EARTH QUAKES CAUSES, HAZARDS

AND SAFETY MEASURES

Conducted By:

Healthcare Services

OUTLINE

INTRODUCTION

EARTH’S INTERIOR

PLATE TECTONICS

FORESHOCKS AND AFTERSHOCKS

THE RICHTER SCALE

FAMILY EARTHQUAKE DRILLS

SUMMARY

“An Earthquake is the way the Earth relieves its stress by transferring it to the people who live on it.”

-on a door at Santa Monica college.

INTRODUCTION

• An earthquake is a series of vibrations on the earth's surface caused by the generation of elastic (seismic) waves due to sudden rupture within the earth during release of accumulated strain energy.

• The earth’s different layers are in constant motion, their movement is due to many different aspects like underground volcanic activity or oceanic movements etc.

• Due this constant motion, small intensity earthquakes occur continuously on all faults around the world.

• Science has yet to discover a sound method of predicting these seismic cataclysms.

• It is always beneficial to be prepared for any situation even if there are no chances of earth quakes.

EARTH’S INTERIOR

• Five billion years ago the Earth was formed in a massive conglomeration and bombardment of meteorites and comets.

• The immense amount of heat energy released by the high-velocity bombardment melted the entire planet, and it is still cooling off today.

• Denser materials like iron (Fe) from the meteorites sank into the core of the Earth, while lighter silicates (Si), other oxygen (O) compounds, and water from comets rose near the surface.

• The earth is divided into four main layers:

• Inner core

• Outer core

• Mantle

• Crust

PLATE TECTONICS

• The Earth releases its internal heat by convection, or boiling much like a pot of pudding on the stove.

• Hot mantle rises to the surface and spreads laterally, transporting oceans and continents as on a slow conveyor belt.

• The speed of this motion is a few centimeters per year, about as fast as your fingernails grow.

• The new crust cools as it ages and eventually becomes dense enough to sink back into the mantle.

• The subducted crust releases water to form volcanic island chains above, and after a few hundred million years will be heated and recycled back to the spreading centers.

PLATE TECTONICS (contd.)

• The earth consists of eight major plates or regions:

• Eurasian plate

• North American plate

• Pacific plate

• Indian-Australian plate

• South American plate

• African plate

• Antarctic plate

• Arabian plate

• In addition to these there are several minor plates like the Philippines plate, the Fiji plate etc.

• Faults are present where two or more plates meet, these regions are more susceptible to the seismic movements of the earth.

PLATE TECTONICS (contd.)

PLATE TECTONICS (contd.)

• The boundary formation at the different faults is categorized according to the type of motion of the plates at the boundary. The types are:

• Divergent Plate Boundary, in which the motion of the adjacent plates is opposite each other.

• Mid-Ocean Ridges are created when plates collide on ocean floors.

PLATE TECTONICS (contd.)

• Convergent plate boundaries, in which adjacent plates collide head-on with each other.

• In Transform plate boundaries, the adjacent plates slide against each other.

• Complex boundaries, comprise of more than one type of movements of the plates.

FORESHOCKS, MAINSHOCK AND AFTERSHOCKS

• A major earthquake never occurs alone.

• The mainshock, which is the earthquake with the highest magnitude, is accompanied by foreshocks and aftershocks.

• The smaller intensity shocks, which occur before the mainshock is called the foreshock.

• The fault that moves in the mainshock experiences massive redistribution of stress and this disrupted surface causes most of the aftershocks.

• The higher the magnitude of the mainshock, the larger the radius in which the aftershocks will be felt. For example, the aftershock zone of magnitude 5 earthquake will be around 5 miles while that of a magnitude 8 will be more than 200 miles.

• The quantity of aftershocks also depends on the magnitude of the mainshock. For example, a magnitude 5 aftershock will produce in a sequence 10 magnitude 4 aftershocks, 100 magnitude 3 aftershocks and 1000 magnitude 2 aftershocks and so on.

THE RICHTER SCALE

• One of Dr. Charles F. Richter's most valuable contributions was to

recognize that the energy radiated by all earthquakes can provide

good estimates of their magnitudes.

• Till now, the Richter Scale is the most accurate method of gauging

the intensity and magnitude of earthquakes.

• An earthquake of magnitude less than 3.5 is generally not felt,

whereas any earthquake below is 6.0 can cause damage to poorly

constructed building and can result in loss of life. Earthquakes with

magnitudes more than 7.0 are major tremors and can cause

widespread destruction.

• Scientists have also determine a way of converting the earthquake

magnitude into the equivalent energy released. An earthquake of

magnitude 7.5 releases energy which is equivalent to 160 million

tons of TNT, which is 5 times greater than the largest thermonuclear

weapon.

FAMILY EARTHQUAKE DRILLS

This will help you and your family plan and react; remembering where to seek shelter and how to protect yourselves.

Identify safe spots and places in each room

• Under a doorway, sturdy table, desk, or kitchen counter.

• Against an inside corner or wall; cover head with hands.

• Know and reinforce these locations by practice.

Beware of danger zones and stay clear of

• Windows that may shatter, including mirrors and picture frames.

• Heating units, fireplace, stove, and area around chimneys.

• Cabinets, refrigerators, and bookcases that may topple.

Practice safe quake actions

• Conduct drills, check reactions and choices.

FAMILY EARTHQUAKE DRILLS (contd.)

Earthquake occurs with no warning; therefore, life protecting actions must be taken at the first indication of ground shaking.

Before the Earthquake

• Identify potential dangers in the home using common sense, fore-sight, and your imagination to reduce risk in the event of an

earthquake.

• Take active security measures, surveying the home for possible hazards.

• Take steps to correct and secure these hazards, reducing risk.

• Tall heavy furniture which could fall; fix it to a wall.

• Hot water heaters that can fall away from pipes need to be anchored to a wall.

• Be sure heavy mirrors or picture frames are placed away from beds and mounted securely to the wall.

FAMILY EARTHQUAKE DRILLS (contd.)

Before the Earthquake

• Cabinets containing breakable items should have latches and heavy objects should be placed low to the ground.

• Flammable liquids must be stored securely away from flame.

• Beds should not be placed near windows.

• Glass bottles should not be placed on high shelves.

During the Earthquake

If inside the house

• Take cover under a table or other sturdy furniture, keeping close to the floor. Be ready to move if the cover becomes unstable or shaky.

• If there is no sturdy cover available, then stay close to a structurally sound interior wall keeping hands on the floor for balance.

During the Earthquake

If inside the house

• Do not stand in doorways and move away from windows, mirrors and other heavy objects which are unsecured.

• If in bed, cover yourself with pillows and blankets.

• Do not try to run outside and never use a lift/elevator. But if the house construction is not sturdy then move outside cautiously.

If outdoors

• Move out in the open and stay there until the shocks die off. Keep away from buildings, streetlights, wires and other structures.

• If the house is badly damaged, try to collect essential items, important documents and leave.

• Do not reenter and stay away from damaged buildings.

FAMILY EARTHQUAKE DRILLS (contd.)

After the Earthquake

• After the main shock, be prepared for aftershocks. They are less in intensity but can cause further damage to structures which are weakened by the main shock.

• Use flashlights instead of candles and lanterns to avoid fire hazards.

• If a building is safe then remain inside but if the structural damage is questionable then evacuate cautiously.

• Provide help to trapped or injured people. Give first-aid if possible.

• Keep abreast of the latest emergency news if possible.

• Stay out of damaged buildings.

• Return home only when the authorities declare it safe.

• Check for electrical damages, gas leakages and other damages.

FAMILY EARTHQUAKE DRILLS (contd.)

The following are recommended drill procedures for a teacher and class of students:

• Take cover under desk or tables.

• Face away from windows.

• Assume “crash” position keeping the head covered with a book or jacket.

• Count aloud to 60. Earthquakes seldom last more than 60 seconds.

The teacher should:

• Issue the take cover order.

• Take cover of 60 seconds.

• Review the action figures.

If the teacher is injured, then the student representatives should be able to give orders.

FAMILY EARTHQUAKE DRILLS (contd.)

SUMMARY

• The Earth consists of several different plates which are in constant

motion.

• Earthquakes occur when built up strain energy is released through increased motion of the tectonic plates.

• Until now there is no method or mechanism to predict an earthquake. Richter scale is used to accurately gauge the magnitude of an earthquake.

• Since there is no warning, the best way is to be prepared for such a calamity.

• Preparedness only comes with constant practice of the drills and precautions discussed.