Fig. 2
![Fig. 2](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs40623-015-0305-0/MediaObjects/40623_2015_305_Fig2_HTML.gif)
Equivalent circles and instrument response. a Schematic of a typical Hi-net seismometer, b the voltage used as an input for the test signal, and c the velocity of the coil bobbin relative to the magnet as a result of the input shown in (b). We refer to this waveform as the instrument response or test signal