Philip C. Emmi

A Monte Carlo simulation of error propagation in a GIS-based assessment of seismic risk

Abstract This paper uses a GIS-based Monte Carlo simulation to gauge the sensitivity of risk assessment results to random perturbations in earthquake ground shaking intensity zone boundaries. Sensitivity to error in intensity estimation is also considered. Zonal boundaries may vary within a 1560 m corridor and still yield property loss estimates that are within five per cent of their original estimate 95 per cent of the time. Yet a five per cent error in ground shaking intensities yields an 11 to 15 per cent error in property loss estimates. The method illustrates the use of GIS in simulating error propagation and identifying strategic error reductions in risk assessments.

Opportunity and mobility in urban housing markets

Opportunity and mobility in urban housing markets : Concepts, models, calibrations and test

The Predictive Accuracy of Residential Vacancy Chain Models

The focus of this report is on the predictive accuracy of residential vacancy chain models. There are two objectives. The first is to define the mathematical structure of a pair of multisectoral residential vacancy chain models. These models simulate the intersectoral transfer of vacant housing opportunities in response to either the creation of new opportunities or the absorption of existing ones. Residential mobility is given as an analytical by-product. The second objective is to calibrate these models and gauge the accuracy of their projections. Models with six housing sectors each are calibrated with 1975-80 data from three different Swedish municipalities (Gävle, Jönköping and Vasteras). Calibrations are used for projections into the proximate 5-year period. Projections of intersectoral residential mobility for 1980-85 are compared statistically with observed moves for the period. Coefficients of determination range between 0.93 and 0.97. Log-linear analysis shows projection error ranging from 3 to 12 per cent. The projective accuracy of these models exceeds that of any known alternative. The empirical success of these models points to their value in understanding processes affecting the formation and change of urban residential structure.

A GIS‐Based Assessment of Earthquake Property Damage and Casualty Risk: Salt Lake County, Utah

This paper offers a probabilistic assessment of expected property damage and casualty risk due to the earthquake ground shaking hazard affecting Salt Lake County, Utah (population = 725,600). Salt Lake County is bisected by a segment of the Wasatch Fault. It is also at risk from twenty-one other nearby fault segments. Findings are based on (1) a microzonation of the earthquake ground shaking hazard, (2) an inventory of buildings by value, structural frame type and use, (3) earthquake damage functions defining the performance of buildings as a function of ground shaking intensity, (4) data on the density of residential and employee populations, and (5) earthquake casualty functions defining casualty risk as a function of building damage. The analysis is supported by the algebraic combination of digital map layers within a vector-based geographic information system. Triangular irregular network models show the expected distributions of casualties. Hazard mitigation policy implications are also considered.

Response to Special Report 298 Driving and the built environment: the effects of compact development on motorized travel, energy use, and CO2 emissions

The National Academy of Sciences (NAS) recently issued the report Driving and the built environment: the effects of compact development on motorized travel, energy use, and CO2 emissions. This repo...

Further Evidence on the Accuracy of Residential Vacancy Chain Models

Residential vacancy chain models simulate the transfer of vacant housing opportunities among sectors of an urban housing market. The Markov model simulates forward-reaching chains in response to vacancy initiations. The Leontief model simulates backward-reaching chains in response to vacancy absorptions. Each simulates residential mobility among housing sectors as a by-product. The accuracy of these models was assessed in earlier work by the authors, using 1975-80 data from Gävle, Jonkoping and Vasteras, Sweden, to project intra-urban residential mobility in each town during the 1980-85 period. Using log-linear analysis to compare projected moves with observed moves, they found projection errors ranging from 3-12 per cent. In this paper, data from the 1985-90 period are used first to repeat these assessments over the subsequent time-period and then to extend the projection period from 5 to 10 years. Projection errors range from 5-11 per cent for the 5-year period and from 8-18 per cent for the 10-year period. Both the Markov and the Leontief models perform equally well. Models with more homogeneous housing sector definitions produce more consistent results.

Urban development, land use planning and political change. The case of Costa Brava, Spain.

Abstract This article explores current issues of urban development on the Costa Brava — Spains highly successful and environmentally sensitive tourist area. It reviews the regions geography and development history, lists current development issues, outlines recent legal and political changes, relates these to the practice of urban land use planning and considers possibilities for improving planning practice. Throughout, the article considers the hypothesis that the quality of local political life influences the quality of urban planning practice.

Residential vacancy chain models of an urban housing market. Exercises in impact and needs assessment

Our purpose is to demonstrate the application of vacancy chain models to housing needs assessment and residential development impact assessment. The empirical base consists primarily of merged data files from the 1975 and 1980 Swedish Census for Population and Housing for the Municipality of Gavle. Our objectives are to calibrate a Markov vacancy chain model for impact assessment, disaggregate that model to identify development impacts on the mobility of specific population subgroups, calibrate a Leontief (input/output‐like) vacancy chain model and demonstrate its use in assessing the need for new housing given a vector of anticipated immigrants and newly formed households. The article concludes with a discussion of the range and limitations of vacancy chain models in applied contexts.

The role of interoccupational relations in regional economic development

Abstract This article explores the interface between regional economic development, demographic change and occupational mobility. The importance of the regional work force to both operational and developmental issues in regional economic development is discussed, A pair of mathematical models are introduced which use Markov and Leontief-like models of job vacancy transfer to represent the regional work force as a set of interrelated occupations among which job opportunities flow. Each model deals with the formation, interoccupational transfer and absorption of job opportunities. The patterns of linkage forged by rates of interoccupational vacancy transfer are considered. Three archetypal patterns of occupational interaction are identified and related to dimensions of labor market performance. Tendencies toward or away from each of these three patterns influence the quality of work force participation in economic development through interoccupational job mobility. Implications of the work force connection for the design of regional economic development policy are discussed.

The benefits of a seismic retrofit program for commercial unreinforced masonry structures: Salt Lake County, Utah

This paper assesses the benefits of a seismic retrofit program for commercial unreinforced masonry structures (CURMs) in Salt Lake County, Utah. A comparative risk assessment embedded in a geographic information systems is the method used. A policy evaluation time horizon of twenty years is set. Future rates of demolition and rehabilitation, with and without a retrofit policy, are assumed. Damage functions for ordinary and retrofitted URMs are used to assess losses having a 10 percent chance of being exceeded over a 50-year exposure period. With a retrofit program, expected losses are reduced by 57 percent or more than a quarter billion dollars when compared to the no-policy scenario. Expected injuries and fatalities are reduced by more than 80 percent. These are minimal benefits expected from enforcement of the seismic provisions of the Uniform Code of Building Conservation.