Figure 3
From: Spatiotemporal characteristics of ground microtremor in advance of rockfalls
Schematic diagram of sensor installation, microtremor signals in the vertical direction of the overhanging block and fast Fourier transform of microtremor signals. (a) Microtremor signals of the overhanging block without an upper trench. (b) Microtremor signals of the overhanging block including an 18 mm-deep upper trench. (c) Microtremor signals of the overhanging block including a 32 mm-deep upper trench.
