INTRODUCTION TO EARTHQUAKE ENGINEERING

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INTRODUCTION TO EARTHQUAKE ENGINEERING
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Sequence

• Plate movement
• Type of faults
• Wave motion
• Energy release
• Urban earthquake risk
• Structural performance level
• Evaluation approach

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8/10
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Large Earthquakes
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Elastic Rebound Theory
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Indian Plate
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Historical Earthquakes in the Himalaya
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Southern Asia
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Plate Movement
4-5 m slip _at_1 cm/yr 4-500 years
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Tibetan Plateau
Himalayas
Indian Plate
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Indian Plate
Tibet
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Indian Plate
Tibet
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Indian Plate
Tibet
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critical stress
Tibet
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great earthquake
Tibet
4-10 m
the longer the inactivity the bigger the 'quake
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Faults
Through the study of faults and their effects,
much can be learned about the size and recurrence
intervals of earthquakes. Faults also teach us
about crustal movements that have produced
mountains and changed continents. Stresses often
continue to build until they exceed the strength
of the bond in that section of crust. The rock
then breaks, and an earthquake occurs, sometimes
releasing massive amounts of energy. Faults vary
in length from a few centimeters to hundreds of
kilometers across. Displacements of one side of
the fault over the other vary from fractions of a
meter to many kilometers. In many cases the
displacement is not confined to a single fracture
but is distributed throughout a fault zone. Many
faults do not rupture the surface, but when the
surface is broken, the fault line is visible as a
fault trace or outcrop.
Contd
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Faults
Vertical or horizontal movement may occur along a
fault plane. Sometimes both vertical and
horizontal movement occur simultaneously. Faults
are named according to the type of movement that
has occurred. The term slip is used to indicate
relative displacement across the fault. When the
movement along the fault plane is generally
horizontal, it is a strike-slip fault. These are
also called lateral faults. Offset streams are
found along active strike-slip faults. A
transform fault is a zone of lateral movement
along which the ridges and rises have been offset
and along which the displacement suddenly stops
or changes form and direction. When the movement
along the fault plane is predominately vertical,
it is a dip-slip fault. There are
sub-classifications within this category.
Contd
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Faults
A normal fault occurs when the earth above the
fracture moves down in respect to the earth below
the fracture. A reverse fault occurs when the
rocks above the fracture move up with respect to
those below. A reverse fault with an angle of
less than 45 degrees is called a thrust fault.
Thrust faults are generally characterized by
older rocks resting on younger rocks, although in
some cases younger rocks may be thrust over older
rocks.
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Fault Motion
Diagram showing the three main types of fault
motion.
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Left Lateral Fault
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Left Lateral Fault
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Left Lateral Fault
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Right Lateral Fault
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Right Lateral Fault
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Right Lateral Fault
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Normal Faulting
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Normal Fault
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Thrust Faulting
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Thrust Fault
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Subduction
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Time Period
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Wave Motion
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Wave Travel
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Wave Path
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Wavefront
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Energy Release
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Energy Release
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October 9,2005 ------ September 15,2002
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ELEMENTS OF URBAN EARTHQUAKE RISK
RISK
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Performance Level

• the permissible amount of damage, given that
  design loading occurs

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Structural Performance Levels
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Serviceability Level

• Negligible structural and nonstructural damage
• Utilities are available
• Facility is available for immediate re-use
• Repair costs are minimal to nil

Joes
Great Food!
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Immediate Occupancy Level

• Negligible structural damage
• Minor nonstructural damage
• Building is safe to occupy but may not function
• Limited interruption of operations
• Repair Cost lt 15

Joes
Great Food!
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Immediate Occupancy
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Life-Safety
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Collapse Prevention Level

• Extensive structural and non-structural damage
• Extended loss of use
• Repair may not be practical
• Repair costs gtgt 30

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Collapse Prevention
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Collapsed
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Collapsed
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Global Response Performance
Loading Severity
Structural Displacement D
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Evaluation Approach
6- Pass or Fail Criterion evaluated on
component by component basis
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