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In characterizing hazards there are a number of indicators, and these tend to be related:
(1) What is the range of potential magnitudes and intensities that you may experience?
(2) Is there a time, day, season, or other factor that constrains when this type of event can happen.  Earthquakes happen at any time of the day, but mass fatality school shootings  happen only when students and staff are in the school buildings.  Can we identify the duration of the event, including pre-event, event impact, and diminishing after-impacts?  Is there a timeline for how the hazard turns into an actual impact?
(3) Can we identify the physical extent of the impact zone?  Floods inundate their flood plain; therefore, the parts of the community within the flood plain are in the hazard impact zone.  Examine hazards in neighboring localities to determine if their impact zones cross into your area.
(4) How frequently does the hazard develop into an actual event?  Frequencies, even if only approximate, become probabilities for decisions under conditions of risk.  If none can be established, another key to prediction is the presence of prodromes (signs that a disaster may be imminent).  For example, in human systems failures, delayed or  nonexistent maintenance is a standard sign of increasing potential for accidents. 
(5) Finally are there are related hazards (for example, tropical cyclones in North America are known to generate relatively weak tornadoes)?  And can the hazard create a cascade of other hazards and impacts as it progresses (serial dam failures are an example)?