Glendale (PDF) - Hazard Mitigation Web Portal - State of California

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Natural Hazards Mitigation PlanCity of Glendale, CaliforniaSection 6 – EarthquakesRisk AnalysisRisk analysis is the third phase of a hazard assessment. Risk analysis involves estimating thedamage and costs likely to be experienced in a geographic area over a period of time. Factorsincluded in assessing earthquake risk include population and property distribution in the hazard area,the frequency of earthquake events, landslide susceptibility, buildings, infrastructure, and disasterpreparedness of the region. This type of analysis can generate estimates of the damages to the regiondue to an earthquake event in a specific location. FEMA's software program, HAZUS, usesmathematical formulas and information about building stock, local geology and the location and sizeof potential earthquakes, economic data, and other information to estimate losses from a potentialearthquake. A HAZUS loss estimation was conducted for the city of Glendale as part of its SafetyElement of the General Plan. That section of the Safety Element is reproduced in the followingpages.HAZUS-99 TM is a standardized methodology for earthquake loss estimation based on a geographicinformation system (GIS). A project of the National Institute of Building Sciences, funded by theFederal Emergency Management Agency (FEMA), it is a powerful advance in mitigation strategies.The HAZUS project developed guidelines and procedures to make standardized earthquake lossestimates at a regional scale. With standardization, estimates can be compared from region toregion. HAZUS is designed for use by state, regional and local governments in planning forearthquake loss mitigation, emergency preparedness, response and recovery. HAZUS addressesnearly all aspects of the built environment, and many different types of losses. The methodology hasbeen tested against the experience of several past earthquakes, and against the judgment of experts.Subject to several limitations noted below, HAZUS can produce results that are valid for theintended purposes.Loss estimation is an invaluable tool, but must be used with discretion. Loss estimation analyzescasualties, damage and economic loss in great detail. It produces seemingly precise numbers that canbe easily misinterpreted. Loss estimation's results, for example, may cite 4,054 left homeless by ascenario earthquake. This is best interpreted by its magnitude. That is, an event that leaves 4,000people homeless is clearly more manageable than an event causing 40,000 homeless people; and anevent that leaves 400,000 homeless would overwhelm a community's resources. However, anotherloss estimation that predicts 7,000 people homeless should probably be considered equivalent to the4,054 result. Because HAZUS results make use of a great number of parameters and data of varyingaccuracy and completeness, it is not possible to assign quantitative error bars. Although thenumbers should not be taken at face value, they are not rounded or edited because detailed evaluationof individual components of the disaster can help mitigation agencies ensure that they haveconsidered all the important options.The more community-specific the data that are input to HAZUS, the more reliable the lossestimation. HAZUS provides defaults for all required information. These are based on bestavailablescientific, engineering, census and economic knowledge. The loss estimations in this reporthave been tailored to Glendale by using a map of soil types for the City. HAZUS relies on 1990Census data, but for the purposes of this study, we replaced the population by census tract data thatcame with the software with the 2000 Census data. Other modifications made to the data set beforerunning the analyses include:• updated the database of critical facilities, including the number and location of the fire andpolice stations in the City,• revised the number of beds available in the three major hospitals in Glendale to betterrepresent their current patient capacity, and2006 PAGE 6 - 35
Natural Hazards Mitigation PlanCity of Glendale, CaliforniaSection 6 – Earthquakes• upgraded the construction level for most unreinforced masonry buildings in the City tobetter represent the City’s retrofitting efforts of the last decade.As useful as HAZUS seems to be, the loss estimation methodology has some inherent uncertainties.These arise in part from incomplete scientific knowledge concerning earthquakes and their effectupon buildings and facilities, and in part from the approximations and simplifications necessary forcomprehensive analyses.Users should be aware of the following specific limitations:• HAZUS is driven by statistics, and thus is most accurate when applied to a region, or a classof buildings or facilities. It is least accurate when considering a particular site, building orfacility.• Losses estimated for lifelines may be less than losses estimated for the general buildingstock.• Losses from smaller (less than M 6.0) damaging earthquakes may be overestimated.• Pilot and calibration studies have not yet provided an adequate test concerning the possibleextent and effects of landsliding.• The indirect economic loss module is new and experimental. While output from pilot studieshas generally been credible, this module requires further testing.• The databases that HAZUS draws from to make its estimates are often incomplete oroutdated (as discussed above, efforts were made to improve some of the datasets used for theanalysis, but for some estimates, the software still relies on 1990 census tracts data and 1994DNB economic reports). This is another reason the loss estimates should not be taken at facevalue.Essential facilities and lifeline inventory are located by latitude and longitude. However, the HAZUSinventory data for lifelines and utilities were developed at a national level and where specific data arelacking, statistical estimations are utilized. Specifics about the site-specific inventory data used inthe models are discussed further in the paragraphs below. Other site-specific data used include soiltypes and liquefaction susceptible zones. The user then defines the earthquake scenario to bemodeled, including the magnitude of the earthquake, and the location of the epicenter. Once all thesedata are input, the software calculates the loss estimates for each scenario.The loss estimates include physical damage to buildings of different construction and occupancytypes, damage to essential facilities and lifelines, number of after-earthquake fires and damage due tofire, and the amount of debris that is expected. The model also estimates the direct economic andsocial losses, including casualties and fatalities for three different times of the day, the number ofpeople left homeless and number of people that will require shelter, number of hospital bedsavailable, and the economic losses due to damage to the places of businesses, loss of inventory, and(to some degree) loss of jobs. The indirect economic losses component is still experimental; thecalculations in the software are checked against actual past earthquakes, such as the 1989 LomaPrieta and 1994 Northridge earthquake, but indirect losses are hard to measure, and it typically takesyears before these monetary losses can be quantified with any degree of accuracy. Therefore, thiscomponent of HAZUS is still considered experimental.HAZUS breaks critical facilities into two groups: essential facilities and high potential loss (HPL)facilities. Essential facilities provide services to the community and should be functional after anearthquake. Essential facilities include hospitals, medical clinics, schools, fire stations, police stations2006 PAGE 6 - 36
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NOTES:This map is intended for gene
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City of GlendaleUpdateHazard Mitiga
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HospitalsPartnershipsWithin City an
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Impact on CityMost significant area
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