ML20151H217

Application of Geographic Info Sys Technology to Urban Seismic Hazards Studies in Pacific Northwest, Presented at 880412-15 Meeting in Olympia,Wa

ML20151H217
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Issue date:	04/12/1988
From:	Tarr A INTERIOR, DEPT. OF, GEOLOGICAL SURVEY
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NUDOCS 8808010188
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APPLICATION OF GEOGRAPHIC INFORMATION SYSTEM TECHNOLOGY

( TO URBAN SEISMIC HAZARDS STUDIES IN THE PACIFIC NORTHWEST by Arthur C. Tarr U. S. Geological Survey INTRODUCTIO!!

Geographic Information System (GIS) technology is a powerful and useful tool that has proved beneficial for achieving the goals of hazards assessment of urban areas which are at risk from earthquakes. A GIS enables large sets of data to be synthesized l I

into informational prodects which will be used by land use plan-ners and public officials for mitigation of seismic hazards.

A GIS is a configuration of computer hardware and software that allows users to organize, manipulate, analy:e, and display large sets of geographical data. Many of the end-products of ur-ban hazards assessment are graphical, such as maps of probabilis-tie acceleration, seismic ground response, landslide susceptibil-ity, and liquifaction potential. Although the graphical end products are the most familiar application of GIS technology, other applications, such as modeling of surfaces, slope determi-nation, earthquake loss estimation, characterization of lar.3 use, density possibic of population, and other statistical attributes, are also I

Thus, a GIS is a powerful, multi purpose tool.

l Inherent in the traditional soismic hazards ascessment pro-cess is the merging and integration of geological, geophysical, and engineering data sets and the use of theoretical models (Figure 1).

Data acquisition and data analysis are done quite independently and the data sets are dispersed, often without re-gard to the inevitable need later for an integrated data base.

Comparison of some critical data sete may not be possible until late stages of the hazards assessment. A different perspective places the GIS at the hub, integrating data acquisition, data base management, and hazards analysis activities (Figure 2). Be-cause each of these activities influences the structure of the others, innovative data comparisons and manipulations are possi-ble early on. In this view, hazards analysis draws upon data sets f rom the data base in e sittplified. integrated systent the hazards analysis should in fact influence what data acquisition activities are undertaker.. Similarly, the design of the data base and structure of the constituent data sets is controlled by

' requirements of the ar.alysis and the character of the data acqui-sition activities.

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The USGS has begun a project of application of GIS technol-ogy to urban hazards assessment of Puget Sound and Portland urban

( areas. In FY 1988, one major objective of this project is to link the interests and personnel from the Geologic Division and National Mapping Division of the USGS, Washington State Depart-ment of Natural Resources, and a variety of local governnental entities from several cities in Washington. As the project de-velops, additional groups and organizations will be encouraged to participate.

OBJECTIVES The overall goal of this project is to apply GIS technology to urban hazards assessment usage. The general objectives are:

e DATA BASE -- Duild, manipulate, and maintain a digital urban hazards data base (UHDD) comprised of fundamental geograph-ical, geological, geophysical, hydrological, engineering, and so-cioeconomi data for urban areas in the Pacific Northwest.

Building the data base will require extensive effort to capture data sets that may or may not be in digital (or computerized) or graphical form. Examples of available digital data include cata-logs of earthquake epicenters and historic intensity observa-tions, some well locations, surface water and ground water data, USGS Digital Line Graph (DLG), and Census (DIME file) data. Ex-amples of data which will require digitization are boundaries of bedrock and surficial geological units, isopachs of surficial units, and isolines of depth to bedrock. Examples of data cap-ture which will require special processing are land use and land cover trasterized) data, hypsography (topographic and bathymetric contours), and air photos, o ANALYSIS -- Perform spatial analyses on data contained in the UHDB and to produce derivative data sets for inclusion in the UHDB. It will be possible to analyze spatial data using GIS ap-plications software. For example, any attribute having spatial variation can be modeled and generalized as a two-dimensional ma-trix of regular polygons or a set of irregular polygons; simi-larly, any numerical attribute having spatial coordinates can be modeled as a surface. Use of the GIS to analyze fundamental data will, in some cases, result in derivative data sets which them-selves may be organized, manipulated, and displayed. Examples of derivative data are isolines of seismic intensities, ground re-sponse, and depth to specific geologic units; slopes derived from hysometric data; thickness of water-saturated units; and ex-ceedance probabilities for acceleration.

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• PRODUCTS -- Design and generate high-quality map and

( graphical products and tabular reports of data attributes. The GIS will permit generation of numerous maps having various data layers overlaying a standard base of (say) hydrography, hypsogra-phy, transportation net, and boundaries. Cne example is a ground response map containing surficial geology, ground response con-tours, and basement depth contours. Another example 12 a land-slide susceptibility map containing surficial geology, slope con-tours, and thickness of water-saturated units.

• RESEARCH -- Perform experiments which seek to discover more offective techniques for generating derivative data sets.

Some existing methodologies and techniques that are inefficient or cumbersome might benefit from use of GIS technology. Consid-erable attention will be given to streamlining the process of in-tegrating and using multiple data sets in the GIS. Improvement in data capture techniques are of great importance. Utilization of query languages and an expert systems approach to access and analyze GIS data seem promising.

More specifically, in the Pacific Northwest, these four ob-jectives will include numerous tasks, such as:

e DATA BASE -- Construct base map products using data sets (hydrography, transportation, boundaries) from existing USGS DLG tapes on a quadrangle-by-quadrangle basis for major urban areas (such as Seattle, Tacoma, Bellevue, Olympia, Portland); scan hyp-sographic plates of the same quadrangles to construct topographic and bathymetric contour line graph and digital elevation model (DEM) data sets; digitize numerous geologic, hydrogeologic, tec-tonic, and isoline maps to capture geologic, hydrologic, and structural units; convert earthquake epicenter and intensity data into GIS data files; capture geotechnical data (borehole geology and velocity, soils analysis) from existing computer files; cap-ture Census tract data from existing data tapes.

• ANALYSIS -- Modeling of topographic surface from DCll; slope determination from surface model; contouring of intensity, seismic response, and geotechnical data; microzonation of urban areas on basis of surficial geology, seismic response, and geotechnical data; revision of urban land use areas, e PRODUCTS -- Preliminary seismic response and landslide susceptibility maps of Olympia and Seattle; preliminary seismo-tectonic map of western Usshington and Oregon, o RESEARCH -- Improved interfaces between graphics software and external data bases; synthesis of a DEH from several eleva-tion data sets of varying resolutions, i

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The UNDB will be implemented using the existing USGS Central Region GIS Laboratory PR1HE computer (located in Lakewood, CO) and a remote workstation and peripherals (located at the Branch of Geologic Risk Analysis in Golden, CO). The new workstation will be a SUN Microsystems 3/60C running ARC / SUN software; pe-ripherals will include a high-accuracy digitizing. table and ter-minal, large fermat pen plotter, and communications equipment.

The workstation will be linked by an EtherNet connection to on-site VAXs and by high-speed data link to the Regional GIS Labora-tory PR1HE computer. The workstation thus will be able to pro-cess data in stand-alone mode or as a high-quality graphics dis-play terminal when connected to the PRlHE computer of the Central Region GIS Laboratory.

The Geologic, National Happing, and Water Resources Divi-siens of USGS and many State and local governments use ESRI's ARC / INFO (Version 4.0) software package to perform CIS operations (data base management, data asnipulation, data display). Usage of the same software package maximizes interchangability of data sets and applications programs, to the benefit of the network of GIS participants.

The overall approach in this project is long-range in scope, attempting to create a GIS environment in which investigators from many disciplines will find common ground (in the GIS facili-i ties and through the UHDB) for performing experiments and complex spatial analyses which only a powerful GIS will perrcit. This ul-timately means coordinating the GIS interests of several USGS op-erating divisions, other Federal agencies and bureaus, the State Geological Surveys of Washington and Oregon, municipal agencies in the major cities, and several university groups.

In tne short term, there are many obstacles to overcome in establishing a network of GIS users, not the least of which are disparate requirements for digital geographic data, incompatible computer systems, incomplete or non-existent data standards, and incompatible data formats. Data capture continues to be a costly and ti=e-consuming task, demanding imagination and innovation.

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GEOLOGY GEOPHYSICS Surficial Seismicity 1 Borehole Intensity Ground Water Ground Response Geotechnical Velocity Model HAZARDS ASSESSMENT C

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i ENGINEERING Building Response Demoge Inventory Soil Mechanics i

Figure 1. -- Schematic diagram showing a traditional seisnic hazards assessment in which data sets and models from three dis-ciplines are integrated.

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HAZARDS DATA ANALYSIS i ACQUISITION I

i Ground Response Seismic Response Prob. Accel Model Reflection / Refraction Expt Vulnerability Analysis Loss Estimation g Borehole Scismology Borehole Geology Landslide Susceptibility Geologic Mapping j Liquefaction Potential Inventory Buildings / Lifeline r inventory Demoge DATA

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Ground Response Geotechnical l Geology / Hydrology

' Building inventory Demoge inventory Building Response Velocity / Response Model Geographic /Bose Dato l

l Figure 2. -- Schematic diagram showing a different approach I to seismic hazards assessment e= ploying a GIS linking three i

classes of activities.

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Figure, 3. -- Schematic diagram showing proposed 'JSGS GIS hardware to be usec for urban seir.mic hazards assessment. High-speed modems link USGS Central Region GIS Laboratory (lower left) with Branch of Geologic Risk Assessment computer facility (top) and new GIS workstation (upper right). Detached configuration (lower right) represents compatible computer systems at collabo-rating institutions.

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