This is the 9147th most frequent Russian word.
североморске
"Североморске" is the locative case of "Североморск," a city in Russia.
This usage demonstrates 'Североморске' as a locative case, specifying the destination for the business trip.
Сын недавно вернулся из командировки в Североморске.
My son recently returned from his business trip in Severomorsk.
Here, 'Североморске' is again used in the locative case to indicate the location of the activity.
Во время отпуска мы отправились на экскурсию по Североморске.
During the vacation, we went on a tour around Severomorsk.
This usage shows the word 'Североморске' as the locative case form of 'Североморск', indicating the location where someone resides.