共查询到20条相似文献，搜索用时 125 毫秒
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1989年4月16日5时,四川省巴塘发生M_s6.7级地震。距离震中约200公里的甘孜地震台,在震前观测到了较明显的地温短临异常。 相似文献
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地下水位短临异常演化特征及其与地震关系的研究 总被引：3，自引：1，他引：3
本文对1976年唐山地震以来华北地区Ms≥5．0地震前的地下水位异常资料进行了系统整理，分析研究了水位短临前兆异常的时空演化特征及其与地震的关系。结果表明：震前水位短临异常的空间分布主要集中在一定范围并沿活动断裂带展布，且不均匀；大部分地震的水位短期异常较临震异常多；震前水位短期异常向临震异常过度时，分布区向震源区收缩，但在震中距100km左右以内这种现象不明显；震级与短临异常展布范围、短期异常幅度有一定关系，而与临震时期异常大小的关系不明显；地震发震时间与异常的超前、持续以及等待时间有关；地震发生地点与异常分布特征有关，震中往往不在短临异常集中区的几何中心，而是在异常范围内的某一侧或异常迁移方向附近。 相似文献
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邢台地震的气象要素异常特征 总被引：1，自引：0，他引：1
通过对邢台地震前后河北省数十年气象资料的研究与分析，发现邢台地震前气象要素存在明显的异常特征。大气压力、大气温 度显示出短临震兆信息，降水量呈现了中长期异常，浅层地温的震前异常升温特征则较为突出，文章汇总了邢台地震前各气象要素的异常变化，并进行了讨论。 相似文献
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1976年唐山7.8级地震前气象要素的异常变化 总被引：2，自引：0，他引：2
系统研究了唐山地震前气象要素的异常变化。地震前约一个月时间，震中及附近地区月平均气压变化幅度最大，月平均气压距平中心区域与震中区吻合，沿区域构造带方向出现气压变化最大梯度区，临震前几天气民较大幅度的升、降变化过程，升压脊 区域构造瞳向吻合。地震前一年，丰润、唐山一带年平均气温距平值最大，地震前一天，气温２４小时变温的升温中心在唐山，升温脊受区域构造带控制。０．８ｍ地温亦有明显的升温异常变化。１９７ 相似文献
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本文研究了强地震发生前半年至一年时间尺度上浅层地温异常变化的分布特征和震前几天至一个月大气压力、气温变化的分布特征,据此提出了强地震短临预报的气象学方法.根据强地震前浅层地温(0.8m～3.2m深的温度)距平存在六个月以上正距平且有一定的幅度和距平等值线给出的升温中心确定强地震发生的背景异常,一般升温中心即未来震中,在此基础上分析浅层地温升温中心区域大气压力和气温的变化幅度及分布特征.研究发现,在地温升温中心区域,地震前约一个月时间内,月平均气压变化幅度最大,气压距平中心与地温升温中心基本吻合,沿构造带走向有气压变化的最大梯度区;大气环流发生突变,单站气压往往发生持续性变化,有持续下降和上升的过程,其低值一般达历年同日平均气压的最低值,变化幅度超过11百帕.根据多个震例的研究,本文提出了3条强震发生的背景异常判别指标和3条临震预报指标,震级强度≥6.0. 相似文献
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张北6.2级地震地温短临异常特征 总被引：5，自引：0，他引：5
张北地震前４０天左右,在距该震中１００－２００ｋｍ的河北阳原三马坊、北京塔院和延庆五里营地温测点先后出现典型地温短临异常,异常幅度为０．００１－０．０１℃,据此作了一定程度的预报姑震级和震中距相近的条件下,三马坊测点在张北地震前的地温异常变化幅度仅为大同阳高地震前的１／１０,这可能与构造条件有关。在该地震的映震范围内有关兆反应的地温测点所占比比例为２７％。 相似文献
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伽师—阿图什6.7级地震阿图什地倾斜异常特征 总被引：2，自引：0，他引：2
１９９６ 年３ 月１９ 日新疆伽师—阿图什地区发生了６．７ 级强烈地震。震前阿图什地震台倾斜仪记录的中短期和短临前兆异常特征为：中短期趋势性异常的方向向背离震中的方向倾斜,持续了１３个月;震前两个月趋势异常出现短期恢复,之后加速异常;临震前５ 天异常快速恢复,并伴有观测值的临震突跳现象,地震发生在异常的恢复之中 相似文献
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本文对2016年青海门源MS6.4地震之前震中周边前兆台站的观测资料进行了回顾性分析,结果显示有15项定点前兆测项震前呈异常,主要集中在距震中300 km的范围内,其中形变类异常最先出现,之后以流体类异常为主,临震阶段以电磁类异常为主。震前前兆异常的演化在时空上具有阶段性和迁移性,震前异常出现时间随震中距的变化划分为三个阶段:α阶段为远源场前兆异常从震中向外围扩散的过程,异常主要出现在震前390—630天;β阶段为前兆异常大范围分布,主要出现在震前100—200天;γ阶段主要为近源场异常向外扩散。 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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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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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
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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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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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Transitional, entraining, cloudy, and coastal boundary layers 总被引：2，自引：0，他引：2
Wayne M. Angevine 《Acta Geophysica》2008,56(1):2-20
Atmospheric boundary layers are marvelously varied and complex. Recent research has examined some of that variety. Boundary
layers over land undergo drastic changes throughout the day as the sun rises and sets, and as clouds form and dissipate. Air
is entrained at the top of the boundary layer at varying rates. As air moves over the coast, the boundary layer reacts to
changes in surface forcing. All of these changes affect pollutant transport and weather formation. In this paper, research
attempting to understand transitional, cloud-topped, and coastal boundary layers, and boundary-layer top entrainment, is reviewed. 相似文献
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Dynamics of dissolved major (Na,K, Ca,Mg, and Si) and trace (Al,Fe, Mn,Zn, Cu,and Cr) elements along the lower Orinoco River 
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下载免费PDF全文 Abrahan Mora Jürgen Mahlknecht Juan Carlos Baquero Alain Laraque Juan A. Alfonso Daniel Pisapia Laura Balza 《水文研究》2017,31(3):597-611
This study addresses the changes in dissolved major and trace element concentrations along the Orinoco River, including the mixing zone between the Orinoco and Apure Rivers. Water samples from the Apure and Orinoco Rivers were collected monthly in four sectors over a period of 15 months. Auxiliary parameters (pH, dissolved oxygen, conductivity, and temperature), total suspended sediments, dissolved organic carbon (DOC), and major (Na, K, Ca, Mg, and Si) and trace (Al, Fe, Mn, Zn, Cu, and Cr) element concentrations were measured in all sectors. The relative contribution of both rivers after the Apure–Orinoco confluence was determined using Ca as a tracer. Moreover, a mixing model was developed to determine whether dissolved species exhibit a conservative behavior during mixing. The results indicate that DOC is removed from waters during the Apure–Orinoco mixing, probably due to absorption of DOC on mineral phases supplied by the Apure River. Dissolved Na, Ca, and Mg behave conservatively during the mixing processes, and their concentrations are controlled by a dilution process. The anomaly in the temporal pattern of K in the Orinoco is caused by the input of biogenic K originating from the Apure River during the high‐water stage. The loss of dissolved Si during the low‐water stage can be explained by the uptake of Si by diatoms. Dissolved Mn, Zn, Al, and Fe showed a non‐conservative behavior during the Apure–Orinoco mixing. The removal of Mn and Zn from the dissolved phase can be explained by the formation of Mn‐oxyhydroxides and the scavenging of Zn onto Mn oxides. Dissolved Fe is controlled by redox processes, although the removals of Fe and Al due to the preferential adsorption of large organometallic complexes by mineral surfaces after the Apure–Orinoco confluence can affect the mobility of both elements during transport. The conservative behavior shown by Cu and Cr can be related to the tendency of both elements to be complexed with small organic colloids, which are not preferentially adsorbed by clays. 相似文献