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大震前地震活动性的加强,是震前地震活动异常变化的普遍现象,伴随着地震活动增强,开始出现区域震群活动.现代统计物理学中突变事件发生前的临界指标包括起伏加剧和起伏加剧时段所显示的复杂系统宏观有序性.研究表明,上述指标不仅能应用于中、强地震短临预报研究,在短临阶段地震活动性资料中同样存在. 相似文献
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结合地震空间分布非均匀性指标Kcv值预测方法和图像信息学算法对河北及邻区2013~2017年ML≥5.0地震发生概率增益进行预测。根据河北及邻区40多年的地震观测资料,对地震空间分布非均匀性指标Kcv值进行了空间扫描和震例统计,得到了此方法应用于河北地区的预测效能,并对河北及邻区2013~2017年ML≥5.0地震发生概率增益进行了预测;对图像信息学算法在研究区进行了地震危险性概率预测的回溯性检验,得到了此方法应用于研究区的预测效能R值及概率增益K值,并进行了5年尺度的地震危险性预测。在上述2个单项预测方法的基础上,基于概率增益综合预测模型,得到了5年尺度河北及邻区ML≥5.0地震发生概率增益的综合预测结果。 相似文献
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晋冀蒙交界地区处于华北地块、鄂尔多斯地块和燕山地块交界处,其地震活动受到构造应力场变化的影响,和未来中强地震有一定关联性.2019年以来,晋冀蒙交界地区出现 ML3．0以上地震显著增强现象,为了评估此区域地震活动起伏的震兆意义,构建有效的预测方法,文章将增强区域作为地震频次的窗口,选取 ML3．0以上地震年滑动频次为预测指标.通过回溯历次5级以上地震前的地震活动情况,确定最优预测规则.经过在预测规则参数空间扫描,以R 值作为目标函数,最终确定的预测窗长和阈值为2年和14次,在此规则下地震频次预测指标有较好的预测效果和较高信度. 相似文献
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2012年5月28日河北省唐山4.8级地震 总被引：5，自引：1，他引：4
2012年5月28日河北省唐山市古冶区与滦县交界发生4.8级地震,地震宏观震中位于古冶区的王辇庄乡.震中烈度为V度,地震发生在NE走向的唐山断裂带附近.地震没有造成人员伤亡和经济损失.震源机制解P轴方位为SEE,T轴方位为SSW,接近水平,这与华北构造应力场的NE-NEE方向不一致.唐山4.8级地震是1976年唐山7.8级地震晚期余震的正常起伏,2004年以来唐山老震区的ML4.0以上地震呈现了很好的准周期性.唐山4.8级地震前地震活动性和测震学参数存在背景性异常,从不同角度反映了老震区地震活动平静、起伏的阶段性特征.前兆异常以中短期异常为主,其中地下流体异常、电磁异常表现更为突出.此次地震虽然震级不高,但无论是地震活动性还是前兆方面都出现了一定数量的异常.异常既有趋势性的,也有短临的,配套性很好. 相似文献
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利用模拟地震观测资料,对临汾盆地、太原盆地、大同盆地小地震活动时间序列,运用A(b)-N法得到的地震活动参数曲线与地震的对应关系作对比研究,得到地震预测的可信度,发现A(b)-N法对不同盆地的地震活动作出的预测不尽相同,进一步明确了A(b)-N法的应用范围.对今后山西断陷带地震活动的研究提供了一定的参考价值. 相似文献
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新疆及周边地区强震成组活动及其预测研究 总被引：4，自引：0，他引：4
系统分析了1900年以来新疆及周边6级以上地震成组活动基本特征。 结果表明, 新疆及周边地区6级以上地震成组活动明显, 并具有持续时间短、 地震强度大、 频度高的特点。 新疆及周边地区7级以上地震有95％发生在地震成组活动期间, 地震成组活动是该区域发生7级以上强震的中期预测指标之一。 地震成组活动一般出现在低活动水平背景下, 而且成组地震活动在空间上相对集中分布, 在地震活动期间强震存在由新疆西南向北东迁移的特点, 其中天山地震带尤其是南天山西段为强震主要的活动区域。 地震成组活动伴随地震条带图像的出现; 在地震成组活动前或活动中新疆地区前兆测项异常明显增加, 具有群体异常的起伏变化过程。 相似文献
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对1998~2010年度地震大形势东北地区预测效果和预测依据进行了总结和评估分析。结果显示1998年以来东北地震大形势预测的5～6级地震危险区主要集中在环渤海、辽蒙交界和黑吉蒙交界地区。地质构造背景和地震活动实况也表明上述三个地区及邻区为东北中强震的主体活动地区,历年报告对东北危险区的把握较好,东北地震大形势第一年度趋势预测准确率为57%,1~2年度预测准确率为71%。东北地震大形势预测判据主要有8项,其中中小地震活动增强、空区和条带以及地震活动性参数扫描等3项地震学指标可靠性较高,R值评分均大于0.22。统计结果显示,预测报告中每年给出的异常指标数量与次年最大震级没有明显的关联,但中强震前中小地震活动增强是东北地区地震活动的主要特征之一。活跃—平静期、构造背景以及历史地震活动等在预测时,虚报的概率较大,二者或许对长趋势的预测起一定的借鉴作用。正确判断东北地区地震活动目前所处的状态（活跃状态还是平静状态）以及活跃—平静期转换的界定指标,可适当提高危险区预测的准确性,减少虚报率。回顾和总结的过程中也发现,目前1~3年地震形势的预测分析以统计性、定性判定依据为主,主要基于震例资料的统计和定性对比分析,反映大地震孕育和发生物理过程的资料非常有限,今后应在努力提高统计分析严谨性的同时,尽可能多地获得并采用多学科观测资料,从地球物理场动态变化的角度来分析地震趋势的发展。 相似文献
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地震空间分布非均匀性指标Cv值作为一种有效的预测指标近几年来得到了广泛应用。然而受空间分布的事件样本数大小的影响,Cv值会有所改变。本文采用Cv值标准化后的Kcv值,统计了河北及邻区的地震事件空间非均匀性分布,并与地震时空概率增益综合预测模型相结合,进行研究区地震预测。依据河北及邻区40多年的地震观测资料进行了Kcv值扫描和震例统计,研究了该方法应用于河北地区的预测效能及最优时间尺度。对研究区2008—2012年M5及以上地震的概率增益、地震发生概率预测与实际地震发生情况的回溯性检验结果表明,此方法应用于河北地区地震发生概率的预测是可行的。依据上述方法,对2013—2017年河北及邻区M5及以上地震发生的概率增益和地震发生概率进行了预测。 相似文献
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印度板块北边界地震活动和中国大陆地震 总被引：17，自引：8，他引：17
本文研究了印度板块北边界地震活动与我国大陆地震活动的关系，给出了两者在时间起伏上的一致性，以及印度板块北边界兴都库会和缅甸两端点附近中深地震对中国大际强震活动所具有的前兆性和相关性。这些特点，对于中国大陆强震活动的预测，尤其是地震大形势预测是十分有意义的。文中还应用了中国大陆强震孕育发生的计算机模型的研究结果，讨论了强震活动的时空分布特征，对于理解中国大陆作为一个孕震系统在周围地质构造块体动力作用 相似文献
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刊用黄金分割对全球及美国西海岸、太平洋西北缘、大洋岛弧、亚欧4条洲际地震带大震活动性进行了研究.研究的主要内容是针对地震活动的能量释放周期、A(b)指数进行的.研究的方法是采取地震活动的几个主要周期相比,若其值约为0.618,则认为它符合黄金分割性.研究表明,全球及各洲际地震活动的主要周期是符合黄金分割的.这项研究可利用地震活动的黄金分割性对全球及各洲际的地震活动高潮作出预测,但为什么地震活动会符合黄金分割性的物理实质的解答尚有一定的困难.文中还利用同样方法对中国华北地区的地震活动性进行了讨论,并对其今后的地震发生作了预测.认为2006年前后华北有发生7级地震的可能性,如不发生,则华北地区就进入长期无大震的平静期. 相似文献
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Soils along catenas of Pinedale (15–20 ka) and Bull Lake (100–130 ka) age moraines at Whiskey Basin in the Wind River Range, Wyoming, USA, were sampled to assess the effects of aeolian processes on soil development here. Aeolian processes appear to have in?uenced soils by both depositing sediments and eroding topsoils. Pedogenic silt (often used as an indicator of wind deposition) accumulated in the Bull Lake soils moderately correlate with pedogenic clay accumulated, suggesting that ?ne sediments may have been deposited and incorporated into soil formation here. Following removal of previous topsoil by wind during Pinedale glaciation, Bull Lake B horizons have developed into contemporary A horizons. These data further link aeolian processes to soil development on piedmont moraines throughout the Wind River Range. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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This paper describes a plant megafossil assemblage from the Pliocene strata of Xiangzi, Zanda Basin in the western Qinghai-Tibet Plateau. Twenty-one species belonging to 12 genera and 10 families were identified. Studies show that the Pliocene vegetation in Zanda Basin was mostly deciduous shrub composed of Cotoneaster, Spiraea, Caragana, Hippophae,Rhododendron, Potentilla fruticosa, etc. Leaf sizes of these taxa were generally small. Paleoclimate reconstruction using Coexistence Analysis and CLAMP showed that this area had higher temperature and precipitation in the Pliocene than today, and distinct seasonal precipitation variability was established. The reconstructed paleoelevation of Zanda Basin in the Pliocene was similar to modern times. In the context of central Asian aridification, the gradual drought in the area beginning in the late Cenozoic caused vegetation to transition from shrub to desert, and the flora composition also changed. 相似文献
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ABSTRACTUnderstanding potential evapotranspiration (PET) changes under climate change is of great importance for hydrological research. The trends of PET changes and their driving forces were investigated in the Lancang (LRB) and Yarlung Zangbo (YRB) river basins, southwest China, using diagnosis graphs and the Mann-Kendall test. Analysis of variance was applied to examine the contribution of different climatic variables to PET. The results show that: (i) there was a statistically significant increase in PET in the period of 1957–2015 in the LRB, while it showed a markedly decreasing trend in the YRB; (ii) PET in both basins is fairly sensitive to wind speed, relative humidity, solar radiation and maximum air temperature, and the interactions between wind speed and relative humidity are also important; and (iii) the increase in PET in the LRB is due mainly to the increase in maximum air temperature and decrease in relative humidity, while declines in wind speed and solar radiation are the main reasons for the decrease in PET in the YRB. 相似文献
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A comprehensive study on geothermal history of the Turpan-Hami Basin by vitrinite reflectance, fluid inclusion geothermometry,
apatite fission track and40Ar-39Ar dating displays that the main effects influencing geotemperature distribution are burial depth of the basement, heat flow,
magmatic activities, as well as tectonic movement, having a rugulation to be higher in the east and north, lower in the west
and south, as well as higher in the past and lower at the present. The heat of the mantle source and the Indo-China tectonic
thermal event have extremely influenced maturation of source rocks of the upper Lower Permian and the Middle and Upper Triassic
in the lndo-China epoch. While, the geothermal gradient and the weak tectonic geothermal event of the Early Yanshan Movement
provided necessary heat for the maturation of source rock in coal-bearing strata of the Middle and Lower Jurassic. 相似文献
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The hydrogeologic framework of fractured sedimentary bedrock at the former Naval Air Warfare Center (NAWC), 1 1 For more information on the USGS Toxics Substances Hydrology Program at the Naval Air Warfare Center visit the NAWC website at http://nj.usgs.gov/nawc/
Trenton, New Jersey, a trichloroethylene (TCE)-contaminated site in the Newark Basin, is developed using an understanding of the geologic history of the strata, gamma-ray logs, and rock cores. NAWC is the newest field research site established as part of the U.S. Geological Survey Toxic Substances Hydrology Program, Department of Defense (DoD) Strategic Environmental Research and Development Program, and DoD Environmental Security Technology Certification Program to investigate contaminant remediation in fractured rock. Sedimentary bedrock at the NAWC research site comprises the Skunk Hollow, Byram, and Ewing Creek Members of the Lockatong Formation and Raven Rock Member of the Stockton Formation. Muds of the Lockatong Formation that were deposited in Van Houten cycles during the Triassic have lithified to form the bedrock that is typical of much of the Newark Basin. Four lithotypes formed from the sediments include black, carbon-rich laminated mudstone, dark-gray laminated mudstone, light-gray massive mudstone, and red massive mudstone. Diagenesis, tectonic compression, off-loading, and weathering have altered the rocks to give some strata greater hydraulic conductivity than other strata. Each stratum in the Lockatong Formation is 0.3 to 8 m thick, strikes N65°E, and dips 25° to 70°NW. The black, carbon-rich laminated mudstone tends to fracture easily, has a relatively high hydraulic conductivity and is associated with high natural gamma-ray count rates. The dark-gray laminated mudstone is less fractured and has a lower hydraulic conductivity than the black carbon-rich laminated mudstone. The light-gray and the red massive mudstones are highly indurated and tend to have the least fractures and a low hydraulic conductivity. The differences in gamma-ray count rates for different mudstones allow gamma-ray logs to be used to correlate and delineate the lithostratigraphy from multiple wells. Gamma-ray logs and rock cores were correlated to develop a 13-layer gamma-ray stratigraphy and 41-layer lithostratigraphy throughout the fractured sedimentary rock research site. Detailed hydrogeologic framework shows that black carbon-rich laminated mudstones are the most hydraulically conductive. Water-quality and aquifer-test data indicate that groundwater flow is greatest and TCE contamination is highest in the black, carbon- and clay-rich laminated mudstones. Large-scale groundwater flow at the NAWC research site can be modeled as highly anisotropic with the highest component of permeability occurring along bedding planes. 相似文献
Trenton, New Jersey, a trichloroethylene (TCE)-contaminated site in the Newark Basin, is developed using an understanding of the geologic history of the strata, gamma-ray logs, and rock cores. NAWC is the newest field research site established as part of the U.S. Geological Survey Toxic Substances Hydrology Program, Department of Defense (DoD) Strategic Environmental Research and Development Program, and DoD Environmental Security Technology Certification Program to investigate contaminant remediation in fractured rock. Sedimentary bedrock at the NAWC research site comprises the Skunk Hollow, Byram, and Ewing Creek Members of the Lockatong Formation and Raven Rock Member of the Stockton Formation. Muds of the Lockatong Formation that were deposited in Van Houten cycles during the Triassic have lithified to form the bedrock that is typical of much of the Newark Basin. Four lithotypes formed from the sediments include black, carbon-rich laminated mudstone, dark-gray laminated mudstone, light-gray massive mudstone, and red massive mudstone. Diagenesis, tectonic compression, off-loading, and weathering have altered the rocks to give some strata greater hydraulic conductivity than other strata. Each stratum in the Lockatong Formation is 0.3 to 8 m thick, strikes N65°E, and dips 25° to 70°NW. The black, carbon-rich laminated mudstone tends to fracture easily, has a relatively high hydraulic conductivity and is associated with high natural gamma-ray count rates. The dark-gray laminated mudstone is less fractured and has a lower hydraulic conductivity than the black carbon-rich laminated mudstone. The light-gray and the red massive mudstones are highly indurated and tend to have the least fractures and a low hydraulic conductivity. The differences in gamma-ray count rates for different mudstones allow gamma-ray logs to be used to correlate and delineate the lithostratigraphy from multiple wells. Gamma-ray logs and rock cores were correlated to develop a 13-layer gamma-ray stratigraphy and 41-layer lithostratigraphy throughout the fractured sedimentary rock research site. Detailed hydrogeologic framework shows that black carbon-rich laminated mudstones are the most hydraulically conductive. Water-quality and aquifer-test data indicate that groundwater flow is greatest and TCE contamination is highest in the black, carbon- and clay-rich laminated mudstones. Large-scale groundwater flow at the NAWC research site can be modeled as highly anisotropic with the highest component of permeability occurring along bedding planes. 相似文献