This study employed tri-component continuous monitoring data from 10 measurement points on both sides of a base isolation layer in the basement of a large-span high-rise building in Beijing,as well as from a free-fiel...This study employed tri-component continuous monitoring data from 10 measurement points on both sides of a base isolation layer in the basement of a large-span high-rise building in Beijing,as well as from a free-field station and roof frame,during a Mw 5.5 magnitude earthquake in Pingyuan,Shandong,in 2023.The H/V spectral ratio method was used to evaluate the structural dynamic response characteristics of the building and analyze the regulatory effect of the base-isolation layer on seismic waves.The results indicate that during the earthquake,the peak frequency of the free-field and the measurement points below the base-isolation layer was stable at 0.17 Hz,whereas the main frequency of the measurement points above the base-isolation layer increased to 0.75–1.18 Hz,which is 4–6 times greater than that of the points below.The amplitude was suppressed by more than 70%,confirming that the base isolation layer effectively isolated the low-frequency energy from the ground and increased the response frequency of the building.When the building was excited by an earthquake,a three-tier frequency gradient was formed throughout the building:“base-isolation layer(0.17 Hz)-main body(1.18 Hz)-roof frame(3.83 Hz)”,which can effectively avoid resonance of the entire building.In addition,the composite base-isolation device changed the dynamic characteristics of the structure.The resonance period was extended from 0.74 s(theoretical value without base isolation)to 5.9 s(calculated value),and the resonance frequency was reduced from 1.35 to 0.17 Hz.This finding indicates that the base-isolation layer can enhance seismic performance by increasing flexibility and damping.展开更多
The quality factor Q,which reflects the energy attenuation of seismic waves in subsurface media,is a diagnostic tool for hydrocarbon detection and reservoir characterization.In this paper,we propose a new Q extraction...The quality factor Q,which reflects the energy attenuation of seismic waves in subsurface media,is a diagnostic tool for hydrocarbon detection and reservoir characterization.In this paper,we propose a new Q extraction method based on the energy ratio before and after the wavelet attenuation,named the energy-ratio method(ERM).The proposed method uses multipoint signal data in the time domain to estimate the wavelet energy without invoking the source wavelet spectrum,which is necessary in conventional Q extraction methods,and is applicable to any source wavelet spectrum;however,it requires high-precision seismic data.Forward zero-offset VSP modeling suggests that the ERM can be used for reliable Q inversion after nonintrinsic attenuation(geometric dispersion,refl ection,and transmission loss)compensation.The application to real zero-offset VSP data shows that the Q values extracted by the ERM and spectral ratio methods are identical,which proves the reliability of the new method.展开更多
本文系统阐述了微动H/V(Horizontal to Vertical)谱比法的计算原理及其在岩土工程勘察中的应用。微动H/V谱比的本质为震动在不同岩土层结构中传播时垂直方向与水平方向的能量分配占比,通过5组实测微动信号的H/V谱比的结果分析,验证了H/...本文系统阐述了微动H/V(Horizontal to Vertical)谱比法的计算原理及其在岩土工程勘察中的应用。微动H/V谱比的本质为震动在不同岩土层结构中传播时垂直方向与水平方向的能量分配占比,通过5组实测微动信号的H/V谱比的结果分析,验证了H/V谱比法在岩土层探测领域的稳定性,即微动H/V谱比能够直接反映地下岩土层的结构变化。研究通过近似地质条件下的实例验证,建立了基岩埋深与H/V谱比最大峰值频率的拟合关系,拟合优度R2均高于0.9,显著提升了土石分界面探测精度。结合H/V谱比剖面和速度剖面的联合解译,进一步提高了土石分界面探测结果的准确性。此外,在古城墙遗址探测中的应用案例表明,该方法对地下人工构筑物具有高灵敏度性,可有效识别地下构筑物及其背景地层。实践证实微动H/V谱比法具备现场操作简便、探测精度高、分辨率强等优势,为岩土工程勘察提供了高效、准确且对环境无干扰的技术手段,具有重要的推广价值。展开更多
Islands are valuable land resources in the ocean,and their detailed subsurface seismic velocity structures are highly important for underground space utilization,engineering construction,and geological disaster preven...Islands are valuable land resources in the ocean,and their detailed subsurface seismic velocity structures are highly important for underground space utilization,engineering construction,and geological disaster prevention.Ambient noise tomography and the horizontal–vertical spectral ratio(HVSR)method use ambient noise recordings instead of earthquake signals to study the underground velocity structure,making them easy to implement on islands and consequently becoming potential optimization schemes for the investigation of detailed island structures.However,the application of these technologies to small granite islands along coasts is relatively insufficient,and the applicability needs to be further verified.This study ambient noise tomography and HVSR analysis were carried out by using a dense array of seismic data on Wuzhizhou Island,Hainan.It was found that natural activities mainly cause the ambient noise below 8 Hz on Wuzhizhou Island.Moreover,high-quality noise cross-correlation functions of 3–8 Hz can be extracted.The results of ambient noise tomography and HVSR analysis show that the underground S-wave velocity structure and sedimentary characteristics of Wuzhizhou Island are coupled with its topography.The high-terrain area of Wuzhizhou Island exhibits low-velocity anomalies,where a sedimentary layer did not develop.On the other hand,the low-terrain area of Wuzhizhou Island exhibits high-velocity anomalies,where a thin Quaternary sedimentary layer developed.These results imply that subsurface magmatic activity controls the island topography and affects the distribution of the island sedimentary layer.This study successfully verifies the feasibility of detection methods based on ambient noise in small granite islands along the coast.It also provides key basic information for studying the geological evolutionary history,island spatial planning,and geological disaster prevention of Wuzhizhou Island.展开更多
基金supported by the Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(Grant No.2025ZD005100)by Beijing Geolight Technology Co.,Ltd.under the project“The Impact of Strong Ground Motion on Buildings”(YF-202520).
摘要This study employed tri-component continuous monitoring data from 10 measurement points on both sides of a base isolation layer in the basement of a large-span high-rise building in Beijing,as well as from a free-field station and roof frame,during a Mw 5.5 magnitude earthquake in Pingyuan,Shandong,in 2023.The H/V spectral ratio method was used to evaluate the structural dynamic response characteristics of the building and analyze the regulatory effect of the base-isolation layer on seismic waves.The results indicate that during the earthquake,the peak frequency of the free-field and the measurement points below the base-isolation layer was stable at 0.17 Hz,whereas the main frequency of the measurement points above the base-isolation layer increased to 0.75–1.18 Hz,which is 4–6 times greater than that of the points below.The amplitude was suppressed by more than 70%,confirming that the base isolation layer effectively isolated the low-frequency energy from the ground and increased the response frequency of the building.When the building was excited by an earthquake,a three-tier frequency gradient was formed throughout the building:“base-isolation layer(0.17 Hz)-main body(1.18 Hz)-roof frame(3.83 Hz)”,which can effectively avoid resonance of the entire building.In addition,the composite base-isolation device changed the dynamic characteristics of the structure.The resonance period was extended from 0.74 s(theoretical value without base isolation)to 5.9 s(calculated value),and the resonance frequency was reduced from 1.35 to 0.17 Hz.This finding indicates that the base-isolation layer can enhance seismic performance by increasing flexibility and damping.
基金supported by the Major Project of the Ministry of Science and Technology of China(No.2011ZX05024-001-01)National Nature Science Foundation of China(No.41140033)
摘要The quality factor Q,which reflects the energy attenuation of seismic waves in subsurface media,is a diagnostic tool for hydrocarbon detection and reservoir characterization.In this paper,we propose a new Q extraction method based on the energy ratio before and after the wavelet attenuation,named the energy-ratio method(ERM).The proposed method uses multipoint signal data in the time domain to estimate the wavelet energy without invoking the source wavelet spectrum,which is necessary in conventional Q extraction methods,and is applicable to any source wavelet spectrum;however,it requires high-precision seismic data.Forward zero-offset VSP modeling suggests that the ERM can be used for reliable Q inversion after nonintrinsic attenuation(geometric dispersion,refl ection,and transmission loss)compensation.The application to real zero-offset VSP data shows that the Q values extracted by the ERM and spectral ratio methods are identical,which proves the reliability of the new method.
摘要本文系统阐述了微动H/V(Horizontal to Vertical)谱比法的计算原理及其在岩土工程勘察中的应用。微动H/V谱比的本质为震动在不同岩土层结构中传播时垂直方向与水平方向的能量分配占比,通过5组实测微动信号的H/V谱比的结果分析,验证了H/V谱比法在岩土层探测领域的稳定性,即微动H/V谱比能够直接反映地下岩土层的结构变化。研究通过近似地质条件下的实例验证,建立了基岩埋深与H/V谱比最大峰值频率的拟合关系,拟合优度R2均高于0.9,显著提升了土石分界面探测精度。结合H/V谱比剖面和速度剖面的联合解译,进一步提高了土石分界面探测结果的准确性。此外,在古城墙遗址探测中的应用案例表明,该方法对地下人工构筑物具有高灵敏度性,可有效识别地下构筑物及其背景地层。实践证实微动H/V谱比法具备现场操作简便、探测精度高、分辨率强等优势,为岩土工程勘察提供了高效、准确且对环境无干扰的技术手段,具有重要的推广价值。
基金supported by the geological survey project(Grant No.DD20220992,Grant No.DD20242841,Grant No.DD20230592 and Grant No.DD20220993)Innovation Foundation of Science and Technology for“Nanhai New Star”Projects(Grant No.NHXXRCXM202353)of Hainan province。
摘要Islands are valuable land resources in the ocean,and their detailed subsurface seismic velocity structures are highly important for underground space utilization,engineering construction,and geological disaster prevention.Ambient noise tomography and the horizontal–vertical spectral ratio(HVSR)method use ambient noise recordings instead of earthquake signals to study the underground velocity structure,making them easy to implement on islands and consequently becoming potential optimization schemes for the investigation of detailed island structures.However,the application of these technologies to small granite islands along coasts is relatively insufficient,and the applicability needs to be further verified.This study ambient noise tomography and HVSR analysis were carried out by using a dense array of seismic data on Wuzhizhou Island,Hainan.It was found that natural activities mainly cause the ambient noise below 8 Hz on Wuzhizhou Island.Moreover,high-quality noise cross-correlation functions of 3–8 Hz can be extracted.The results of ambient noise tomography and HVSR analysis show that the underground S-wave velocity structure and sedimentary characteristics of Wuzhizhou Island are coupled with its topography.The high-terrain area of Wuzhizhou Island exhibits low-velocity anomalies,where a sedimentary layer did not develop.On the other hand,the low-terrain area of Wuzhizhou Island exhibits high-velocity anomalies,where a thin Quaternary sedimentary layer developed.These results imply that subsurface magmatic activity controls the island topography and affects the distribution of the island sedimentary layer.This study successfully verifies the feasibility of detection methods based on ambient noise in small granite islands along the coast.It also provides key basic information for studying the geological evolutionary history,island spatial planning,and geological disaster prevention of Wuzhizhou Island.