Important Concepts
Monday, August 17, 2009
1:05 PM
Earthquake Engineering is a branch of Civil Engineering that requires expertise in
geology, seismology, civil engineering and risk assessment. Project requiring
earthquake engineering are best comprised of a multi-disciplinary team having
geologists, seismologists, geotechnical engineers, structural engineers, applied
statisticians, and planners.
 Geology - Science that deals with the study of the earth and the processes
that formed and continue to shape the earth’s interior and exterior.
 Seismology - Science that deals with the study of earthquake waves and
other artificially produced vibrations and how these waves are propagated
through the earth’s interior and crust.
 Geotechnical Engineering - Discipline of civil engineering that deals with
soil mechanics and the assessment and design of soil and foundation
systems.
 Structural Engineering - Discipline of civil engineering that deals the design
and construction of man-made structures such as building, bridges, etc.
Earthquake hazards prose a significant risk to hundreds of millions of people
worldwide. The health and prosperity of many local, regional, and nation economies
are at risk from damage and loss of life resulting from moderate to larger
earthquakes in earthquake prone regions.
Earthquake hazards can be categorized as:
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Ground Shaking Hazards and Structural Collapse
Fault Rupture
Liquefaction
Earthquake-Induced Landslide, Mud Flows and Debris Flows
Failure of Embankments
Failure of Earth Retaining Structures
Tsunami and Seiche
Definitions:
○ Ground Shaking and Structural Collapse - - Strong ground shaking
resulting from seismic waves can cause significant damage to, and even
collapse of, constructed works. This is the most important of all seismic
hazards, because most other seismic hazards are a consequence of strong
ground shaking. Structural collapse of poorly constructed buildings and
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ground shaking. Structural collapse of poorly constructed buildings and
bridges has caused a significant loss of life, especially in underdeveloped
countries with no seismic provisions in building codes.
Fault Rupture - Fault rupture is a crack or fracture in the rock or soil
caused by shifting of the earth’s crust during earthquakes. Generally
adjacent surfaces are differentially displace along the plane of fracture.
Liquefaction - - A form of earthquake-induced form of ground failure
resulting from high pore pressures and a marked loss of shear strength in
granular, saturated soils due to strong ground shaking. The term
“liquefaction” generally encompasses several types of failure including: (1)
flow failure, (2) lateral spread, (3) ground oscillation, (4) bearing capacity
failure, (5) liquefaction- induced settlement.
Earthquake-Induced Landslide, Mud Flow, and Debris Flow - - Slope
failures in steep and saturated terrain, where the slope has been
destabilized by strong ground shaking.
Failure of Embankments and Retaining Structures - Earthen dams,
embankments and other retaining structures (e.g., bulkheads, quay wall,
retaining walls) are often damaged due to ground shaking or ground
failure. These facilities may be particularly vulnerable to damage when in
waterfront, port or harbor areas, where they retained earth remains
saturated.
Tsunami and Seiche - Tsunami are very large, long-period waves produced
in the ocean by fault rupture or crustal deformation during earthquakes.
As the wave form approaches shore, decreasing water depth cause the
wave speed to decrease and the height of the wave to increases. In some
coastal areas, the shape of the sea floor may accentuate the height of the
wave, producing a near vertical wall of water, which produces great
destruction inland. Seiche are waves that oscillate in lakes, bays, or gulfs
from a few minutes to a few hours as a result of seismic waves.
Risk Analysis - Discipline of applied statistics that uses laws of probability to
assess the potential loss and consequences due to either natural or man made
events.
Mitigation of seismic hazards requires proper planning, earthquake-resistant
design and construction and rapid emergency response.
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Strong Motion - Building Damage
Monday, August 17, 2009
2:29 PM
"Earthquakes don't kill people, buildings do."
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Strong Motion - Waves
Monday, August 17, 2009
5:13 PM
Primary wave
animation
Shear wave
animation
Love wave
animation
Rayleigh wave
animation
What is the difference between a Rayleigh wave and a water wave?
Rayleigh wave animation
Water wave
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Strong Motion - Accelerograms
Tuesday, August 18, 2009
12:33 PM
These two accelerograms (i.e., acceleration time histories) were recorded from the same earthquake at
approximately the same distance to the earthquake source. How are they different and why?
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Strong Motion - Variation of pga
Tuesday, August 18, 2009
2:30 PM
Peak ground acceleration (g) for San Francisco Bay Area
Why are the values of pga so variable on this map?
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Strong Motion - Soil Effects
Tuesday, August 18, 2009
2:37 PM
Map of Bay Mud in San Francisco Bay
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Are higher or lower pga values found where the Bay Mud is present?
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Changes in strong motion due to soil deposits are often called soil or site effects.
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Strong Motion - Structural Damage
Tuesday, August 18, 2009
2:46 PM
Damage to structures in San Francisco/Oakland (1989 Loma Prieta Earthquake):
(a) Life-threatening collapse of unreinforced masonary building in Oakland City Center
(b) Sporadic damage occurred to unreinforced masonary structures in San Francisco Note that the
building remains standing, despite the loss of the bearing wall.
(c) Extensive masonary loss and shear cracking was noted in this steel frame building in Oakland.
(d) The masonary walls of this steel frame department store in Oakland had extensive damage.!
Inside many hollow clay tile partition walls shattered
What is the definition of unreinforced masonary?
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Fault Rupture
Tuesday, August 18, 2009
2:55 PM
Fault rupture can be: (1) extensional, (2) compression or (3) strike-slip.
Which type of faulting is shown above?
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Fissures in front of house near Summit Road (1989 Loma Prieta Earthquake)
Significant extensional as well as vertical displacement shown.
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