郯庐断裂带苏皖段重力变化的多尺度分解与构造活动分析     

林承灏  黎哲君  徐如刚  袁泉 《大地测量与地球动力学》2019,39(9):884-889

基于多期绝对重力与相对重力联测资料，获取不同时空尺度的郯庐断裂带苏皖段及周边地区重力场动态变化，采用小波多尺度分解方法计算不同深度的重力变化，结合区域地质构造，从深度层次的横向变化与时间尺度的纵向变化2个方面进行分析。结果表明，研究区重力变化主要由中、上地壳密度变化或断裂构造活动引起。沿郯庐断裂带苏皖段走向断裂活动分布不均，受周边深大断裂带交切作用的影响表现出明显的分段活动特征。淮阴-响水口断裂、滁河断裂等深大活动断裂带构造活动对局部重力变化具有一定的控制作用，沿断裂带走向分布有明显的重力变化梯度带；郯庐断裂带郯城-泗县段、大别山构造带霍山-六安及江苏溧阳-镇江地区在小波细节动态变化中存在重力变化梯度带异常区，但强度不高，考虑到多条深大断裂交切于此，后期需要重点关注。  相似文献   

氨氮急性攻毒对水产经济动物棘胸蛙(Paa spinosa)蝌蚪死亡率、排氨率、耗氧率及窒息点的影响     

牛春格  杨程  申屠琰  郑晓静  王志铮 《海洋与湖沼》2019,50(1):188-196

以体长(1.932±0.204)cm、体质量(1.386±0.055)g的棘胸蛙蝌蚪为实验动物,在水温(24±0.2)℃、DO(7.30±0.01)mg/L、pH 7.30±0.01条件下,采用静水停食法开展了氨氮对蝌蚪的急性攻毒实验,并以此为基础,测定了不同氨氮质量浓度胁迫下棘胸蛙蝌蚪的排氨率、耗氧率、氧氮比及窒息点。结果表明:(1)蝌蚪对氨氮急性攻毒具明显的运动避毒行为,濒死个体的背部皮肤和肝脏均具明显的色变症状;(2)氨氮对蝌蚪的急性致死率具明显的剂量—时间效应,24h、48h、72h、96h LC50依次为177.5、151.7、148.6和146.8mg/L,毒性时段蓄积程度系数呈持续下降趋势,24—48h、48—72h、72—96h的时段MAC值分别为84.04%、10.1%和5.86%;(3)蝌蚪夜均、昼均、日均及时段排氨率随氨氮质量浓度增加均呈阶梯式下降趋势,其中时段排氨率与对照组均无显著差异的为9.80mg/L实验组,夜均、昼均、日均及时段排氨率与对照组均无显著差异的仅为2.45mg/L实验组(P0.05);(4)氨氮对蝌蚪呼吸耗氧具低毒兴奋效应,其夜均、昼均和日均耗氧率随氨氮质量浓度增加均呈先升后降趋势,峰值氨氮质量浓度范围均为4.90—7.35mg/L(P0.05),与对照组均无显著差异的仅为14.70mg/L实验组(P0.05),窒息点含氧量随氨氮质量浓度增加呈先降后升趋势,谷底出现于4.90mg/L实验组(P0.05),与对照组无显著差异的仅为9.80mg/L实验组(P0.05);(5)实验期间,蝌蚪氧氮比(O:N)波动于18.87—25.34之间,昼均和日均氧氮比(O:N)随氨氮质量浓度增加均依次呈"上升—稳定—下降—再稳定"之趋势,两者的峰值氨氮质量浓度范围分别为4.90—14.70mg/L和4.90—9.80mg/L,夜均氧氮比(O:N)呈先升后降趋势,峰值出现于7.35mg/L实验组(P0.05)。  相似文献   

Monitoring of coral communities in the inner Gulf of Thailand influenced by the elevated seawater temperature and flooding   总被引：1，自引：0，他引：1  

PENGSAKUN Sittiporn  YEEMIN Thamasak  SUTTHACHEEP Makamas  SAMSUVAN Watchar  KLINTHONG Wanlay  CHAMCHOY Charernmee 《海洋学报(英文版)》2019,38(1):102-111

There were two severe coral bleaching events at Ko Khang Khao, the inner Gulf of Thailand, occurred during the prolonged period of the elevated sea surface temperature (SST) in 2010 and low salinity as well as turbidity due to heavy flooding in 2011. The bleaching index (BI) and mortality index (MI) are calculated to compare the susceptibilities of coral species in the two bleaching events. The BI and MI vary significantly among the study sites and bleaching events. The most susceptible corals during both bleaching events are Acropora millepora, Pocillopora damicornis and Pavona decussate, while the most resistant species were Galaxea fascicularis, Fungia fungites, Pavona frondifera, Oulastrea crispate, and Symphyllia recta. The corals Favia favus, Goniopora columna, Platygyra pini, Symphyllia agaricia were relatively more tolerant to high SST but they are relatively more susceptible to low salinity. Coral bleaching is a phenomenon that the dissociation stress of the symbiotic relationship between zooxanthellae and their cnidarian host results in the reduction in photosynthetic pigment concentration. Among stressors, both prolonged exposure of high SST and low salinity, above and below their thresholds, respectively. The long-term resilience of coral communities at Ko Khang Khao and other coral communities close to the mouth of large rivers may depend on the frequency and duration of the exposure on the elevated SST due to atmospheric heating and low salinity due to river flooding.  相似文献   

VARIATION OF THE TRAVEL TIME DIFFERENCE BETWEEN TELESEISMIC PS CONVERTED WAVE AND PP TRANSMITTED WAVE IN FOCAL REGION BEFORE AND AFTER WENCHUAN M_S8.0 EARTHQUAKE          下载免费PDF全文

SONG Chun-yan  SHAO Xue-zhong  MA Jin 《地震地质》2019,41(3):726-742

When P waves from distant earthquakes meet a velocity discontinuity in the earth's crust and upper mantle, they give rise to a series of converted PS waves besides PP refracted waves. It is possible to monitor the variation of the physical properties of the medium in the limited formation space above the transition zone of the seismogenic zone by measuring the time difference between the teleseismic PS converted wave and the first arrival P wave, that is, time-variation Δt_PS=t_PS-t_P. The advantage of this method is that the transition point of the teleseismic source with similar source is relatively stable at the transition interface, and the accuracy of the measured relative time is high, and the change of the medium in a small range of the seismogenic zone above the conversion interface can be monitored. This paper studies the variation of the travel time difference Δt_PS in focal region before and after Wenchuan M_S8.0 earthquake. We select 2001 to 2012 as the research period, use teleseismic waveforms which occurred in the southern region of Sumatra and Hindu Kush area recorded by Sichuan station YZP and JJS. These teleseisms satisfy 5.0 ≤ M ≤ 6.5, and their waveform signal-to-noise ratio is high with clear initial P-wave motion. The epicentral distance of teleseisms is less than 3 degrees. Then we obtain the variation of the travel time difference Δt_PS between teleseismic PS converted wave and PP transmitted wave recorded during the study period in the two stations. The results show that there is a slow increasing trend of Δt_PS before 2006, and an obvious low value process of Δt_PS appeared in the period about 2 years before the Wenchuan earthquake. The maximum decline was about 0.2~0.3s, more than 4~5 times the measurement error. The low value has a certain degree of return about 2~3 months before the earthquake. The change of arrival time difference indicates that the medium is in different states in different periods of seismogenic process. The sharp decrease in Δt_PS from 2006 to January 2008 may be due to the strong disturbance caused by the stress accumulation of the medium. At this stage, the velocity of P wave and S wave increases with the increase of stress, and the increase of S wave velocity will result in the decrease of Δt_PS. The change of Δt_PS is greatly affected by S wave velocity, so Δt_PS appears to decrease rapidly. Regarding the low value that has a certain degree of return about 2~3 months before the Wenchuan earthquake, the possible reason is that the release of stress is much higher than the accumulation of stress in meta-instability stage. At this stage, the velocity of S wave decreases and the decrease of S wave causes Δt_PS to increase. Then, the Wenchuan earthquake of magnitude 8.0 occurred. It is shown that the teleseismic converted wave method in this paper can monitor the variation of medium's wave velocity before large earthquakes, and it has a good prospect in seismic monitoring and worth further experimental study.  相似文献   

APPLYING 3D INVERSION OF SINGLE-PROFILE MAGNETOTELLURIC DATA TO IDENTIFY THE SHADE AND YUNONGXI FAULTS          下载免费PDF全文

JIANG Feng  CHEN Xiao-bin  DONG Ze-yi  CUI Teng-fa  LIU Zhong-yin  WANG Pei-jie 《地震地质》2019,41(6):1444-1463

Many synthetic model studies suggested that the best way to obtain good 3D interpretation results is to distribute the MT sites at a 2D grid array with regular site spacing over the target area. However, MT 3D inversion was very difficult about 10 years ago. A lot of MT data were collected along one profile and then interpreted with 2D inversion. How to apply the state-of-the-art 3D inversion technique to interpret the accumulated mass MT profiles data is an important topic. Some studies on 3D inversion of measured MT profile data suggested that 2D inversions usually had higher resolution for the subsurface than 3D inversions. Meanwhile, they often made their interpretation based on 2D inversion results, and 3D inversion results were only used to evaluate whether the overall resistivity structures were correct. Some researchers thought that 3D inversions could not resolute the local structure well, while 2D inversion results could agree with the surface geologic features much well and interpret the geologic structures easily. But in the present paper, we find that the result of 3D inversion is better than that of 2D inversion in identifying the location of the two local faults, the Shade Fault(SDF)and the Yunongxi Fault(YNXF), and the deep structures. In this paper, we first studied the electrical structure of SDF and YNXF based on a measured magnetotelluric(MT) profile data. Besides, from the point of identifying active faults, we compared the capacity of identifying deep existing faults between 2D inversion models and 3D models with different inversion parameters. The results show that both 2D and 3D inversion of the single-profile data could obtain reasonable and reliable electrical structures on a regional scale. Combining 2D and 3D models, and according to our present data, we find that both SDF and YNXF probably have cut completely the high resistivity layer in the upper crust and extended to the high conductivity layer in the middle crust. In terms of the deep geometry of the faults, at the profile's location, the SDF dips nearly vertically or dips southeast with high dip angle, and the YNXF dips southeast at depth. In addition, according to the results from our measured MT profile, we find that the 3D inversion of single-profile MT data has the capacity of identifying the location and deep geometry of local faults under present computing ability. Finally, this research suggests that appropriate cell size and reasonable smoothing parameters are important factors for the 3D inversion of single-profile MT data, more specifically, too coarse meshes or too large smoothing parameters on horizontal direction of 3D inversion may result in low resolution of 3D inversions that cannot identify the structure of faults. While, for vertical mesh size and data error thresholds, they have limited effect on identifying shallow tectonics as long as their changes are within a reasonable range. 3D inversion results also indicate that, to some extent, adding tippers to the 3D inversion of a MT profile can improve the model's constraint on the deep geometry of the outcropped faults.  相似文献   

Interannual variability in glacier contribution to runoff from a high‐elevation Andean catchment: understanding the role of debris cover in glacier hydrology     

Flavia Burger  Alvaro Ayala  David Farias  Thomas E. Shaw  Shelley MacDonell  Ben Brock  James McPhee  Francesca Pellicciotti 《水文研究》2019,33(2):214-229

We present a field‐data rich modelling analysis to reconstruct the climatic forcing, glacier response, and runoff generation from a high‐elevation catchment in central Chile over the period 2000–2015 to provide insights into the differing contributions of debris‐covered and debris‐free glaciers under current and future changing climatic conditions. Model simulations with the physically based glacio‐hydrological model TOPKAPI‐ETH reveal a period of neutral or slightly positive mass balance between 2000 and 2010, followed by a transition to increasingly large annual mass losses, associated with a recent mega drought. Mass losses commence earlier, and are more severe, for a heavily debris‐covered glacier, most likely due to its strong dependence on snow avalanche accumulation, which has declined in recent years. Catchment runoff shows a marked decreasing trend over the study period, but with high interannual variability directly linked to winter snow accumulation, and high contribution from ice melt in dry periods and drought conditions. The study demonstrates the importance of incorporating local‐scale processes such as snow avalanche accumulation and spatially variable debris thickness, in understanding the responses of different glacier types to climate change. We highlight the increased dependency of runoff from high Andean catchments on the diminishing resource of glacier ice during dry years.  相似文献   

锦州沈家台水氡高值波动异常识别     

王喜龙  王海燕  付聪  王松阳  杨振鹏 《地震》2019,39(4):158-171

讨论了锦州沈家台水氡活度浓度出现的高幅度波动异常变化与地震活动的关系。 沈家台水氡测项自2004年开始观测以来, 数据变化稳定, 氡活度浓度一般在4~5 Bq/L范围波动, 且具有很好的年周期变化规律。 但在2016年11月20日开始出现高幅度异常变化, 较正常波动范围平均高出约5 Bq/L。 针对此次出现的异常变化, 在排除外界干扰的基础上, 应用临界慢化方法进行高频异常识别分析。 结果表明, 提取的水氡高频信息成分和方差均存在异常变化, 且高频异常与原始数据异常出现时间具有同步性变化特征。 综合测点映震效能、 区域地震活动性、 井水地球化学分析及水氡异常形成机理等分析结果, 认为这次沈家台水氡出现的异常变化与辽西及环渤海地区应力场调整关系密切, 该区应力增强及井水文地质条件的制约是造成水氡出现高值波动的主要原因。  相似文献   

南北地震带地震震源机制解和现今应力特征     

崔子健  陈章立  王勤彩  李君 《地震》2019,39(1):1-10

基于CAP方法, 使用地震波形资料, 计算得到了2009年1月~2017年8月期间南北地震带及周边区域466个3.5级以上地震震源机制解。 在补充收集1976年1月~2017年8月GCMT公布的259个4.5级以上地震震源机制解的基础上, 分析了南北地震带地震震源机制解和应力特征。 震源机制空间分布显示, 不同断裂带、 块体间表现出不同的震源机制空间分布特征, 该特征与南北地震带不同段落活动构造性质基本吻合。 作为青藏高原东边界的南北地震带, 由于动力环境复杂, 其内部P轴方向具有明显的差异性。 这种差异主要表现为: 南北地震带北段P轴呈NE向分布; 龙门山断裂带及周边除NE段P轴取向为NW—NNW向外, 其他地段P轴近EW向; 川滇菱形块体内部P轴呈NNW向, 而其西边界以西呈NNE向, 东边界以东呈NW向, 应力方向转换带的与川滇菱形块体边界基本一致。 整体而言, 南北地震带及近邻P轴方向由北到南发生了顺时针转动。  相似文献   

内蒙古中部地区形变主要干扰的时频响应特征分析     

张小艳  熊峰  王旭东  赵星  刘永梅  刘芳 《中国地震》2019,35(4):718-725

选取内蒙古中部地区定点形变观测中受降雨、大风、气压干扰以及地震波影响的典型数据，采用S变换，对该地区形变观测中4种主要干扰信号的时频响应特征进行分析与讨论。结果表明，降雨干扰信号主要集中在低频区域，其频率先增大后减小；大风干扰表现为高频干扰，时频域能量强度与观测曲线受风扰影响变化幅度成正比；气压干扰信号的优势频率分布在低频段内；地震波影响中VP垂直摆和JCZ地震计记录的地震波较为相似，但VP垂直摆记录的频段要小于JCZ地震计，VP垂直摆主要记录的是低频地震波。同时，4种干扰信号的时频域频率、能量强度随时间变化趋势与数据观测时域变化趋势相一致。  相似文献   

地震速报区域的自动确认——以内蒙古测震台网为例     

张珂  王鑫  郝美仙  苏柱金  刘芳 《中国地震》2019,35(4):753-761

针对当前省级区域测震台网在判别边界地震是否需要速报的问题，基于内蒙古自治区行政区域的边界数据，利用几何学中包络线原理，在Matlab中将内蒙古地震速报范围以包络线的形式呈现，解译Msdp地震分析软件的数据接口，实现内蒙古地震速报区域在Msdp软件中的自动确认；对比分析地震速报区域自动确认功能的结果与现阶段手动量取方式判别地震事件是否需要速报的结果，表明地震速报区域的自动确认可提高速报业务软件系统的自动化程度，简化地震速报工作的操作流程，减少速报用时，提高速报工作的准确度。  相似文献