Suppose that local fire
and rescue crews had
to prioritize which of
the "Strong Shaking
Case Studies" areas to
search first for
earthquake survivors
and casualties.
Which area (N1, N2,
E1, or E2) should get
priority? Why?
1
Structural Damage, 1989 Loma Prieta Earthquake, J.K. Nakata, USGS
Why did the first floor of this apartment building collapse, whereas the
upper stories were mostly unaffected?
M 6.9 Loma Prieta (CA) October 17, 1989
Depth: 18.0 km
Ground type: Artificial fill
2
This activity addresses the following learning
objectives:
1. Students will relate earthquake damage to
rock/soil type and distance from epicenter.
2. Students will identify factors that contribute
to building damage associated with
earthquakes, and will describe potential
strategies to mitigate seismic damage to
buildings.
3
What effect does an earthquake’s depth have on the damage it does?
Mw 6.8 Nisqually (WA), Feb 28, 2001
Depth: 52 km
Ground type: Dominantly glacial and
river sediments and volcanic rocks.
Mw 6.7 Northridge (CA)
Jan 17, 1994
Depth: 18 km
Ground type: Alluvial and marine
sediments; crystalline (igneous
and metamorphic) rocks.
4
Buildings on loose fill may sink as sediment liquefies
during an earthquake.
Collapsed building in the Marina District, San Francisco, 1989 Loma Prieta Earthquake, D. Perkins, USGS
M 6.9 Loma Prieta (CA) October 17, 1989
Depth: 18.0 km
Ground type: Artificial fill (right), alluvial sediment? (left)
5
Earthquakes can trigger landslides
Government Hill landslide, Anchorage, Alaska, 1964 Prince William Sound Earthquake, USGS
M 9.2 Prince William Sound (AK) March 27, 1964
Depth: 6.3 km
Ground type: Clay-rich?
6
Building materials greatly affect seismic safety. Unreinforced masonry
or wood are particularly prone to damage.
 Unreinforced masonry
building in Fillmore, 1994 Northridge
Earthquake, J. Dewey, USGS
Mw 6.7 Northridge (CA) January 17, 1994
Depth: 18 km
Ground type: Alluvial and marine sediments;
crystalline (igneous and metamorphic) rocks.
Damage to an old Buddhist temple. Note
that the (more modern) building next door is
unharmed. Photo: R. Hutchison, NOAA.
Mw 6.9 Kobe (Japan) January 16, 1995
Depth: 22 km
Ground type: Unknown
7
How do undivided floor plans affect a building’s seismic safety?
The first floor of this building contained large open spaces (“soft stories”), in this case stores.
Photo: R. Hutchison, NOAA
Mw 6.9 Kobe (Japan) January 16, 1995
Depth: 22 km
Ground type: Unknown
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Mitigating Construction Problems
• Reinforcement: Bracing, shear walls (best for
soft stories)
• Base isolation: Flexible link between building
and foundation
• Vibration damping: Add devices to resist
shaking
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Mitigating Settlement / Liquefaction
• Reinforce structure to mitigate small motion
• Improve foundation: deep piles, flexible piles,
mat foundation
• Stabilize soil: dewater, grout, densify, buttress
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Mw 6.8 Nisqually (WA), February 28, 2001
Depth: 52 km
Ground type: Dominantly glacial and river sediments,
volcanic rocks.
Mw 6.7 Northridge (CA) January 17, 1994
Depth: 18 km
Ground type: Alluvial and marine sediments;
crystalline (igneous and metamorphic) rocks.
These two buildings were both constructed of unreinforced masonry. The building on
the right experienced more damage: why?
11
Leaning apartment houses in Niigata, Japan, 1964 Niigata Earthquake, NOAA National Geophysical Data Ctr
Why do some of these buildings lean, while others are upright?
Mw 7.5 Niigata, Japan June 16, 1964
Depth: 40 km
Ground type: Sand, younger deposits on left, older and more consolidated toward right
12
Cars crushed by brick, 1989 Loma Prieta Earthquake, C.E. Meyer, USGS
Why did one of these buildings experience
major damage, particularly to its façade,
when its neighboring building was
relatively unaffected by the same
earthquake? Examine the rubble pile and
building facades for clues.
M 6.9 Loma Prieta (CA) October 17, 1989
Depth: 18.0 km
Ground type: Artificial fill
13
Structural Damage, 1989 Loma Prieta Earthquake, J.K. Nakata, USGS
The first floor of this wooden San Francisco apartment was mainly garages. It is now
“pancaked,” whereas the second and third floors are unaffected. Why?
M 6.9 Loma Prieta (CA) October 17, 1989
Depth: 18.0 km
Ground type: Artificial fill
14
Collapsed apartment in Reseda, 1994 Northridge Earthquake, J. Dewey, USGS
The first floor of apartment building near Northridge was mainly garages. It is now
“pancaked,” whereas the second and third floors tilted like rigid blocks. Why?
Mw 6.7 Northridge (CA) January 17, 1994
Depth: 18 km
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Ground type: Alluvial and marine sediments; crystalline (igneous and metamorphic) rocks.
What made this building so risky?
Mw 7.4 Kocaeli/Izmit, Turkey August 17, 1999
Depth: 15.9 km
Ground type: Unknown
16
Assess risk at public school campuses around San Francisco
Marina1
Marina2
Francisco1
Francisco2
Garfield1
Garfield2
HHoover1
HHoover2
Guadalupe1
Guadalupe2
Sunset1
Sunset2
(from class
discussion)
Recommendation
Analysis
Risk Factor
E: Unreinforced
Masonry
F: Vertical or Plan
Irregularity
G: Number of
Students
D: Soft Stories?
Vulnerability Value
C: Landslide
Potential
B: Liquefaction
Potential
Name of School
A:
Peak Ground
Acceleration
Hazard
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Discussion Questions
1. Which two schools should receive $10 million
for seismic retrofitting?
2. What measures would you recommend to
mitigate seismic risk at each school campus?
At some schools, other measures may be
more effective at mitigating risk than seismic
retrofitting.
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Discussion Questions
3. As a result of learning about calculated risk,
you may have changed the way you think
about prioritizing emergency services in the
event of an earthquake. Would you change
your answer from the prework? If so, what
about it would you change, and why? If not,
what convinced you that it was correct?
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Writing Assignment
Based on your risk assessment of the five schools in
this activity, make the case for funding upgrades to
buildings at two schools.
Prepare a set of bullet points to be presented to the
City of San Francisco that uses data from your
analysis to support your recommendations. If
additional measures are necessary to mitigate risk
at other schools, outline them and support them as
well.
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