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本文对比研究了平原地区井下和地面的地震波记录特征,对其走时关系和振幅关系进行了推导,得出: 1.在层状均匀介质条件下,在地面记录到的地震波走时tc大于在井下记录到的地震波走时th,二者之差为 △t=tc——th=cosic/Vch与此相应,地面震相观测到时Tc滞后于井下震相观测到时Th,其到时差为△T。 2.定义地面振幅Ac与井下振幅Ah之比为 K=Ac/Ah在特定的条件下,K>1。因而称K为地面振幅相对于井下振幅的放大因子。 分析了静海地震台井下和地面的地震观测资料,得到单台的△T和K的对比结果,并将其记录特征分别与基岩地震台的记录特征进行了比较,认为: 1.对于运动学参数,井下较之地面,更逼近于基岩地区的情况。 2.对于动力学参数,统计得出基岩地震台的地动振幅A与Ah,Ac的关系: A=3.50Ah A=0.34Ac。 相似文献
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用数字记录资料测定腾冲火山区的微震参数 总被引：6，自引：3，他引：3
利用数字化地震记录资料 ,测定了腾冲火山及其周围地区的地震基本参数 ,结果表明 ,腾冲火山区内的地震活动以微震为主 ,震级多数在 1～ 2 5级之间 ,且地震活动频度低 ;而周围地区的构造地震活动频繁 ,且强度大。在腾冲火山区内地震活动的空间分布也表现出明显的非均匀性 ,以腾冲县城以北 (即 2 5°N以北 )的火山区内地震活动少 ,而县城以南的火山区 (热海热田地区 )微震活动相对多 ,且以微震群的形式发生。根据C F Richter震级标度测定的震级结果 ,火山区的微震活动事件可达 0 4震级单位。震源深度的定位结果给出 ,火山地区的微震震源深度绝大多数在 1～ 6km的范围 ,属于典型的浅源地震 ,而周围地区构造地震的震源深度多多数大于 2 0km。腾冲火山区的微震活动分布、地震强度、及震源深度特征所表现的现象可能与地下岩浆体活动相关 ,显示了与火山热物质孕震机理有关的明显特征。 相似文献
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本文对比和分析了天津遥测地震台网井下地震波地动位移和地动速度记录的特点,结果表明:(1)台网增加速度记录有利于地震参数的测定,是位移记录的必要补充;(2)有利于监测本区微震活动;(3)是提高平原地区遥测地震台网控震能力的一种有效途径。 相似文献
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在美国弗吉尼亚洲布坎南县煤矿区，用直接安置在地下长壁矿上面的一台地震仪监测了三个月的微震活动。该活动为具有冲击的、短暂的地震性质，在距离为５００ｍ处的持续时间为几秒，表明尾波随时间的延长向低频移动。本研究的目的是：确定矿内覆盖塌落（沉降）之前的微震活动性是否有增加的前兆．如果有的话，是否能披地面上的地震仪探测到。最初的记录是在被监测矿山进行回采作业的前两周进行的。对微震发生“前”“后”的水平进行比较表明：随着采煤作业的进展，地震次数增加了６倍，即由每小时１次事件增加到每小时７次事件。在监测期间记录到的微震总数超过了１５０００次，其中大多数发生在实际的采煤作业期间。采煤时发生的地震每小时超过３０次，与非工作时的每小时７次的低比率形成对照。犁煤之前的岩石断裂和煤层断裂，是造成这些地震中绝大多数的震级非常小的原因。塌落和岩爆（强烈的喷发将岩石碎片推人矿内），也对总的地震活动性起作用。似乎塌落（其中某些大的也可在地面上感觉到）是与犁煤无关的地震活动性的主要根源，因为地下有广阔的自由表面区。任何有关塌落的地质活动性前兆都被工作时的高功率干扰有效地屏蔽掉了。因此，采用了地面地震监测，以试图记录塌落地震活动性增强的一些前 相似文献
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对昆明基准地震台山洞内放置的宽频带地震仪BBVS-60及井下放置的GL-S60B深井宽频带地震仪所记录的地震进行信噪比、P波到时差、波形相关性和频谱分析,得出地面与井下记录地震的差异情况。结果表明:①井下台信噪比与地面台信噪比相比提高有限,仅NS向提升明显;②地面台和井下台记录地震的P波到时基本一致;③在震中距小于3.1°时,地面台和井下台记录地震波波形相关度较低甚至不相关;在震中距大于3.1°后,波形相关度较高;④1.5～8.0Hz背景噪声差异,是震中距小于3.1°时地面台和井下台地震波形差异的主要原因。 相似文献
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腾冲火山地区微震观测（1） 总被引：5，自引：5，他引：0
本综述了腾冲火山地区微震观测台网的建立与所取得的具有研究价值的地震记录。内容包括观测系统性能、台站布局、、地震记录。由观测资料表明腾冲火山地区存在微震活动。 了台网需要努力的目标。 相似文献
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井下微震监测获得的地震记录往往包含大量的噪声,记录信噪比很低.有效地震信号的识别与提取是进行后续地震定位等工作之前需要优先解决的问题.经过研究发现,井下水压裂微地震信号具有稀疏分布的特征,而井下环境噪声则具有更多的Gaussian分布特征.为此,本文提出将图像处理领域适宜于稀疏分布信号降噪处理的稀疏码收缩方法应用于井下微震监测数据处理.为解决需要利用与待处理数据中有效信号成分具有相似分布特征的无噪信号序列估算正交基以及计算效率等问题,将原方法与小波变换理论相结合.即通过优选小波基函数作为正交基进行小波变换将信号分解为不同级的小波系数,利用稀疏码收缩方法中对稀疏编码施加的非线性收缩方式作为阈值准则对小波系数进行改造.通过多方面的数值实验证明了该方法在处理地震子波及井下微地震信号方面准确可靠.含噪记录经过处理后有效地震信号的到时、波形、时频谱特征等均能得到良好的识别和恢复.并且该方法具有很强的抗噪能力,当信噪比低至-20~-30db时,仍然能够发挥作用.在处理大量实际井下微震监测数据的过程中,面对多种复杂情况,本方法展现出了计算效率高、计算结果可靠、应用简单等优势,证明了其本身具有实际应用价值,值得进一步的研究和推广. 相似文献
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腾冲火山地区微震观测(Ⅰ) 总被引：4，自引：0，他引：4
Ye Jianqing Chen Mingong Liu Xuejun Cai Shaoping Cai Mingjun Qin Jiazheng Huangfu Gang Liu Zuyin 《地震研究》1998,(4)
本文综述了腾冲火山地区微震观测台网的建立与所取得的具有研究价值的地震记录。内容包括观测系统性能、台站布局、地震记录。由观测资料表明腾冲火山地区存在微震活动。讨论了台网需要努力的目标。 相似文献
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The Sakarya prefecture is an interesting area with various seismicity types. This activity comes from earthquakes occurring at the North Anatolian Fault Zone and from a few quarry blast areas in the region. These quarry blast recordings produce errors in the determination of active faults and mapping of the microearthquake activity. Therefore, to recognize the tectonic activity in the region, we need to be able to discriminate between earthquakes and quarry blasts in the catalogues. In this study, a statistical analysis method (linear discriminant function) has been applied to classify seismic events occurring in the Sakarya region. We used 110 seismic events that were recorded by Sakarya University Seismic Station between 2012 and 2014. Time and frequency variant parameters, maximum S wave and maximum P wave amplitude ratio (S/P), the spectral ratio (Sr), maximum frequency (fmax), and total signal duration of the waveform were used for discrimination analyses. The maximum frequency (fmax) versus time duration of the seismic signal gives a higher classification percentage (94%) than the other discriminants. At the end of this study, 41 out of 110 events (44%) are determined as quarry blasts, and 62 (56%) are considered as earthquakes. 相似文献
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Using hydrogeochemical signatures of stream water to assess pathways for rainfall events: towards a predictive model 
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下载免费PDF全文 J. A. Figueiredo E. A. Menor M. T. Taboada‐Castro M. M. Taboada‐Castro M. L. Rodríguez‐Blanco E. S. Braga 《水文研究》2014,28(4):2302-2311
Thanks to its simple division into agricultural and forestry land use, the Corbeira catchment (Galicia, Spain) is used as a case study to build a predictive model using hydrogeochemical signatures. Stream data acquired under recessional flow conditions over a one year period were obtained from a sampling station near the downstream end of the catchment, and using principal component analysis, it is shown that some of the analytical parameters are covariant, and some are negatively correlated. These findings support inferences about the pathways of rainfall in the catchment. Specific signatures may be associated with the dominant hydrological source, either surface runoff or subsurface waters: additionally, the dominant land use in that part of the catchment, where the flow originated, can also be predicted. The dominant runoff shows a strong covariance between suspended solids (SS) and particulate phosphorus (PP), with a clear negative correlation with pH. Dissolved organic carbon (DOC) data are associated with this covariant set when these compounds are available in the soils in question. Dissolved phosphorus, total organic nitrogen and dissolved nitrates are also associated with the same covariant set when the runoff flows through areas of extensive agricultural use. The SS ? PP covariance is less significant at lower flows. Typical base flow regimes show a significant covariance between salinity and pH, with a marked negative correlation with SS ? PP set, confirming the dominance of subsurface waters in the baseflow, as expected. Seasonally divergent DOC ? SS behaviour proves to be a useful tracer for rainfall regimes. The DOC trend shows a sinusoidal annual variation in amplitude, determined by the rainfall regime. As a result, flow from the catchment is dominated by surface water whenever there is synchronicity between the peaks of DOC and SS. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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G.‐Akis Tselentis Paraskevas Paraskevopoulos Nikos Martakis 《Geophysical Prospecting》2010,58(5):845-859
We determine the attenuation structure of a three‐dimensional medium based on first pulse‐width measurements from microearthquake data. Ninety‐five microearthquakes from a seventy stations local network were considered in this study. Measurements of the first half cycle of the wave, the so‐called rise time τ were carried out on high quality velocity seismograms and inverted to estimate the P‐waves intrinsic quality factor Qp. The results of this investigation indicate that first pulse width data from a local microearthquake network permit retrieval with sufficient accuracy of the heterogeneous Qp structure. The inferred attenuation variability corresponds to the known geological formations in the region. 相似文献
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The Shillong Plateau signifies the intense tectonic processes that the region has experienced during the Tertiary Indo-Tibetan
and Indo-Burman collisions. An attempt has been made to study the microearthquake and radon emanation rate to understand and
identify the seismotectonic zones. 相似文献
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Reliable quantification of suspended sediment (SS) and particulate phosphorus (PP) transport, and identification of the various delivery pathways at the catchment level, is an important and necessary aid to appropriate catchment management. In this study we measured storm event, seasonal and annual losses of SS and PP from a Danish arable catchment, Gelbæk Stream, using a multisampling strategy. SS losses for the study years May 1993–April 1994 and May 1994–April 1995 ranged from 71 to 88 kg ha−1, while PP losses ranged from 0·32 to 0·36 kg P ha−1. In both cases losses mainly occurred during infrequent storm events. In comparison with intensive storm sampling, infrequent (fortnightly) sampling underestimated annual transport during the two study years by −24 and −331%, respectively, for SS, and by −8·6 and −151%, respectively, for PP. Reliable estimation of the transport of sediment and sediment-associated nutrients and other substances thus necessitates the use of an intensive monitoring approach. Turbidimeters proved to be a good substitute for direct measurement of SS, especially during storm events, although careful calibration is needed at the seasonal and storm event levels. Experience shows that in artificially drained and geologically complex catchments such as Gelbæk, simultaneous comparative monitoring of different sources (e.g. subsurface drainage water) is an important means of reliably discriminating between the various diffuse sources of sediment and phosphorus. Subsurface drainage water was found to account for 11–15% of the annual SS export from the catchment; the corresponding figure for PP being 11–18%. Surface runoff was only a source of SS and PP during the first study year, when it accounted for 19% of SS and 7% of PP catchment export. Stream bank/bed erosion must therefore have been the major diffuse source of SS and PP in both study years. The study also revealed that analysis of the trace element content (e.g. 137Cs, 210Pb) of the SS transported in subsurface drainage water and stream water during storm events is a useful means of discriminating between diffuse losses of SS delivered from topsoil and subsoil compartments. © 1997 by John Wiley & Sons, Ltd. 相似文献
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为探索大地震发生前孕震区内微震辐射波谱的变化,在新疆西克尔地区,用选频测震仪对微震波谱进行了观测和研究。选频测震仪分为6个频道,各道中心频率分别为6.0周、8.1周、15.7周、30.0周、50.0周、75.0周。初步结果表明:在一个地震系列中,随着临近较强地震（ML≥3.2）的发生,微震P波在10周-60周频率范围内的谱值增高,其置信水平一般在70％以上。较强地震发生以后,微震P波在相应频率范围内的谱值下降。 文中还简要地分析了选频地震记录的物理意义,并对较强地震前,微震辐射波谱变化的原因作了初步说明。 相似文献
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Arwen Deuss 《Surveys in Geophysics》2009,30(4-5):301-326
SS and PP precursors are currently the only body wave data types that have significant coverage in both oceanic and continental regions to study the existence and characteristics of mantle discontinuities on a global scale. Here, the techniques used by global seismologists to observe SS and PP precursors are reviewed. Seismograms, aligned on SS or PP, are stacked using normal move out (NMO) techniques to obtain common depth point gathers. Bootstrap methods are employed to determine 95% confidence levels of the stacks and robustness of the observations. With these relatively simple techniques, a range of discontinuities has been found in the mantle up to 1,200 km depth. The stacks are dominated by the transition zone discontinuities at 410, 520 and 660 km depth, but additional discontinuities at 220, 300–350, 800–900 and 1,100–1,200 km depth are also seen in certain regions. An overview is given of the most recent observational results with a discussion of their mineral physical interpretation and geodynamical significance. Both seismology and mineral physics agree on the level of complexity at the transition discontinuities: a simple 410, a more complicated 520 and a highly complicated 660-km discontinuity are consistently found in both disciplines. 相似文献
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Distributed physically based erosion and phosphorus (P) transport models, run by the overland flow model described in Taskinen and Bruen (2006. Hydrological Processes 20 : this issue), are described. In the erosion model, the additional components to the basic model were the outflow of the particles by infiltration and a new model component, i.e. deposition when rainfall stops. Two ways of calculating the shielding factor due to the flow depth were compared. The P transport model had both dissolved P (DP) and particulate P (PP) components. The processes included in the DP model were desorption from the soil surface, advection, storage in the overland flow and infiltration. The PP model accounted for advection, storage in the flow, infiltration, detachment from the soil surface by flow and rainfall and deposition both when transport capacity of suspended solids (SS) is exceeded and when rainfall ceases. When the models were developed and validated in small agricultural fields of cohesive soil types in southern Finland, comparisons were made between corresponding processes and the significance of added components were estimated in order to find out whether increased model complexity improves the model performance. The sedigraphs were found to follow the dynamics of rainfall, emphasizing the importance of the rainfall splash component. The basic model was too slow to react to changes in rainfall and flow rates, but infiltration and deposition that acts during the cessation in rainfall improved the model significantly by enabling the modelled SS to fall sharply enough. The shielding effect of flow depth from the splash detachment was found to play a significant role. Transport capacity should also be included in erosion models when they are applied to cohesive soils. In this study, the Yalin method worked well. A strong correlation was obvious between the measured SS and total P concentrations, indicating that the main form of P in runoff is PP. This emphasizes the importance of a good sediment transport model in P transport modelling. The submodel used for DP desorption from the soil surface produced plausible results without any calibration. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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1986至1989年,我们在云南鹤庆地震台进行了超微震探测,利用超微震来研究小地震的孕震过程,和大、小地震活动的关系,资料表明:鹤庆台附近2.6级地震的孕震过程,与大震的孕育过程有相似之处。说明利用对小震的研究加快对大震的认识是一条值得探索的途径。 相似文献
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为配合汶川地震断裂带科学钻探工程(WFSD),中国地震局地球物理研究所在四川省绵竹市天池乡和灌县—安县断裂附近分别架设了15套微震仪器和17个短周期地震台.基于WFSD-3附近的微震、短周期和区域台网的固定台站记录的近震数据,通过横波窗内S波分裂计算,得到其上地壳各向异性参数,即快波偏振方向和慢波的时间延迟,并分析了研究区的上地壳各向异性特征.结果显示,研究区大部分区域的快波偏振方向为NE向,与龙门山断裂带走向一致,但在研究区微震台阵布设小区域内,快波偏振方向表现出东西分区特征,东部为NE向,西部为NW向.上地壳各向异性主要是受到岩层中随应力分布排列的微裂隙和岩石或矿物结构的影响,研究区内快波偏振方向主要表现为NE方向,与断裂走向一致,反映了研究区上地壳各向异性主要受控于结构控制的各向异性,局部区域的快波偏振方向为NW向,与区域最大主压应力方向一致,说明区域应力场对研究区上地壳各向异性也有影响.通过分析微震台阵的归一化时间延迟随时间的变化情况可以反映区域应力场的变化情况.微震台阵的慢S波时间延迟在2012、2013年较为离散,在2014年有收敛的趋势,反映了强震后区域应力场逐渐稳定的趋势. 相似文献