1 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?

2 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 kmGround type: Artificial fill

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

4  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. What effect does an earthquake’s depth have on the damage it does?

5 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)

6 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?

7 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

8 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 How do undivided floor plans affect a building’s seismic safety?

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 9

Mitigating Settlement / Liquefaction Reinforce structure to mitigate small motion Improve foundation: deep piles, flexible piles, mat foundation Stabilize soil: dewater, grout, densify, buttress 10

11 These two buildings were both constructed of unreinforced masonry. The building on the right experienced more damage: why? 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.

12 Leaning apartment houses in Niigata, Japan, 1964 Niigata Earthquake, NOAA National Geophysical Data Ctr Mw 7.5 Niigata, Japan June 16, 1964 Depth: 40 km Ground type: Sand, younger deposits on left, older and more consolidated toward right Why do some of these buildings lean, while others are upright?

13 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

14 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 kmGround type: Artificial fill

15 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 Ground type: Alluvial and marine sediments; crystalline (igneous and metamorphic) rocks.

16 Mw 7.4 Kocaeli/Izmit, Turkey August 17, 1999 Depth: 15.9 km Ground type: Unknown What made this building so risky?

17 HazardVulnerabilityValueAnalysis Name of School A : Peak Ground Acceleration B : Liquefaction Potential C : Landslide Potential D : Soft Stories? E : Unreinforced Masonry F : Vertical or Plan Irregularity G : Number of Students Risk Factor Recommendation (from class discussion) Marina1 Marina2 Francisco1 Francisco2 Garfield1 Garfield2 HHoover1 HHoover2 Guadalupe1 Guadalupe2 Sunset1 Sunset2 Assess risk at public school campuses around San Francisco

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. 18

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? 19

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. 20