Radius: A simplified tool for earthquake risk assessment
The multi-disciplinary team at RMSI (Risk Management Software India) is working in the field of IT-enabled disaster management for various natural perils. It has been involved in many disaster management projects, and has worked on a wide range of tools, ranging from simplified Excel-based tools (RADIUS tool) to sophisticated GIS based solutions for catastrophe risk management, depending upon specific user needs.
Risk Assessment Tool for Diagnosis of Urban areas against Seismic disasters (RADIUS) tool was developed for IDNDR (International Decade for Natural Disaster Reduction) by OYO Corporation, Japan and RMSI to enable a city administrator to do quick assessment of earthquake risk to a city. The tool was showcased at IDNDR (International Decade for Natural Disaster Reduction) seminar, Mexico in 1999 to many city planners and administrators.
The goal of this tool is to aid users in understanding the seismic hazard and vulnerability of their cities and to guide them in starting preparedness programs against future earthquakes. Designed in MS Excel to provide a simple and very familiar interface, the tool is user friendly, and provides risk-mapping functionality. The area of a city and probable loss to infrastructure and life is displayed as a mesh of rectangular cells that allows the user to get a graphical view of the data. Outputs are seismic intensity, building damage, lifeline damage, and causalities, which are presented in tabular as well as map forms.
Although the damage estimations provided by this tool are rough, the results of the program can be used in various ways. Through using this tool, users can gain a better understanding of earthquakes and the disasters associated with them. The potential extent of damage and the vulnerable points of the city are highlighted by the use of this tool. The information presented through this tool is very important and useful to manage effective seismic disaster reduction measures, including preparedness, emergency response activities, and seismic retrofit and recovery actions and policies. It can be concluded that the calculations of the damage amount should not be considered as a final goal of earthquake damage estimation, but instead as a starting point for seismic disaster reduction.
Damage estimation leads to the knowledge/awareness of the extent of damage, which the city will incur if the scenario earthquake were to occur in the city. It is possible to know not only the total amount of the damage but also the weak points of the city through the analysis. This information is very important to manage effective seismic disaster reduction measures, including preparedness, emergency response activities, and seismic retrofit and recovery actions and policies. Often, however, the budget and efforts that are readily available to implement seismic disaster reduction actions are limited in almost all countries of the world.
Therefore, the knowledge of what will happen if an earthquake were to occur is indispensable for earthquake prone cities since this information can help to set priorities in using these limited resources. To merely calculate the damage amount is not the goal of the earthquake damage estimation. The goal is for this estimation to serve as a starting point for effective seismic disaster mitigation. For any detailed or more accurate analysis, the tool can be further improved using the experts in the regions for which the analysis needs to be done.
The tool uses the data collected from the cities participating in the RADUS program. While it is possible that this data be used as a starting point if the exact city-specific data is available, it is however advisable to only use this tool using reasonably correct data. Anyway the data requirements are not very high. The tool also provides detailed help files to guide the users and it could be used as an effective educational tool for earthquake risk management. This tool uses very simple technology, and if the detailed data can be made available, more sophisticated and accurate tools can be developed, using engineering, GIS, and software skill. It also proves the potential of information technology and knowledge-based tools in managing natural disasters.
Coping with Earthquake Hazard and Risk in the National Capital Region.
Delhi has a history of regional earthquakes. Small magnitude earthquakes occur frequently, attesting to the seismically active status of the region. The damage in Delhi that occurred due to the 1991 Uttarkashi earthquake and Chamoli earthquakes of Himalaya is noteworthy. It draws our attention to the vulnerability of the region to even distant earthquakes.
According to a recent study (Khattri, 1999) a great earthquake in the Garhwal Himalaya can generate severe ground motions in Delhi, producing peak ground accelerations of over 20%g. These ground motions will have long durations and long period oscillation - tall building will be severely exposed to shaking. The probability of occurrence of such as great earthquake (M 8.5) in the Garhwal Himalaya in the next 50 years in 31 %. An alternative analysis of expected Peak Ground Accelerations (PGA) shows that in Delhi a PGA of about 20%g can occur with a probability of 10% in 50 years.
Thus the probability of hazard from earthquakes ios thrice that obtained from the probabilistic analysis, which has not taken into account recent understanding of the Himalayan seismological processes. An important factor that controls the ground motion severity is site characteristics. Sites covered by loose soft soil are liable to amplify ground motion. In NCR there are many such regions. Various studies are used for site investigation (i.e. dominant period and amplification level). Techniques such as noise studies, shallow refraction and swell boring are use for site characteristics. Using this information a detailed map of expected ground motion characteristics could be prepared. Such a map will be suitable basis for vulnerability mapping.