This work provides an up-to-date overview of modern instruments used in earthquake seismology as well as a description of theoretical and practical aspects of seismic instrumentation. The main topics are:• Choosing and installing equipment for seismic stations• Designing and setting up seismic networks and arrays• Maintaining and calibrating seismic instrumentsIt also provides detailed descriptions of the following:• Seismic sensors• Digitizers• Seismic recorders• Communication systems• Software used for seismic station and networksIn this second edition, new seismic equipment is presented and more comprehensive sections on topics like MEMS accelerometers, sigma-delta AD converters, dynamic range discussion and virtual networks have been included. This book is primarily intended for seismologists, engineers and technicians working with seismological instruments. It combines practical “know-how” with sufficient theory to explain the basic principles, making it also suitable for teaching students the most important aspects of seismic instrumentation. The book also gives a current overview of the majority of instruments and instrument manufacturers on the market, making it easy to compare the capability of instruments from different sources. SEISAN software was used for several examples in the book. This widely extended seismic analysis software is freely available from the University of Bergen website. The content of this book draws on the authors’ (a seismologist and a physicist) combined experience of working in this field for more than 35 years.