HISTORY OF ENGINEERING-BASED EARTHQUAKE CASUALTY MODELING

Research Participants & Sponsor Hope A. Seligson, Kimberley I. Shoaf, Corinne Peek-Asa, And Maya Mahue- Giangreco Support for this research was provided by National Science Foundation Grant Numbers CMS and CMS

Definitions Engineering-based earthquake casualty models predict building damage-related casualties (and in some cases, other types of casualties). These models have typically been developed by engineers from limited anecdotal, historical data (not from epidemiological studies, nor involving health-related researchers). These models are typically used for emergency response, planning and mitigation by government agencies at various levels, but are less useful for health preparedness planning.

1970’s: NOAA Scenarios NOAA published scenarios in 1972 (SF Bay area) and 1973 (LA area) that estimated building-related casualties. Tabulated aggregate damage and casualty statistics for historic earthquakes. Used generalized casualty rates per 100,000 population based on previous earthquakes. “Mystery” ratios of 4:1 serious injuries (i.e., requiring hospitalization) to deaths and 30:1 minor injuries to deaths. Included estimates for sidewalk deaths and freeway collapse. The final results were judgment-based, scenario specific casualty estimates, rather than a broadly applicable casualty estimation methodology

1980’s: ATC-13 and Expert Opinion In 1985, the Applied Technology Council (ATC-13) took a more comprehensive look at estimating building damage for classes of structures using expert opinion. Percent damage and damage state for 17 structural classes are estimated from Modified Mercalli Intensity (MMI), similar to earlier work by Whitman, et. al (1974). Mean casualty rates associated with damage states, were applied to the exposed population. Rates based on historic EQs, previous models and “judgmental evaluation” “Mystery” ratios still in use.

ATC-13 Casualty Rates Note: for light steel and wood-frame construction, multiply all numerators by 0.1

1990’s: “State of the Art” Computer Models - HAZUS (NIBS/FEMA) Uses advanced ground motion parameters and detailed engineering analyses to determine building damage states and associated damage state probabilities. Represents a significant advance in the automated application of loss estimation techniques. Indoor and outdoor casualty rates by damage state and model building type, based on ATC-13 and “limited historical data” for 4 injury severity levels: »Injuries requiring basic medical aid »Hospitalized »Life threatening Injuries »Deaths

HAZUS® Earthquake Loss Estimation Methodology - Indoor Casualty Rates (HAZUS®99, SR-2) Notes: URM = unreinforced masonry, LRWF = low-rise wood frame, HR URMI = high rise steel or concrete frame structures with URM Infill walls, MH = mobile home, SLF = steel, light frame, HR PC = high rise precast concrete structures

More “State of the Art” Computer Models: EPEDAT EPEDAT (Early Post-Earthquake Damage Assessment Tool) was developed by ABS Consulting/ EQE International for the CA Office of Emergency Services. It is a GIS-based program designed to produce regional damage and casualty estimates for emergency response and planning purposes. For casualty models, Beta distribution applied to ATC-13 and Whitman casualty rates to distribute casualties within range of potential damage in each damage state (i.e., more injuries with more damage in a given damage state).

Current Research: Earthquake Data and Opportunities for Improvement NSF (and other funding) allowed researchers (inter-disciplinary team from UCLA, LA County DHS, and ABS/EQE) to collect and correlate data from the Northridge and other earthquakes: building characteristics and damage data coroner’s data hospital admission data ED logs Survey data on damage and injuries Research goal: capitalize on the high-quality data to improve the way engineering-based models estimate building-related casualties, and make the results more meaningful to health care providers.

Application of Northridge Data Comparison of model prediction to actual Northridge data to develop “after-market” modifications that make results more useful to medical community. Translates estimates of “Injuries” and “Deaths” to: –Fatalities (non-hospital, i.e., DOA) –Fatalities requiring hospital care (i.e., ICU) –Trauma cases –Non-Trauma Hospital Admissions –ED Treat & Release –Out of Hospital Treatment

Refinements to EPEDAT’s casualty models for injury planning and response

Additional Research Products A literature review of the medical, epidemiological, public health, and engineering literature. See: Development of a standardized classification scheme for all aspects of earthquake-related casualties (e.g., injury mechanism, building damage). See: An integrated review of available casualty and damage data (e.g., Northridge, Kobe, Nisqually EQs) classified according to the new classification scheme - in progress.

Conclusions Engineering-based casualty models allow for rapid estimation of regional population impacts for response, planning and mitigation purposes. While many advances have been made in the area of loss estimation, casualty modeling has not received the attention dedicated to the development of other model components. Future enhancement of the such models will benefit greatly from coordinated data collection and analysis, as well as inter-disciplinary research incorporating medical and public health perspectives. This integrated approach will facilitate the use of data from recent and future events to refine engineering-based casualty models.

Standardized Classification Scheme for Earthquake-Related Injuries

Purpose of Standardized Classification Scheme To establish a systematic, multi-disciplinary and collaborative approach to the study of risk assessment, loss estimation for earthquakes To create a common language to define the event, the victims and responses for any given earthquake Reduce variability of data for reported deaths and injuries

Components of Classification Scheme Individual Level Building Level Hazard Level DemographicsBuilding Description Earthquake Source InjuryBuilding Damage Local Site Hazard Location Activity

Use of Existing Measures Abbreviated Injury Score International Classification of Diseases, 9 th. Revision ATC 20

Hazard Level Variables Earthquake Source –Earthquake Name –Event Number or ID –Magnitude –Magnitude Scale –Date –Time –Day of Week –Earthquake Location –Rupture Length –Rupture Area –Presence of Surface Rupture –Deepest Point of Rupture –Shallowest Point of Rupture –Fault Source Local Site Hazard –Earthquake ground motion –Local Site Conditions

Building Level Variables Building Description –Structural System –Building Height –Building Size –Building Year –Seismic Design Quality –Debris Generation Potential –Occupancy Type –Estimated Occupancy –Actual Occupancy Building Damage –Building Safety Inspection Status –Safety Tag –Dollar Damage –Damage Percent –Damage State –Building Collapse

Individual Level Variables Demographics –Age –Gender –Race/Ethnicity –Level of Education –Occupation –Income –Disabilities and Pre- existing Conditions Injury Characteristics –Cause of Injury Relation of EQ Structural Relatedness Secondary Hazards Injury Mechanisms –Injury Severity –Treatment Level of Treatment Immediacy –Diagnoses –Costs Direct Medical Care Costs Indirect Costs

Individual Level Variables, cont. Location –Injured individual’s physical location –Injured individual’s geographic location Activity –Starting position –Activity