Brian Kennett has established himself as a leading seismologist through his contributions to theory, interpretation and field experiment. His early work on the theory of wave propagation in stratified media, culminating in his classic monograph on the subject, led to some of the first interpretations of the full seismic waveform. Later theoretical developments include extensions to heterogeneous media and waveguide propagation. He has made numerous discoveries relating to deep Earth structure, was instrumental in establishing the accepted model by which earthquakes are located, and has conducted a systematic study of the seismic properties of the whole Australian continent.