Where does tremor collide?

In neurology, a tremor is an involuntary, roughly rhythmic oscillation of a body part produced by alternating or synchronous muscle contractions, as in essential tremor or the resting tremor of Parkinson's disease. Deuschl, Bain, and Brin's 1998 Consensus statement of the Movement Disorder Society on tremor classifies tremors by the situation that brings them out (at rest, holding a posture, or moving) and by their frequency. The referent is a clinical movement sign in a person, measured by its frequency and amplitude and the conditions under which it appears, and it is an entirely different thing from ground shaking deep in the crust.[1]

Unit

The frequency and amplitude of rhythmic involuntary movement

Recovery means

Not applicable

Measured by

Assessed clinically and with accelerometry or electromyography by oscillation frequency, amplitude, and activation condition (rest, postural, kinetic)

In seismology, tremor is a weak, sustained ground vibration lacking the sharp onset and clear body-wave arrivals of an ordinary earthquake, a long, low rumble rather than a jolt. Obara's 2002 Nonvolcanic deep tremor associated with subduction in southwest Japan identified a deep, nonvolcanic (tectonic) tremor along a subduction zone, now understood as the seismic signature of slow fault slip at depth. The referent is a prolonged, emergent seismic signal from the Earth, tracked by its duration, location, and coincidence with slow slip, and it shares only the word with the clinical shaking of a limb.[2]

Unit

The duration, amplitude envelope, and source location of sustained weak ground vibration

Recovery means

Not applicable

Measured by

Detected by envelope cross-correlation across stations and located at depth, often accompanying slow-slip episodes