Results and experiences of application of the Refraction Microtremor method for the geophysical investigation ofthe new subway lines in Madrid (Spain)

摘要

Geophysical exploration with seismic methods in urban zones presents several disadvantages: the presenceof numerous sources of seismic noise, the scanty penetration when the seismic source is a hammer andthe disability to detect buried low-velocity beds. Recently (Louie, 2001) a new method of seismicinvestigation has been developed, which allows vertical modeling of Raleygh waves from spectral analysis(Vphase/frequency) using the seismic signal registered with conventional seismographs and geophones.This method allows to detect low-velocity buried beds of great interest in tunneling, and to reachdepths below 50 meters. In this work we discuss the conditions of application and experiences obtainedduring the 2005 geophysical surveys carried out in Madrid before the excavation of the new subwaytunnels