The range of amplitudes is very large. The natural background noise, highly
frequency dependent, sets the limit for the smallest amplitudes we can measure, which is
typically 1 nm displacement at 1 Hz (Chapter 2), while the largest displacement is in the order
of 1 m. This is a dynamic range of 109
. The band of frequencies we are interested in, also has
large range, from 10-5 to 1000 Hz (Table 1). The challenge is therefore to construct seismic
instruments, both sensors and recorders, which cover at least part of this large frequency and
dynamic range.