In this study,the Beibu earth fissure site in the northeastern part of Weihe Basin,which contains four nearly parallel earth fissures,was studied.A long straight microtremor measuring line,containing 49 measuring poin...In this study,the Beibu earth fissure site in the northeastern part of Weihe Basin,which contains four nearly parallel earth fissures,was studied.A long straight microtremor measuring line,containing 49 measuring points across four earth fissures,was established to investigate the dynamic response of this site using Fourier spectrum,response acceleration spectrum,Arias intensity,and HVSR analyses.The main results are as follows:(1)The fundamental frequencies of 44 measuring points obtained from HVSR analysis are concentrated within 1.67 Hz-2.25 Hz,and the existence of the earth fissures has little effect on the fundamental frequency changes.(2)There is an amplification effect near a single earth fissure.The dynamic responses are large at the measuring points near the earth fissure,and the values decrease with increasing distance from the earth fissure.In areas between two adjacent earth fissures,these values decrease and are even lower than those in sites without amplification effects.(3)In this earth fissure site,the general area(or less affected area)and affected areas were delineated based on the amplification effect.In engineering applications,construction design should avoid these affected areas and existing structures should be reinforced to satisfy the seismic fortification requirements.展开更多
The faults and fractures are known as two of the most important parameters in earthquake occurrence.During the construction in urban areas, faults and fractures may be covered in depth and thus are not visible at the ...The faults and fractures are known as two of the most important parameters in earthquake occurrence.During the construction in urban areas, faults and fractures may be covered in depth and thus are not visible at the ground surface. In this context, non-invasive geophysical prospecting methods(microtremor and geoelectrical methods) and borehole data were used to detect subsurface geological structures(hidden faults) in a suburb of Shiraz in Iran. The horizontal to vertical spectral ratio(HVSR) method was used to obtain the dynamic parameters(predominant frequency and resonance amplitude) of the soil, to detect hidden faults. The results show that the abrupt changes in the sediment thickness and predominant frequencies at a specific direction(NW-SE) can be related to the displacement of a nearly vertical fault with NW-SE trend. In addition, the electrical resistivity method using continuous resistivity profiling(CRP) and Schlumberger arrays was employed to detect a hidden fault and the results were compared with previous data. The obtained results of both arrays illustrate the presence of a nearly vertical fault with NW-SE trend in the region. Comparison of all results shows that the detected faults by both methods are consistent with each other. Therefore, it can be conclusive that combination of the two methods is a useful and reliable approach to study and detect hidden faults.展开更多
基金National Natural Science Foundation of China under Grant No.41772275the Fundamental Research Funds for the Central Universities under Grant No.CHD300102268203。
文摘In this study,the Beibu earth fissure site in the northeastern part of Weihe Basin,which contains four nearly parallel earth fissures,was studied.A long straight microtremor measuring line,containing 49 measuring points across four earth fissures,was established to investigate the dynamic response of this site using Fourier spectrum,response acceleration spectrum,Arias intensity,and HVSR analyses.The main results are as follows:(1)The fundamental frequencies of 44 measuring points obtained from HVSR analysis are concentrated within 1.67 Hz-2.25 Hz,and the existence of the earth fissures has little effect on the fundamental frequency changes.(2)There is an amplification effect near a single earth fissure.The dynamic responses are large at the measuring points near the earth fissure,and the values decrease with increasing distance from the earth fissure.In areas between two adjacent earth fissures,these values decrease and are even lower than those in sites without amplification effects.(3)In this earth fissure site,the general area(or less affected area)and affected areas were delineated based on the amplification effect.In engineering applications,construction design should avoid these affected areas and existing structures should be reinforced to satisfy the seismic fortification requirements.
基金supported by the Center of Excellence for Environmental Geohazards and the Research Council of Shiraz University
文摘The faults and fractures are known as two of the most important parameters in earthquake occurrence.During the construction in urban areas, faults and fractures may be covered in depth and thus are not visible at the ground surface. In this context, non-invasive geophysical prospecting methods(microtremor and geoelectrical methods) and borehole data were used to detect subsurface geological structures(hidden faults) in a suburb of Shiraz in Iran. The horizontal to vertical spectral ratio(HVSR) method was used to obtain the dynamic parameters(predominant frequency and resonance amplitude) of the soil, to detect hidden faults. The results show that the abrupt changes in the sediment thickness and predominant frequencies at a specific direction(NW-SE) can be related to the displacement of a nearly vertical fault with NW-SE trend. In addition, the electrical resistivity method using continuous resistivity profiling(CRP) and Schlumberger arrays was employed to detect a hidden fault and the results were compared with previous data. The obtained results of both arrays illustrate the presence of a nearly vertical fault with NW-SE trend in the region. Comparison of all results shows that the detected faults by both methods are consistent with each other. Therefore, it can be conclusive that combination of the two methods is a useful and reliable approach to study and detect hidden faults.
