Go to wayward cave on route 206, right below the bike path. There's a secret entrance to the cave somewhere directly below the path, you have to look for it. You also need a bike. If you hop around in there, you'll eventually find it, and you can also catch Gible in the cave.
Answeryou must go to the professor and talk to him.When he is finished, just press B,A,B,B,B,X,Y,B,A,X,X,Y,Y, UP,DOWN,LEFT,RIGHT.Then he will tell you:Wow!you knew the secret password!And he'll give you TM26.Chat with our AI personalities
Silph Co.
It's in kyogre's cave
Earthquake (TM26) is your reward after you beat Giovanni
TM 26 (Earthquake) is a reward for beating the 8th Gym Leader in Viridian City
go to seafloor tavern..... you'll see a pokeball and pick it up.... there TM 26 Earthquake