My new favorite piece of exercise equipment is the Bodyblade. When I recently switched health clubs, it was the only thing missing, so I purchased my own and love it. Why? Because it strengthens what matters. You have to shake it and force it to move, requiring your body to stabilize itself to counteract the force you're putting on it - enhancing your core strength. (It is actually supposed to strengthen the muscles in my neck and core to prevent further injury after my lovely slipped disc.)
I recently listened to a sermon entitled "Shakedown" by Steven Furtick. He was teaching on how when our world is shaken it is often to reveal the treasure (2 Cor. 4:7) that is inside of us. Everything that is not solid - falls off; things like people, money, or stuff that we depend on too much.
While the bodyblade helps to strengthen our core (where all of our physical strength comes from) by shaking what's around us - God uses the earthquakes in our lives to strengthen our grasp on our treasure, letting anything superficial fall off.
The Old Testament refers to shaking the dust off of our feet before we go somewhere new; something that has to be done before we are free.
Amos 9 - throwing Israel into a sieve and shaking them good - shaking out all the sin.
Isaiah 52:2 - "Shake off your dust; rise up...Free yourself from the chains on your neck..."
Nehemiah 5 - talks of a man be shaken out and emptied.
God is constantly shaking things up to see what's inside; to get rid of the wasteful things; to show Himself golden to those who are clinging to Him. He's the only stable thing there is - and because of that, He's a treasure worth holding onto with all we've got.
Psalm 99:1 says "The Lord reigns... Let the earth shake!"