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对2016年10月20日江苏射阳M4.4地震的强震动记录进行初步分析,介绍强震动记录的一些基本特征。与ShakMap小震回归公式的预测数据比较,发现实际观测值总体高于预测值。通过对强震动记录的反应谱分析,认为本次地震对震中区建筑的影响轻微。在地震动等值线图产出过程中,采用数据偏差校正、场地效应及空间插值方法,使地震动等值线图的空间表达更为合理。其等值线图长轴呈北西向,与此次地震的主破裂面方向一致。结合地震现场调查结果,讨论了震中区的烈度分布与仪器烈度。 相似文献
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2021年5月21日云南省漾濞县发生密集强烈地震,震中区大量农房受损。本文先是根据部分台站强震动观测记录对地震动特性进行分析;然后归纳了震中8度区内各种结构类型农房的建筑结构特点;最后在对各类房屋震害现象进行实地踏勘的基础上,分析房屋的震害特征及震害原因。结果表明:当地大量采用的"三间四榀"传统木结构土墙围护住宅墙体破坏严重,经农危改加固的房屋木结构体系基本完整,未加固房屋的木构架有歪斜和节点拔榫现象;生产用房中单层砖木结构房屋震损较轻,土木结构房屋墙体严重破坏,局部坍塌,井干式房屋多数倾斜或扭转变形。 相似文献
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2015年7月3日新疆皮山MS6.5级地震灾区地处塔里木盆地南缘,该地自然条件恶劣,经济极为落后,灾区农村的民房除了抗震安居工程建设的房屋外,还有大量抗震性能较差的民居,在地震中受损严重,经济损失较大。灾区大部分位于山前溢出带,地下水位浅、地基土层软弱等场地条件对地震动有放大作用,震害影响范围较大。灾后重建中应继续加大安居富民工程的经费投入力度。灾区北部人口密集,地基土层软弱,工程地质条件差,建议在今后的安居富民建设中加强地基处理。 相似文献
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利用远场台阵反投影技术可以较少地依赖先验经验,于震后快速获得震源破裂过程时空分布特征,并据此估算矩震级。本文使用美国阿拉斯加宽频带台阵记录到的远场直达P波数据,基于反投影方法,对2023年9月9日摩洛哥MW6.9地震震源破裂过程及震级进行分析。结果显示,地震破裂走向以NE-SW向为主,地震能量在10～20s集中在震中距10km范围内释放,与震源机制解和震中区亚特拉斯山脉走向基本一致。震源破裂持续时间结合在全球分布均匀的GSN台网记录到的P波最大位移数据,在震后约15min即可快速估算出本次地震矩震级为MW7.0,与中国地震台网中心和美国地质调查局发布震级基本一致。 相似文献
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During surveillance on the toxicity of invertebrates such as bivalves inhabiting the coasts of Hiroshima Bay in 2001 and 2002, the carnivorous gastropod rapa whelk Rapana venosa collected in the estuary of Nikoh River, was found to contain toxins which showed paralytic actions in mice; the maximum toxicities (as paralytic shellfish poison, PSP) were 4.2 MU/g (May 2001) and 11.4 MU/g (April 2002). Their total toxicities were 224 and 206 MU/viscera of one specimen throughout the monitoring period. Attempts were made to identify the toxic principle in the gastropod. The viscera were extracted with 80% ethanol acidified with acetic acid, followed by defatting with dichloromethane. The aqueous layer obtained was treated with activated charcoal and then applied to a Sep-Pak C18 cartridge. The unbound toxic fraction was analyzed by high-performance liquid chromatography techniques. The gastropod toxin was rather unexpectedly identified as PSP. It was comprised of high toxic component (gonyautoxin-3; GTX3, GTX2, saxitoxin; STX) as the major components, which accounted for approximately 91 mol% of all components along with C1 and C2, which are N-sulfocarbamoyl derivatives. Judging from their toxin patterns, it is suggested that the PSP toxification mechanism of the gastropod that PSP toxins produced by phytoplankton such as Alexandrium tamarense, are transferred to and accumulated in plankton feeders such as the short-necked clam, and then transferred to this carnivorous rapa whelk R. venosa through predation. 相似文献
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An Aphanomyces sp. (Oomycetes) was found to be an important egg parasite of Eudiaptomus gracilis (Copepoda) in Lake Mondsee (Austria). The infection is evidenced by densely packed infection hyphae, attached with holdfasts and wrapped around the female's abdomen. The infection hyphae give rise to hyphae which penetrate the egg sac, and subsequently kill all eggs. The infection obviously has no pathogenetic effects on the egg-carrying female. Infected females appear during summer and fall, mainly in warm water layers. Infected egg clutches are found at all seasons of the year, indicating considerable birth control of the Eudiaptomus population by parasite infection. It seems possible that the actual Aphanomyces sp. is not the only parasite involved. 相似文献
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The littoral plankton of Lake Peipsi (3555 km2, mean depth 7.1 m) was studied in summer 1980 and 2000–2002, and the epiphyton was studied on two dominating macrophytes, Phragmites australis (Cav.) Trin. ex Steud. and Potamogeton perfoliatus L., in 2000. The purpose of the study was to estimate to what extent the littoral phytoplankton and epiphytic algae (their biomass, chlorophyll a content and dominant species) can be used as a criterion for the trophic state of the lake. In wind-open areas, phytoplankton biomass in the littoral is commonly more than ten times higher than in open water due to the presence of the macroscopic cyanobacterium Gloeotrichia echinulata (J.S. Smith) P. Richter. This alga is abundant in the moderately eutrophic northern lake's part and rare in the strongly eutrophic southern part; hence also biomass in the southern part is considerably lower. In open water, phytoplankton biomass increases southward with increasing trophy. Algal biomass in the littoral depends on wind direction and can change completely in a few days. Epiphyton biomass and Chla content increased southward with increasing trophic state. They both revealed significant Spearman correlations (P < 0.05) with wind index and transparency (negative), and with abundance of the host plant, both reed and pondweed (positive). The phytoplankton biomass of the littoral of the large and shallow Lake Peipsi can not be used as a criterion of trophic state, however, the species composition of the dominants, particularly cyanobacteria, is well applicable for this purpose. The biomass and Chla content of the epiphyton can be used as a criterion for trophic state. 相似文献
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Eliška Rejmánková Ji?í Komárek Margaret Dix Jaroslava Komárková Nancy Girón 《Limnologica》2011,41(4):296-302
Lake Atitlan, one of the most important lakes not only in Central America but in the whole world, is facing serious problems with increasing water pollution. Over the last several decades, the uncontrolled nutrient input into the lake has lead to high P levels and low N:P ratios, initiating cyanobacterial blooms. The first bloom occurred in December of 2008, followed by more extensive bloom in October 2009. The blooms are formed by cyanobacteria from the rare planktic Lyngbya hieronymusii/birgei/robusta complex. Based on the species morphology, the Atitlan population corresponds to L. robusta and this is the first case of reported bloom of this species worldwide. Remote sensing images documented that at the maximum bloom development, 40% of the 137 km2 of the lake area were covered by dense patches of Lyngbya, with the chlorophyll a concentration reaching over 100 μg L−1. The only toxins detected in the 2009 bloom were trace levels of cylindrospermopsin and saxitoxin with 12 and 58 ng g−1, respectively. The nitrogen fixation followed a pattern expected in non-heterocytous cyanobacteria, i.e., the nitrogenase activity was minimal during the day, while during the night the activity reached 2.2 nmol C2H4 μg Ch a−1 h−1. Delta 15N of −0.86‰ was well in the range given for nitrogen fixing organisms. The cell C, N and P content was 36.7%, 5.9% and 0.9%, respectively, resulting in the molar ratio of 105:14.4:1. A well designed and executed lake monitoring program, strict control of nutrient input into the lake, and public education are the necessary prerequisites for potential prevention of even more severe blooms than the one from 2009. 相似文献
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Tameshige Tsukuda 《Pure and Applied Geophysics》1988,128(1-2):261-279
To detect any temporal change in coda-Q associated with an earthquake of M 6.2, digitized data from analog magnetic records of microearthquakes for a small confined region just around its hypocenter have been processed, with special attention to measuring errors. The M 6.2 earthquake took place at the Misasa town, Tottori Prefecture, in southwest Japan with preceding anomalous seismicity changes. TheQ values were elevated 20% around three years before the M 6.2 event for frequencies of 5 to 20 Hz, and tended to decrease around two years before. Data with high quality show undulated temporal variation with a period of 5–6 years before the earthquake, which is correlated with the regional seismic activity. There is a possibility that the observedQ change stands for precursory effect of the medium-scale earthquake. The aftershock sequence also shows an undulated temporal variation ofQ with a period of 150 days for around 10Hz, correlating also with the seismic activity. The fracturing processes by numerous microearthquakes may be responsible for the attenuation property of randomly scattered seismic waves. 相似文献
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Floristic surveys, vegetation mapping, and detailed transect analyses rendered a macrophyte flora of 14 native and five alien taxa of flowering plants in the River Erft, a contributory of the River Rhine in Northrhine-Westphalia. Water temperatures of this river do not fall below 10 °C all the year round, for reasons of geothermically heated water discharged from nearby opencast mining areas. Macrophyte stand structures, composed of the neophytes Azolla filiculoides and Lemna minuta (floating) and Myriophyllum aquaticum, Egeria densa, and Vallisneria spiralis (rooted in the muddy or sandy ground of the river) are described and the ecological requirements of these taxa are characterized. The alien species can be seen as elements that increase the α-diversity of the aquatic vegetation of the River Erft. They do not replace any of the native species, even if shifts in the competition dynamics occur. The colonization by neophytes of the abnormally warmed River Erft can be appreciated as paradigmatic for trends in the macrophyte vegetation of medium-sized rivers in Central Europe when climate-related or discharge-based heating of the waterbody occurs and propagules of alien plants imported by waterfowl or – more important – plants from aquarium waste will find suitable places of existence and spread. 相似文献
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Rh. germanica is a European species that, due to human impacts, has progressively disappeared from its original territories and is now considered rare. In SwitzerlandRh. germanica has disappeared from the Aare, Broye and Kleine Emme rivers and is actually found in a limited reach of the River Rhine and some of its tributaries (Limmat, Sihl, Thur and Töss rivers).Rh. germanica is a univoltine species, hatching probably in summer. The emergence occurs from February to the beginning of April. It takes place on the water surface. Laboratory observations have shown that the subimaginal stage lasts four days.Rh. germanica occurs on different substrate types, ranging from stones and cobbles to pebbles and gravel. The larvae are more abundant in zones of erosion with coarse and porous sediments than in depositional zones with fine sediments and silts. They are most abundant in riffles with water velocities from 20 to 150 cm/sec. The species tolerates moderately organic-polluted waters.The particular strategy concerning growth and emergence ofRh. germanica is also discussed. 相似文献
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The weight-specific respiration rate (μl O2 mg−1 AFDW h−1) of three species of leech from Lake Esrom, Denmark, Glossiphonia concolor, G. complanata and Helobdella stagnalis was measured in a closed stirred chamber with a micro electrode. At declining oxygen concentration (mg O2 l−1) all three species expressed moderate ability to regulate respiration, in G. concolor and G. complanata down to 2 mg O2 l−1, in H. stagnalis down to 0.75 mg O2 l−1. Survival in anoxia was measured in closed bottles. The time to 50% survival (LD50) was 30 days in G. concolor at 20 °C and 30 and 4 days in H. stagnalis at 10 and 20 °C, respectively. The results were discussed in relation to habitat and spatial distribution of the three species in the lake. 相似文献
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A. Hofstetter A. Shapira K. Bulehite T. Jones K. Mafi A. Malitzky A. Papabatu G. Prasad M. Regnier G. Shorten A. Singh M. Stephen L. Vuetibau 《Journal of Seismology》2000,4(3):285-296
We studied the relationships between the frequency ofoccurrence and the magnitudes in seismogenic areasthat will affect four capital cities in the SouthPacific, namely: Honiara in Solomon Islands, Port Vilain Vanuatu, Suva in Fiji and Nuku'alofa in Tonga. Weused the NEIS catalogues for the period 1973–1997, formagnitudes greater than about 5, in the proximity tothe city under investigation. The definitions of thegeographic boundaries of the seismogenic zones arebased on the classical concepts of the distribution ofthe tectonic plates, the overwhelming number ofstudies that describe the seismotectonics in thoseactive regions and on the observed seismicity andstudies of the local people. Completeness of thecatalogue is assumed because of the high seismicity inthese areas, despite the relatively short time span.We have used a hybrid process combining least squaresfitting and Newtonian search process to find the bestfit of the statistical parameters. The characteristicb value is 1.27, and seems to be irrespective of thedepth and/or region. 相似文献
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2017年8月8日四川九寨沟发生MS7.0地震,该地震发生在巴颜喀喇块体的东北边界,震中区域构造条件复杂,是巴颜喀喇块体北侧左旋走滑环境向东侧逆冲挤压环境过渡的位置,附近地区历史强震较多。九寨沟地震是一次主-余型地震,余震活动水平较弱,主震发生后短时间内ML≥4.0余震的“等待时间”存在异常,震后较长时间余震活动恢复到正常状态,序列h值、余震视应力等符合主-余型序列特征。序列b值为0.84,G-R关系推测序列最大余震的震级约为ML5.4（MS5.0）,8月9日发生的MS4.8地震是目前该序列的最强余震。通过与1970年以来附近地区7级左右地震序列的对比认为,九寨沟地震与1976年松潘-平武2次7.2级地震序列在余震空间位置、发震构造和震源机制等方面存在较大差异,因此,不具备发育为震群型序列的条件。九寨沟地震主震视应力为0.36～0.38MPa,属于应力下调模型,序列余震的平均视应力水平接近龙门山断裂带附近中小地震的平均背景水平。 相似文献