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安徽三分区小震活动水平的统计预测 总被引：2，自引：0，他引：2
利用马尔可夫(Markoff)模型对安徽的霍山区、淮河中游区和沿江江南区的小震活动水平进行统计预测，结果显示，一年之内霍山地区一般会发生Ms≥2．5级地震，发生Ms≥3．0级地震的可能性不大。淮河中游区和沿江江南区一般会发生Ms≥2．0级地震，有可能发生Ms≥2．5级地震。淮河中游区发生Ms≥3．0级地震可能性不大，沿江江南区发生Ms≥3．0级地震可能性则很小。 相似文献
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安徽淮河构造变形带及邻近块体现代构造应力场特征 总被引：3，自引：1，他引：3
针对安徽省较特殊的构造环境及历史地震分布特点，利用直达波最大振幅比和系统聚类分析方法，在对安徽淮河中游区1974年以来近百个中小地震震源机制反演、聚类及空间合成的基础上，分析了华北断块南缘的安徽淮河构造变形带及邻近块体震源断层滑动方式、构造应力场分布及块体运动方式、应力场随时间变化等。结果显示：淮河构造变形带及其邻近块体上震源断层总体上以近走滑型或斜滑型破裂为主，但倾滑型破裂也占一定比例；该地区构造应力以水平作用为主，但也存在一定的垂向作用。其中淮北和皖中块体仍可能分别向SWW和NEE方向运动，并在淮河构造变形带上产生左旋剪切作用，呈现一定的继承性活动特征；各块(带)上主压应力P轴走向随时间的变化在总体上较为一致，而各时段之间P轴方位存在一定差异，显示安徽淮河中游区受华北和华南应力场的共同作用，但其地震活动可能主要受控于华北应力场。 相似文献
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引言1974年7月—10月,淮河中游出现了大量的宏观异常,随后虽有所缓和,但1975年、1976年又相继出现,特别在1976年7月以后,已发展到长江、黄河中下游,包括江苏、安徽、山东、河南、湖北和江西九江一带,然而却未发生Ms≥5级的地震,因此分析这些宏观异常的原因,对于今后监视地震是有所裨益的。 相似文献
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淮河流域中强震活动区的地震构造背景 总被引：1，自引：0，他引：1
介绍了沿淮河干流展布的淮河构造变形带的断裂构造特征，分析了该构造变形带内中强地震与断层构造的关系，并结合淮河流域地球物理场资料的分析，提出了中强地震发生的地震地质标志。 相似文献
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全球及主要构造带大震活动状态研究 总被引：2，自引：0，他引：2
在定性分析全球、环太平洋地震带、低纬度环球剪切带和大三角地区(我国大陆西部及邻区)地震活动特征的基础上,使用 Morlet小波变换对其周期成分进行了定量计算,并应用 Nowcasting方法对各研究区域当前大震风险进行定量评估.结果显示,①全球大震活动显著周期为48.6 年,8.5 级以上地震的潜在危险性评分为 0.91.2004年开始的大震活跃时段可能仍将持续,发生 8.5 级以上地震危险性较大.②环太平洋地震带地震活动显著周期为48.6 年,其大震活动起伏特征与全球大体一致,8.5 级以上地震的潜在危险性评分为 0.91.2010 年开始的8.5级以上地震活跃时段持续时间尚短,发生 8.5 级以上地震的危险性较大.③低纬度环球剪切带地震活动显著周期为33.1 年,反映了该区8.0级以上地震的起伏活动,8.0级以上地震的潜在危险性评分为0.46.2004年开始的活跃时段可能趋于结束,未来 10年左右该区发生 8.0级以上地震的可能性较小.④大三角地区地震活动显著周期为 23.4年,发生 7.8级以上地震的潜在危险性评分为0.72.2001 年以来该区 7.8 级以上地震活跃,其活动状态与 20 世纪前 50年类似.23.4年的周期成分反映了20世纪前50年7.8级以上地震活动韵律特征.2015 年兴都库什7.8级地震后,该区可能进入了 7.8级以上地震相对平静时段,该时段可能持续 7～12 年,未来几年存在发生 7.8 级以上地震的可能,但危险性较小. 相似文献
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晋豫陕三省交界地区,是我国历史地震活动较强烈的地区.本文根据晋豫陕地震联防区编制的地壳厚度图,结合地面地质构造特征,对发生在该区的5级以上地震活动与上述构造的关系进行探讨,说明5级以上地震的发生与地面地质构造有一定的关系,且多发生在深部莫霍面隆起构造的斜坡上. 相似文献
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兰州地区活动构造的基本特征 总被引：5，自引：0，他引：5
兰州地区发育了NWW向和NWW向2组主导性活动构造带。大致以河口为界，东部地区主要为NWW向的马衔山－兴隆山左旋逆走滑活动断裂系，其新活动明显，是区内的主要控震断裂，1125年兰州7级地震就发生在其中的马衔山北缘断裂带的西端。河口以西为拉脊山北缘断裂和庄浪河断裂等1组NWW向的弧形逆冲断褶带，变形方式以断裂扩展褶皱为主，其新活动可能导致了138年金城－陇西63／4级地震、1440年永登61／4级地震和1995年永登5.8级地震的发生。兰州市区所在的兰州盆地则夹持在上述2组活动构造之间，其内同样发育了NWW向和NWW向的次级断裂，如刘家堡断裂、金城关断裂、雷坛河断裂及深沟桥断裂等，其上具有孕育和发生中强震的构造条件。 相似文献
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利用垂直向和波振幅比方法计算了2003年1月至2009年10月间宁夏北部及邻区的31个中小地震震源机制解,然后对计算所得的31个地震震源机制解进行系统聚类及应力场分析,并利用格点尝试法研究阿拉善区域（I区）和银川盆地及以北地区（II区）的平均震源机制解。结果表明：31个中小地震中走滑型地震占了近77％,显示出宁夏北部及邻近地区地震错动方式以近走滑为主;I区域地震产生的震源区构造变形是近南北向发生压缩,近东西向发生相对扩张;II区域构造应力场主压应力方向以水平作用为主,地震产生的震源区构造变形是北东向发生压缩,北西向发生相对扩张。 相似文献
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阪神·淡路大震灾后 ,日本着手对原有的地震观测体制作彻底改革 ,多项全国性配置地震计的计划同时开始启动。地震引起的地面晃动的程度不尽相同 ,无感微小地震引发的晃动仅有 0 .0 0 1 μm,频率为1 0 Hz;巨大地震引起的地面晃动的幅度高达 2～ 3 m,周期也有几十秒。虽说都称之为地震计 ,但由于地震动的振幅和频率涉及的范围太大 ,所以应针对观测对象选用不同类型的地震计。下面介绍不同类型的观测网。1 强震观测网 ( K- NET)无论大地有多大的晃动都能将其准确记录下来的地震计称之为强震计。它构造坚实 ,信号明确 ,通常设置在地表 ,对了… 相似文献
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In this study, we have checked the location and focal depth of the Yecheng earthquake (m b = 6.0, maximum intensity VII) of February 14, 1980. The result shows that this is an intermediate event with a focal depth of 90 km. The microepicenter is located at 36. 4°N, 76, 9°E, while the macroepicenter is at 37.3°N, 76.9°E, 90 km to the north of the microepicenter. This is the first destructive intermediate event in China which led to a damage as severe as of intensity VII. The focal mechanism of the event is determined to be of thrust type. Combined with the analysis of seismological and geological data in surrounding area, the possible relation between the event and plate movement has been discussed. The result in this paper indicates that in some particular place, the destructive effect of intermediate event should be considered in seismic hazard assessment. 相似文献
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Michael O. Garcia Diane Hanano Ashton Flinders Dominique Weis Garrett Ito Mark D. Kurz 《Bulletin of Volcanology》2012,74(6):1445-1463
The size, shape, and magmatic history of the most recently discovered shield volcano in the Hawaiian Islands, Mahukona, have been controversial. Mahukona corresponds to what was thought to be a gap in the paired sequence (Loa and Kea trends) of younger Hawaiian volcanoes (<4?Ma). Here, we present the results of marine expeditions to Mahukona where new bathymetry, sidescan sonar, gravity data, and lava samples were collected to address these controversies. Modeling of bathymetric and gravity data indicate that Mahukona is one of the smallest Hawaiian volcanoes (～6,000?km3) and that its magmatic system was not focused in a long-lived central reservoir like most other Hawaiian volcanoes. This lack of a long-lived magmatic reservoir is reflected by the absence of a central residual gravity high and the random distribution of cones on Mahukona Volcano. Our reconstructed subsidence history for Mahukona suggests it grew to at least ～270?m below sea level but probably did not form an island. New 40Ar–39Ar plateau ages range from 350 to 654?ka providing temporal constraints for Mahukona’s post-shield and shield stages of volcanism, which ended prematurely. Mahukona post-shield lavas have high 3He/4He ratios (16–21?Ra), which have not been observed in post-shield lavas from other Hawaiian volcanoes. Lava compositions range widely at Mahukona, including Pb isotopic values that straddle the boundary between Kea and Loa sequences of volcanoes. The compositional diversity of Mahukona lavas may be related to its relatively small size (less extensive melting) and the absence of a central magma reservoir where magmas would have been homogenized. 相似文献
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Sun, climate, hunger, and mass migration 总被引：9，自引：1，他引：8
Kenneth J. Hsu 《中国科学D辑(英文版)》1998,41(5):449-472
Paleoclimatic studies indicate four epochs of global cooling during the last 4 000 years, i. e. during the few centuries before
and after 2000 BC, 800 BC, 400 AD, and 1 600 AD; the quasiperiodicity corresponds to cyclic variation of solar activity. Global
temperature changes influenced regional precipitation patterns: Northern Europe was wetter while the middle- and low-latitude
lands were more arid during colder epochs. Both sets of cold climatical conditions were unfavorable for agricultural production.
Historical records show that large demographic movements in history took place because of crop failures and mass starvation,
rather than escaping from war zones. The “wandering” of the Germanic tribes during the first two or three centuries of the
Christian Era is one example. Whereas the accelerated release of carbon dioxide from the burning of fossil fuels is ultimately
to cause global warming, historical evidence indicates, however, that global warming has been on the whole a blessing to mankind.
Global cooling, on the other hand, has curtailed agricultural production and has led to famines and mass migrations of people.
Perhaps the most important task at the present is not so much computer-modelling of greenhouse effect on global climate, but
water-management and agricultural researches to insure food-supply for an everincreasing world population. 相似文献
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In this study, we experimentally established the relationship between physical properties, vitrinite reflectance, and microstructure of coal, Taiyuan Formation, Qinshui Basin, China using representative coal samples collected from three different mines via the rock mechanics testing system (MTS). We analyzed the organic macerals, vitrinite reflectance, and microstructure of 11 coal samples using petrography and scanning electron microscopy (SEM). The experimental results suggest that (1) the elastic parameters can be described by linear equations, (2) both P-and S-wave velocities display anisotropy, (3) the anisotropy negatively correlates with vitrinite reflectance, and (4) the acoustic velocities and Young’s modulus are negatively correlated with the volume of micropores. The derived empirical equations can be used in the forward modeling and seismic inversion of physical properties of coal for improving the coal-bed methane (CBM) reservoir characterization. 相似文献
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Abu Sayeed Shafiuddin Ahmed Mohammad Belal Hossain Saad Mohammad Omar Faruque Babu Moshiur Rahman Jun Sun Mohammad Shafiqul Islam Sarker 《国际泥沙研究》2022,37(1):83-96
Sediment samples from the Gomti River basin were investigated to determine and evaluate trace metal concentrations,their biological effect,and potential ecological and human health risks for adults and children.The mean concentrations of trace metals were organized in the descending order of mercury(Hg)(0.08 mg/kg)>chromium(Cr)(0.06 mg/kg)>lead(Pb)(0.05 mg/kg)>arsenic(As)(0.02 mg/kg)>cadmium(Cd)(0.01 mg/kg).The current study illustrated that metals were attributed to the area from natural sources and different anthropogenic sources especially from industries.However,the concentration levels were lower than the sediment quality guidelines(SQGs)based on the effect-range classifications of threshold effect concentration(TEC)and probable effect concentration(PEC).Therefore,the concentration of the elements showed no adverse biological effects on aquatic organisms.The evaluated potential ecological risk index also revealed the low toxicity to the aquatic environment.Moreover,the applied sediment quality indices,geo-accumulation index(Igeo),contamination factor(CF),and contamination severity index(CSI)suggested that the contamination levels of the elements were in the acceptable range,and the contamination had not notably impacted on the sediment quality.The risk index(HI)concerning age groups was significantly less than the threshold limit of 1 indicating that the contamination had no non-carcinogenic risk effect.The total carcinogenic risk(TCR)was less than a risk value of 1×104.Hence,the current study suggests that immediate remediation is not required due to an absence of alarming conditions in the study area.Proper monitoring of the attribution of the metal elements should be done for the betterment of human and environmental health。 相似文献