HISTORY OF ENGINEERING-BASED EARTHQUAKE CASUALTY MODELING.

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-9900062 and CMS-0085314

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 ScenariosNOAA 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 RatesDamage

State Range Minor

Injuries Serious Injuries

Deaths

Slight 0-1 3/100,000 1/250,000 1/1,000,000

Light 1-10 3/10,000 1/25,000 1/100,000

Moderate 10-30 3/1,000 1/2,500 1/10,000

Heavy 30-60 3/100 1/250 1/1,000

Major 60-100 3/10 1/25 1/100

Destroyed 100 2/5 2/5 1/5

Rate=30A Rate = 4A Rate = A

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)

CASUALTY SEVERITY LEVEL Damage State

Severity 1 (%) Severity 2 (%) Severity 3 (%) Severity 4 (%)

Slight 0.05 0 0 0 Moderate 0.2 – 0.25

(URM* = 0.35) 0.025 – 0.030 (URM = 0.40)

0 (URM = 0.001)

0 (URM = 0.001)

Extensive 1.0 (URM = 2.0)

0.1 (URM = 0.2)

0.001 (URM = 0.002)

0.001 (URM = 0.002)

Complete (No Collapse)

5.0 (URM = 10.0)

1.0 (URM = 2.0)

0.01 (URM = 0.02)

0.01 (URM = 0.02)

Complete (With Collapse)

40.0 20.0 5.0 (LRWF* = 3.0,

MH* = 3.0, SLF* = 3.0)

10.0 (LRWF = 5.0,

MH = 5.0, SLF = 5.0)

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.

27

6

DOA

Die in hospital

9

129

Hospitalized/Trauma Cases

Hospitalized/Non-Trauma

8,200

16,400

Emergency DepartmentTreat & Release

Out of HospitalTreat & Release

221,400

Injured notreatment

InjuryPyramid:

NorthridgeEarthquake

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

Pyramid Level Recommended Model Description of Injury Category

Non-Hospital Fatalities 82% of EPEDAT “best estimate” of Deaths

DOA

In-Hospital Fatalities 18% of EPEDAT “best estimate Deaths

Majority require intensive care

Trauma Cases 6.5% of EPEDAT “best estimate” Serious Injuries

ISS* >15 (some require intensive care)

Hospital Admits (Non-Trauma)

93.5% of EPEDAT “best estimate” Serious Injuries

ISS 15

Emergency Department (ED) Treat & Release

16.5% EPEDAT upper bound Total Injuries

Extremities (esp. in night), falls, blunt trauma, lacerations

Out of Hospital Treat & Release

33% EPEDAT upper bound Total Injuries

Similar to ED, may spill over into ED

Additional Research Products• A literature review of the medical, epidemiological,

public health, and engineering literature. See: http://www.ph.ucla.edu/cphdr/projects.html.

• Development of a standardized classification scheme for all aspects of earthquake-related casualties (e.g., injury mechanism, building damage). See: http://www.ph.ucla.edu/cphdr/scheme.pdf

• 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

Demographics Building Description

Earthquake Source

Injury Building Damage

Local Site Hazard

Location

Activity

Use of Existing Measures

• Abbreviated Injury Score

• International Classification of Diseases, 9th. 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