The Whitecaps took the lead as Fernandez picked up the ball in the midfield and powered a shot at goal from 30 yards which sailed into the top corner past the outstretched hand of Stefan Frei.
Kekuta Manneh had the chance to double the home side's advantage when he latched onto a through ball, but Frei came out to narrow the angle and make a good stop with his body.
In the second half, Lamar Neagle nearly found an equaliser for Seattle when he drilled a low shot at goal from outside the box that went inches past the post.
Hurtado was presented with an excellent chance to put his side in a commanding position when Pedro Morales released him through the middle, but he got his effort all wrong as he scuffed his shot at Frei.
The Sounders pushed late in the game for a leveller and almost found it through Marco Pappa when he launched a curling shot which went inches over the bar, as the Whitecaps held out for the win.