青藏高原及邻区未来地震活动性趋势数值分析          下载免费PDF全文

董培育  石耀霖  程惠红  乔学军 《地球物理学报》2020,63(3):1155-1169

区域中长期地震危险性数值分析研究,需要对其初始构造应力场有所了解,但目前以及未来一段时期内仍无法直接观测到深部孕震层区域的应力场状况.本文首先基于岩石库仑-摩尔破裂准则,利用青藏高原及邻区百年历史范围内的强震信息,来反演估算该区域的初始应力场.然后,考虑区域构造应力加载及强震造成的应力扰动共同作用,重现了历史强震的发展过程.然而对于初始应力场的反演估算,本文仅能给出区域其上下限的极限值,并不能唯一确定.因此,采用Monte Carlo随机法,进行大量独立的随机试验计算,生成数千种有差异的区域初始应力场模型,且保证每种模型都能令历史强震有序发生,但未来应力场演化过程不尽相同.最后,将数千种模型在未来时间段内的危险性预测结果集成为数理统计结果,据此给出了区域未来的地震危险性概率分布图.初步结果显示未来强震危险性概率较高地区集中在巴颜喀拉块体边界及鲜水河断裂带地区.  相似文献   

An endemic freshwater mussel species from the Orontes River basin in Turkey and Syria represents duck mussel’s intraspecific lineage: Implications for conservation     

《Limnologica》2020

Amik Lake or, historically, Lake of Antioch, was a large freshwater body in the lower Orontes River basin (Hatay Province, Turkey) that was drained in the 1940s–1970s. Several endemic animal species were described from this lake, including the freshwater mussel Anodonta pseudodopsis Locard, 1883 (Bivalvia: Unionidae) characterized by a large rounded shell covered by a peculiar yellow or yellowish-brown periostracum. Molecular analyses of topotypes of this nominal taxon collected from the former lake’s tributaries in the Amik Plain indicate that it is an intra-specific lineage of the widespread Anodonta anatina (Linnaeus, 1758) based on the mitochondrial COI and 16S rRNA, and the nuclear 28S rRNA gene fragments. Geometric morphometric analyses using the lectotype and topotypes of Anodonta pseudodopsis support our DNA-based hypothesis on the status of this nominal taxon. A new synonymy is provided as follows: Anodonta anatina = Anodonta pseudodopsis syn. nov. The syntype of Anodonta pseudodopsis SMF 5129 “See von Antiochia” (Senckenberg Research Institute and Natural History Museum, Frankfurt, Germany) is designated here to be the lectotype of this nominal taxon. Finally, we conclude that Anodonta anatina range covers the Orontes River basin in Turkey and Syria and the Nahr al-Kabir al-Shamali River in the Latakia Governorate of Syria. This intraspecific lineage of Anodonta anatina and other freshwater mussels of the Middle East are highly threatened due to multiple anthropogenic impacts and must be a focus of international conservation efforts. The Karasu River in eastern Turkey hosts viable populations of all freshwater mussel species of the Orontes’s fauna and can be considered one of the most important water bodies for the conservation of these imperiled animals in the region.  相似文献   

Coastal ridge constructive processes at a multi-decadal scale in Barreta Island (southern Portugal)     

Xabier Herrero  Susana Costas  Katerina Kombiadou 《地球表面变化过程与地形》2020,45(2):411-423

Multiple ridges across prograding coasts may display variable geometries, commonly expressed through varying elevations. Changes in ridge elevation have been traditionally related to the occurrence of fluctuating progradation rates, which might, in turn, be driven by shifting environmental conditions. Here, we explore the geometry and growth mechanisms of multiple ridges, generated at Barreta Island (Ria Formosa, southern Portugal), as a consequence of the rapid progradation of the island over the last 70 years, following the artificial fixation of the downdrift Faro-Olhão inlet with jetties in 1955. The variability in the morphology of these features was analysed in combination with available wind and wave data, in order to better distinguish growth mechanisms and understand the main parameters determining the final geometry of the observed ridges. The results suggest that (1) most of the identified ridges fall in the beach ridge classification, as they have been mostly built by marine processes, and (2) the parameters derived from, or closely related to wave climate variability (e.g. progradation rates, storm occurrence) can jointly explain most of the observed morphological changes, while aeolian processes played a secondary role. Indeed, ridge geometry appears mainly controlled by progradation rates, with higher ridges associated with lower progradation rates. Progradation rate, in turn, is mostly related to longshore wave power, storminess, and the occurrence storm groups. Yet, the final configuration of ridges can also be affected by runup levels and onshore winds. Therefore, establishing the relation between ridge geometry and wave climate is not a straightforward task, because of the complex processes and interactions that control coastal morphodynamics. © 2019 John Wiley & Sons, Ltd.  相似文献   

Simultaneous water and vapour transfer in an unsaturated mudstone in badlands terrain,southwestern Taiwan     

Kohei Higuchi  Masahiro Chigira  Der-Her Lee  Jian-Hong Wu 《地球表面变化过程与地形》2020,45(13):3323-3335

The simultaneous transfer of pore fluid and vapour was studied in the unsaturated shallow subsurface of a Plio-Pleistocene marine mudstone badland slope in southwestern Taiwan during the dry season using field monitoring data and numerical simulations. Data from field monitoring show mass-basis water contents of ~0.05 to ~0.10 that decrease towards the unsaturated ground surface and were invariant during the middle part of the dry season, except for daily fluctuations. In addition, the observed daily fluctuations in water content correlate with fluctuations in bedrock temperature, especially at depths of 2.5–5.0 cm. Periodic increases in water content occurred most notably during the day, when the bedrock temperature showed the greatest increase. Water contents then decreased to the previous state as bedrock temperature decreased during the night. Calculated vapour fluxes within the mudstone during the day increased up to 6 × 10⁻⁶–1 × 10⁻⁵ kg m⁻² s⁻¹, deriving a 0.01–0.02 increase in mass-basis water content at 2.5 cm depth for a 12-h period. This agrees with field monitoring data, suggesting that increases in water content occurred due to vapour intrusions into the bedrock. Pore water electrical conductivity (EC) showed periodic variations due to vapour intrusion, and gradually increased between the ground surface and depths of 2.5–5.0 cm. In contrast, pore water EC gradually decreased between 15 and 40 cm depth. Calculated water fluxes at depths of 2.5–40.0 cm varied from −4 × 10⁻⁶ to −2 × 10⁻⁹ kg m⁻² s⁻¹. These fluxes generated an increase in solute concentrations at the ground surface, with negative values of water flux indicating an upwards movement of water towards the surface. We show that the increase in solute content due to solute transfer from depth is highly dependent on variations in water flux with depth. © 2020 John Wiley & Sons, Ltd.  相似文献   

Runoff response of a small agricultural basin in the argentine Pampas considering connectivity aspects     

María Guadalupe Ares  Marcelo Varni  Celio Chagas 《水文研究》2020,34(14):3102-3119

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Investigation of the elevation of saltwater wedge due to subsurface dams     

Qinpeng Chang  Tianyuan Zheng  Youyuan Chen  Xilai Zheng  Marc Walther 《水文研究》2020,34(22):4251-4261

Subsurface dams are rather effective and used for the prevention of saltwater intrusion in coastal regions around the world. We carried out the laboratory experiments to investigate the elevation of saltwater wedge after the construction of subsurface dams. The elevation of saltwater wedge refers to the upward movement of the downstream saltwater wedge because the subsurface dams obstruct the regional groundwater flow and reduce the freshwater discharge. Consequently, the saltwater wedge cannot further extend in the longitudinal direction but rises in the vertical profile resulting in significant downstream aquifer salinization. In order to quantitatively address this issue, field-scale numerical simulations were conducted to explore the influence of various dam heights, distances, and hydraulic gradients on the elevation of saltwater wedge. Our investigation shows that the upward movement of the saltwater wedge and its areal extension in the vertical domain of the downstream aquifer become more severe with a higher dam and performed a great dependence on the freshwater discharge. Furthermore, the increase of the hydraulic gradient and the dam distance from the sea boundary leads to a more pronounced wedge elevation. This phenomenon comes from the variation of the freshwater discharge due to the modification of dam height, location, and hydraulic gradient. Large freshwater discharge can generate greater repulsive force to restrain the elevation of saltwater wedge. These conclusions provide theoretical references for the behaviour of the freshwater–seawater interface after the construction of subsurface dams and help optimize the design strategy to better utilize the coastal groundwater resources.  相似文献   

Characterizing spatial and temporal variation in 18O and 2H content of New Zealand river water for better understanding of hydrologic processes     

Jing Yang  Bruce D. Dudley  Kelsey Montgomery  Will Hodgetts 《水文研究》2020,34(26):5474-5488

Time series of hydrogen and oxygen stable isotope ratios (δ²H and δ¹⁸O) in rivers can be used to quantify groundwater contributions to streamflow, and timescales of catchment storage. However, these isotope hydrology techniques rely on distinct spatial or temporal patterns of δ²H and δ¹⁸O within the hydrologic cycle. In New Zealand, lack of understanding of spatial and temporal patterns of δ²H and δ¹⁸O of river water hinders development of regional and national-scale hydrological models. We measured δ²H and δ¹⁸O monthly, together with river flow rates at 58 locations across New Zealand over a two-year period. Results show: (a) general patterns of decreasing δ²H and δ¹⁸O with increasing latitude were altered by New Zealand's major mountain ranges; δ²H and δ¹⁸O were distinctly lower in rivers fed from higher elevation catchments, and in eastern rain-shadow areas of both islands; (b) river water δ²H and δ¹⁸O values were partly controlled by local catchment characteristics (catchment slope, PET, catchment elevation, and upstream lake area) that influence evaporation processes; (c) regional differences in evaporation caused the slope of the river water line (i.e., the relationship between δ²H and δ¹⁸O in river water) for the (warmer) North Island to be lower than that of the (cooler, mountain-dominated) South Island; (d) δ²H seasonal offsets (i.e., the difference between seasonal peak and mean values) for individual sites ranged from 0.50‰ to 5.07‰. Peak values of δ¹⁸O and δ²H were in late summer, but values peaked 1 month later at the South Island sites, likely due to greater snow-melt contributions to streamflow. Strong spatial differences in river water δ²H and δ¹⁸O caused by orographic rainfall effects and evaporation may inform studies of water mixing across landscapes. Generally distinct seasonal isotope cycles, despite the large catchment sizes of rivers studied, are encouraging for transit time analysis applications.  相似文献   

结合BM3D和多级非线性加权平均中值滤波的遥感影像混合噪声去噪方法     

任超  李现广  邓开元  潘亚龙  朱子林  张志刚  施显健 《测绘通报》2020,(1):89-93

提出了一种基于三维块匹配（BM3D）和多级非线性加权平均中值滤波的遥感影像混合噪声去噪方法，使用coief3小波和sym2小波替换传统三维块匹配算法中的bior1.5和hear参数，将三维块匹配算法和多级非线性加权平均中值滤波相结合以提高算法对混合噪声的去噪能力。进行一个仿真对比试验和一个真实遥感影像去噪试验，试验表明，本文提出的方法在遥感影像混合噪声去噪方面效果要优于传统混合噪声去噪方法。  相似文献   

无人机技术在海岛测绘中的应用     

李雪瑞  魏征  田松  李明杰 《测绘通报》2020,(1):150-153

为提高海岛测绘的技术手段，将无人机引入海岛地形调查中，以Swallow-P小型固定翼无人机开展惠州市大亚湾虎洲海岛大比例尺测图为例，系统归纳了无人机外业数据采集与内业数据处理的具体流程，并制作了DEM和DOM成果；经过实测地面点精度分析得出虎洲无人机大比例尺测图成果平面位置中误差和高程中误差符合1∶1000测图精度要求。  相似文献   

利用CEEMD分析中国沿海GNSS站高程时序变化     

刘豪  周东旭  王盼龙  张化疑  王永康  姜传苓 《测绘通报》2020,(3):39-43,77

利用完备经验模态分解方法（CEEMD）对我国沿海地区6个GNSS基准站（2010—2018）的高程时序数据进行了处理分析。结果表明：CEEMD在高程时间序列分析中具有一定的优越性，可准确分解出各GNSS站高程时序中存在的周、月、季节、年等变化周期项，其中周年运动是主要贡献项，各站高程时间序列的短周期变化与潮汐变化周期具有密切关联性；沿海GNSS站的地面沉降既具有区域的一致性，又存在区域间差异性，其中D区DBJO、DZJJ站呈现先下降后上升的趋势，N区NZUH、NWZU站呈下降趋势，B区的BZMW呈上升趋势，而同海区的BLHT站则呈显著的下降趋势。  相似文献