What is the characteristic difference between tilt induced signal and other noise sources?
Tilt signals appear predominately on the horizontal channels, most often with the tilt vector varying in both direction and magnitude. A consistent direction may indicate an identifiable source of tilt, such as a loose leveling foot, unstable pad, tree nearby, etc. Secondary tilt effects may be observed due to thermal expansion of the immediate environs, particularly in late afternoon. By low-pass filtering the vertical channel (say, 4 poles at 0.033 Hz.) you may be able to correlate signals on the vertical channel with the much higher amplitude signals on the horizontals. Sensor pings, a sudden step in acceleration, are usually observed on a single channel (or element in the case of STS-2 with corresponding outputs scaled by the rotation matrix). Site disturbances by animals, including humans, often show vertical signals corresponding to footsteps and then wild tilting on the horizontals.
