Refraction Microtremor (ReMi) is a technique based on Rayleigh surface waves, developed since 2004 by Dr. John Louie and colleagues. As long as the waves travel within a dispersive medium, they can be recorded by a linear array of 4.5 Hz vertical geophones, allowing for the analysis of the slowness and frequencies of the waves captured by the array.

Considering the penetrative properties of various frequencies, it is possible to model a 1D profile of the subsurface by estimating the velocity and depth of the layers. Depending on the maximum length of the layout used, it is possible to reach greater depths compared to MASW, using the same layout with just a few minutes of passive recording.

Dataset acquisito con il DoReMi.

By exploiting the natural noise generated by various sources, such as traffic, human activity, and vibrations induced by natural phenomena like wind affecting structures and trees, it is possible to generate a final seismogram lasting a few minutes. From this, the spectrum can be calculated for picking and subsequent modeling.