基于卫星遥感影像和DEM融合的地质断裂带研究

应用遥感影像进行地表地质分析,具有数据量大、耗时短、费用低廉等优势,可以快速获取大范围区域的相关地质信息,因此,近年来,卫星遥感影像广泛应用于地质分析工作中。但是由于卫星影像在不同时期内的特征不同,且有大量不同的数据源,在不同影像上获取地质特征困难,因此,如何利用影像处技术增强影像中的地质特征,成为遥感影像地质判读的研究重点。地质断裂带调查一般借助各种直接与间接的调查方法以确认断裂带的存在与否和位置,了解断裂带的活动性,并提供点状或剖面数据材料。卫星影像在追踪研究贯穿地表且可为影像所解析的断裂带上,提供真实的影像证据,有助于直接分析影像中断裂带走向和延展。利用遥感影像处理计算,将卫星影像数据叠加到DEM上编制三维地形图,并利用计算机仿真,通过不同方向的投射光源,找出最适合的观察角及最能凸显出重点区域线状地类的状态。对于地质现象的分析及解释上,可提供较平面影像细致、准确的参考依据。     

罗布泊东阿奇克谷地雅丹地貌与库姆塔格沙漠形成的关系

阿奇克谷地位于罗布泊洼地之东, 93°E以西, 东西长约150km, 南北宽20~30km。为新生代北山与阿尔金山之间的地堑凹地的一部分, 与东面河西走廊的地堑凹地相通。根据出露的雅丹地层河湖相沉积样品所作的ESR测年(2272~10094kaBP)和本区的地质地貌特征可将阿奇克谷地演化与库姆塔格沙漠的发育史归纳为4个时期。①早更新世至中更新世罗布泊古湖扩大时期, 东部湖湾宽约50~60km, 向东延伸至93°15′E或更东; ②中更新世晚期山地上升与古湖湾退缩消失时期, 距今30万年前左右, 青藏高原强烈隆升, 阻挡了海洋水汽的进入, 亚洲内陆加速变干, 由于阿尔金山的左旋向东滑动, 在北面古湖区地层发生了与阿尔山斜交的羽毛状断裂谷群, 并因东北向的断裂上升与东西向的河西地堑谷地斜交, 阻断了疏勒河水不再向西流入罗布泊, 使东部湖湾向西退缩并逐步消失; ③中更新世晚期至晚更新世初, 暴雨径流与强烈的风蚀作用时期, 阿奇克谷地北部的洪积湖相沉积台地支沟口形成雅丹土丘群, 谷地南面库姆塔格沙漠北面羽毛状断裂谷群形成雅丹垄脊和风蚀谷, 谷地中央呈现出季节性的盐碱沼泽和零星雅丹土丘; ④晚更新世末至全新世库姆塔格沙漠扩大, 向北埋没了羽毛状断裂谷(风蚀谷)和雅丹垄脊, 形成了世界上独特的羽毛状沙丘。     

浑江市幅区域化探异常遥感评价筛选研究

本文介绍了根据国家计委和地矿部的要求,应用遥感地质方法,即主要通过航卫片解译,结合本区已有地质矿产分布和物化探资料的综合分析,对吉林省浑江市幅区域化探异常进行遥感评价、筛选研究的概况。文中主要阐述了区内金、多金属矿成矿地质特征,论述了断裂构造和环状构造与金、多金属矿及化探异常的关系,简介了区域化探异常遥感评价筛选和野外验证结果以及圈定的若干找矿靶区的情况。     

Conjugate ruptures and seismotectonic implications of the 2019 Mindanao earthquake sequence inferred from Sentinel-1 InSAR data

In 2019, four strong earthquakes of Mw>6.4 occurred successively in Mindanao, Philippines. Based on the reports from the USGS and PHIVOLCS, these earthquakes were dominated by strike-slip ruptures. Whether these earthquakes are temporally and spatially related remained unknown. We characterized the coseismic displacement fields during the earthquake sequence using an InSAR technique with Sentinel-1 SAR data. The InSAR deformation measurements convincingly reveal that the four earthquakes produced distinct coseismic displacement patterns. We estimated the source parameters of the earthquakes with a two-step inversion strategy. The optimal model suggests that the earthquake sequence resulted from the reactivation of a conjugate fault structure that involves two nearly vertical left-lateral strike-slip faults and two high-angle right-lateral strike-slip faults. We calculated Coulomb stress changes from the earthquake sequence, suggesting that the previous strong earthquakes had significant stress-encouraging effects on the following events. The regional velocities based on the GPS analysis suggest that the formation of this conjugate structure is mainly due to the westward movement of the subducting Philippine Sea Plate. This earthquake sequence provides a seismotectonic background for subsequent strong earthquakes and helps to better understand the formation mechanisms and seismotectonic implications of conjugate structure rupturing.     

Palaeoseismic records in lacustrine sediments—A case study of the Daqingshan piedmont fault and Hasuhai Lake in Inner Mongolia,China

As a traditional method for palaeoseismic studies, trenching can be combined with dating techniques to identify palaeoseismic events and the earthquake recurrence interval. However, when using trenches to study palaeoearthquakes, factors such as the active tectonic background of the earthquake‐caused structure, the lithology on both sides of the fault, the geomorphology location and type and the samples and methods for dating will affect the location of the trench. Thus, trenches should be carefully selected and used to identify the impact of ancient earthquakes. The results have substantial uncertainties and limitations. In recent years, scholars have made considerable progress in using other methods to reveal the palaeoseismic information of faults. Moreover, the history of fault activity may have been recorded in the lacustrine sediment adjacent to the fault. Hasuhai Lake is adjacent to the middle segment of the Daqingshan piedmont fault in Inner Mongolia. Since the Holocene, the region has experienced a temperate continental semi‐arid climate with little interference, and Hasuhai Lake and peripheral waters present weak hydrodynamic conditions that provide an ideal location for the study of palaeoseismic records in lacustrine sediments. Sediment samples and samples for dating were collected from three trenches excavated on the periphery of the Hasuhai Lake. Their variations in grain size and magnetic susceptibility revealed that wind and flowing water jointly produced the sedimentary conditions of Hasuhai sediments. The ¹⁴C dating results and variations in the grain size distribution, grain size components and magnetic susceptibility of sediments caused by seismic events obtained in this study were compared with those caused by a series of palaeoseismic events at the middle segment of the Daqingshan piedmont fault reported by previous studies using trenches, knickpoints and palaeosol records. The results identified seven palaeoseismic events recorded near Hasuhai Lake since 12,000 years. The combined use of lacustrine sediment variation characteristics and dating techniques is an effective method for studying palaeoseismic events.     

Where Are the Women? Accounting for Discrepancies in Female Doctorates in U.S. Geography

Although there have been noticeable improvements in recent years, geography continues to be a predominantly male discipline. The percentage of women receiving PhDs in geography has tracked lower than the U.S. average of female PhDs. Previous studies of women's contribution to geography have focused on personal accounts or on the study of some of the most prominent practitioners, with a few studies using basic data on PhDs awarded and Association of American Geographers membership to determine trends. This article provides a comprehensive overview of doctoral degrees in geography by gender, over time, and across all universities in the United States by examining an alternative database, that of doctoral dissertations. The analysis yields three separate types of results. First, historical and contemporary variations among U.S. universities are examined. Second, data indicate that male and female doctoral students differ in the sex of their advisor. Third, a simple regression model explains some of the discrepancies in the proportion of female doctoral students by department. In sum, this article provides a comprehensive empirical study of the factors that might contribute to the continued disparities in female doctoral students in geography.     

雄安新区牛东断裂带碳酸盐岩热储探测及其对地热勘探的启示

雄安新区在暂不考虑开采砂岩热储地热资源的前提下,探明碳酸盐岩热储东部边界断裂牛东断裂带的分布位置与地热资源品质,对新区地热资源开发利用规划的编制与整体能源利用布局均有着重要意义。以雄安新区高铁片区第一口碳酸盐岩热储勘探井D09孔的探测数据为依据,结合地震剖面解释成果,分析了牛东断裂带内碳酸盐岩热储的空间展布特征、储集层物理性质与单井产能参数,并简述其对地热勘探的指导意义。探测结果表明,牛东断裂带的碳酸盐岩热储主要为蓟县系雾迷山组含硅质的白云岩,分布在断裂西侧基岩宽缓背斜顶部,层状稳定,厚约2000m,顶板埋深1000~1200m,井口水温约70℃,单井水量约102m3/h。D09孔揭示,在距风化壳顶部678m的地层内共发育122个裂隙带,累计厚度达251.20m,裂隙发育率37%,平均孔隙度9.26%,裂隙发育率与平均孔隙度明显比断裂带外地热井高出50%。D09孔与牛东断裂带周缘地热井的地层地温梯度、地热水水化学特征、储集层导水系数等对比分析表明,垂直断距达7000m的牛东断裂带是一条导水导热的盆内隐伏型深断裂,其限定了雄安新区碳酸盐岩热储含水系统的东部边界,构成了西侧牛驼镇凸起的导水通道与东侧霸县凹陷油气运移的阻隔屏障,控制了牛驼镇凸起面积达1000km2的整装地热田的形成。     

1605年海南岛琼州大地震及其发震构造的初步探讨

琼北地区铺前−清澜断裂是一条关系到1605年琼山7½级大地震发震构造判断的重要断裂。为准确厘定该断裂的最新活动特征,针对琼北地区第四纪玄武岩盖层和巨厚海相砂沉积等地质条件,采用大吨位震源的浅层人工地震勘探和小间距钻孔联合地质剖面探测相结合的方法,分别在海口江东三江镇岐山头村和东寨村展开探测。结果表明：(1) 铺前−清澜断裂断错了多个标志地层,最浅断错至全新统烟墩组淤泥层,上断点埋深10 m左右,钻探所揭示的断层面明显具有走滑兼具逆冲性质,是一条具有一定宽度、多分支、多期次活动的大规模断裂带;(2)钻孔联合地质剖面所揭示的地层深度范围内,被断错地层的位移量随着深度增加而加大,铺前−清澜断裂自8 346~7 153 a cal BP以来有过活动,全新世累计垂直位移量4~5 m,垂直位移速率为0.53~0.63 mm/a,推断其为1605年琼山大地震的发震断裂。本研究取得的铺前−清澜断裂全新世活动的新证据,为国土空间规划和区域地震危险性评价提供了科学依据。