Figure 1. Flowchart of the Earthquake Loss Methodology
Defining Issue: Application of GIS technology in
natural hazard risk assessment and emergency management.
GIS Solution: Risk Management Solutions, Inc., a
leading software and service provider for the federal, state and
local emergency management agencies as well as international insurance
and reinsurance industry, developed HAZUS-ArcView, a GIS-based
natural disaster assessment software program using Esri GIS technology.
Application or Methodology: The recent development
of a GIS-based earthquake risk assessment software system is sponsored
as a part of a three-year project by the Federal Emergency Management
Agency (FEMA) and the National Institute of Building Sciences
(NIBS). The goal of the project is to create a nationally applicable
computer program which can be used in the assessment of nationwide
catastrophic risk and providing local, state and regional officials
with the tools necessary to plan and stimulate efforts to mitigate
losses from natural hazards and to prepare for emergency response
and recovery from disasters. The methodology is programmed to
run on a desk top computer and makes use of Esri's ArcView user
interface and functionality to open and modify inventory data,
conduct spatial analysis, as well as display study results. Included
in the paper are examples of the types of outputs that the software
can produce and maps and results showing ground failure and bridge
functionality changes.
Software: The application HAZUS-ArcView is written
using C++ and Avenue, and other system supporting tools. HAZUS
was also developed on MapInfo platform written in C++ and MapBasic
programs. The paper introduces the ArcView GIS based earthquake
loss estimation methodology, also shares experience in cross platform
development and system porting between different software programs.
In 1993, the Federal Emergency
Management Agency (FEMA) and the National Institute of Building
Sciences (NIBS) sponsored a project for the creation of a Standardized
Regional Earthquake Loss Estimation Methodology. The methodology
has evolved into the development of a very powerful GIS-based
software tool named HAZUS.
The earthquake loss estimation methodology is intended
to provide local, state and regional officials with the tools
necessary to assess the risks from earthquakes. This will help
them in preparing for emergency response and recovery.
Traditional loss estimation methodologies performed
since the early 1970's following the 1971 San Fernando earthquake
can be characterized as stagnant: inventory data and geologic
attributes were collected, one or more scenarios were evaluated
and the a report was written. Emphasis was given to one parameter
over another based on what the author(s) considered the "controlling
factor" and there was no mechanism to carry out what-if-analysis
to account for the inventory variability, the geo-hazard data
accuracy, and the uncertainty in the overall approach. Depending
on the complexity of the study, the final report could end up
by being "unclear" to all but few seasoned engineers.
A GIS-based software tool was meant to change all
that (of course!!). Tailored for different audiences with different
needs, it uses a segmented modular approach which can be tailored
by the users in any way they see fit with the timeline and budget
constraints they may face.
The 4 main modules of the methodology are: 1) the inventory, 2) the hazard, 3) the analysis parameters, and 4) the results.
The flexibility of the methodology in terms of inventory
starts by supplying what is termed Level 1 Data. which
covers the entire U.S. The goal was to allow the user to proceed
with a complete analysis few minutes after defining his/her study
region boundaries.
The type of inventory data supplied with the methodology can be grouped into the following categories:
As a consequence of the methodology tight integration
and its implementation as a GIS-system framework, the entire inventory
data mentioned above lends itself to all kind of GIS-type queries
presenting the user a great amount of information without any
analysis run yet.
Beyond Level 1 Data, the user can supply what
is termed Level 2 Data which is in essence an enhanced
type of inventory carried out either by editing the Level 1
Data or completely replacing it. The open and modular architecture
of the methodology makes the editing process relatively easy.
The database attributes for each inventory type not only covers the earthquake hazard, which was the original goal, but was expanded to be multi-hazard: flood, hurricane, tornado. The idea was to optimize the effort in collecting data (at the Level 2 stage) such that it does not have to be done for each type of hazard. Currently, the methodology implements the earthquake hazard only, but it is FEMA's goal to expand it to other hazards starting next year.
Figure 1. Flowchart of the Earthquake
Loss Methodology
The methodology allows the user to use 3 types of
earthquake hazard scenario for the analysis: deterministic hazard,
probabilistic hazard, and user-defined.
The deterministic hazard can be either a historical
epicenter event, a source fault event (for the Western U.S), or
any arbitrary event the user defines.
The probabilistic hazard is based on the United States
Geological Survey (USGS) Project 97 maps which can be assessed
at 100-year, 1000-year or 2500-year return period.
The user-defined hazard is an option for the user
to simulate any kind of event which the deterministic or probabilistic
would not recreate accurately. The user-defined hazard is supplied
to the methodology via PGA (Peak Ground Acceleration) and response
spectra maps.
Figure 2. Highways/Roads and Historical
Earthquake Epicenters in San Diego County
One of the main goals of the methodology is for it to be an open architecture, be highly customizable and completely documented. This goal is best reflected in the amount of information available to the user as analysis parameters. All of the damage functions, capacity curves, factors, assumptions, default values are exposed to the user and made editable.
The methodology supplies the user with more than
500 result files which can be presented or mapped through the
GIS interface in an unlimited number of ways. The user can look
at the results either at the census tract level (which is the
lowest resolution the methodology supports), or aggregated by
county via more then 50 summary reports. Figure 3 below shows
the PGA (Peak Ground Acceleration) results mapped by census tract.
Figure 4 shows the same map with the hazardous materials sites
and schools shown for the metropolitan San Diego.
Note:
The sample results were carried out for all of San
Diego County using a deterministic hazard. A repeat of the 1862
event was assumed with assuming a magnitude of 6.9 (the original
event was 5.9). All the input data was level 1 data and the default
analysis parameters were used as is.
Figure 3. Ground Motion Results
The analysis modules and results included with the methodology cover:
Figure 4. Ground Motion Results with
Schools and Hazardous Materials Sites for San Diego Metropolitan
Area
Figure 5 shows the results shown in tabular format
allowing the user to look at the detailed data if needed. Each
variable (column) can be thematically mapped by the user.
Figure 5. Bridges
Functionality Results in Tabular Format
The power of the GIS is extended even further - beyond the thematic mapping - the querying system. The methodology offers powerful yet easy to use querying wizard which allows a user to get answers to questions like "Give me all the hospitals which are 10 miles from the fault and would sustain a damage greater than 50% yet be at least 80% functional" or "list the hazardous material sites stocking Ammonia which have a high landslide potential and are located in census tracts with more than 3000 people." Obviously, the possibilities are endless.
The software implementation started in June of 1994. The original platform was MapInfo 3.0 running Windows 3.1. The choice of a personal-computer-based GIS implementation was warranted by the need of users such as emergency response organizations and local government agencies for a low-cost platform. By mid-summer 1997, the final version will ship supporting both MapInfo 4.1 and ArcView 3.0. Both a 16-bit version running under Windows 3.1 and a 32-bit version running under Windows 95/NT 4.0 are available.
A sophisticated methodology has been developed that will allow a wider group of individuals to participate in and have access to results of regional loss estimation studies. The methodology has been implemented using integrated GIS technology which provides the user with a very powerful tool to display and query results. The choice of a personal-computer-based GIS system fulfills the needs of the target users such as emergency response organizations and local government agencies and yet balances conflicting issues such as moderate cost and accuracy. The Flexible data entry and the modularity of the methodology make for easy inventory augmentation, customization and parameter modification. The ability of the user to rapidly perform multiple scenarios using the same inventory provides a mechanism to examine alternatives, explore the sensitivity of results to input data and ask "what if" questions, leading ultimately to the optimum conclusion.
The development of the methodology was the work of a large number of individuals and was supported by funding from the Federal Emergency Management Agency (FEMA), under a cooperative agreement with the National Institute of Building Sciences (NIBS). The authors are solely responsible for the accuracy of the statements and interpretations contained in this publication. Such interpretations do not necessarily reflect the views of FEMA, NIBS, or members of the committees that oversaw the production of this work.
Risk Management Solutions, Inc. 1997. Development of a Standardized Earthquake Loss Estimation Methodology. Report prepared for the National Institute of Building Sciences. Menlo Park, California.
Mourad Bouhafs, Director,
Software Engineering. mouradb@riskinc.com
Chessy Si, Senior GIS
Engineer. chessys@riskinc.com
Robert Scott Lawson, Associate
Vice President, Technical Services. scottl@riskinc.com
Jawhar Bouabid, Engineering Manager. jawharb@riskinc.com
Risk Management Solutions, Inc., 149 Commonwealth Drive, Menlo Park, California 94025, USA
Tel.: (415)617-6500, Fax: (415)617-6602