Course:EOSC311/2022/Urban Planning in Seismically Dangerous Regions on the example of San Francisco

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The 1906 earthquake gave a strong impetus to the development of seismic safety in San Francisco. Being on the border of two faults, the city experienced an earthquake with a magnitude of 7.7 points. The disaster claimed the lives of many people and caused irreparable economic damage. Soon after, the city administration, namely the urban planning department, took measures to increase the seismic safety of the city. This project will provide examples of tools used, as well as seismic engineering and techniques to prepare the population for possible shakes.

Geology and my Major

I am majoring in Sociology and my idea for the term project is to study how urban social management interferes with the geological environment that we live in. For this project, I want to focus on urban planning in hazardous environments (seismically active regions). Being born and raised in Almaty, the city at the foot of the mountains, I have experienced many small shakes myself. However, it was not until 2013 that a stronger earthquake occurred and I started questioning seismic safety in the city, especially in the newer buildings which have recently been built in hundreds. Looking at the example of San Francisco, I see how much improvement the city underwent in terms of preparedness for the possible quake, and hope to maybe apply this knowledge to Almaty or Vancouver, both seismically active zones.

Geography and Climate

Figure 1: Map of San Francisco's nearby faults. Percentage shown on each fault line reflects the likelihood of an earthquake magnitude 6.7 or greater will occur along the fault by 2043.

San Francisco's climate is Mediterranean, with rainy, moderate winters and dry summers[1]. The weather of San Francisco is heavily impacted by the Pacific cold currents, which minimize temperature fluctuations and generate a year-round environment with little seasonal temperature variance. Summers in San Francisco are characterized by fog. San Francisco boasts a variety of microclimates due to its unique geography and coastal influences. The city's western neighbourhoods are often colder and wetter than the city's eastern neighbourhoods. The mean monthly temperatures are warmest in September (17℃) and coldest in January (11℃), while the wettest month (January) averages 114 mm of precipitation, with the driest month (August) averaging 2.5 mm of precipitation and the driest month (August) averaging 2.5 mm of precipitation[2].

San Andreas fault

San Andreas fault zone is somewhat fractured, covering the "distance extending from just north of San Bernardino to just north of Indio, some 110 kilometres (70 miles)"[3]. Ancient and inactive strands of the San Andreas fault may be seen in this are since this deformation has been going on for over a million years. Other faults in the vicinity have lately "reawakened" after hundred years of dormancy. According to Southern California Earthquake Data Center, there's also evidence that there's no active, continuous main trace of the San Andreas fault running all the way down the pass, even at depth, meaning that the San Andreas fault is now forming a new fault route through this location[4]. However, because the mechanics of fault rupture are still unknown, the discontinuity may have minimal influence in dampening a significant earthquake along this section of the San Andreas fault zone.

Hayward fault

The Hayward Fault is one of the most dangerous in the world, since it runs beneath a highly populated area of California and is due for a huge earthquake. As mentioned in the report published by the California Geological Survey, in the next three decades, the Hayward Fault has a 31% probability of producing a magnitude 6.7 or higher earthquake[5]. The fault runs parallel to the San Andreas Fault and to the east of it. The Hayward Fault extends “from San Jose about 74 miles northward along the base of the East Bay Hills to San Pablo Bay.”[6] Apart from magnitude and reputation, "aseismic creep" is a significant distinction between the Hayward and San Andreas faults. The San Andreas Fault is trapped in many locations, and earthquakes unleash most of its energy. Creep does, however, occur in some areas along the Hayward Fault. Every year, the ground shifts a few millimetres, tearing out sidewalks, pipelines, and other infrastructure that lay on the fault.

Figure 2: Graphical representation of differences between stable and liquified soils, implications are shown on the example of buildings.

Soil Liquefaction

Soil liquefaction occurs when sediments below the water table lose shear strength and behave more like a viscous liquid than a solid[7]. The soil remains stable if the pressure is kept low enough. However, as the water pressure reaches a particular level, the soil particles are forced to migrate relative to one another, causing the soil's strength to diminish and failure to occur. When a shear wave passes through saturated soil layers during an earthquake, the granular soil structure deforms, causing the vulnerable area of the soil to collapse. Because the bottom layer is filled with collapsed soil, the pore water pressure in this layer rises. If the increased water pressure is not discharged, it will continue to build up until the soil's effective stress reaches zero. If this happens, the soil layer loses its shear strength and is unable to determine the entire weight of the soil layer above it, allowing the upper layer soils to flow down and act like a viscous liquid.

Earthquakes in San Francisco

1906 Earthquake

On the morning of April 18, 1906, a “devastating earthquake and subsequent inferno razed San Francisco”[8]. Witnesses said the city's streets rose and fell like a ribbon blown by the wind. The tremors sparked a three-day fire that destroyed 500 city blocks and 28,000 structures. Around 400,000 people were displaced, or half of the population. Many people had to abandon the city since they couldn't afford to stay.

Description

The first tremors of the earthquake have been recorded at 5:12 am, “Originating from an epicenter offshore from San Francisco” [9], the earthquake jolted all of coastal northern California and breached the San Andreas fault in two directions, to the north and south. Strong shaking lasted 45–60 seconds, according to careful witnesses, many reputable witnesses also reported two powerful shaking pulses separated by 25–30 seconds[10]. The tremor came as a complete surprise. In the days, weeks, and months leading up to the 1906 earthquake, there was no exceptional seismic activity[11]. Residents did notice shaking, which was thought to be caused by a foreshock that occurred 30 seconds before the main shock [12][13]. The Richter magnitude of the 1906 earthquake is commonly referred to as 8.3[14]. The Richter magnitude scale, on the other hand, was created for local earthquakes detected by high-frequency seismometers.

Figure 3. San Francisco in 1906: Black lines are 8 -inch and larger water mains thicker the line, larger the diameter. Yellow area is primarily wood-frame construction, while pink is primarily masonry; crosshatched pink area downtown is the “congested area,” that is, the central business district. Ignitions following the 1906 earthquake are shown as red squares.

Fire

Fires erupted all around San Francisco just minutes after the shaking stopped. “The earthquake and resulting fires caused an estimated 3,000 deaths and $524 million in 1906 dollars in property loss” [15]. Because there was no water to put out the fires that broke out in San Francisco shortly after the earthquake, they burned for three days. San Francisco suffered catastrophic damage, with 28,000 structures destroyed, 80 percent of which were burned owing to the fire rather than the shaking, fires exacerbated the damage at Fort Bragg and Santa Rosa, California [16]. After the earthquake, the number of flames and/or explosions was estimated to be between 50 and 52[17] (sites shown in Figure 3).

Implications of earthquake

Of course, the magnitude of the loss surprised everyone, probably even more so the insurers than the public. The insurance industry moved fast, establishing a mechanism for adjusting claims before the flames were out (Whitney 1906) and, in general, covered most of the damages, albeit several complications arose, such as paying out claims for "burnt debris"[18]. More than 5,000 people perished in the Kobe earthquake, which struck early in the morning while most inhabitants were still at home, mostly as a result of building collapse. More than 30,000 people were injured [19].

Figure 4: Devastating implications of the 1906 earthquake: a fault in the middle of the road
Economic implications

The insurance business, having been burnt before, now required the building of the high-pressure system Dennis Sullivan had requested if San Francisco ever wanted another insurance policy filed. As a result, in 1908, San Francisco city engineer Marsden Manson designed the Auxiliary Water Supply System (AWSS), which was funded by a $5.2 million bond issue and was mostly finished by 1912[20]. Aside from the deaths, more than 225,000 people were made homeless, and 28,000 structures were damaged, resulting in an estimated economic loss of $10.5 billion in today's money[21]. In comparison, from 1812 to 1901, there were only about 200 earthquake deaths in California, and the property loss from the next major earthquake following 1906, the Long Beach Earthquake of 1933, was roughly 750 million dollars today[22].

1989 earthquake

A powerful earthquake known as Loma Prieta hit the whole San Francisco Bay region on October 17, 1989, at 17:04 Pacific Daylight Time [23].

Description

The rupture of a segment of the San Andreas Fault, with the epicentre around 16 kilometers northeast of Santa Cruz, triggered the Loma Prieta earthquake, which had a magnitude of 7.0. The magnitude of the surface wave was determined to be 7.1 [24]. Jablonski also states, that “[w]ithin a period of 12 days after the main shock, 80 aftershocks of magnitude 3.0 and larger were recorded, the largest one being magnitude 5.2”[25].

Implications of earthquake

With $10 billion in economic losses, 64 verified deaths, and more than 3700 injuries, the Loma Prieta earthquake is considered one of the most devastating natural disasters in US history [26]. A 76-by-50-foot (23 m x 15 m) part of the top deck on the eastern cantilever side of the San Francisco–Oakland Bay Bridge crashed onto the deck below, causing significant damage.

Economic implications

The earthquake wreaked havoc in a few specific parts of the Bay Area, most notably on San Francisco's and Oakland's fragile terrain. After the earthquake, Oakland City Hall was evacuated until 1995, when seismic retrofit and hazard abatement work cost $80 million [27]. The Federal Emergency Management Agency (FEMA) turned persons who were homeless before to the earthquake away from homeless shelters and offered refuge to those who had homes previous to the earthquake, 12,000 homes and 2,600 businesses were damaged[28]. Moreover, the “[e]stimated building-related economic losses are about $19 billion, including business interruption, roughly 25% greater than the actual loss estimate of $15 billion” [29].

Differences between the 1906 and 1989 earthquakes

Since the 8.3 magnitude earthquake in San Francisco on April 18, 1906, 1989 earthquake was the biggest in northern California. Outside of the epicentre, the most severe damage was centred in San Francisco's Marina District, which was built on fill following the 1906 earthquake. The earthquake of 1906 was not only more strong, but it also lasted longer. In 1989, the length was about 15 seconds, while the tremor lasted over a minute in 1906. A whole minute of tremors, 16 times stronger than what was felt in 1989[30].

Seismic safety

Building safety is critical in San Francisco, which is built on three earthquake faults. The city has been campaigning for a more crowded and vertical downtown after decades of popular opposition to skyscrapers, there are already 160 buildings in San Francisco that stand taller than 240 feet, with a dozen more planned or under construction[31].

Department of Building Inspection

To safeguard schools and hospitals against a catastrophic earthquake, California has stringent building codes. Skyscrapers, on the other hand, are a different story, since “[a] five-story building has the same strength requirements as a 50-story building”[32]. Thus, the Department of Building Inspection was created in 1994, and its purpose is “[t]o serve the City and County of San Francisco and the general public by ensuring that life and property within the City and County are safeguarded and to provide a public forum for community involvement in that process” [33]. The Department of Building Inspection is also responsible for the safety of nearly 200,000 structures in San Francisco, including both residential and commercial buildings.

Building Occupancy Resumption Program (BORP)

After accepting a written inspection program, this award-winning DBI program allows San Francisco building owners to pre-certify private post-earthquake inspections of their buildings by competent engineers. The goal of a pre-certified emergency inspection program is to allow competent people who are familiar with the building's structural design and life-safety systems to quickly and thoroughly assess potential structural damage[34]. The Building Occupancy Resumption Program consists of three stages:

  • The first stage includes the assessment of the building and the preparation of the BORP program, which implies the delivery of the building emergency inspection program and the inspection plan.
  • The second stage includes annual activities to update inspection supplies and equipment and a possible update of the inspection plan.
  • The third stage is the implementation of the program after a shake, it includes ATC-20 Detailed Evaluation, on the basis of which an inspection plan is built after an earthquake [35]

Mandatory Soft Story Program (MSSP)

MSSP was created in 2013 by community's joint efforts headed by Earthquake Safety Implementation Program. The goal of the program is "to ensure the safety and resilience of San Francisco's housing stock through the retrofit of older, wood-framed, multi-family buildings with a soft-story condition."[36] Program's ordinance applies to three or more story buildings with five or more resident units and with construction permit application submitted prior to January 1, 1978 that were not seismically strengthened. The largest number of such dwellings is found in such districts as Mission, Western Addition, Richmond, North Beach, and Marina District.

Hazard Maps

Department of Building inspection also provides the following AnchorHazard maps: Association of Bay Area Governments maps, California Division of Mines and Geology maps, UC Berkeley - maps and info about recent quakes and USGS maps. The data on these maps are meant to help state and local governments plan for emergency evacuations and earthquake responses[37].

Community Action Plan for Seismic Safety (CAPSS)

The Community Action Plan for Seismic Safety (CAPSS), which began in 1998 with the Department of Building Inspection, was a nine-year, $1 million project to better understand, explain, and decrease the danger of earthquakes in San Francisco [38]. The City commissioned the Community Action Plan for Seismic Safety (CAPSS) project, which was completed by the Applied Technology Council (ATC), to research four potential earthquakes that may occur in the city and discovered that future earthquakes will cause severe damage to thousands of structures, rendering them uninhabitable.

Personal Preparedness

Department of Building inspection also provides the following materials for Personal Preparedness in case of earthquakes: San Francisco Fire Department Neighbourhood Emergency Response Training (NERT), US Geological Survey - emergency information, Earthquake Safety Checklist, Earthquake Safety Guide for Homeowners, PG&E emergency information re: utility shutoff, etc [39].

Seismic engineering

Making buildings more earthquake-resistant is the overarching goal of seismic engineering. Buildings that won't be significantly damaged or collapse in the case of a large earthquake are the goal of an earthquake (or seismic) engineer.

Figure 5: Information about the processes going on during each phase of the Golden Gate Bridge Seismic Retrofit Project .  

Bridges - Seismic Retrofit Construction Project

The Golden Gate Bridge connects San Francisco to the counties to the north by crossing the Golden Gate Strait. It provides a major transportation link for the San Francisco Bay Area, serving up to 40 million cars each year. The Bridge is managed by a California special district established in 1928. The Golden Gate Bridge, Highway and Transportation District (GGBHTD) expanded its purpose in 1971/1972 to include the operation of the Golden Gate Transit bus system and the Golden Gate Ferry system. The 1989 shake, despite not causing significant damage to the Bridge, lead to the start of an extensive retrofit construction project that is still happening today. GGBHTD's vulnerability study suggested that in the case of any shake magnitude 7.0 or greater, the Bridge would be under a risk of severe damage, and in the case of the shake magnitude 8.0 or greater, the Bridge would be seriously damaged and cause collapse of the San Francisco and Marin Approach Viaducts and the Fort Point Arch. The Seismic Retrofit Construction Project was introduced in 1996 and three stages were established:

  • Phase 1: Retrofit the Marin (north) Approach Viaduct (Completed December 2001)
  • Phase 2: Retrofit the San Francisco (south) Approach Viaduct, San Francisco (south) Anchorage Housing, Fort Point Arch, and Pylons S1 and S2 (2001 to 2006)
  • Phase 3A: Retrofit Marin (north) Anchorage Housing (2007 to 2013)
  • Phase 3B: Retrofit the Main Suspension Bridge (Main Span and Tower)

The work done in Phase 1 included installing isolators, replacing and adding some bracing members, replacing towers, adding cover plates, strengthening foundation, replacing expansion joints, and closing roadway joints. In the Phase 2, work done at South Viaduct included installing isolators, replacing and bracing members, adding cover plates, strengthening foundation, replacing expansion joints, and closing deck joints. At the Pylon S2 and S1, they were strengthened with still plates (internally and externally, and anchor to bedrock). The South Anchorage Housing was strengthened by reinforcing internally, west wall and portions of east wall were replaced, and foundation was strengthened as well. At the Fort Point Arch, energy dissipation and expansion joints were installed, bracing was added, members were strengthened, and bearings modified. In the Phase 3A, the work done at North Anchorage Housing included strengthening by reinforcing internally and replacing roadway deck [40].

Buildings - new seismic standards

The 2001 San Francisco Building Code (SFBC), which is made up of the 2001 California Building Code (CBC) and the 2001 San Francisco Amendments, governs all new building construction in San Francisco. The 2001 CBC is based on the 1997 Uniform Building Code (UBC), whose purpose is “to provide minimum standards to safeguard life or limb, health, property, and public welfare by regulating and controlling the design, construction, quality of materials, use and occupancy, location and maintenance of all buildings and structures within this jurisdiction and certain equipment specifically regulated herein”[41].

Work with population

San Francisco Department of Building Inspection has organized many Preparedness Programs designed to help the population get prepared, such programs include the Neighborhood Emergency Response Training (NERT) Program, Building Occupancy Resumption Program (BORP) (discussed above), and Seismic Safety Outreach Program[42].

Neighborhood Emergency Response Training (NERT)

NERT is a free training program available for citizens of San Francisco. The goal of the program is to help population of the city and county learn basic emergency skills needed for emergency situations such as earthquakes. The program is intended to be completed in 20 hours, with 6 classes approximately 3 hours each. The topics that program covers are the following:

  • Class Session 1 - Earthquake Awareness, Preparedness, and Hazard Mitigation
  • Class Session 2 - Basic Disaster Skills
  • Class Session 3 - Disaster Medicine
  • Class Session 4 - Light Search and Rescue
  • Class Session 5 - Team Organization and Management
  • Class Session 6 - Skills Development and Application [43]

Seismic Safety Outreach

DBI launched the Seismic Safety Outreach Program in 2015 in collaboration with Community Youth Center (CYC) and Self Help for the Elderly (SHE) to provide San Francisco's diverse populations with hands-on training and education on how residents, young and old, can prepare before, during, and after an earthquake As stated on the Department of Building Inspection website, “[i]n January 2018, this program was expanded to provide in-language workshops citywide in San Francisco’s 11 Supervisorial Districts”[44]. The topics that program covers during workshops are the following:

  • Personnel Preparedness
  • Basic First Aid and Citizen CPR
  • Earthquake Mitigation
  • Response and Recovery
  • Fire Safety

Earthquake Handbooks

California Seismic Safety Commission (CSSC) every year publishes Homeowner’s Guide to Earthquake Safety. This handbook assists the population in preventing injuries, saving lives, and avoiding costly property damage as a result of earthquakes. It provides information on the most common earthquake-related hazards that can damage homes, how to find and then fix the potential structural risks in a home, and how to find more information on earthquake safety[45].

Schools

In 2014, the proposed Earthquake Performance Evaluation of Private Schools Act compels private institutions to meet criteria that are higher than those set by the state of California, putting further strain on schools that are already operating on thin margins. If the seismic safety threshold is raised from "life and safety" to "recovery status", vital time and resources will be diverted away from the education of one-third of The City's youngsters[46].

Evaluation of the Connections

Since the 1906 earthquake, San Francisco's Urban Planning department has done a tremendous job to ensure the seismic safety of the city and its residents. Numerous programs aimed at housing and commercial buildings are an excellent example of preventing and mitigating the effects of high-magnitude earthquakes. The techniques used in seismic engineering of such particularly large and significant objects as the Golden Gate Bridge can be the foundation for further construction not only in the city itself, but also in places with similar geography (located near tectonic faults), such as Vancouver. The administration pays special attention to carrying out work with the population in order to prepare it for a possible repeated strong shaking. Similar programs have been introduced in Vancouver: for example, the city conducts workshops to teach the population basic earthquake survival skills, created a volunteer disaster relief network, and also introduced 25 support centers to facilitate receiving assistance after an earthquake[47]. In relation to Almaty (a city located near Dzhalair-Naiman Fault), due to limited financial opportunities compared to San Francisco and Vancouver, it seems possible that the administration's focus should be on preparing residents for an earthquake and implementing different programs aimed at teaching. At the moment, the city is experiencing an urban development boom, and many of the buildings constructed do not look safe or at least capable of surviving an earthquake with a magnitude of 5.0. Perhaps the city needs to relive an earthquake similar to the Kebin earthquake in 1911[48] in order to revise its urban planning policy and focus on seismic safety. Hopefully, the lessons of history will be learned from theory rather than practice, and that the Urban Planning Department will take appropriate measures.

References

  1. ↑ Johnson, K. A. (September 22, 2018) Geology of San Francisco, California, United States of America. Geology of the Cities of the World Series.https://www.aegweb.org/assets/docs/updated_final_geology_of_san.pdf
  2. ↑ Johnson, K. A. (September 22, 2018) Geology of San Francisco, California, United States of America. Geology of the Cities of the world Series, 6. https://www.aegweb.org/assets/docs/updated_final_geology_of_san.pdf
  3. ↑ Southern California Earthquake Data Center (2017). "Earthquake Information: San Andreas Fault Zone". SCEDC.
  4. ↑ Southern California Earthquake Data Center (2017). "Earthquake Information: San Andreas Fault Zone". SCEDC.
  5. ↑ California Department of Conservation (2008). "Hayward Fault Fact Sheet".
  6. ↑ California Department of Conservation (2008). "Hayward Fault Fact Sheet".
  7. ↑ Moustafa, Abbas (2012). Advances in Geotechnical Earthquake Engineering - Soil Liquefaction and Seismic Safety of Dams and Monuments. IntechOpen. p. 64. ISBN 978-953-51-0025-6.
  8. ↑ Fuller, T., Singhvi, A. & Williams, J. (2018, April 17). "San Francisco's big seismic gamble". The New York Times. Retrieved June 7, 2022. Check date values in: |date= (help)CS1 maint: multiple names: authors list (link)
  9. ↑ Zoback, M. L. (2006). "The 1906 earthquake and a century of progress in understanding earthquakes and their hazards" (PDF). U.S. Geological Survey: 1 – via GSA TODAY.
  10. ↑ Zoback, M. L. (2006). "The 1906 earthquake and a century of progress in understanding earthquakes and their hazards" (PDF). U.S. Geological Survey – via GSA TODAY. line feed character in |title= at position 49 (help)
  11. ↑ Gilbert, G. K. (1907). "The focus of the 1906 California earthquake". U.S. Geological Survey Bulletin. 324: 1–13.
  12. ↑ Bolt, B. A. (1968). "The focus of the 1906 California earthquake". Bulletin of the Seismological Society of America. 50: 457–471.
  13. ↑ Lomax, A. (2005). "A reanalysis of the hypocentral location and related observations for the Great 1906 California Earthquake". Bulletin of the Seismological Society of America. 95: 861–877.
  14. ↑ Richter, C. F. (1958). Elementary Seismology. W H Freeman & Co. p. 340. ISBN 978-0716702115.
  15. ↑ Scawthorn, C., O'Rourke, T. D., & Blackburn, F. T. (2006). "The 1906 San Francisco Earthquake and Fire—Enduring Lessons for Fire Protection and Water Supply". Earthquake Spectra. 22: 135.CS1 maint: multiple names: authors list (link)
  16. ↑ Scawthorn, C., O'Rourke, T. D., & Blackburn, F. T. (2006). "The 1906 San Francisco Earthquake and Fire—Enduring Lessons for Fire Protection and Water Supply". Earthquake Spectra. 22: 135.CS1 maint: multiple names: authors list (link)
  17. ↑ Scawthorn, C., O'Rourke, T. D., & Blackburn, F. T. (2006). "The 1906 San Francisco Earthquake and Fire—Enduring Lessons for Fire Protection and Water Supply". Earthquake Spectra. 22: 135.CS1 maint: multiple names: authors list (link)
  18. ↑ Whitney, A. W. (1906). On Insurance Settlements Incident to the 1906 San Francisco Fire, manuscript reprinted as Caltech Report DRC 72-01, California Institute of Technology, Pasadena, CA.
  19. ↑ United Nations Centre for Regional Development (UNCRD). (1995). Comprehensive Study of the Great Hanshin Earthquake, Research Report Series No. 12, Nagoya, Japan
  20. ↑ Scawthorn, C., O'Rourke, T. D., & Blackburn, F. T. (2006). "The 1906 San Francisco Earthquake and Fire—Enduring Lessons for Fire Protection and Water Suppl". Earthquake Spectra. 22: 141.CS1 maint: multiple names: authors list (link)
  21. ↑ Algermissen, S. T. (1972). "A study of earthquake losses in the San Francisco Bay Area: Data and analysis". US Department of Commerce, National Oceanic & Atmospheric Administration.
  22. ↑ Algermissen, S. T. (1972). "A study of earthquake losses in the San Francisco Bay Area: Data and analysis". US Department of Commerce, National Oceanic & Atmospheric Administration.
  23. ↑ Jablonski, A. (2006). "The San Francisco area earthquake of 1989 and implications for the Greater Vancouver area". Canadian Journal of Civil Engineering. 17(5): 1.
  24. ↑ Jablonski, A. (October 1990). "The San Francisco area earthquake of 1989 and implications for the Greater Vancouver area". Canadian Journal of Civil Engineering. 17(5): 1 – via ResearchGate.
  25. ↑ Jablonski, A. (1990). "The San Francisco area earthquake of 1989 and implications for the Greater Vancouver area". Canadian Journal of Civil Engineering. 17(5): 1.
  26. ↑ Jablonski, A. "The San Francisco area earthquake of 1989 and implications for the Greater Vancouver area". Canadian Journal of Civil Engineering. 17(5): 2.
  27. ↑ Mathews, J. (1989). "Earthquake swells ranks of homeless". The Washington Post.
  28. ↑ Mathews, J. (1989). "Earthquake swells ranks of homeless". The Washington Post.
  29. ↑ Kircher, C. A., Seligson, H. A., Bouabid, J., & Morrow, G. C. (2006). "When the big one strikes again—estimated losses due to a repeat of the 1906 San Francisco earthquake". Earthquake Spectra. 22: 297–339.CS1 maint: multiple names: authors list (link)
  30. ↑ Jablonski, A. (1990). "The San Francisco area earthquake of 1989 and implications for the Greater Vancouver area". Canadian Journal of Civil Engineering. 17(5).
  31. ↑ Fuller, T., Singhvi, A., & Williams, J. ((2018, April 17)). "San Francisco's big seismic gamble". The New York Times. Retrieved June 7, 2022. Check date values in: |date= (help)CS1 maint: multiple names: authors list (link)
  32. ↑ Fuller, T., Singhvi, A., & Williams, J. (2018, April 17). "San Francisco's big seismic gamble". The New York Times. Retrieved June 7, 2022. Check date values in: |date= (help)CS1 maint: multiple names: authors list (link)
  33. ↑ Department of Building Inspection (n.d.). "Earthquake Preparedness". Department of Building Inspection. Retrieved June 7, 2022.
  34. ↑ Department of Building Inspection (n.d.). "Earthquake Preparedness". Department of Building Inspection. Retrieved June 7, 2022.
  35. ↑ Department of Building Inspection (n.d.). "BORP Guidelines for Engineers". Department of Building Inspection.
  36. ↑ Department of Building Inspection (n.d.). "Mandatory Soft Story Program". Department of Building Inspection.
  37. ↑ Department of Building Inspection. "Earthquake Preparedness". Department of Building Inspection.
  38. ↑ SFGOV (n.d.). "Community Action Plan for Seismic Safety". Check date values in: |archive-date= (help)
  39. ↑ Department of Building Inspection. "Earthquake Preparedness". Department of Building Inspection.
  40. ↑ Golden Gate Bridge, Highway and Transportation District. "Seismic retrofit". Golden Gate.
  41. ↑ Department of Building Inspection (n.d.). "Earthquake Preparedness". Department of Building Inspection. Retrieved June 7, 2022.
  42. ↑ Department of Building Inspection. "Earthquake Preparedness". Department of Building Inspection. Retrieved June 7, 2022.
  43. ↑ NEIGHBORHOOD EMERGENCY RESPONSE TEAM (n.d.). "Neighborhood Emergency Response Team: Training Curriculum & Course Content".
  44. ↑ Department of Building Inspection (n.d.). "Earthquake Preparedness". Department of Building Inspection. Retrieved June 7, 2022.
  45. ↑ California Seismic Safety Commission. (2021). Homeowner’s Guide to Earthquake Safety [Brochure]. Sacramento, CA: Author. p. 3
  46. ↑ Examiner Staff (March 31, 2014). "SF's earthquake safety requirements will be detrimental for private schools". San Francisco Examiner. Retrieved June 17, 2022.
  47. ↑ City of Vancouver. "Earthquake Preparedness Strategy". City of Vancouver. Retrieved June 20, 2022.
  48. ↑ Wikipedia (January 3, 2014). "1911 Kebin Earthquake". Wikipedia. Retrieved June 20, 2022.


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