Bilge keels are passive stability systems. On commercial shipping the bilge keel is the form of a strake, or small keel or blister, running along much of the length of the hull. They are typically fitted one on each side, low down on the side of the hull, so as not to increase the draft of the vessel.
Intensity is a measure of the strength of shaking experienced in an earthquake. The Modified Mercalli Scale represents the local effect or damage caused by an earthquake; the intensity reported at different points generally decreases away from the earthquake epicenter.
Intensity is proportional to the square of the amplitude. So if amplitude is squared, intensity is quadrupled. Intensity varies in diagnostic ultrasound because it's highest at the center of the beam and falls off near the periphery. It also varies along direction of travel due to focusing and attenuation.