Introduction

Abstract

Seismology would be a very different science without instruments. The real big advances in seismology happened from around 1900 and onwards and were mainly due to advancement in making more sensitive seismographs and devising timing systems, so that earthquakes could be located. Later, the importance of accurate measurement of the true ground motion became evident for studying seismic wave attenuation, and the Richter magnitude scale depends on being able to calculate the ground displacement from our recorded seismogram (Figure 1.1).

The ability to do earthquake location and calculate magnitude immediately brings us into two basic requirement of instrumentation: Keeping accurate time and determining the frequency dependent relation between the measurement and the real ground motion. In order to get there, we need to know a bit more.