Shear wave velocity data survey and estimation of necessary depth for dynamical analysis of deposit effect in Mashhad

Average of the shear wave velocity of the upper 30 meters despite the numerous weaknesses in accurate explanation of the site dynamic characteristics, is one of the reliable parameters in ground seismic classification in the view of different building codes, until now. This study evaluated the results of shear wave velocity in 79 points in Mashhad, and then empirical relationship between average of the shear wave velocity of the upper 30 meters and lower depths is obtained. Based on the velocity profiles information in 79 boreholes and resonance period data of the Mashhad, the proper depths for dynamic analysis of the site effect are recommended. Therefore the velocity profiles required for analysis of the deposits effects in Mashhad, except for the south and north elevations margin is more than 30 m. For central, eastern and northeastern areas which have resonance period more than 0.7 s, this depth is estimated as 80m. Therefore, investigation depth of 30 meters in Mashhad is only adequate for site classification based on the building codes and deeper studies are needed for the theoretical analysis.