Tilt Noise
Tilt Noise : A noise on a horizontal-component seismogram created by rotation (local tilt) around a horizontal axis. Slight tilts produce large apparent accelerations as a component of the acceleration of gravity is coupled into the horizontal components. See section 5.3.3 with Figs. 5.8 and 5.9 in Chapter 5 of this Manual, and Webb (2002)