Engineering bedrock depth estimation and ground response analysis of the northern Jeddah urban area, western Saudi Arabia

摘要

The engineering bedrock depth was determined in the northern Jeddah urban area via multichannel analysis of surface waves (MASW) conducted at 76 locations. Depths corresponding to the velocity ranges were estimated below the ground surface and mapped. The engineering bedrock depth was evaluated and it varies from 0 to approximately 36.23?m whereas the depth increased eastward. Further, ground response analysis was conducted to assess the seismic hazard in terms of peak ground acceleration, where it ranges from 3.37 to 17.71?cm/s2, considering the fundamental resonance frequency and amplification potential at the sites of measurement. These variations are due to differences in the soil profile at each location; ground surface acceleration increased at sites with thick layers of soft sediments. In addition, the spectral acceleration and response spectra were assessed at the ground surface with a 5% damping ratio for the identified lithological units. Peak spectral acceleration varies from 16.8 to 62.6?cm/s2. The eastern zone has a higher spectral acceleration than the western zone while the frequency corresponding to the spectral acceleration varies from 1.05 to 14.28?Hz. The spectral acceleration and response spectra are used for assessment the spectrum of structures. Ground response analysis shows that because of the soil condition, potential amplification of wave amplitudes is observed at the ground surface when compared to the engineering bedrock level acceleration. These results should be provided to civil engineers, land-used planners, and decision makers during the designing of either new buildings or rehabilitation of pre-existing structures.