Displacement of large-scale open solar magnetic fields from the zone of active longitudes and the heliospheric storm of November 3–10, 2004: 1. The field dynamics and solar activity

The dynamics of the large-scale open field and solar activity at the second stage of the MHD process, including the origination and disappearance of the four-sector structure during the decline phase of cycle 23 (the stage when the blocking field is displaced from the main zone of active longitudes), has been considered. Extremely fast changes in the scales of one of new sectors (from an extremely small sector (“singularity”) to a usual sector that originated after the uniform expansion (“explosion”) of singularity with a “kick” into the zone of active longitudes, westward motion of the MHD disturbance front in the direction of solar rotation, and formation of an active quasi-rigidly corotating sector boundary responsible for the heliospheric storm of November 2004) have been detected in the field dynamics. It has been indicated that a very powerful group of sunspots AR 10656 (which disappeared after the explosion) with an area of up to 1540 ppmh (part per million hemisphere), a considerable deficit of the external energy release, and zero geoeffectiveness in spite of the closeness to the Earth helioprojection existed within singularity. It has been assumed that the energy escaped from this group with effort owing to the interaction between coronal ejections and narrow sector walls (singularity), and a considerable part of the energy was released in the outer layers of the convective zone, as a result of which singularity exploded and this explosion was accompanied by the above effects in the large-scale field and solar activity.     

利用遥感图像对震损建筑结构变形检测的识别研究

为识别震后建筑变形损坏状况,提出震损建筑结构变形检测的遥感图像识别分析方法。利用无人机采集震灾区域的遥感图像,将建筑结构变形检测问题转变为构件间坐标测量问题,提取所采集遥感图像中样本矢量点,将其划分为不同种类区域,在此基础上对图像进行聚类分割,以获得震后图像的不同类别建筑结构特征,实现识别不同样本矢量点的地震受灾情况。通过实验分析发现,所提出的图像识别分析方法在一定程度上可以识别出损毁建筑物,但仍需要进一步研究,以提高其识别精度。     

Quaternary volcanic and tectonic segmentation of Central America

Central America is divided into seven segments based on differences in the strikes and positions of volcanic lineaments in the historically active volcanic chain. This block-like pattern is also seen in the contrasting volcano morphology, recent fault patterns and the distribution of shallow earthquakes. Discontinuities in the deep seismic zone can be identified at some segment margins. The boundary areas between the segments are characterized by faulting transverse to the volcanic lineaments, frequently accompanied by basalt cinder cone fields, by concentrations of shallow earthquakes and by catastrophic historic eruptions. This volcanological, structural and seismological data can be explained by a segmented converging plate margin. At shallow depths the underthrust lithosphere is broken along tear faults into 100 to 300 km long segments. The separate segments descend into the mantle with different strikes and dips and give the geology its segmented character. Evidence for similar segmented converging plate margins is found in Mexico and in other parts of the circumpacific and alpine belts.     

丽江地区遥感影像线环结构特征与场地稳定性分析

丽江地区活动性构造发育,地震发生频繁。以遥感影像线环结构理论论述了该区主要活动断裂和活动环块的遥感影像特征和地质地貌特征,并分析活动构造与场地稳定性的关系,进而划分出该区内易发震地区与相对稳定的地区。     

Imprints of sub-glacial volcanic activity on a glacier surface—SAR study of Katla volcano,Iceland

The Katla central volcano, covered by the fourth largest Icelandic glacier Mýrdalsjökull, is among the most dangerous and active volcanoes in Iceland. Due to the ice cover, several indicators of its volcanic activity can only be identified indirectly. We analysed a total of 30 synthetic aperture radar (SAR) images with special focus on identifying circular and linear depressions in the glacier surface. Such features are indicative of sub-glacial geothermal heat sources and the adjacent sub-glacial tunnel (melt water drainage) system. The time series comprises images from five different SAR sensors (ERS-1, ERS-2, JERS-1/SAR, RADARSAT and ENVISAT-ASAR) covering a time period of 12 years, starting in 1994. Individual SAR scenes only partly map the glacier surface morphology due to the environmental influences on the SAR backscatter intensity. Thus, only surface features detectable in several SAR scenes at the same location were considered and merged to form an overall picture of the surface morphology of Mýrdalsjökull and its modification by sub-glacial volcanic activity between 1994 and 2006. Twenty permanent and 4 semi-permanent ice cauldrons could be identified on the surface of Mýrdalsjökull indicating geothermally active areas in the underlying caldera. An analysis of their size was not possible due to the indistinct outline in the SAR images. The spatial distribution of the geothermally active areas led to a new, piecemeal caldera model of Katla volcano. All cauldrons are connected to tunnel systems for melt water drainage. More than 100 km of the sub-glacial drainage system could be identified under the Mýrdalsjökull in the SAR time series. It has been found that the tunnel systems are not in agreement with estimated water divides. Our results allow improved assessment of areas of potential Jökulhlaup hazard accompanying a sub-glacial eruption.     

Active tectonics of the area of the two Kaliningrad earthquakes on September 21, 2004

Resulting from the seismotectonic study of the Sambian Peninsula based on the interpretation of remote sensing data (satellite images and digital elevation maps), lineaments have been identified. They may be interpreted as active faults and flexure-fracture zones. These active faults, which are expressed in the form of gentle linear swells or steps in the relief, have been found and studied during the carried out field works. There are many discovered paleoseismic dislocations in the studied areas of active faults: fracture displacements, marks of liquefaction (sand dykes), near-fault folds. These seismic dislocations may indicate seismic shocks of 7–8 intensity points occurring in the neighborhood of a modern Kaliningrad city in recent geological history. The identified active structures (Yantarny Fault Zone and Bakalino flexure-fracture zone) could control sources of the 2004 Kaliningrad earthquakes.     

沂沭全新世活动断裂分段边界的地质特征

本文以不同的成因机制为基础,对沂沭活断层的全新世活动部分进行了分段,继而主要讨论了分段边界的地表地质特征。 沂沭全新世活断层北起莒南左山,南至泗洪峰山。通过卫片解译分析、对横切主断层的北西向断层的野外调查和主断层的断层几何分析,笔者认为,位于郯城东北的分段边界,是一个以横向构造(归义—山左口断层)和主断层的错列起主要作用的、可能基岩岩性起一定影响的、空间上沿断裂方向延伸约10km的障碍体。     

隐伏区活动断层遥感地质解译研究——以新乡—商丘断裂南支为例

综合利用GF-1、PALSAR雷达数据、Landsat 8 OLI等多种数据源,分析了商丘路河地区地质地貌的遥感影像特征,进行了水文地质解译和地层遥感解译,综合判定新乡—商丘断裂南支为NW走向并建立了该断层解译标志,有效地弥补了传统技术手段无法在较深覆盖区进行活动断层探测的缺陷,对覆盖区隐伏活动断层探测工作具有借鉴意义。     

Interannual variations in the areas of thermokarst lakes in Central Yakutia

At present, close attention is given to studies of thermokarst lakes from the standpoint of cryolite zone response to global climate warming. However, other factors, which have an effect on the variation in areas of lakes, in particular, the atmospheric precipitation, receive little attention, while the atmospheric precipitation is one of the main sources of water recharge for many water objects. In this connection, interannual variations in the areas of lakes as a function of precipitation were analyzed on the territory of Central Yakutia. The studies were based on the analysis of space images taken at different time. As the result, it was shown that precipitation has a considerable effect on variations in the areas of thermokarst lakes; there is a direct relationship between variations in lake areas and precipitation; only some single high-water or low-water years have no effect on these variations. Variations in areas of lakes during summer were also analyzed with a view to use the results in choosing the images for studies of interannual variations. It has been revealed that the areas of thermokarst lakes decrease from June to August; this means that the images obtained within a short period at the end of the summer period should be used.     

Distributions of hydrothermal activity along the Mid-Atlantic Ridge: interplay of magmatic and tectonic controls

Hydrothermal activity has been investigated along three different sections of the slow-spreading Mid-Atlantic Ridge (MAR): 11°20′–30°N, 36–38°N and the Reykjanes Ridge, 57°45′–63°06′N. When considered in total, the incidence of venting along these three sections of the MAR compares well with the predictions of a model in which frequency of venting is linearly related to ridge-crest spreading-rate. At the scale of individual study areas, however, departure from the model is observed by up to an order of magnitude. Venting is anomalously rare along the Reykjanes Ridge but anomalously abundant along the MAR 36–38°N. Whilst such variability may be within the error of the linear spreading-rate model, we note that the interplay between magmatic and tectonic processes also differs between the three study areas. In the case of the Reykjanes Ridge we propose that the low incidence of venting reported may reflect a limitation of the sampling/investigative strategy because the style of venting which predominates may not give rise to conventional black-smoker hydrothermal plumes. Along the oblique and broadly segmented MAR 36–38°N, we propose that vigorous hydrothermal venting in broad segment-end non-transform discontinuities may be focussed along deeply penetrating active faults with the requisite heat supply being supported through some combination of along-axis magmatic intrusions and thermal release associated with the serpentinisation of crustal peridotites.     

上海及其邻近地区三维地壳结构层析成像

利用上海及其邻近地区地震台网的地震记录及人工爆破资料,采用地震层析成像方法反演研究区地壳三维P波、S波速度结构模型。成像结果表明:不同深度的P波、S波速度扰动呈北西向展布特征;地震大多数分布在低速区的块体内,说明地震不仅与断裂活动有关,有可能还与物质结构和性质有关;上海及其邻近地区上地壳速度结构,断裂活动和物质性质三者之间存在密切关系。     

基于机器学习的极光图像自动分割方法

极光是太阳风能量注入到极区的指示器,从观测视野中准确分割出极光区域对研究极光演变如亚暴过程有非常重要的意义.本文基于全卷积神经网络提出了一种弱监督极光图像自动分割策略,数据标记时仅需指定极光区域的一个像素点即可,极大解决了机器学习人工标注数据的压力.首先利用简单单弧状极光图像训练一个初始分割模型Model 1,然后基于该模型,结合热点状和复杂多弧状极光图像获得一个增强的分割模型Model 2,最后对分割结果做进一步优化.本文对2003—2007年北极黄河站越冬观测的2715幅极光图像进行了分割,并和最新论文结果及人工标签进行了定量和定性比较,其中分割结果与人工标签的“交并比”高达60%,证明了本文方法的有效性.     

A reappraisal of active faults in central-east Iran (Kerman province)

Fault lineaments are the main input data in earthquake engineering and seismology studies. This study presents a digitally-based active fault map of the Kerman region in central-east Iran which experienced several devastating earthquakes on poorly exposed and/or not identified active faults. Using Landsat 8 data, we have carried out the image-based procedures of fault mapping, which include applying the contrast stretching technique, the principal component analysis, the color composite technique, the spectral rationing, and creating the false-color composite images. Besides, we have cross-checked the resulting map with the geological maps provided by the Geological Survey of Iran to decrease the associated uncertainties. The resulting map includes 123 fault segments, still, a part of which has been expressed in the previously compiled active-fault maps of Iran. Indeed, the new one is mapping the poorly exposed active faults, so-called secondary faults, which are able to produce strong events. These faults are primarily associated with poorly defined areas that accommodate low levels of seismicity; however, sporadic strong events are likely to occur. It has also been investigated that these kinds of faults are seismogenic and are able to produce destructive events. In total, the outcome of this study can also be jointed with seismic studies for investigating parts of the earthquake activity in central-east Iran, in particular for the fault-based approaches in impending earthquake-resistant buildings.     

Recent developments in the direct-current geoelectrical imaging method

There have been major improvements in instrumentation, field survey design and data inversion techniques for the geoelectrical method over the past 25 years. Multi-electrode and multi-channel systems have made it possible to conduct large 2-D, 3-D and even 4-D surveys efficiently to resolve complex geological structures that were not possible with traditional 1-D surveys. Continued developments in computer technology, as well as fast data inversion techniques and software, have made it possible to carry out the interpretation on commonly available microcomputers. Multi-dimensional geoelectrical surveys are now widely used in environmental, engineering, hydrological and mining applications. 3-D surveys play an increasingly important role in very complex areas where 2-D models suffer from artifacts due to off-line structures. Large areas on land and water can be surveyed rapidly with computerized dynamic towed resistivity acquisition systems. The use of existing metallic wells as long electrodes has improved the detection of targets in areas where they are masked by subsurface infrastructure. A number of PC controlled monitoring systems are also available to measure and detect temporal changes in the subsurface. There have been significant advancements in techniques to automatically generate optimized electrodes array configurations that have better resolution and depth of investigation than traditional arrays. Other areas of active development include the translation of electrical values into geological parameters such as clay and moisture content, new types of sensors, estimation of fluid or ground movement from time-lapse images and joint inversion techniques. In this paper, we investigate the recent developments in geoelectrical imaging and provide a brief look into the future of where the science may be heading.     

A desktop image processing and photogrammetric method for rapid volcanic hazard mapping: application to air-photo interpretation of Mount Pelée,Martinique

 A desktop image processing and photogrammetric method was developed for digitizing black-and-white aerial photographs. The technique was applied to airborne optical images of Mt. Pelée, Martinique, a historically active volcano in the tropical Lesser Antilles island arc, to evaluate its utility for rapid geologic mapping and hazard assessment in vegetated areas. The digital approach provides several advantages over traditional air-photo interpretation by allowing for change detection in time-series images, morphologic characterization, development of digital elevation models from stereopairs, and geo-referencing with other digital data sets. A digital mosaic of Mt. Pelée was created from air photos acquired in 1951, which covered the region affected by the 1902 eruption. Severe mismatches occurred along edges of adjacent photographs prior to correction, which precluded quantitative morphologic analysis of the volcanic edifice. Geometric corrections and histogram equalization of digitized air photos allowed creation of a continuous mosaic. Comparison of the mosaic and a map based on differences in gray scale and texture to a volcanostratigraphic map revealed that not only the various deposits produced during the 1902 event were easily differentiated, but that older eruptive products were identified, suggesting that this approach may be used for rapid hazard evaluation of historically active tropical volcanoes. Received: 22 January 1996 / Accepted: 26 July 1996     

探地雷达在探测隐伏活动断层中的应用

以东昆仑断裂带东部采用探地雷达探测隐伏活动断层为例。 在浅覆盖区, 利用合理的采集参数和数据处理流程; 雷达剖面图像能够清晰地显示出隐伏断层的形态特征和岩土分层; 结合沉积序列, 可以分析和评价断层的活动性。 实验证明, 探地雷达是一种有效探测浅覆盖区隐伏活动断层的方法。     

The response of vegetation cover and dune activity to rainfall,drought and fire observed by multitemporal satellite imagery

The stable longitudinal dunes in the northern Simpson Desert, Australia, were observed in satellite imagery to become more active after vegetation cover was reduced by fire and drought. Subsequent rainfall events also resulted in significant vegetation regrowth and dune stabilization. These switches between more active and stable conditions have not been previously described in the largely vegetated dune fields of central Australia. The observations, made on 12 dune sites, relied on high spatial resolution satellite imagery to observe dune crest activity, and seasonal Landsat fractional cover imagery to observe vegetation cover changes. The non-photosynthetic vegetation (NPV) component of the fractional vegetation cover images revealed significant changes in hummock grass cover on the dunes between 1988 and 2018, with a positive relationship with the three-year cumulative rainfall, disrupted by two periods of patchy burning. Only those sites that had burnt became active, and only after vegetation cover had remained low (NPV < 16%) during the ‘Millennium Drought’. There is no threshold in vegetation cover, below which dune crests become active, but active dune features require four-years of low NPV cover (< 16%) to develop. The large rainfall event that ended the drought increased NPV cover, stabilizing the dunes. Similar hummock grass covered dunes are present across large areas of the arid zone, and are likely to respond in similar ways, given that fire and drought are common occurrences in Australia. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.     

曲线坐标系因式分解程函方程及其走时计算

地震波走时广泛应用于静校正、层析成像、Kirchhoff偏移成像、地震定位等研究.复杂地表条件是影响走时计算精度的重要因素.近年来,发展的曲线坐标系程函方程为精细刻画起伏地表条件下的地震波走时场特征提供了新的思路.然而,基于有限差分程函方程的求解方法不可避免地受到震源奇异性的影响,即震源附近波前的曲率较大,此时使用平面波近似假设的差分格式会导致较大误差.而震源误差会随着波前的传播到达整个计算区域,从而影响整个区域的求解精度.针对该问题,本文借鉴因式分解的思想,推导建立了曲线坐标系因式分解程函方程,并针对性地发展了其数值求解方法,从根源上解决了复杂模型走时计算中的震源奇异性问题.数值实例表明因式分解法能够有效降低震源误差,显著提高起伏地表走时计算的精度和效率,为起伏地表地震波走时计算提供更佳的选择,在复杂模型的地震资料处理中展现出广泛的应用前景.     

Automatic Synthetic Aperture Radar based oil spill detection and performance estimation via a semi-automatic operational service benchmark

Today the health of ocean is in danger as it was never before mainly due to man-made pollutions. Operational activities show regular occurrence of accidental and deliberate oil spill in European waters. Since the areas covered by oil spills are usually large, satellite remote sensing particularly Synthetic Aperture Radar represents an effective option for operational oil spill detection. This paper describes the development of a fully automated approach for oil spill detection from SAR. Total of 41 feature parameters extracted from each segmented dark spot for oil spill and ‘look-alike’ classification and ranked according to their importance. The classification algorithm is based on a two-stage processing that combines classification tree analysis and fuzzy logic. An initial evaluation of this methodology on a large dataset has been carried out and degree of agreement between results from proposed algorithm and human analyst was estimated between 85% and 93% respectively for ENVISAT and RADARSAT.     

Displacement of large-scale open solar magnetic fields from the zone of active longitudes and the heliospheric storm of November 3–10, 2004: 2. “Explosion” of singularity and dynamics of sunspot formation and energy release

A more detailed scenario of one stage (August–November 2004) of the quasibiennial MHD process “Origination ... and dissipation of the four-sector structure of the solar magnetic field” during the decline phase of cycle 23 has been constructed. It has been indicated that the following working hypothesis on the propagation of an MHD disturbance westward (in the direction of solar rotation) and eastward (toward the zone of active longitudes) with the displacement of the large-scale open solar magnetic field (LOSMF) from this zone can be constructed based on LOSMF model representations and data on sunspot formation, flares, active filaments, and coronal ejections as well as on the estimated contribution of sporadic energy release to the flare luminosity and kinetic energy of ejections: (1) The “explosion” of the LOSMF singularity and the formation in the explosion zone of an anemone active region (AR), which produced the satellite sunspot formation that continued west and east of the “anemone,” represented a powerful and energy-intensive source of MHD processes at this stage. (2) This resulted in the origination of two “governing” large-scale MHD processes, which regulated various usual manifestations of solar activity: the fast LOSMF along the neutral line in the solar atmosphere, strongly affecting the zone of active longitudes, and the slow LOSMF in the outer layers of the convection zone. The fronts of these processes were identified by powerful (about 10³¹ erg) coronal ejections. (3) The collision of a wave reflected from the zone of active longitudes with the eastern front of the hydromagnetic impulse of the convection zone resulted in an increase in LOSMF magnetic fluxes, origination of an active sector boundary in the zone of active longitudes, shear-convergent motions, and generation and destabilization of the flare-productive AR 10696 responsible for the heliospheric storm of November 3–10, 2004.