Transcript FAMILY EARTHQUAKE DRILLS (contd.)

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, foresight, 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.
FAMILY EARTHQUAKE DRILLS (contd.)
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.
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.