iPhoto won't open library

My computer shut down yesterday when a breaker tripped while work was being done on the house. Since then, I cannot open iPhoto: it asks for a library, with a blank field. When I browse for my library, it shows up, but won't open.

I have read previous threads. I have tried holding down alt & command while opening iPhoto, but it still just asks for a library with a blank field: it does not show a window asking whether I would like to rebuild or repair the library.

I am running OSX 10.9.5 on an iMac. iPhoto version is 9.5.1. I have the library file backed up via Time Machine on an AirPort Time Capsule. Everything is in the default places.

What to do?