从生态系统响应和游客主观认知的双重视角，对六盘山旅游区旅游步道对人类旅游践踏干扰的响应进行了研究。结果表明：①自然状态下旅游践踏干扰主要集中在旅游步道边缘1—3m范围内，但不同生态系统差异较大。在调查的3个景区中，小南川...从生态系统响应和游客主观认知的双重视角，对六盘山旅游区旅游步道对人类旅游践踏干扰的响应进行了研究。结果表明：①自然状态下旅游践踏干扰主要集中在旅游步道边缘1—3m范围内，但不同生态系统差异较大。在调查的3个景区中，小南川景区乔灌草生态统主要集中在旅游步道1m左右；凉殿峡景区高山草甸生态系统集中在1—2m之间；野荷谷景区华北落叶松林下生态系统则达到3m左右；②采用地表覆盖物响应指数（Index of Land Cover Impact，IL-CI）和游客可接受改变限度（Limits of Acceptable Change，LAC）来衡量受干扰旅游步道响应程度，在1m范围内各调查样区ILCI均达到4级或5级严重冲击程度；1—2m间以凉殿峡景区ILCI值较高（39％），介于1—2级之间，而小南川与野荷谷景区儿口值属1级轻微影响；3m及以外三者影响基本较小。游客对游道沿线土壤裸露度可接受改变限度为55．7％，3个调查样区1m范围内植被覆盖减少率（CR）均超过此水平；③调查样区旅游步道响应强弱与游道坡度、边坡坡度以及游道宽度具有一定相关性；④地表覆盖物响应指数因与其它各响应变量间显著相关，可作为评估旅游干扰系统响应的一项简易而有效的指标。研究结果也表明，目前旅游践踏干扰已对游道沿线环境以及游客游憩体验产生了一定的负面影响。因此，改变目前景区开发无序状态，加强旅游步道规划设计和游客行为规范，建立长期环境监测系统，将对制定防治游憩冲击策略，促进六盘山生态旅游区可持续发展具有重要指导价值。展开更多
利用绝对地震定位方法(Hpyo2000)对青藏高原中部地区(32°N～36°N,90°E～93°E)于2016年6月至2017年6月期间发生的中小地震进行了重定位。与中国地震台网测定结果相比,定位后结果整体上更加聚集,水平位差距超过10km,...利用绝对地震定位方法(Hpyo2000)对青藏高原中部地区(32°N～36°N,90°E～93°E)于2016年6月至2017年6月期间发生的中小地震进行了重定位。与中国地震台网测定结果相比,定位后结果整体上更加聚集,水平位差距超过10km,深度上集中在0～8km范围内,这表明青藏高原内部上地壳构造活跃。2017年6月共发生8次3.0级以上地震,定位后的震中位置集中分布在格拉丹东附近。定位前后M<3.0的小地震的结果也显示明显的差异。为此,我们采用CAP(Cut and Paste)方法反演了M≥3.0地震的震源机制,结果显示其与地表构造性质较为吻合,青藏高原内部仍受到印度板块强烈的挤压作用。其中2017年6月格拉丹东附近发生的8次地震均为正断或走滑兼正断型,根据前人研究结果,猜测这是壳幔活动剧烈的地表响应。展开更多
Conventional surface seismic exploration in areas with complex surfaces such as karst landforms has been faced with the problem of poor excitation and reception conditions.RVSP(reverse vertical seismic profile)seismic...Conventional surface seismic exploration in areas with complex surfaces such as karst landforms has been faced with the problem of poor excitation and reception conditions.RVSP(reverse vertical seismic profile)seismic exploration adopts a geometry in which the sources are downhole and receivers are on the ground which can reduce the influence of complex surfaces on seismic wave propagation(to some extent).Through numerical simulations and real data analysis,it was noted that in areas with complex surfaces and large numbers of underground karst caves,seismic waves generated in shallow boreholes are easily affected by various surface and multiple waves as well as by scattering from karst bodies.Therefore,the quality of the reflected seismic data is extremely low.Also,it is difficult to improve the signal to noise ratio(SNR)with conventional noise filtering methods.However,when the source depth is increased,the quality of the reflected waves can be improved.This is exactly what the RVSP method accomplishes.Besides,for the RVSP method,due to its particular geometry,the apparent velocities of the reflected waves and most interference waves are quite different,which can help to filter most noise to further improve the SNR of the reflected signals.In this study,a 3 D-RVSP exploration study using 8-hole joint acquisition was conducted in a typical karst landform.The results show that the 3 D-RVSP method can obtain higher quality seismic data for complex surface conditions that have large numbers of underground karst caves.Furthermore,multi-hole joint acquisition for 3 D-RVSP has higher data collection efficiency and better uniformity of underground coverage.Therefore,in this study,38 faults were accurately revealed and at high resolution based on the 3 D-RVSP imaging results.展开更多
Based on the data from typical sites in the Jianghuai region,many kinds of soil layer seismic response are modeled by increasing and decreasing the measured values of shear velocity to a certain scale. The seismic res...Based on the data from typical sites in the Jianghuai region,many kinds of soil layer seismic response are modeled by increasing and decreasing the measured values of shear velocity to a certain scale. The seismic response of soil layer sites are calculated using the one-dimensional equivalent linear method in the frequency domain by choosing the Taft,Kobe and El-centro records as the ground motion input. The results show that the impact of shear velocity variability on the surface ground motion is in relation to the soil layer structure and ground motion input parameters such as amplitude and spectral characteristic. With the increase of shear velocity,the PGA( peak ground acceleration)on the surface of site will increase,however,the characteristic period of the acceleration response spectra is decreasing.展开更多
By using the finite element method and viscoelastic artificial boundary, a soil-structure interaction system is established to simulate the influence of surface buildings on the seismic response of subway structures. ...By using the finite element method and viscoelastic artificial boundary, a soil-structure interaction system is established to simulate the influence of surface buildings on the seismic response of subway structures. The conditions of different relative positions between ground building and subway structure are analyzed. The result~ indicate that when considering the existence of surface buildings, the relative story displacements and internal forces of subway structures are changed greatly. Further the influence of surface buildings on subway structure changes as the distance increases.展开更多
文摘从生态系统响应和游客主观认知的双重视角，对六盘山旅游区旅游步道对人类旅游践踏干扰的响应进行了研究。结果表明：①自然状态下旅游践踏干扰主要集中在旅游步道边缘1—3m范围内，但不同生态系统差异较大。在调查的3个景区中，小南川景区乔灌草生态统主要集中在旅游步道1m左右；凉殿峡景区高山草甸生态系统集中在1—2m之间；野荷谷景区华北落叶松林下生态系统则达到3m左右；②采用地表覆盖物响应指数（Index of Land Cover Impact，IL-CI）和游客可接受改变限度（Limits of Acceptable Change，LAC）来衡量受干扰旅游步道响应程度，在1m范围内各调查样区ILCI均达到4级或5级严重冲击程度；1—2m间以凉殿峡景区ILCI值较高（39％），介于1—2级之间，而小南川与野荷谷景区儿口值属1级轻微影响；3m及以外三者影响基本较小。游客对游道沿线土壤裸露度可接受改变限度为55．7％，3个调查样区1m范围内植被覆盖减少率（CR）均超过此水平；③调查样区旅游步道响应强弱与游道坡度、边坡坡度以及游道宽度具有一定相关性；④地表覆盖物响应指数因与其它各响应变量间显著相关，可作为评估旅游干扰系统响应的一项简易而有效的指标。研究结果也表明，目前旅游践踏干扰已对游道沿线环境以及游客游憩体验产生了一定的负面影响。因此，改变目前景区开发无序状态，加强旅游步道规划设计和游客行为规范，建立长期环境监测系统，将对制定防治游憩冲击策略，促进六盘山生态旅游区可持续发展具有重要指导价值。
文摘利用绝对地震定位方法(Hpyo2000)对青藏高原中部地区(32°N～36°N,90°E～93°E)于2016年6月至2017年6月期间发生的中小地震进行了重定位。与中国地震台网测定结果相比,定位后结果整体上更加聚集,水平位差距超过10km,深度上集中在0～8km范围内,这表明青藏高原内部上地壳构造活跃。2017年6月共发生8次3.0级以上地震,定位后的震中位置集中分布在格拉丹东附近。定位前后M<3.0的小地震的结果也显示明显的差异。为此,我们采用CAP(Cut and Paste)方法反演了M≥3.0地震的震源机制,结果显示其与地表构造性质较为吻合,青藏高原内部仍受到印度板块强烈的挤压作用。其中2017年6月格拉丹东附近发生的8次地震均为正断或走滑兼正断型,根据前人研究结果,猜测这是壳幔活动剧烈的地表响应。
基金funded jointly by National Key Research and Development Program of China(2017YFC0804105)Fundamental Research Funds for the Central Universities of China(2015XKMS036)+1 种基金Natural Science Foundation of Jiangsu Province(BK20160245)a Project Funded by Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘Conventional surface seismic exploration in areas with complex surfaces such as karst landforms has been faced with the problem of poor excitation and reception conditions.RVSP(reverse vertical seismic profile)seismic exploration adopts a geometry in which the sources are downhole and receivers are on the ground which can reduce the influence of complex surfaces on seismic wave propagation(to some extent).Through numerical simulations and real data analysis,it was noted that in areas with complex surfaces and large numbers of underground karst caves,seismic waves generated in shallow boreholes are easily affected by various surface and multiple waves as well as by scattering from karst bodies.Therefore,the quality of the reflected seismic data is extremely low.Also,it is difficult to improve the signal to noise ratio(SNR)with conventional noise filtering methods.However,when the source depth is increased,the quality of the reflected waves can be improved.This is exactly what the RVSP method accomplishes.Besides,for the RVSP method,due to its particular geometry,the apparent velocities of the reflected waves and most interference waves are quite different,which can help to filter most noise to further improve the SNR of the reflected signals.In this study,a 3 D-RVSP exploration study using 8-hole joint acquisition was conducted in a typical karst landform.The results show that the 3 D-RVSP method can obtain higher quality seismic data for complex surface conditions that have large numbers of underground karst caves.Furthermore,multi-hole joint acquisition for 3 D-RVSP has higher data collection efficiency and better uniformity of underground coverage.Therefore,in this study,38 faults were accurately revealed and at high resolution based on the 3 D-RVSP imaging results.
基金sponsored by the Anhui Natural Science Foundation Project(10040606Q24)the Youth Seismic Research Program of Anhui Province,China(20120707)and(20140301)
文摘Based on the data from typical sites in the Jianghuai region,many kinds of soil layer seismic response are modeled by increasing and decreasing the measured values of shear velocity to a certain scale. The seismic response of soil layer sites are calculated using the one-dimensional equivalent linear method in the frequency domain by choosing the Taft,Kobe and El-centro records as the ground motion input. The results show that the impact of shear velocity variability on the surface ground motion is in relation to the soil layer structure and ground motion input parameters such as amplitude and spectral characteristic. With the increase of shear velocity,the PGA( peak ground acceleration)on the surface of site will increase,however,the characteristic period of the acceleration response spectra is decreasing.
基金sponsored by the National Key Technology R&D Program(2006BAC13B02),ChinaSpecial Program for Earthquake Research of CEA (200708003)
文摘By using the finite element method and viscoelastic artificial boundary, a soil-structure interaction system is established to simulate the influence of surface buildings on the seismic response of subway structures. The conditions of different relative positions between ground building and subway structure are analyzed. The result~ indicate that when considering the existence of surface buildings, the relative story displacements and internal forces of subway structures are changed greatly. Further the influence of surface buildings on subway structure changes as the distance increases.
