Effect of Low Velocity Zones on Seismic Hazard Assessment - The Case of Taygetos Fault

摘要

Shallow layers with low shear wave velocities may heavily influence the amplification of strong ground motion in a specific site. Such zones are often not taken into account in calculations of seismic hazard for a region, resulting in underestimated values of calculated ground acceleration. This issue is of great significance in areas that are adjacent to large seismic zones. We assessed the effect of low velocity layers in the calculation of the amplification of ground motion, as well as in the calculation of the maximum values of acceleration. Additionally we evaluated the ability of several near surface geophysical techniques in detecting velocity reversals. We tested the MASW, MALW and refraction tomography techniques in conjunction with crosshole tomography. We found that only the MASW near surface methodology was able to reliably detect velocity reversals. We also proved that by not taking into account such low velocity layers in the calculation of seismic hazard, the results could be underestimated up to 25%.