Real-time waveforms

Ground motion as it is being measured right now by the stations of the Belgian seismic network, on three components: vertical, north-south and east-west. The signal is displayed with a delay of a few seconds.

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Reading the signal

The record scrolls to the left: the most recent data come in on the right. Time is given in Coordinated Universal Time (UTC).
Three components describe the ground motion: vertical (Z), north-south (N) and east-west (E). A seismometer measures the velocity of the ground, an accelerometer its acceleration.
The vertical scale adjusts to the displayed signal and the mean of the window is removed: a large trace does not mean a strong motion. The axis values give the actual amplitude.
Physical units are obtained by dividing the raw digitizer value (counts) by the instrument sensitivity published in the station inventory, without correcting for its frequency response. They are indicative outside the passband of the sensor.
Not everything visible is an earthquake: traffic, wind and human activity also shake the ground.