(a) A city office shall become vacant upon the occurrence of any of the following:
(1) The expiration of the term of office;
(2) The death of the incumbent;
(3) A resignation, when accepted by the appointing authority;
(4) A removal from office in any manner provided by law;
(5) Ceasing to possess at any time the qualifications for eligibility for office required by this charter for election or appointment to office, or the holding thereof;
(6) Final conviction of a felony crime, any act constituting malfeasance in office under this charter, or of an offense involving a violation of his oath of office;
(7) A judicial determination that the incumbent is mentally ill;
(8) A decision of a competent tribunal declaring the election or appointment of the incumbent void;
(9) Failure to take the oath or make the affirmation, or file the bond required for the office, within thirty (30) days from the date of election or appointment.
(10) Except the Mayor and Councilmen, absence from the city or failure to perform the duties of such office for ninety (90) consecutive days, unless such absence from the city or failure to perform the duties of office shall be excused by the Council prior to the expiration of such ninety-day period.