Array Exploration of Microtremors
The ground surface is constantly trembling because
of industrial activities, ocean waves and winds. They are, of course, too small
to be felt by human bodies, and can be detected only by microtremor
sensors (high-sensitivity seismic sensors). These small tremors are called microtremors (random noise). Simultaneous measurement using
more than one microtremor sensors installed on the
ground surface is called array measurement of microtremors.
Array measurement of microtremors allows one to infer
phase velocities of surface waves (propagation velocities of waves called
Rayleigh waves and Love waves), on the basis of which one can then infer soil
properties (velocity structures). By the term "array exploration of microtremors" we refer to the whole flow of procedures
that start with array measurement of microtremors and
end with evaluation of subsurface structures.