12.2 EARTHQUAKES G-6

12.2 EARTHQUAKES G-6

pp. 325-329

An Earthquake

• is the shaking or trembling of Earth's crust caused by volcanic eruptions, sudden displacement of Earth's crust along a fault, or collision of plates in the deep zones of Earth.

Where do earthquakes occur?

• focus or hypocenter is the point where the sudden rupture of the rocks or plates takes place.

• epicenter is the point on Earth's surface directly above the focus.

CIRCUM-PACIFIC BELT

or RING OF FIRE

• the world's largest earthquake belt.

• located around the coast of the Pacific Ocean and Alaska to Kurile, Japan, Mariana, and the Philippine trenches.

Seismograph

• Seismologists are scientists who study earthquakes and their effects.

• Seismograph is an instrument used to record the intensity, direction, and duration of the movement of the ground.

• The intensity gives a qualitative description of the severity of shaking.

• Modified Mercalli Intensity Scale is the descriptive scale.

Magnitude

• The magnitude of an earthquake indicates the quantitative measure of the size of the earthquake at its source.

• It represents the amount of energy released by an earthquake.

• Richter Magnitude Scale is the scale used to measure the earthquake's magnitude.

Aftermath of an Earthquake

• Damage to communities such as collapsed buildings and etc.

• Damages to industrial facilities that may result to contamination of environment with toxic chemical substances.

• Death due to fire, chemical poisoning, and falling debris from collapsing structures

• Psychological and emotional damages to survivors due to fear and loss of loved ones and properties.

Changes in the natural landscapes like:

• disappearance of small hills due to landslides.

• sinking of the ground when the soil loses its strength and stiffness due to the vibration caused by an earthquake.

• formation of sinkholes caused by the shaking.

Formation of tsunami

or a huge sea wave, produced by sudden movement of the ocean induced by eartquakes.

The most destructive tsunami was caused by magnitude 9 earthquake in northeastern Japan last March 11, 2011.

Safety Tips Before, During, and After an Earthquake

Earthquake is a natural calamity that cannot be prevented from occuring.However, damages, especially to human lives can be prevented, by being always prepared.

PHIVOLCS' EARTHQUAKE PREPAREDNESS GUIDE

• PHIVOLCS has prepared handout material that tells what to do before, during, and after an earthquake.

BEFORE

• Know the earthquake hazards in your area.

• Follow structural design and engineering practices when constructing a house or building.

• Evaluate the structural soundness of the buildings and houses; strengthen or retrofit when necessary.

Prepare your homes, workplace, or schools:

• Strap or bolt heavy furniture/ cabinets to the walls.

• Check the stability of hanging objects like ceiling fans and chandeliers.

• breakable items, harmful chemicals, and flammable materials should be stored properly in the lowermost secured shelves.

Familiarize yourself with the exit routes.

• know where fire extinguishers, first aid kits, alarms, and communication facilities are located.

• Learn how to use them beforehand.

prepare a handy emergency supply kit

• with first aid kit, canned food and can opener, water, clothing, blanket, battery-operated radio, flashlights, and extra batteries.

• Conduct and participate in regular earthquake drills.

DURING...

• Stay calm.

• When you are inside a structurally sound building or home, stay there!

• If possible, quickly open the door for exit.

• Duck under a sturdy desk or table, and hold on to it, or protect your head with your arms.

• Stay away from glass windows, shelves, cabinets, and other heavy objects.

• Beware of falling objects. Be alert and keep your eyes open.

If you are outside, move to open area!

• Stay away from trees, power lines, posts, and concrete structures.

• Move away from steep slopes which may be affected by landslides.

• If you are near the shore and feel an earthquake, especially if it is strong, move quickly to higher grounds. Tsunamis might follow.

• If you are in amoving vehicle, stop and get out! Do not attempt to cross bridges, overpasses, or flyovers which may have been damaged.

AFTER..

• Be prepared for aftershocks. Once tha shaking stops, take the fastest and safest way out of the building.

• DON'T

• use elevators;

• enter damaged buildings;

• use telephones unless necessary; and

• panic

CHECK...

• yourself and others for injuries;

• water and electrical lines for damages;

• for spills of chemical, toxic and flammable materials; and

• control fires which may spread.

• If you need to evacuate your residence, leave a message stating where you are going and bring your supply kit.

• Keep updated on disaster prevention instructions from battery-operated radios.