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971.
对前郭M_S5.8地震后6个月(2013年10月31日~2014年4月30日)内的地震事件进行了重新定位,并利用吉林区域地震台网提供的地震目录研究了序列活动特征。精定位结果显示,余震区呈NW走向分布,长轴约11km,短轴约6km。震源深度为5~15km。结合区域构造特征认为,该序列可能与NW走向的通榆-长春隐伏断裂活动有关,序列具有b值较低、5级地震频次高、发震时间集中的特点。序列主要起伏活动可以分为3个时段:主震后10天,余震强度衰减不明显;此后的2次起伏活动,地震活动分别表现出平静-增强(震级爬升)-发生强震和增强(震级爬升)-平静-再增强(震级爬升)-发生强震的特点;在序列早期阶段,震级-频度无法拟合成1条直线,G-R关系在低震级段和高震级段呈现2个线性段;在M_S5.8地震前h值有变小的趋势,且接近1;而M_S5.8地震后h值明显增大;M_S5.5地震后15天序列衰减比较慢,p值为0.76;M_S5.8地震后15天序列衰减较快,p值为1.17。 相似文献
972.
背景场项目中iDirect卫星通信系统设计 总被引:1,自引:1,他引:0
介绍背景场项目中i Direct卫星通信系统,主要从背景场项目对卫星通信的需求、系统设计、数据接入、系统应用等方面进行阐述,具体介绍卫星信系统为行业网备份的数据接入方案以及数据应用案例,可独立为国家测震台提供数据传输信道,保障测震速报业务的正常开展。 相似文献
973.
A miniaturized flume experiment was carried out to measure impact forces of viscous debris flow. The flow depth (7.2–11.2 cm), velocity (2.4–5.2 m/s) and impact force were recorded during the experiment. The impact process of debris flow can be divided into three phases by analyzing the variation of impact signals and flow regime. The three phases are the sudden strong impact of the debris flow head, continuous dynamic pressure of the body and slight static pressure of the tail. The variation of impact process is consistent with the change in the flow regime. The head has strong–rapid impact pressure, which is shown as a turbulent‐type flow; the body approximates to steady laminar flow. Accordingly, the process of debris flows hitting structures was simplified to a triangle shape, ignoring the pressure of the tail. In order to study the distribution of the debris flow impact force at different depths and variation of the impact process over time, the impact signals of slurry and coarse particles were separated from the original signals using wavelet analysis. The slurry's dynamic pressure signal appears to be a smooth curve, and the peak pressure is 12–34 kPa when the debris flow head hits the sensors, which is about 1.54 ± 0.36 times the continuous dynamic pressure of the debris flow body. The limit of application of the empirical parameter α in the hydraulic formula was also noted. We introduced the power function relationship of α and the Froude number of debris flows, and proposed a universal model for calculating dynamic pressure. The impact pressure of large particles has the characteristic of randomness. The mean frequency of large particles impacting the sensor is 210 ± 50–287 ± 29 times per second, and it is 336 ± 114–490 ± 69 times per second for the debris flow head, which is greater than that in the debris flow body. Peak impact pressure of particles at different flow depths is 40–160 kPa, which is 3.2 ± 1.5 times the impact pressure of the slurry at the bottom of the flow, 3.1 ± 0.9 times the flow in the middle, and 3.3 ± 0.9 times the flow at the surface. The differences in impact frequency indicate that most of the large particles concentrate in the debris flow head, and the number of particles in the debris flow head increases with height. This research supports the study of solid–liquid two phase flow mechanisms, and helps engineering design and risk assessment in debris flow prone areas. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
974.
975.
The travel time and amplitude of ground-penetrating radar (GPR) waves are closely related to medium parameters such as water content, porosity, and dielectric permittivity. However, conventional estimation methods, which are mostly based on wave velocity, are not suitable for real complex media because of limited resolution. Impedance inversion uses the reflection coefficient of radar waves to directly calculate GPR impedance and other parameters of subsurface media. We construct a 3D multiscale stochastic medium model and use the mixed Gaussian and exponential autocorrelation function to describe the distribution of parameters in real subsurface media. We introduce an elliptical Gaussian function to describe local random anomalies. The tapering function is also introduced to reduce calculation errors caused by the numerical simulation of discrete grids. We derive the impedance inversion workflow and test the calculation precision in complex media. Finally, we use impedance inversion to process GPR field data in a polluted site in Mongolia. The inversion results were constrained using borehole data and validated by resistivity data. 相似文献
976.
为了研究地形对频率域航空电磁法的影响程度,以及如何有效提取由于地形产生的航空电磁场,笔者利用频率域有限差分法开展了复杂地形条件下的频率域航空电磁响应计算和分析研究。计算结果表明,坡度较陡的地形对频率域航空电磁响应影响较大(尤其在沟谷位置地形影响最大),以至于增加了电磁异常的复杂程度,影响了电磁异常的解释结果。在综合研究的基础上,采用二维和三维的地形校正方法对典型地形地电模型进行校正,有效去除和压制了地形引起的电磁干扰异常,突出了异常体引起的电磁异常,提高了频率域航空电磁的解释效果。 相似文献
977.
Comparison of ground truth location of earthquake from InSAR and from ambient seismic noise:A case study of the 1998 Zhangbei earthquake 下载免费PDF全文
Because ambient seismic noise provides estimated Greenos function (EGF) between two sites with high accuracy, Rayleigh wave propagation along the path connecting the two sites is well resolved. Therefore, earthquakes which are close to one seismic station can be well located with calibration extracting from EGF. We test two algorithms in locating the 1998 Zhangbei earthquake, one algorithm is waveform-based, and the other is traveltime-based. We first compute EGF between station ZHB (a station about 40 km away from the epicenter) and five IC/IRIS stations. With the waveform-based approach, we calculate 1D synthetic single-force Greenos functions between ZHB and other four stations, and obtain traveltime corrections by correlating synthetic Greenos functions with EGFs in period band of 10-30 s. Then we locate the earthquake by minimizing the differential travel times between observed earthquake waveform and the 1D synthetic earthquake waveforms computed with focal mechanism provided by Global CMT after traveltime correction from EGFs. This waveform-based approach yields a location which error is about 13 km away from the location observed with InSAR. With the traveltime-based approach, we begin with measuring group velocity from EGFs as well as group arrival time on observed earthquake waveforms, and then locate the earthquake by minimizing the difference between observed group arrival time and arrival time measured on EGFs. This traveltime-based approach yields accuracy of 3 km, Therefore it is feasible to achieve GT5 (ground truth location with accuracy 5 km) with ambient seismic noises. The less accuracy of the waveform-based approach was mainly caused by uncertainty of focal mechanism. 相似文献
978.
A case study of long-term field performance of check-dams in mitigation of soil erosion in Jiangjia stream,China 总被引:3,自引:0,他引:3
This paper examines the long-term field performance of the check-dams in mitigation of soil erosion in the Duozhao catchment
of Jiangjia stream, southwest China. Since their construction between 1979 and 1982, the check-dams have been functioning
effectively. The examination is made via comparisons between the environmental conditions of the Duozhao catchment with its
adjacent Menqian catchment in the stream, because no check dams were constructed in the Menqian catchment. The examination
is based on recent field investigations and aerial photograph analyses, and covers four aspects: (a) bed gradients of catchment
channels; (b) stability of bank slopes; (c) rates of land erosion; and (d) vegetations on bank slopes. The field data demonstrate
that the check-dams have had the following good functions for mitigation of soil erosion: (1) restricting the channel depth
and lateral erosions, (2) protecting the channel erosion base, (3) reducing the bed gradients of debris-flow channels, (4)
fixing the channel bed, (5) stabilizing the bank slopes, as well as (6) facilitating the growth of vegetations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
979.
Zhongwu Li Yong Fang Guangming Zeng Jianbing Li Qi Zhang Qingshui Yuan Yamei Wang Fangyi Ye 《Environmental Geology》2009,58(1):101-107
Selecting the Liuyanghe River watershed as an example, using monitoring data of water quality of nearly 10 years and the improved
synthesis pollution index method to evaluate the water quality, the research studied the temporal and spatial characteristics
of surface water quality of a typical basin in the red soil hilly region, and analyzed reasons for the surface water quality
change. The results indicated the improved synthesis pollution index had a better serviceability than other methods, such
as, Pollution Index method, Fuzzy Evaluation method, Grey-System method etc. As for the temporal characteristic, because of
no-point source pollution, the water quality of Liuyanghe River watershed had become a more and more serious problem over
a ten-year period. The spatial characteristic indicated that the pollution degree increased from upstream to downriver. Water
quality upstream was better, and the content of the heavy metals was higher in the middle of the river, and the pollution
of ammonia nitrogen intensified downriver. The result suggested the improved universal pollution index could be used in the
assessment of the water environment. 相似文献
980.
Geology and Lead-Isotope Study of the Baiyinnuoer Zn-Pb-Ag Deposit, South Segment of the Da Hinggan Mountains, Northeastern China 总被引:6,自引:0,他引:6
Qingdong Zeng Jianming Liu Zuolun Zhang Changshun Jia Changming Yu Jie Ye Hongtao Liu 《Resource Geology》2009,59(2):170-180
The Baiyinnuoer deposit (32.74 Mt ore with grades of 5.44% Zn, 2.02% Pb and 31.36 g t?1 Ag), the largest Zn‐Pb‐Ag deposit in northern China, is hosted by crystalline limestone and slate of the Early Permian Huanggangliang Formation. Detailed cross‐section mapping indicates stratigraphic and fold structural controls on the mineralization. The Zn‐Pb‐Ag mineralization is hosted predominantly by skarn, which occurs as bedding‐parallel lens that pinch out at the margins of the main economic zone. Three skarn stages are identified at the deposit: (i) garnet‐clinopyroxene; (ii) sulfides; and (iii) carbonate‐epidote. Lead isotopic compositions were determined for galena and sphalerite of the ores, whole rock samples of the Yanshanian granite and granodiorite, Permian marble and tuff, and Jurassic volcanic and subvolcanic rocks in and around the Baiyinnuoer area in order to discuss the sources of ore‐forming materials and the relationship between the ore formation and these whole rocks. Galena and sphalerite of the Baiyinnuoer ore have uniform isotopic ratios (206Pb/204Pb, 18.267–18.369; 207Pb/204Pb, 15.506–15.624; 208Pb/204Pb, 38.078–38.394) consistent with the granite and granodiorite (206Pb/204Pb, 18.252–18.346; 207Pb/204Pb, 15.504–15.560; 208Pb/204Pb, 38.141–38.320), whereas the ratios for Jurassic volcanic and subvolcanic rocks are variable and radiogenic (206Pb/204Pb, 18.468–18.614; 207Pb/204Pb, 15.521–15.557; 208Pb/204Pb, 38.304–38.375). These results indicate that the mineralization was not related to the Jurassic volcanism, but to the Yanshanian magmatism. The Permian strata may have a slight contribution to the mineralization. All features show that the Baiyinnuoer deposit is related to the Yanshanian granitic magmatism, and can be classified as a zinc‐lead‐silver skarn deposit. 相似文献