The potential energy for a tsunami is generated by plate tectonics. More specifically by an event called subduction where one plate is forced under another. This builds tension that is eventually...
That big old tree was just waiting to fall down: that's potential energy.
Now those big branches are falling down fast on your head: that's kinetic energy.
No, it doesn't become "larger" - the peak potential is always the same - it is a digital signal. Stronger stimulus will cause the nerve cell to fire more often - therefore stimulus strength is...