100 volts measured in fuse socket!
One of your service lines might be low.

Do your incoming lines have correct power (be careful with an open panel)?

Your incoming service line consists of 3 wires - 120V, Neutral, and 120V - you might have 120V on one of those incoming lines and 100V on the other.  

Verify this information and if it is low on the incoming line - contact your power company and let them know the line voltage for that line is LOW. As the Hurricane has been there -  there could be several reasons for this - one of which is your transformer - but more likely they have to restore proper power to your power pole/transformer. 

EDIT 9-16-2017

Adding info here instead of in comments.

If incoming power is good. Your wiring to the socket could be loose or the socket can be bad. In either case I would replace the socket as loose wires became loose for a reason. 

Cut off the main power coming in and replace the socket. The price of a fuse 'socket' is cheap insurance against any potential issues including electrical fire.