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

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