Shallow Seismic Investigations of an Abandoned Mine

The near-surface rock structure that covers an abandoned marl mine nearby the village of Montevecchia (Italy) was investigated through a combination of seismic surveys performed in two different survey campaigns. The methods selected for these investigations were Refraction Seismics and Multichannel Analysis of Surface Waves (MASW). A sort of transillumination experiment was also attempted. All the methods were successful and gave complementary information. Refraction seismics was used to characterize the shallower low velocity layers and a deeper high velocity layer of the near-surface structure. The MASW method was necessary to assess the existence of a velocity inversion revealing the presence of a low velocity layer between the faster layer identified by refraction seismics and a 4th high velocity layer covering the upper mine gallery. The transillumination experiment validated the presence of the 4th layer and gave an estimate of the average velocity that represents a lower boundary for the P-wave velocity within this layer. Both refraction and transillumination data were analysed to derive average estimates of attenuation level and rock quality factor.