Application of Microzoning and GIS in Oil Facilities for Seismic Risk Emergency Planning
Authors: Franke M. 
Published: December 2007

A proposal on emergency response planning for oil facilities in seismic active regions is presented, considering an oil refinery. Most Venezuelan oil facilities are located in areas of moderate to high seismic activity. Therefore, it is recommended to carry out seismic and geotechnical microzonations to assess the vulnerability of existing structures, and optimize the earthquake resistant design of new ones. This information together with the facility inherent data are used in a Geographical Information System (GIS) to allow for better managing of the seismic hazard and its associated human, environmental, and economic risks.

Introduction

Venezuela is a region of moderate to high seismicity (Fig. 1), where several destructive earthquakes have occurred in the last 500 years. Probabilistic seismic hazard assessments revealed expected horizontal peak ground accelerations of more than 0.25 g3 in western and over 0.35 g4 in eastern Venezuela for the 500 year return period earthquake (Fig. 2). Because the majority of Venezuela's oil facilities are in areas of moderate to high seismic risk, it is recommended to carry out seismic and geotechnical microzonation studies in order to evaluate the seismic vulnerability of existing installations, lay down mitigation measures, and optimize the seismic design of new structures.

The potential of a Geographical Information System (GIS) and the technological advances of the computer science (e.g. in data base management) permit the processing of large data sets, their fast graphical analysis and appropriate presentation in two or three dimensions (2D or 3D, respectively).

The proposal of the application of GIS technology will be exemplified by means of an oil refinery. Because GIS is a complex tool, a three-stage installation of the system has been developed in order to guarantee its operation from the beginning on. Each new level includes a larger data base which permits more complex queries, so that it can address problems from basic engineering design (BED) to on-line emergency response. (1) At the first "static" level, all the results of the microzonation will be loaded in data base of the GIS, e.g. soil profiles, dynamic soil response, and design spectra. Thereafter, it is possible to obtain different maps, as needed for projects like BED, retrofitting, and land use. (2) The second "interactive" level would add information on dynamic interaction of soil-structure and associated risks like possible number of affected persons, economic losses, and environmental impact in case of an emergency. At this stage, the proposed method gives interactively graphics, depending on given seismic hazard scenarios, in order to define areas with different characteristic risks and to calculate potential damages to structures. Therefore, the system will support decisions about mitigation measures as well as improvements on emergency plans. (3) At the third "dynamic" level, the GIS will have a module which processes on-line information about meteorological and seismological data, as well as transient operation and production data. Thus in the case of a strong earthquake, the GIS can display in real time maps of probable damages, fires, and numbers of affected persons. In summary, GIS will help in the decision making process before, during, and after an earthquake, and will help to mitigate its negative social-economic impacts.

Geographic Information System (GIS)

The GIS is a computer technology which permits the solutions of complex planning and management problems by means of spacial autocorrelations, functions and processes to calculate, manipulate, process, analyse, change, and present spacial data in a graphic form. GIS's integrate three different aspects of computer technology:data base management,special analysing tools, andgraphic capabilities (Fig. 3).

The most important functional advantages of GIS's are i.e.:graphical presentation skills for data and information in 2D and 3D;easy data base maintenance;data base information could be digital or analog, quantitative or qualitative;capability to generate new information through data correlation by comparison, integration, and data relation;

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