Integrated approach to the study of geohazards with application in southern Afar

In the relation expressing risk to an object of interest as a product of hazard and the vulnerability of the object of interest, in principle, the risk could result from a variety of hazards and their higher order effects. Therefore, for a robust risk assessment it would be proper to consider all possible hazards and their secondary and higher order effects that could lead to the realization of the risk. In carrying out this task the selection of an object of interest is fundamental. It will be the risk to this object of interest that will be evaluated. The possible variety of hazards and their higher order effects could be identified from scenario analysis based on records of geology, geophysics, geography and the vulnerability of various entities that could be involved in the realization of the risk in question. The probability of realization of the risk through first and higher order effects could be evaluated from probability models appropriate for each first and higher order effect. In this manner the total number of ways or the mean rate of occurrence of the risk in question will be known. This mean will be used in a Poisson distribution, which is appropriate for rare events, to determine the probability of occurrence of risk events during a specified period of time. This probability will be significantly different from that usually evaluated when risk is attributed to a single cause.