word choice - Some other or another

I wonder if "some other" means exactly the same as "another" in the following sentences. Is there any difference between them?

1. 
   
   • There must be another explanation.
   
   
   • There must be some other explanation.
   
   


2. 
   
   • In this case we will go to some other city.
   
   
   • In this case we will go to another city.
   
   



3. 
   
   • After that they saw some other house.
   
   
   • After that they saw another house.