The Microtremor Survey Method

The earth is full of geophysical signals. Passive geophysical methods such as gravity, magnetic, and magnetotelluric surveys detect these signals. The microtremor survey method listens to the natural seismic signals from road traffic, machinery, ocean waves, and meteorological sources and analyzes for subsurface acoustic properties, in particular the shear-velocity profile for the earth at a scale of a few meters to a few kilometers. The required instrumentation is simple and can be applied where conventional seismic surveying is difficult, particularly in urban areas. This book describes the nature of the microtremor noise field, the use of appropriate surface arrays of geophones, and the two principal classes of array-processing techniques (high-resolution beamforming and the spatial autocorrelation method, or SPAC). Applications of the method exist in earthquake-hazard site zonation and in engineering seismic investigations. This is the first comprehensive textbook of the microtremor survey method written in English. The translation and publication from the original Japanese text have been a joint project of SEG, the SEG of Japan, and the Australian SEG.