The days length could be changed by an imperceptible fraction of a second.
I wouldn't worry though, this planet has had millions of these quakes since it's formation - almost all before humans evolved. The tectonic plate movements is what builds the mountain ranges like the Alps, Rocky mountains etc.
The Planet Earth weighs about 6 billion trillion tonnes, or 5.97 septillion kilogrammes to be exact, so a thing like that would not move it that much. Would the meteorite that killed the dinosaurs move the Earth off its' axis, as that was over 6 miles wide, and was not part of the Earth to start with, so would have added mass to the planet.
Nothing that happens on the planet can shift the axis of rotation in space. Only external mass can cause that.
It did cause it to wobble a tiny bit more.
It also shortened the length of the day by over a microsecond. This happened because the the average radius of the Earth reduced. Just like the dancer or skater who moves their arms from the expanded to contracted position this increased the rotational rate to conserve angular momentum.