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1.
2021年5月21日云南漾濞县发生M_S6.4地震、5月22日青海玛多县发生M_S7.4地震,分别分析漾濞震中500 km内12个地电场台数据、玛多震中500 km内8个地电场台数据,获知:(1)漾濞地震周围罗茨等8台优势方位角在震前出现了异常变化,弥渡等4台看不出明显异常变化;盐源等7台相关系数在震前2～6个月出现了大幅度下降,元谋、苴林等5台相关系数看不出明显异常变化。(2)玛多地震周围门源等4台方位角在震前出现了异常变化,都兰等4台方位角看不出明显异常变化;门源等5台在玛多地震前2～6个月相关系数出现了大幅下降、变化范围明显变窄等现象,都兰、白水河、金银滩等3台优势方位角和相关系数都看不出明显异常变化。(3)两次地震分析中地电场优势方位角和相关系数异常变化在时间上皆具有同步或准同步性。 相似文献
2.
为基于谱比方法研究海底地震动场地效应,选取日本DONET1台网的20个海底台站2014—2021年记录的1634组地震数据,对其进行筛选和处理后,利用水平与竖向谱比（HVSR）方法考虑不同布设对海底5组节点台站（KMA、KMB、KMC、KMD、KME）谱比特征的影响。研究结果表明:KMA与KME节点台站具有相似的场地特征,KMB与KMD节点台站分散布置在2种场地,KMC节点台站场地与其他节点均不相似,这与长期地质调查结果相似;海底台站谱比曲线呈多峰值现象,其中KMB、KMC、KMD分组台站利用HVSR方法识别的主频变异性较高,KMA、KME分组台站主频较稳定;相同地形条件下,布设方式相同的海底台站谱比曲线随频率分布相似,海底复杂场地条件下,采用装沙沉底方式布置的台站识别场地条件时出现偏差;海底复杂因素对掩埋沉箱方式布设的台站谱比曲线的影响主要集中在频率<5 Hz的低频处;海底复杂因素对未埋入海底台站谱比曲线的影响主要集中在频率为5—10 Hz的高频处。研究结果可为海底地震动场地效应研究提供参考。 相似文献
3.
选取位于东部沿海的高邮、新沂、陵阳、昌黎4个台站2011年全年12个月的地电场分钟值观测资料,利用小波变换法计算其半日波,与位于内陆的大同、石嘴山、古丰台进行对比,分析沿海地区地电场半日波日变幅的变化规律,研究得到:(1)高邮等4台在2011年部分月份单月发生2次半日波日变幅增大、减少的现象,同一台站不同月份此现象的发生时间几乎一致(阴历日期),不同台站同一月份此现象的发生时间不同,而位于内陆地区的地电场台站未观测到此现象。(2)通过研究台站测区及周围环境与半日波日变幅变化的相关性,初步分析认为位于沿海地区的台站是否容易观测到半日波日变幅周期性变化可能与测区是否紧邻大型水系有关;而位于沿海地区的台站观测到地电场半日波日变幅每月2次增大、减少的发生时间可能与台站的地磁经度有关。(3)探讨了引起东部沿海地区半日波日变幅周期性变化的可能原因。 相似文献
4.
云南孟连西7.3级、武定6.5级、丽江7.0级三次强震前地震波振幅比的时空演化特征 总被引：1，自引：0，他引：1
１９９５年７月１２日至１９９６年２月３日短短７个月,云南地区连续发生了孟连西中缅边境７．３级、武定５．５级、丽江７．０级３次强震,本文研究了近期这几次强震前５个地震台地震图垂直分量Ｓ、Ｐ波最大振幅比的时空演化特征,动态追踪了振幅比明显偏离平稳态的突变过程。发现主震前５—８年,７级大震震中１００ｋｍ范围出现振幅比高（低）值突变,６级强震震中１３０ｋｍ范围出现振幅比高值突变,当振幅比的突变在缓升（降）的背景上骤升（降）,或突变异常的地震次数明显增加,则中长期异常进入中短期阶段。在强震震中１３０ｋｍ范围内的地震台（近台）振幅比值高达１５．２以上,而远离强震震中２５０ｋｍ以外的地震台（远台）振幅比最大值仅为９．８,近台的突变幅度至少比远台大３０％。而强震成组发生前一年半时间内,位于强震震中１１０ｋｍ范围内的近台振幅比的突变幅度比远在２５０ｋｍ外远台大５５—７５％。对振幅比的突变和时空演化特征从非线性动力学模型和模拟实验结果进行了初步成因探讨。 相似文献
5.
新疆地震台网对新疆呼图壁大容量气枪震源信号的接收能力及其影响因素分析 总被引：4，自引：4，他引：0
利用新疆地震台网资料和功率谱密度法,以台站噪声的功率谱密度中值曲线作为评估台站噪声水平的依据,对6个台站的噪声水平进行了评估。对比不同台站的功率谱密度和气枪震源信号的识别情况发现,通过2000次叠加,可以识别气枪震源信号的台站的噪声水平均低于无法识别气枪震源的台站,噪声功率谱密度最大差值为40dB,最小差值15dB。最后通过对噪声水平的评估,判断部分台站无法识别气枪震源信号的主要原因是台站噪声水平较高造成的。 相似文献
6.
Peroxisomal proteomics was applied to assess possible biological effects after the Prestige’s oil spill. Mussels were sampled in July 2004 and 2005 in four stations in the NW (closest to the spill) and NE coasts of the Iberian Peninsula. Principal components analysis (PCA) suggested differences in protein expression among stations and sampling years. Several proteins were putatively identified by mass spectrometry and immunolocalization. PC1 separated the NW stations in 2004 from the rest of the stations and sampling years mainly due to up-regulation of peroxisomal β-oxidation proteins and PMP70. PC3 separated the NE stations, based on up-regulation of the antioxidant enzyme catalase in 2004 compared to 2005. PC4 separated the stations in the NE and the NW. This work shows that environmental proteomics, together with multivariate data analysis, could provide information to interpret the effects of oil spills at cellular level in mussels. 相似文献
7.
基于北京市测震台网连续三分量地震计波形数据，计算28个测震台站台基噪声，利用Welch方法计算噪声功率谱密度（PSD），进而计算地震台台基1-20 Hz地动噪声均方根值（RMS）和观测动态范围。结果表明，依照《地震台站观测环境技术要求》，北京市测震台网中有11个Ⅰ类台、9个Ⅱ类台、6个Ⅲ类台、2个Ⅳ类台。通过分析北京市测震台网数字地震台背景噪声水平，为测震台网的规划建设提供数据支持。 相似文献
8.
目前基于海底实测记录的分析发现海底与陆地地震动特性存在明显差异,但难以进一步确定海底地震动特性的影响因素。在以往研究的基础上对比同次地震中相邻海底台站间地震动特性的差异,并分析造成差异的原因。以日本K-NET地震台网中6个海底强震台站及其相邻不同场地条件陆地台站监测的8次强震记录为研究对象,通过分析强震记录的峰值加速度、水平放大系数谱、竖向与水平反应谱的比谱等,对比分析不同海底台站地震动的特性,以及海底台站与相邻不同场地条件陆地台站地震动特性的差别。研究发现：（1）海底与陆地竖向地震动存在明显差异;（2）不同海底台站间地震动特性亦存在较大差异和明显的规律性,海底场地条件、地形等场地因素对海底地震动特性的影响较大;（3）海底水平向地震动反应谱的特征周期较大,谱特性介于陆地中硬土与软土场地间。 相似文献
9.
Sediment quality of the lower St. Johns River (LSJR) estuary, Florida was evaluated using synoptic data on benthic community structure, levels of potential stressors (chemical contaminants, ammonia and sulfide), and other basic habitat characteristics (depth, dissolved oxygen, salinity, temperature) collected at seven stations, three times a year from July 2000-July 2002. Un-ionized ammonia and hydrogen sulfide were detected at toxic levels on at least one sampling occasion at four stations. Chemical contamination of sediment at probable bioeffect levels also was observed at four stations. Concentrations of pesticides or other chemical substances typically associated with human activities (e.g., PCBs) were detectable at all stations, though not always present at concentrations likely of causing significant bioeffects. A total of 251 taxa and 9783 individuals were identified and enumerated from the benthic infaunal samples. Polychaete worms and molluscs dominated the benthic fauna at all seven stations. The opportunistic and pollution-tolerant polychaete Streblospio benedicti was the most abundant species overall (from all samples combined), appearing as a dominant at five of the seven stations. Overall, the sites sampled as part of this study indicate a highly stressed benthos resulting from multiple anthropogenic impacts. 相似文献
10.
雷电危害是影响地震台站稳定运行的重要因素之一,对台站进行雷电防护具有重要意义。介绍冬奥会保障项目地电阻率台站改造中避雷系统的设计,并重点分析研究地电阻率台站架空线路防雷、地埋线路防雷等关键技术点出现的问题,探讨地电阻率台站综合防雷系统在接地网、供电、综合布线等方面的整体设计,最后设计完成宝昌台防雷技术系统。在此基础上,完成项目全部8个台站的避雷系统方案设计,全面提升冬奥会项目台站的防雷实效。通过计算,在项目深化研究中得到一些新的技术成果:(1)地电阻率台站应尽量将供电及测量线路进行埋地;(2)埋地供电及测量线路应避开接地体10 m以上;(3)仍采用架空线路的台站可以安装相应电流值的信号防雷器。研究成果可供今后全国台站防雷系统建设时参考。 相似文献
11.
Non-stationary frequency analysis of extreme precipitation in South Korea using peaks-over-threshold and annual maxima 总被引：2，自引：2，他引：0
Sungwook Wi Juan B. Valdés Scott Steinschneider Tae-Woong Kim 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(2):583-606
The conventional approach to the frequency analysis of extreme precipitation is complicated by non-stationarity resulting from climate variability and change. This study utilized a non-stationary frequency analysis to better understand the time-varying behavior of short-duration (1-, 6-, 12-, and 24-h) precipitation extremes at 65 weather stations scattered across South Korea. Trends in precipitation extremes were diagnosed with respect to both annual maximum precipitation (AMP) and peaks-over-threshold (POT) extremes. Non-stationary generalized extreme value (GEV) and generalized Pareto distribution (GPD) models with model parameters made a linear function of time were applied to AMP and POT respectively. Trends detected using the Mann–Kendall test revealed that the stations showing an increasing trend in AMP extremes were concentrated in the mountainous areas (the northeast and southwest regions) of South Korea. Trend tests on POT extremes provided fairly different results, with a significantly reduced number of stations showing an increasing trend and with some stations showing a decreasing trend. For most of stations showing a statistically significant trend, non-stationary GEV and GPD models significantly outperformed their stationary counterparts, particularly for precipitation extremes with shorter durations. Due to a significant-increasing trend in the POT frequency found at a considerable number of stations (about 10 stations for each rainfall duration), the performance of modeling POT extremes was further improved with a non-homogeneous Poisson model. The large differences in design storm estimates between stationary and non-stationary models (design storm estimates from stationary models were significantly lower than the estimates of non-stationary models) demonstrated the challenges in relying on the stationary assumption when planning the design and management of water facilities. This study also highlighted the need of caution when quantifying design storms from POT and AMP extremes by showing a large discrepancy between the estimates from those two approaches. 相似文献
12.
采用基于概率的完整性震级（PMC）方法，选取上海测震台网13个地震台站及周边省市地震台2008-2019年记录的171个地震，计算各地震台及上海测震台网地震监测能力，并模拟增加新的地震台站后台网监测能力的变化。结果显示：①地表基岩台的监测能力较深井台强，且受噪声和地铁影响，市区深井台监测能力较低；②整体上，台站密布的松江和青浦地区，地震监测能力较强，最小完整性震级为ML 0.7。台站稀疏的浦东、奉贤、崇明地区，地震监测能力较弱，最小完整性震级为ML 1.3；③若在上海南部增设奉贤海湾台，可整体提高上海测震台网的监测能力。 相似文献
13.
本文把模糊模式识别的直接方法用于综合分析多台多种手段观测到的地震前兆资料,以便提取较大地震前几个月内可能出现的中短期前兆异常信息。 所用方法的基本技巧是,对每一个台的每一种前兆观测手段建立起适当的前兆从属函数,并进而确定出多手段或多台的综合前兆从属函数。首先以综合前兆从属函数为基础,识别出某一地区较大地震前出现的中短期前兆异常,然后将其归纳成可用于地震预报的中短期前兆模式。 借助于所提出的方法,本文着重分析处理了1979——1986年间日本东海地区及其邻近地区3个倾斜台、2个验潮站、2个水氡观测站、2个水位观测点和30个体积应变观测点的大量前兆观测资料,识别出了这一期间在该地区内发生的10余次6级以上地震前的中短期前兆异常时间,并得出了两类地震前兆模式:第一类前兆模式适用于在该地区内进行多种前兆手段的综合分析预报;第二类前兆模式适用于单种前兆手段(体积应变)的多台综合分析预报。 为对比起见,文中同时给出了我国唐山7.8级地震及其6.9级强余震前多台水氡含量变化的中短期前兆综合分析识别结果,所得出的前兆模式与日本东海地区的第二类前兆模式相符。 相似文献
14.
Investigation of spatial and temporal variability of precipitation in Iran over the last half century 总被引：4，自引：1，他引：3
Keivan Khalili Mohammad Nazeri Tahoudi Rasoul Mirabbasi Farshad Ahmadi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(4):1205-1221
Investigation of the precipitation phenomenon as one of the most important meteorological factors directly affecting access to water resources is of paramount importance. In this study, the precipitation concentration index (PCI) was calculated using annual precipitation data from 34 synoptic stations of Iran over a 50-year period (1961–2010). The trend of precipitation and the PCI index were analyzed using the Mann–Kendall test after removing the effect of autocorrelation coefficients in annual and seasonal time scales. The results of zoning the studied index at annual time scale revealed that precipitation concentration follows a similar trend within two 25-year subscales. Furthermore, the PCI index in central and southern regions of the country, including the stations of Kerman, Bandarabbas, Yazd, Zahedan, Shahrekord, Birjand, Bushehr, Ahwaz, and Esfahan indicates a strong irregularity and high concentration in atmospheric precipitations. In annual time scale, none of the studied stations, had shown regular concentration (PCI < 10). Analyzing the trend of PCI index during the period of 1961–2010 witnessed an insignificant increasing (decreasing) trend in 16 (15) stations for winter season, respectively, while it faced a significant negative trend in Dezful, Saghez, and Hamedan stations. Similarly, in spring, Kerman and Ramsar stations exhibited a significant increasing trend in the PCI index, implying significant development of precipitation concentration irregularities in these two stations. In summer, Gorgan station showed a strong and significant irregularity for the PCI index and in autumn, Tabriz and Zahedan (Babolsar) stations experienced a significant increasing (decreasing) trend in the PCI index. At the annual time scale, 50 % of stations experienced an increasing trend in the PCI index. Investigating the changes in the precipitation trend also revealed that in annual time scale, about 58 % of the stations had a decreasing trend. In winter, which is the rainiest season in Iran, about 64 % of stations experienced a decreasing trend in precipitation that caused an increasing trend in PCI index. Comparing the spatial distribution of PCI index within two 25 years sub-periods indicated that the PCI index of the second sub-period increased in the spring time scale that means irregularity of precipitation distribution has been increased. But in the other seasons any significant variations were not observed. Also in the annual time scale the PCI index increased in the second sub-period because of the increasing trend of precipitation. 相似文献
15.
《Journal of Atmospheric and Solar》2002,64(3):307-313
The virtual (or minimum) height of the F-region (h′F), recorded over a number of solar cycles for 11 equatorial and mid-latitude ionosonde stations, was used to deduce the hemispheric (i.e. southern or northern hemisphere) character of equatorial stations. The semi-annual median monthly height (h′F) variations consist of two components: major local summer maximum and winter sub-maximum (about 5 percent of the summer maximum). This hemispheric pattern was most consistently observed for equatorial stations (within 5° of the geomagnetic equator) in a period centred on the local midnight (21-03 LT) but was also present, to a lesser extent, at mid-latitude stations and at other time intervals. It is evident that the physical parameter h′F defines the hemispheric character of an equatorial station which has different (sometimes opposite) geographic and geomagnetic latitudes.There is a sharp transition in the latitudinal character of the stations on both sides of the equator leading to hypothesis that the equal maxima in h′F in December and June solstices are observed at a near-equator position labelled as ionosonde deduced equator (IDE). Such a signature was observed for an American equatorial (both geographic and geomagnetic) station Talara (Peru) which is an experimental support of the hypothesis. The IDE can be another useful parameter characterising the equatorial ionosphere. This finding reveals a new application of the standard ionosonde data in defining the geophysical character of equatorial stations, being an important contribution to space climatology. 相似文献
16.
K. B. Mather 《Pure and Applied Geophysics》1969,75(1):332-354
Summary The main characteristics of surface winds are tabulated for 34 Antarctic stations. Using these data, supplemented by traverse records, the average wind flow is interpolated for each region and presented as a map showing the pattern of surface wind flow for the whole continent. Attention is focused on the flow in relation to surface contours. Statistics are presented for surface slope, wind speed, temperature, seasonal variations of speed and temperature, diurnal variation (including power spectra) of the wind speed and times of maximum and minimum speed at coastal and inland stations, wind frequency versus direction, the occurrence of calms, the deviation of the plateau wind from the downslope direction, the wind direction near the front of ice shelves, the proportion of cloud cover, and wind chill factors. In all cases data are grouped according to the environs of the stations in an attempt to isolate systematic differences depending on location: coastal stations near the foot of the ice slope and fully exposed to katabatic flow, coastal stations on offshore islands, coastal stations on peninsulas, coastal stations on extensive rock areas, ice shelf stations and inland stations. 相似文献
17.
An in situ monitoring of the sediment characteristics and macrobenthic communities was undertaken at a marine fish culture site in subtropical waters of Hong Kong before and after the deployment of biofilters which were made of cement concrete artificial reef (AR) structures. According to the distance to the boundary of the fish cages, 6 points were selected as sampling stations: 2 at the fish cages, 2 near the boundary of the fish culture area, and 2 reference sites further away from the culture area. Bimonthly sediment samples were collected for analysis of silt-clay fraction (SCF), moisture content (MC), total organic carbon (TOC), total Kjeldahl nitrogen (TKN) and total phosphorus (TP). The macrobenthos (>0.5mm) present in the sediment were sorted, identified and enumerated. TOC, TKN and TP levels at the fish cage stations were consistently higher than those at the reference stations over the 1-year pre-AR and 2-year post-AR deployment monitoring period. The diversity of macrofauna was significantly reduced at the fish cage stations relative to the reference sites. The intermediary stations near the fish culture area showed a transitional state of disturbance. Over the 2-year post-AR deployment period, TOC, TKN and TP showed a decreasing trend at the fish cage and intermediary stations. More diverse macrofaunal communities were recorded at the fish cage stations, with species diversity H'increasing from 0-1 at the beginning of the AR deployment to H'>2 at the end of the study. The present results demonstrated that artificial reefs can improve the benthic abiotic environment and biotic conditions beneath fish rafts which are deteriorated due to farming activities. 相似文献
18.
The trends in annual maximum rainfall (AMR) intensity data in New South Wales, Australia, were examined. Data from 60 stations were used covering three study periods, 1955–2010, 1965–2010 and 1978–2010. Mann-Kendall (MK) and Spearman’s rho (SR) tests were applied to assess trends at local stations. Pre-whitening (PW), trend-free pre-whitening (TFPW) and the variance correction (VC) tests were used to assess the effects of serial correlation on trend results. For regional trend analysis, the regional MK test was employed. The impacts of climatic variability modes on the observed trends in AMR intensity and seasonal maximum rainfall data were investigated. It was found that positive trends were more frequent than the negative ones. The PW, TFPW and VC tests resulted in a slight reduction in the count of stations exhibiting significant positive trends. The number of stations exhibiting significant trends decreased when the impact of climate variability modes was considered. 相似文献
19.
This study employed three chemometric data mining techniques (factor analysis (FA), cluster analysis (CA), and discriminant analysis (DA)) to identify the latent structure of a water quality (WQ) dataset pertaining to Kinta River (Malaysia) and to classify eight WQ monitoring stations along the river into groups of similar WQ characteristics. FA identified the WQ parameters responsible for variations in Kinta River's WQ and accentuated the roles of weathering and surface runoff in determining the river's WQ. CA grouped the monitoring locations into a cluster of low levels of water pollution (the two uppermost monitoring stations) and another of relatively high levels of river pollution (the mid-, and down-stream stations). DA confirmed these clusters and produced a discriminant function which can predict the cluster membership of new and/or unknown samples. These chemometric techniques highlight the potential for reasonably reducing the number of WQVs and monitoring stations for long-term monitoring purposes. 相似文献
20.
—SKS phases observed at broadband stations in Germany show significant shear-wave splitting. We have analyzed SKS and SKKS phases for shear-wave splitting from 13 stations of the German Regional Seismic Network (GRSN), from 3 three-component stations of the Gräfenberg array (GRF) and from one Austrian station (SQTA). The data reveal strong differences in the splitting parameters (fast direction φ and delay time δt from a single event at various stations as well as variations at the individual stations for events with different backazimuths. The backazimuthal variations of the splitting parameters at some stations can be explained by two-layer anisotropy models with horizontal symmetry axes. The best resolved two-layer model is the GRA1 model (upper layer φ = 40°, δt = 1.15s; lower layer φ = 115°, δt = 1.95s). The upper layer can be attributed to the lithosphere. Because of the magnitude of the delay time of the upper layer, the lower layer must lie within the asthenosphere. At other stations splitting parameters are consistent with an anisotropic one-layer model for the upper mantle. Stations near the Bohemian Massif show fast directions near EW. Throughout NE Germany the directions are oriented NW/SE. The reason for this direction is probably the nearby Tornquist-Teisseyre line. The observed fast axes are subparallel to this prominent Transeuropean suture zone. At stations in southern Germany near the Alps we observed ENE/WSW directions. Below some stations we also found indications of inclined anisotropic layers. 相似文献