Blanka Mitrovic

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• Blanka Mitrovic

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How Earthquakes Occur

• An earthquake occurs when rocks break and slip
  along a fault in the earth. Energy is released
  during an earthquake in several forms, including
  as movement along the fault, as heat, and as
  seismic waves that radiate out from the "source"
  and causes the ground to shake, sometimes
  hundreds of kilometres away.

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The Three Main Types of Waves

• P WAVES cause rock to move
• back and forth
• S WAVES shakes the earth up and
  down
• L WAVES move side to side
• R WAVES cause surface material to
  move in vertical circles

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Where They Occur

• Wherever the tectonic plates that make up the
  Earth's crust subduct, crumple, or grind past
  each other, earthquakes occur. Earthquakes occur
  all over the world however, most occur on active
  faults. 90 of the world's earthquakes occur
  along these plate boundaries. The "Ring of Fire"
  circling the Pacific Ocean, and including
  Canada's west coast, is one of the most active
  areas in the world.
• Mountains are built by tectonic and volcanic
  activity. Everywhere in the world where these
  activities happen, earthquakes occur with them.
  Besides North America, two large regions in
  particular are at high risk
• The Pacific Rim
• The Mediterranean and Middle East regions

•    Divergent boundaries
• Along sides of rift valley
• Indicate horizontal extension
• Transform boundaries
• Shallow focus
• Convergent boundaries
• Collision boundaries between continents
• Subduction

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Earthquake Map
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Seismographs

• Seismographs are instruments used to measure
  earthquake waves.
• A seismogram is the record they produce of the
  arrival times and magnitude of earthquake waves.
• Modern seismometers amplify the wave motion
  electronically and can detect even very weak or
  very distant signals.
• Seismographs enable us to measure the size of
  earthquakes and to locate them accurately.

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The Damage Earthquakes Create

• Earthquake damage depends on what area is hit. If
  an unpopulated region is struck, there will be
  low loss of life or property. If it hits a large
  city, there may be many injuries and destruction.
  Many of the areas at risk on the Ring of Fire are
  largely populated. Major earthquakes hitting
  those areas today could produce terrible damage.
• Earthquakes have the power to uproot trees and
  send them crashing into buildings. They can
  trigger landslides and avalanches, and cause
  flooding and tsunamis. Human structures are also
  at risk. Buildings with thick, heavy walls do not
  resist shock waves very well. Violent earthquakes
  often cause structures to collapse, burying
  people underneath. Brick buildings are the most
  vulnerable. Chimneys and heavy roof tiles are
  often shaken off during the tremors, and can
  crash into bystanders or people passing by. The
  shaking of the earth is sometimes not the
  greatest disaster. It is in the ensuing fires and
  floods that often the greatest damage occurs.

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Preparing For An Earthquake

• In those parts where strong earthquakes may occur
  people build their houses upon firm ground. Only
  the most elastic materials should be used, like
  wood and reinforced concrete instead of brick or
  stone. They would try to avoid overloading the
  higher parts of the building and do everything
  possible to keep the center of gravity of the
  whole low. Brick chimneys on the rooftops tend to
  fall off at an intensity of VI.
• People that live in third world countries are
  usually the ones who have the most damage after
  an earthquake, because their houses are not
  strong enough to withstand an earthquake. People
  living in the first world countries are less
  vulnerable to the dangers of an earthquake
  because their houses are better built.

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Effects of Earthquakes

• Ground motion
• Fires
• Landslides
• Liquefaction
• Aftershocks
• Tsunamis

Fire
Liquefaction
Tsunami
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The 5 Tips

• In a case of an earthquake
• You should get under dining tables or anything
  that can
• support a lot of weight. Cover your neck and
  face so that
• its better protected from falling objects and
  broken glass.
• If possible, face away from any glass. Hold onto
  the table or desk because most likely it will
  move, so be prepared to move with it. Hold that
  position until the shaking stops. If a table or
  desk is not available, you should stand in the
  doorway.
• Medical aid, water, transportation, electricity,
  and communication may be unavailable or severely
  restricted for several days or weeks after a
  large earthquake. You should be prepared to take
  care of yourself for at least three days.
• In the case of an earthquake, do not run outside
  or use staircases or elevators.
• If you are driving during an earthquake, you
  should move to the shoulder. Stay away from
  overpasses, bridges, large buildings, and power
  lines. Stay in your car until the shaking stops.
• The most important thing of all is to stay
  calm.

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The Measurement of Earthquakes

• The Richter Scale
• M1 to 3 Recorded on local seismographs, but
  generally not felt M3 to 4 Often felt, no
  damage
• M5 Felt widely, slight damage near epicentre
• M6 Damage to poorly constructed buildings and
  other structures within 10's km
• M7 "Major" earthquake, causes serious damage up
  to 100 km (recent Taiwan, Turkey, Kobe, Japan,
  and California earthquakes).
• M8 "Great" earthquake, great destruction,
  loss of life over several 100 km (1906 San
  Francisco, 1949 Queen Charlotte Islands).
• M9 Rare great earthquake, major damage over a
  large region over 1000 km (Chile 1960, Alaska
  1964, and west coast of British Columbia.

• Modified Mercalli Intensity Scale
• (I) - Not felt except by a very few under
  especially favourable conditions.
• (II) - Felt only by a few persons at rest,
  especially on upper floors of buildings.
  Delicately suspended objects may swing.
• (III) - Felt quite noticeably by persons indoors,
  especially on the upper floors of buildings. Many
  do not recognize it as an earthquake. Standing
  motor cars may rock slightly. Vibration similar
  to the passing of a truck. Duration estimated.
• (IV) - Felt indoors by many, outdoors by few
  during the day. At night, some awakened. Dishes,
  windows, doors disturbed walls make cracking
  sound. Sensation like heavy truck striking
  building. Standing motor cars rocked noticeably.
  
• (V) - Felt by nearly everyone many awakened.
  Some dishes and windows broken. Unstable objects
  overturned. Pendulum clocks may stop.
• (VI) - Felt by all many frightened and run
  outdoors, walk unsteadily. Windows, dishes,
  glassware broken... books off shelves... some
  heavy furniture moved or overturned a few
  instances of fallen plaster. Damage slight.
• (VII) - Difficult to stand... furniture
  broken..damage negligible in building of good
  design and construction slight to moderate in
  well-built ordinary structures considerable
  damage in poorly built or badly designed
  structures some chimneys broken. Noticed by
  persons driving motor cars.
• (VIII) - Damage slight in specially designed
  structures considerable in ordinary substantial
  buildings with partial collapse. Damage great in
  poorly built structures. Fall of chimneys,
  factory stacks, columns, monuments, walls. Heavy
  furniture moved.
• (IX) - General panic... damage considerable in
  specially designed structures, well designed
  frame structures thrown out of plumb. Damage
  great in substantial buildings, with partial
  collapse. Buildings shifted off foundations.
• (X) - Some well built wooden structures
  destroyed most masonry and frame structures
  destroyed with foundations. Rails bent."
• (XI) - Few, if any (masonry) structures remain
  standing. Bridges destroyed. Rails bent greatly.
  
• (XII) - Damage total. Lines of sight and level
  distorted. Objects thrown into the air.

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The Mexico Earthquake Article

• Natural Hazards Slides Vol. 2 - Earthquake
  Events Earthquake of 9/19/1985, Mexico City
• EARTHQUAKE OF SEPTEMBER 19, 1985 MEXICO CITY,
  MEXICO
• On September 19, 1985, at 717 A.M., a Richter
  magnitude 8.1 earthquake occurred on the Pacific
  coast of Mexico. The damage was concentrated in a
  25 km2 area of Mexico City, 350 km from the
  epicenter. Of a population of 18 million, an
  estimated 10,000 people were killed, and 50,000
  were injured. In addition, 250,000 people lost
  their homes, and property damage amounted to 5
  billion. Over 800 buildings crumbled, including
  hotels, hospitals, schools, and businesses.
  Communications between the Mexican capitol and
  the outside world were interrupted for many days.
  
• Surrounding areas affected by the earthquake
  included the Mexican States of Jalisco, Guerrero,
  and Michoacan. Damage in the epicentral area was
  restricted to a few tourist resorts and
  industrial estates along the Mexico Pacific
  coast. A two-meter tsunami also caused some
  damage in this area.
• There are geologic reasons why Mexico and
  especially Mexico City are vulnerable to
  earthquake damage. Along the west coast of
  southern Mexico and Central America the Cocos
  Plate dips beneath the North American Plate
  producing a very active seismic zone. Since the
  beginning of the twentieth century 35 earthquakes
  of magnitude greater than 7.0 have occurred in
  this zone. The location of the 1985 earthquake's
  epicenter near the coast at the border between
  the states of Michoacan and Guerrero was not a
  surprise. Prior to the 1985 earthquake this area,
  located between two areas that had experienced
  recent earthquakes, was known as the "Michoacan
  Gap." The "gap" was filled in 1985 by the main
  shock and a severe aftershock (magnitude 7.5)
  that occurred the next day.
• Mexico City itself lies in a broad basin formed
  approximately 30 million years ago by faulting of
  an uplifted plateau. Volcanic activity closed the
  basin and resulted in the formation of Lake
  Texcoco. The Aztecs chose an island in this lake
  as an easily defended location for their capitol.
  The expansion of the capitol (Mexico City) and
  the gradual draining of the lake left the world's
  largest population center located largely on
  unconsolidated lake-bed sediments. These soft
  sedimentary clay deposits amplified the seismic
  waves, or they subsided carrying buildings down
  with them. Double resonance coupling between the
  earthquake waves, the subsoils, and the buildings
  caused intensity IX shaking in some areas,
  lasting up to three minutes. Earthquakes in 1957
  and in 1979 also damaged Mexico City. However,
  neither of these earthquakes was quite as
  devastating as the 1985 earthquake.
• In the area of greatest damage in downtown
  Mexico City, some types of structures failed more
  frequently than others. In the highest damage
  category were buildings with six or more floors.
  Resonance frequencies of these buildings were
  similar to the resonance frequencies of the
  subsoil. Because of the "inverted pendulum
  effect" and unusual flexibility of Mexico City
  structures, upper floors swayed as much as one
  meter and frequently collapsed. Differential
  movements of adjacent buildings also resulted in
  damage. A flexible building often failed if it
  was held by adjacent, more rigid lower buildings.
  Damage or failure often occurred where two
  swaying buildings came in contact. Corner
  buildings were also vulnerable to damage. Lessons
  learned from the patterns of earthquake damage
  need to be quickly applied to prevent another
  disaster when an earthquake releases stress that
  is building in another area--along the Mexican
  coast between Acapulco and Zihuatanejo.

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The Kobe Earthquake Article

• Natural Hazards Slides Vol. 2 - Earthquake
  Events Kobe Earthquake
• KOBE
• The Earthquake
• At 546 A.M. local time on January 17, 1995, a
  major earthquake occurred near the City of Kobe,
  Japan. The 6.9 magnitude earthquake had 40 km of
  bilateral rupture from a hypocenter 10 km under
  the northern tip of the island of Awaji in the
  Sea of Japan. The greatest intensity of shaking
  was in a narrow corridor of two to four
  kilometers stretching 40 km along the coast of
  Osaka Bay. The ground moved as much as five
  meters in some places. The worst destruction ran
  along the previously undetected fault on the
  coast, east of Kobe. Kobe's major business,
  industrial and port facilities, and residences
  are located in this strip.
• Note This earthquake is also called the
  Hyogo-Ken Nambu, Japan, Earthquake and Southern
  Hyogo Prefecture Earthquake.
• The DamageThe earthquake caused extensive
  damage to the coastal cities that border Osaka
  Bay and to the northern portion of Awaji Island.
  Inland cities located near the northern end of
  the fault rupture sustained significant damage.
  Osaka (Japan's second largest city), Kyoto, and
  Shiga, farther to the northeast, reported
  extensive damage from the quake. The earthquake
  caused 5,480 deathsthe highest death toll in
  Japan since the Great Kanto Earthquake of 1923
  (142,000 deaths). About 94,900 people were
  injured nearly 317,000 people moved to
  evacuation centers.
• BuildingsMore than 192,700 houses and
  buildings were totally destroyed by the
  earthquake. Most of the damaged buildings were
  unsafe to occupy and had to be torn down later.
  The repair costs to buildings were estimated at
  more than 100 billion (U.S. Dollars). The design
  code in effect at the time of the construction
  was a major factor in determining the extent of
  damage to the commercial and residential
  buildings. Modern high-rise buildings typically
  fared better than older residential construction.
  
• TransportationKobe is located within the main
  transportation corridor between central and
  southern Honshu. The Hanshin Expressway,
  supported by large hammerhead reinforced concrete
  piers, failed over a twenty kilometer length. The
  supporting steel girders of the Wangan Expressway
  (along the harbor shore) were dislodged from
  their seats, although few collapsed.
• Rail facilities were particularly hard hit. All
  three main lines through the corridor sustained
  embankment failures, overpass collapses,
  distorted rails, and other severe damage. The
  elevated viaduct that carries the Bullet Train
  was severely damaged when supporting columns
  underwent shear failure. There was damage to the
  subway systems, including a rare instance of
  severe earthquake damage to a modern tunnel for
  reasons other than fault displacement near the
  portal. Rail and road transportation disruption
  affected a number of companies relying on rapid
  production systems. Due to effects on
  transportation, automobile and motorcycle
  manufacturers temporarily shut down factories
  located far from the earthquake site.
• Port DamageThe port of Kobe, one of the
  largest container facilities in the world,
  sustained major damage. Shipping had to be
  diverted to other ports. Cessation of port
  functions impeded the shipment of raw materials
  and parts between businesses in Japan and their
  subsidiaries or partners overseas. This impacted
  the electronics, apparel, and auto manufacturing
  industries. There was severe and widespread
  liquefaction as a result of the earthquake.
  Lateral ground deformation caused the piers of
  the highway bridge and electric rail bridge
  between Port Island and Kobe to lean between two
  and three degrees toward the waterfront. Of 186
  heavy shipping berths, 179 were inoperable after
  the earthquake.
• UtilitiesElectric power and telecommunications
  services were not disrupted, but most of Kobe
  lost essential services such as water, water
  treatment, and gas utilities. Electrical power
  performed well with very little reduction in
  service during the earthquake, and was completely
  restored within one week. Underground water
  pipelines sustained severe damage in the
  earthquake. Numerous breaks resulted in a general
  lack of service in Kobe, Ashiya, and Nishinomiya.
  Water was restored within two weeks and gas was
  restored within a month.
• FiresAlmost 150 fires started, most within
  minutes of the earthquake, and primarily in
  densely built-up low rise areas of the city. The
  fires destroyed one million square meters of
  residential area in Kobe.

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Kobe and Mexico City Earthquakes

• The Kobe earthquake of magnitude 7.2 struck the
  region of Kobe and Osaka in south-central Japan.
  This region is Japans second-most populated and
  industrialized area, after Tokyo. The shock
  occurred at a shallow depth on a fault running
  from Awaji Island through the city of Kobe, which
  in itself has a population of about 1.5 million.
• A powerful Mexico City earthquake registering
  magnitude of 8.1 rocked central Mexico. The quake
  was centered in the coastal mountains of the
  Michoacan Province and caused substantial damage
  throughout central Mexico, including in Mexico
  City - some 240 miles east of the epicentre.
• The Kobe earthquake struck on Tuesday, January
  17th 1995, at 546 a.m. local time.
• The Mexico City earthquake struck at 717 a.m.
  September 19th, 1985.
• Damage was recorded over a 100-kilometer radius
  from the epicentre, including the cities of Kobe,
  Osaka, and Kyoto, but Kobe and its immediate
  region were the areas most severely affected.
  Damage was particularly severe in central Kobe,
  in an area roughly 5 kilometres by 20 kilometres
  parallel to the Port of Kobe. This coastal area
  is composed primarily of soft alluvial soils and
  artificial fills. Severe damage extended well
  northeast and east of Kobe into the outskirts of
  Osaka and its port.
• Severe damage occurred to about 500 buildings in
  Mexico City with widespread light to moderate
  damage in other parts of the country. Although
  quake killed over 8,000 people, causalities would
  nave been much higher if the quake had occurred
  just a couple hours later when the schools and
  office buildings would have been full with
  people.

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• Japan is known to have a lot of minor and a few
  major earthquakes.
• Mexico City has been rocked several times in the
  past. It is largely built upon soft, poorly
  consolidated lake sediments from the former Lake
  Texcoco, which was drained by the Spanish
  following their occupation of the region. Thick
  sequences of soft sediments like these tend to
  amplify seismic waves and cause the ground to
  shake much more vigorously than the surrounding
  bedrock.
• The Kobe earthquake lasted about twenty seconds.
• The Mexico City earthquake was about three
  minutes long, but to a lot of people it seemed
  like an eternity.
• People did not have any warning for either of the
  two earthquakes.
• Nearly 5,500 deaths have been confirmed, with the
  number of injured people reaching about 35,000.
  Nearly 180,000 buildings were badly damaged or
  destroyed, and officials estimate that more than
  300,000 people were homeless on the night of the
  earthquake.
• In the Mexico City quake, at least 9,500 people
  were killed, about 30,000 were injured, more than
  100,000 people were left homeless, and severe
  damage was caused in parts of Mexico City and in
  several states of central Mexico. The death toll
  from this earthquake may be as high as 35,000. It
  is estimated that the quake seriously affected an
  area of approximately 825,000 square kilometres,
  caused between 3 and 4 billion U.S. dollars of
  damage, and was felt by almost 20 million people.

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• Kobes current estimates of the repair costs in
  the earthquake have been reported in the range of
  95 billion to U.S.147 billion, many times the
  damage inflicted by the 1994 Northridge
  Earthquake. These figures do not include the loss
  to building contents such as equipment and
  inventory, which will also be substantial.
• Mexico City got help from the states of the
  (Mexican) Republic and from people and institutes
  from abroad did not have to be waited for. The
  assistance was immediate. Aid and relief brigades
  came from Germany, Belgium, Algeria, Brazil,
  Canada, Colombia, Costa Rica, Cuba, Spain, the
  United States, France, Great Britain, the
  Netherlands, Israel, Panama, Switzerland,
  Venezuela, etc. Between September 19, 1985 and
  January 5, 1986, assistance reached the country,
  with 296 flights originating from 45 different
  countries. A figure that does not include the
  countries that made donations exclusively in
  cash. Aid by land came from 6 countries.

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The Kobe Earthquake
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The Mexico City Earthquake
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Bibliography

• Encyclopedia of Earthquakes and Volcanoes, 2001.
  New Edition.
• http//earthquake.usgs.gov/recenteqsww/world_merc.
  html\
• http//pubs.usgs.gov/gip/earthq1/
• http//www.crustal.ucsb.edu/ics/understanding/
• http//www.pgc.nrcan.gc.ca/seismo/eqinfo/q-a.htm
• http//www.seismo.unr.edu/ftp/pub/louie/class/100/
  plate-tectonics.html

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• National Geographic. Volume 169, No.5, (May
  1986) pg. 654
• National Geographic. Volume 188, No. , (July
  1995) pg. 112.
• Tazieff, Haroun. When The Earth Trembles. New
  York Harcourt, Brace World, Inc, 1964.