上海数字强震观测网

上海市数字强震观测网是我国第1个具有一定规模的数字强震观测网，是上海市“九五”期间建设完成的，它由3部分组成；地面观测网，结构观测网和深井强震观测系统，每一部分都有不同的功能和目的，本文详细介绍该强震网的整个概况。功能及取得的部分观测成果。     

浅析宏观观测网的建设

结合临汾市地震宏观观测网的建设情况,叙述了宏观观测网建设的必要性,并就当前地方地震系统怎样抓好地震监测主战场的工作提出了一些看法。     

日本强化地震观测网防范首都地震

日本文部科学省日前决定，从2007年起利用5年时间强化覆盖东京及周边地区的地震观测网，详细调查这一区域的地下构造，以防范可能发生的首都直下型地震。     

我国地震井水位观测网监测效能评估

"十五"数字化网络项目完成后,我国地震井水位观测网已颇具规模。为了摸清其监测现状,为未来台网优化改造、仪器更新提供依据,开展了观测网的清理和监测效能评估。评估结果显示,总体上,观测网中有61.8%的水位观测站监测效能良好。有73.5%的观测站的观测环境符合地震井水位观测要求;观测网的运维状态总体趋好,有75%的观测仪器的运行率在95%以上;大部分的水位观测站监测地壳应力变化、地震活动的能力较强。但仍然有些观测站,因观测井先天不足、环境干扰、仪器老化、运维水平低等问题,亟待通过观测环境改造、仪器更新、运维管理培训等措施来提高监测效能。大约有6.5%的观测站因观测环境不合格需要停测。     

不断改进的日本气象厅地震观测网与处理系统

气象厅的地震观测网和处理系统一直在不断地调整、更新和强化 ,因此检测能力也在不断提高 ,这早已是有目共睹的了。总的来说 ,气象厅开展确定震源的工作是1 92 6年以后开始的 (其中有一部分是 1 92 3年关东地震时收集的资料 ,计算震源时需要参考过去的和未来一段时间的一些资料 )。 1 884年以前的震源资料从理科年表 ( 2 0 0 1年版 )中的灾害地震表查找 ;1 885～ 1 92 5年的依据宇津( 1 982 ,1 986)的资料 ;1 92 6～ 1 960年期间的可以从地震月报增刊第 6号 ( 1 982 )查找 ,这些数据都是经过再次计算过的。虽说“增刊第 6号”是最新的结果 ,…     

两位院士建议建立电磁观测网预测地震

20 0 2年 3月下旬 ,我国著名地震学家马宗晋院士和著名无线电通讯专家陆建勋院士建议 ,建立电磁观测网 ,以同时捕捉地震活动“源和场”的异常信息。如果这种综合技术系统被应用 ,就可能使我国地震预测进入一个全新的阶段。这种电磁观测网以极低频 /超低频技术为核心 ,是既可以监测地壳深层结构的变化 ,同时又可以对地震的电磁波扰动和电离层变化进行观测的综合性的最新技术。陆建勋院士说 ,地震预测仍是地球科学的世界性难题。其难点包括科学和技术两个方面 ,前者主要是指由于地震成因和孕震过程复杂 ,地震学家至今对地震发生机理缺乏足够的…     

日本即时公开全国规模强震观测网的记录

强烈地震动的计测称之为强震观测。强震观测不仅记录大地震的走时过程，而且还测到具有广义强震观测的强地震动的最大值和计测烈度。强震观测在经历阪神大震灾后10年期间有了很大的变化，取得引人注目的进展和成果。     

我国地震前兆观测井水位观测网监测效能评估分析

“十五”数字化网络项目完成后,我国地震前兆观测井水位观测网已颇具规模。为了摸清其监测现状,为未来台网优化改造、仪器更新提供依据,开展了观测网的清理和监测效能评估。评估结果显示,总体上,观测网中有61.8%的水位观测站监测效能良好。 73.5%的观测站观测环境符合地震井水位观测要求,75%的观测仪器运行率在95%以上。观测网的运维状态总体趋好,大部分的井水位监测地壳应力变化、地震活动的能力较强。但仍然有些观测站,因观测井先天不足、环境干扰、仪器老化、运维水平低等问题,亟待通过观测环境改造、仪器更新、运维管理培训等措施来提高监测效能水平。大约有6.5%的观测站因观测环境不合格需要停测。     

立式浮顶储罐并联基础隔震模拟地震振动台试验研究

立式浮顶储罐在强震作用下会发生罐壁屈曲、卡顶、浮顶下沉等震害。为降低储罐地震响应,以1 000 m3储罐为原型,按1:5的几何相似比设计缩尺模型,并以隔震周期为0.5 s进行并联隔震装置设计,给出其力学本构关系。采用模拟地震振动台试验方法,选取四种不同频谱特性的地震动对模型罐进行地震响应分析,结果表明:隔震层顶部加速度卓越频率有所降低,周期延长;隔震后储罐加速度、层间位移及动应力地震响应明显降低,但晃动波高有所放大;三向地震激励与单向地震激励相比,加速度地震响应明显放大,对晃动波高影响较小。建议储罐抗震减震设计时应考虑三向地震作用。     

试论我国地下水位动态观测网布局原则、方法与效果

1979年,我国决定建立第二代地震地下水观测网。本文总结了自邢台地震以来地震地下水研究方面的主要经验、教训,参照国外有关建网的资料,提出深浅结合、点面结合,开展场的观测.控制活动性断裂等一套具有我国特色的建网思想。在近几年建网工作中,此文提出的原则与方法已付诸实施     

Age, geology, geophysics, and geochemistry of Mahukona Volcano, Hawai`i

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.     

The Yecheng,Xinjiang, China,earthquake of February 14, 1980

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.     

Physical properties,vitrinite reflectance,and microstructure of coal,Taiyuan Formation,Qinshui Basin,China

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.     

山西高平地震

阐述了发生在山西高平的地震和对高平有影响的地震，分析了高平市的地震灾害，通过分析得出高平地震与晋获断裂带活动有关的结论。     

Spatial distribution,source apportionment,and associated risks of trace metals (As,Pb, Cr,Cd, and Hg) from a subtropical river,Gomti, Bangladesh

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。     

Seismicity at Fuego,Pacaya, Izalco,and San Cristobal Volcanoes,Central America, 1973–1974

Seismic data collected at four volcanoes in Central America during 1973 and 1974 indicate three sources of seismicity: regional earthquakes with hypocentral distances greater than 80 km, earthquakes within 40 km of each volcano, and seismic activity originating at the volcanoes due to eruptive processes. Regional earthquakes generated by the underthrusting and subduction of the Cocos Plate beneath the Caribbean Plate are the most prominent seismic feature in Central America. Earthquakes in the vicinity of the volcanoes occur on faults that appear to be related to volcano formation. Faulting near Fuego and Pacaya volcanoes in Guatemala is more complex due to motion on a major E-W striking transform plate boundary 40 km north of the volcanoes. Volcanic activity produces different kinds of seismic signatures. Shallow tectonic or A-type events originate on nearby faults and occur both singly and in swarms. There are typically from 0 to 6 A-type events per day withb value of about 1.3. At very shallow depths beneath Pacaya, Izalco, and San Cristobal large numbers of low-frequency or B-type events are recorded with predominant frequencies between 2.5 and 4.5 Hz and withb values of 1.7 to 2.9. The relative number of B-type events appears to be related to the eruptive states of the volcanoes; the more active volcanoes have higher levels of seismicity. At Fuego Volcano, however, low-frequency events have unusually long codas and appear to be similar to tremor. High-amplitude volcanic tremor is recorded at Fuego, Pacaya, and San Cristobal during eruptive periods. Large explosion earthquakes at Fuego are well recorded at five stations and yield information on near-surface seismic wave velocities (α=3.0±0.2 km/sec.).     

Sun, climate, hunger, and mass migration

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.