Drop, cover, and hold on’ drills. • Learn how to turn on and shut off gas, water, and electricity valves. • Keep heavy objects secured. • Have important contacts written down as uncharged phones are useless.

12. Damage control • Indoor response • Outdoor response • Redesigning buildings for future earthquakes • Preparing for aftershock • Humanitarian aid • Locating edible food and usable water

13. Indoor response • Do not use elevators. • ‘Drop, cover, and hold on’. • If there are no objects to duck under, stand near a sturdy wall. • Stay indoor as one might get hit by a falling object and injure himself even more. • Check for the smell of gas after the earthquake. • Stay calm, and shut off electricity, gas, and water.

14. Outdoor response • Pull the car over when driving. • Watch out for collapsing structures and stay away from them. • Avoid hazardous areas, and move to a clear area. • Have proper protection. If this is not possible, maximize protection. • Evacuate to a higher elevation if there is a risk for tsunami or flood.

15. Redesigning buildings for future earthquakes • Now that scientists and engineers know the collapsed building was not strong enough to withstand the earthquake’s intensity, if they decide to build a new building make sure to have improvements from the previous structure. • While a new shelter is being built, have family and friends know where one is at so that they will worry less, and even offer one to stay with them.

16. Preparing for aftershock • Turn on radio. • Do not enter damaged buildings. • Find resources in the meanwhile.

17. Humanitarian aid • In event of a catastrophic earthquake, humanitarian aid was taken place to help the affected region recover. • Most recently 2010 Haiti earthquake garnered humanitarian aid upon Haiti’s ambassador’s request to the United States. • Many governments, organizations, and individuals around the world sent aid in different forms including rescue teams and survival supplies.

18. Locating usable water • Water from the tank of toilet, melted ice from freezer, unopened bottled drinks, and juice from canned food are drinkable fluid. • Swimming pool and spa water are adequate for personal hygiene. • Boiling water kills harmful bacteria. • Chlorine tablets and iodine tablets can treat water.