(1) “Chief administrative officer” means the mayor of any municipality incorporated under the general law pursuant to title 6, chapter 1, part 2, or of any metropolitan government as chartered pursuant to title 7, chapter 1; and the city manager of any municipality incorporated pursuant to title 6, chapter 18, or of any municipality incorporated pursuant to title 6, chapter 30. In the case of other municipalities the chief administrative officer shall be the city manager or if there be none, the mayor. Any municipality, however, may by ordinance, specially designate any official as chief administrative officer for purposes of this chapter;

(2) “Civil emergency” means:

(A) A riot or unlawful assembly characterized by the use of actual force or violence or a threat to use force, if accompanied by the immediate power to execute, by three (3) or more persons acting together without authority of law;

(B) Any natural disaster or man-made calamity, including, but not limited to, flood, conflagration, cyclone, tornado, earthquake or explosion within the geographic limits of a municipality resulting in the death or injury of persons, or the destruction of property to such an extent that extraordinary measures must be taken to protect the public health, safety and welfare; and

(C) The destruction of property, or the death or injury of persons brought about by the deliberate acts of one (1) or more persons acting either alone or in concert with others, when such acts are a threat to the peace of the general public or any segment of the general public;

(3) “Curfew” means a prohibition against any person or persons walking, running, loitering, standing or motoring upon any alley, street, highway, public property or vacant premises within the corporate limits of the municipality, except persons officially designated to duty with reference to the civil emergency, or those lawfully on the streets as defined in this chapter; and

(4) “Substitute officer” means an official who shall act in the absence or inability to act of the chief administrative officer as provided in this chapter. Each municipality shall by ordinance designate a “substitute officer” for the purpose of this chapter.