So earthquakes generally don't and can't change the planet's orbit (the path it takes around the sun) for basically the reason you said. But an earthquake can change it's rotation (how it spins around on its axis).

Very very simply, a shift in tectonic plates, while it doesn't change the mass of the Earth can change the distribution of mass. How fast the Earth rotates, and the degree to which it "wobbles" as it does so, much like a top, is based not just on its mass, but the distribution of that mass.

Change the distribution, change the rotational axis.

It doesn't affect earths orbit, rather it affects the speed at which the earth spins by either slowing or speeding it up by minute amounts. This can affect perception of linear time as the day/night cycle changes. Normally however, these changes are small and outside of nuclear clocks, most people won't ever notice.

As the other commenters have said, it does not change the Earth's orbit, but it can change its rotation. Think of it like a figure skater bringing her arms in to spin faster. The same thing can happen if an earthquake brings mass closer to the center of the Earth (lower elevation)

And you can move a sled, not far but if you kick out your legs or suddenly sit up or lay down you should get several inches movement.

But you need friction for that

Earthquakes, and tectonic activity in general, redistribute mass in the Earth's crust. This doesn't affect the Earth's orbit but it does effect the Earth's rotation (https://youtu.be/M6PuutIm5h4). The change is small enough to be irrelevant in day-to-day life, even if it is ultimately changing the length of a day.

you need friction to stay on a sled, yes. ???

What I meant is that to move the sled by kicking out your legs you need to have friction. So you are essentially pushing of the ground which means that this example is not comparable to an earthquake changing the earth's orbit.

Thats what I thought anyway. Might be wrong.

I thuoght the orbit thing was covered and was responding to the sled.

But they are comparable in the sense that if the rider or the earth change their shape the center of mass doesn't change but from points of view not on the center of mass things appear to change.