Question

Define the term 'frequency ' and 'magnitude ' explaining what was established by Heinrich Traingle.What are the usual ways to classify a risk-Discuss.

Answer 1

ANSWER:

Frequency. The frequency of a natural hazard event is the number of times it occurs within a specified time interval.

Magnitude. The magnitude of a natural hazard event is related to the energy released by the event. It is distinguished from intensity which is related to the effects at a specific location or area.

The magnitude of a natural hazard event varies in its frequency of occurrence over time in an inverse power relationship. The relationship is often depicted as log-normal (Figure  1) where the magnitude increases linearly (e.g., 1, 2, 3, …) whereas the frequency decreases as an inverse power function (e.g., 1/3, 1/9, 1/81) with increasing magnitude (Keller et al., 2008, p. 23). In other words, the larger and the more energetic the event, the rarer it is in time.

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120 1815 (115,000 cfs) 100 1856 (95,000 cfs) 80 60 C 1.01 100 200 1.1 1.3 1.5 2 3 4 5 10 30 40 50 Recurrence interval (years) 20 40 20 cubic feet per second Discharge in thousands of

The most famous result is the incident/accident pyramid, also known as the “safety pyramid” or the “accident triangle”. The pyramid, as illustrated by Heinrich in the 1941 edition of his book, is shown below.

THE FOUNDATION OF A MAJOR INJURY MAJOR INJURY 29 MINOR INJURIES 300 NO-INJURY ACCIDENTS oo.3% OF ALL ACCIDENTS PRODUCE MAJOR INJURIES-- 8.8OF ALL ACCIDENTS PRODUCE MINOR INJURIES g0.9% OF ALL ACCIDENTS PRODUCE NO INJURIES-- THE RATIOS GRAPHICALLY PORTRAYED ABOVE1--29-300 SHOW THAT IN A UNIT CROUP OF 330 SIMILAR ACCIDENTS, 300 WILL PRODUCE NO INJURY WHATEVER, 29 WILL RE SULT ONLY IN MINOR INJURIES AND 1 WILL RESULT SER- OUSLY. THE MAJOR INJURY MAY RESULT FROM THE VERY FIRST ACCIDENT OR FROM ANY OTHER ACCIDENT IN THE GROUP MORAL-PREVENT THE ACCIDENTS AND THE INJURIES WILL TAKE CARE OF THEMSELVES.

The “accident pyramid”, as depicted by H. Heinrich in the second edition of his book Industrial Accident Prevention: A Scientific Approach. Note the last sentence: “Moral — prevent the accidents and the injuries will take care of themselves”.