Surface Wave Experiments and Ground Penetrating Radar Tomography for

Abstract

NGI and VNU have jointly carried out geophysical investigations in the Hatay area east of Hanoi. The purpose of the investigations was to obtain a better understanding of the sub-surface soil conditions for future development of the area. Surface wave experiments using the MASW method (multichannel analysis of surface waves) was performed to estimate the subsurface shear wave velocity of the soil. This information is required for assessment of the amplification of earthquake waves and earthquake analyses of the planned facilities. The shear wave velocity in the shallowest layer ranged from 100-120 m/s and generally increases with depth to values in the order of 350 m/s at a depth of about 45 meters. Ground penetrating radar tomography for two sections was also performed in the same area to scan the subsurface soil conditions. The tomograms from these investigations showed that the wave attenuation from one soil section was larger than the other section. This is due to the fact that a high attenuating wave section has higher water content than the other section due to a nearby lake on the surface. Such investigations are useful for planning infrastructure development in the area.