From FEMA's site ...
The primary mission of the Federal Emergency Management Agency (FEMA) is to reduce the loss of life and property and protect the Nation from all hazards, including natural disasters, acts of terrorism, and other man-made disasters, by leading and supporting the Nation in a risk-based, comprehensive emergency management system of preparedness, protection, response, recovery, and mitigation.

The organization structure is given below.

Office of the Administrator
-Gulf Coast Recovery
-Law Enforcement Advisor to the Administrator
-Center for Faith-Based and Community Initiatives
-Office of Policy and Program Analysis
-Executive Secretariat
-Office of External Affairs
-Associate Deputy Administrator
-Office of Equal Rights
-Disability Coordinator
-Office of Chief Counsel
-Office of Chief Financial Officer

-Management
--Assistant Administrator
--National Capital Region Coordination

The country is divided into 10 regions. Some organizational units work on close coordination with one another. Each regions has the following structure:

-- Logistics Management
-- Disaster Assistance
-- Disaster Operations
-- Grant Programs Coordinator
-- National Preparedness
-- United States Fire Administration
-- National Continuity Programs
-- Mitigation