Safe Enough to Stay - ABAG Earthquake and Hazards Program

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Safe Enough to StaySection I:How much of San Francisco’shousing needs to meet shelterin-placestandards?SPUR defines “seismic resilience” as the ability of the city to containthe effects of earthquakes when they occur, to carry out recoveryactivities in ways that minimize social disruption and to rebuildfollowing earthquakes in ways that mitigate the effects of futureearthquakes. The more quickly a community can rebound from amajor event, the more resilient the community.A critical component of resilience is that residents choose to remainin the city during the recovery period. There are many factors thatdetermine whether a resident will chose to stay after a disaster or pickup and leave the city. Residents may be able to cope with no wateror sewer services for a few weeks, but most will be unwilling to putup with these difficulties for a period of months. Similarly, if roads,bridges or public transportation systems are not fully functional,residents may need to relocate in order to commute to jobs andschools. The closure of schools, medical facilities or businesses couldaffect residents’ decisions about whether to stay in town or leave SanFrancisco. Some residents may leave right away and then return astheir fears subside, when their toilet works again or as they completerepairs to their property. Others may stay initially but will leave asthey learn how slowly their neighborhoods will be rebuilt. Someresidents who leave may develop ties in their new community andnever return.The availability of housing, jobs and community resources such asschools is critical to a city’s seismic resilience. We assume that if twoout of these three resources are in place, residents will choose tostay. For example, if a resident can shelter in place in her home andher employer has chosen to remain in the city, she is more likely tostay than if her employer has left the city or if she is unable to remainin her home.Economic recovery and housing recovery are interdependent. Ifemployers choose to leave the city or region, they take jobs withthem. If residents leave, the workforce that employers rely upon is nolonger available, leading to further disinvestment. Young and mobileresidents, such as high-tech workers who have not yet establisheddeep ties to the community, may leave after the earthquake if thecharacteristics that attracted them to San Francisco — exciting jobs,an active cultural life and a vibrant social scene — are no longer inplace. Keeping San Francisco’s workforce from leaving is key to thecity’s economic recovery.It is also crucial that San Francisco plan for its most vulnerablepopulations: low-income households, the elderly, non-Englishspeakers and the disabled. It is clear that some residents will suffermore severe consequences than others if they are displaced fromtheir homes by an earthquake. Wealthy residents have options:They can stay in a hotel in the short term, find rental housing forthe medium term, secure loans, begin repairs on buildings theyown before insurance payments come through, and purchasereplacements for personal items that they lost. Low-income residentscan do few of these things. They will rely heavily on city shelters andservices. Many of them may leave, unable to afford new rental unitsin a market with reduced availability.For low-income property owners, selling damaged property may bemore feasible than obtaining financing and undertaking repair andreconstruction. Middle-class residents, already tightly squeezed bySan Francisco’s expensive real estate market, will also have difficultystaying in the city. Elderly residents will be heavily affected. Seniorsof all income levels, but particularly seniors on a fixed income,will find it difficult to relocate, repair or rebuild their homes andreestablish needed social services and networks. A large earthquakecould permanently alter city demographics and increase the pace ofchange in many neighborhoods. San Francisco’s diversity and culturewill be threatened if vulnerable populations leave due to lack ofaffordable and accessible housing.While this report is focused on one factor — housing — there isno doubt that other factors are also important to recovery. SanFrancisco’s downtown is a major regional job center, home to morethan 250,000 jobs. About 42 percent of these downtown workerslive in San Francisco, and about 38 percent commute from the EastBay. Many of San Francisco’s major employers (such as PG&E, WellsFargo, the Gap, Charles Schwab, Macy’s West, Levi’s and McKesson)have corporate headquarters or significant numbers of employees inSan Francisco’s downtown core. These employers, along with smallerones, represent important sectors of the San Francisco economy thatwill be key to recovery: public utilities, tourism, and hospitality andbusiness services.6 SPUR Report > January 2012
Why 95 percent is the rightshelter-in-place targetIt’s not easy to determine how much housing in a city can bedamaged by an earthquake before the city’s viability is undermined.We conducted the following analysis to determine what shelter-inplaceperformance target makes sense for San Francisco.1. We researched the existing capacity for short-term housing(shelter beds) and medium-term or interim housing (hotel rooms,trailers) in San Francisco after a large earthquake.2. We reviewed efforts by others to model and quantify disasterresilience.3. We analyzed how housing damage in recent relevant disastersaffected community resilience.Based on our analysis of the best available data, we conclude that95 percent is an appropriate goal. While this may seem to be a hightarget, the lessons from recent disasters show that losing more than 5percent of housing stock is likely to lead to substantial outmigration,which could slow recovery for years. The city’s lack of interim-housingcapacity and its relatively low vacancy rate will only exacerbate thissituation.San Francisco’s emergency-shelter and interimhousingcapacitySan Francisco’s Department of Emergency Management estimatesthat its top shelter capacity is 60,000 people, or roughly 7.5 percentof San Francisco’s overall population. Sheltering 60,000 peoplewould require maximizing shelter space at large convention facilitieslike the Moscone Center and also mixing in some outdoor or softsidedshelters to supplement indoor space. If we were to use indoorfacilities only, without the big convention centers or outdoor sites,capacity would be reduced to 45,000 people, or roughly 5.5 percentof San Francisco’s population. 3Emergency-shelter beds will provide places for residents to stay fordays or weeks, but it will take years before most heavily damagedhousing will be usable again. In the meantime, residents will needto find interim housing before repairs on damaged housing arecompleted or new replacement housing is constructed. There arefederal and state plans and guidelines that identify a variety of optionsfor interim housing and priorities for their use. 4In general, these plans call for a hierarchy of actions: first, providing3 Email correspondance with Robert Stengel, Department of EmergencyManagement, September 1, 2011.4 National Disaster Housing Strategy and Annexes (Federal EmergencyManagement Agency, 2009); 2009 Disaster Housing Plan (Federal EmergencyManagement Agency, 2009); and Regional Catastrophic Earthquake InterimHousing Plan: Annex to the San Francisco Bay Area Regional EmergencyCoordination Plan (California Emergency Management Agency, 2011).Defining the ExpectedEarthquakeEarthquakes are commonly reported in terms of their Richtermagnitude. That measure was defined in the early 1940sand is useful only for quantifying the energy released overallby a single earthquake. It offers little information in terms ofhow buildings or infrastructure will fare or how they should bedesigned.In order to evaluate an existing facility or design a new one,earth scientists and engineers today use different measures toquantify the intensity of the expected shaking at a specific site.These engineering measures account for the possible effectsof different earthquakes on multiple faults, and therefore aredefined in probabilistic terms. For example, a building mightbe designed for the level of shaking expected to occur with 10percent probability over a 50-year time period.A third way of defining earthquakes involves “scenario events”:specific hypothetical earthquakes defined by the location ofthe fault rupture and the magnitude of the energy released.Scenario earthquakes are especially useful for citywide orregional planning. They are easier to grasp than probabilisticmeasures and therefore are effective for communicatingearthquake risk to policymakers and the public.In 2003, the San Francisco Department of BuildingInspection’s Community Action Plan for Seismic Safety chosefour scenario earthquakes as the basis for its planning andmitigation programs. For the purposes of defining resilience,SPUR uses one of these scenario earthquakes: a magnitude7.2 earthquake on the peninsula segment of the San AndreasFault, off San Francisco’s western shore.We refer to this scenario as the “expected earthquake” becausean event of this magnitude can be expected — conservativelybut reasonably — to occur once during the useful life of astructure or system, and more frequently if the structure isrenovated to serve more than one or two generations. Ofcourse, this defined scenario would produce different levels ofshaking at different locations, but for most of the city its effectswould be similar, in probabilistic terms, to those with a 10percent chance of occurring over a 50-year period.We define resilience in terms of this expected earthquake.Other earthquakes are possible, of course. In a smaller, moreroutine earthquake, buildings would be expected to performbetter (i.e., to withstand the shaking with little or no damage).In a more extreme event, residents would have to tolerate moredamage than what we project here.SPUR Report > January 2012 7
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Safe Enough to Stay - ABAG Earthquake and Hazards Program

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