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1.
单键群方法与昆仑山—阿尔金山弧型构造顶部地震时空群集特征 总被引：9，自引：2，他引：9
本文以单键群分析方法为基础，进行以下研究；１．对一个地区的地震目录进行分析得到特征键开，并用其对该区地震的时空群集性和离散性进行分析，进而建立分类子目录，以便作针对性的细致处理；２．定义了几个描述ＳＬＣ构架特点的参数，发展和实现了按时间逐段滑移计算ＳＬＣ构架和这些参数的办法及程序，考察这些参数随时间的变化；３．用以上各软件处理昆仑山阿尔金山弧型顶部区域的地震目录，得到了一些有意义的结果。 相似文献
2.
For faster and more robust ray tracing in 1-D velocity models and also due to the lack of reliable 3-D models, most seismological centers use 1-D models for routine earthquake locations. In this study, as solution to the coupled hypocenter-velocity problem, we compute a regional P-wave velocity model for southern Iran that can be used for routine earthquake location and also a reference initial model for 3-D seismic tomography. The inversion process was based on travel time data from local earthquakes paired reports obtained by merging the catalogues of Iranian Seismic Center (IRSC, 6422 events) and by the Broadband Iranian National Seismic Network (BIN, 4333 events) for southern Iran in the period 2006 through July 2017. After cleaning the data set from large individual reading errors and by identifying event reports from both networks belonging to same earthquake (a process called event pairing), we obtained a data set of 1115 well-locatable events with a total number of 24,606 P-wave observations. This data set was used to calculate a regional minimum 1-D model for southern Iran as result of an extensive model search by trial-and-error process including several dozens of inversions. Significantly different from previous models, we find a smoothly increasing P-velocity by depth with velocities of 5.8 km/s at shallow and velocities of 6.4 km/s at deepest crustal levels. For well-locatable events, location uncertainties are estimated in the order of ±?3 km for epicenter and double this uncertainty for hypocentral depth. The use of the minimum 1-D model with appropriate station delays in routine hypocenter location processing will yield a high-quality seismic catalogue with consistent uncertainty estimates across the region and it will also allow detection of outlier observations. Based on the two catalogues by IRSC and BIN and using the minimum 1-D model and station delays for all stations in the region, we established a new combined earthquake catalogue for southern Iran. While the general distribution of the seismicity corresponds well with that of the two individual catalogues by IRSC and BIN, the new catalogue significantly enhances the correlation of seismicity with the regional fault systems within and between the major crustal blocks that as an assembly build this continental region. Furthermore, the unified seismic catalogue and the minimum 1-D model resulting from this study provide important ingredients for seismic hazard studies. 相似文献
3.
Using the method of Single-link Cluster(SLC),analyzing the pattern of time sliding of SLCparameters,the earthquake activity in the western Sichuan-Yunnan of China is studiedcombining with the regional earthquake catalogue since 1970 and the tectonic background.Comparing with the high level of earthquake activity in 1970’s and the low in 1980’s,theearthquake activity is in general at the middle level in 1990’s.This paper suggests that SLCmethod,which considers the temporal and spatial relationship among earthquake events,could be adopted to analyze the trend of regional earthquake activity,it is very useful forstudying seismic activity. 相似文献
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5.
识别前震余震的单键群方法 总被引：3，自引：0，他引：3
本文提出一种从地震目录中识别强震的前震和余震并形成序列目标的新方法,即：以单键群（ＳＬＣ）分析方法为基础,定义在ＳＬＣ构架中,由于小于或等于特征键长的键所形成的许多链中,那些处在某个强震联通的链上的地震就与该强震构成一个地震序列;在此序列中,该强震为主震,之后的为余震,用此方法,可以按强震逐个识别其前震余震,并形成其序列目录。我们用它识别处理了海城７．４级和昆仑山－阿尔金山弧型顶部地区６．０级以上 相似文献
6.
Uncertainty in recurrence rates of large magnitude events due to short historic catalogs 总被引：2，自引：0，他引：2
Seismic hazard analysis requires knowledge of the recurrence rates of large magnitude earthquakes that drive the hazard at low probabilities of interest for seismic design. Earthquake recurrence is usually determined through studies of the historic earthquake catalogue for a given region. Reliable historic catalogues generally span time periods of 100–200 years in North America, while large magnitude events (M?≥?7) have recurrence rates on the order of hundreds or thousands of years in many areas, resulting in large uncertainty in recurrence rates for large events. Using Monte Carlo techniques and assuming typical recurrence parameters, we simulate earthquake catalogues that span long periods of time. We then split these catalogues into smaller catalogues spanning 100–200 years that mimic the length of historic catalogues. For each of these simulated “historic” catalogues, a recurrence rate for large magnitude events is determined. By comparing recurrence rates from one historic-length catalogue to another, we quantify the uncertainty associated with determining recurrence rates from short historic catalogues. The use of simulations to explore the uncertainty (rather than analytical solutions) allows us flexibility to consider issues such as the relative contributions of aleatory versus epistemic uncertainty, and the influence of fitting method, as well as lending insight into extreme-event statistics. The uncertainty in recurrence rates of large (M?>?7) events is about a factor of two in regions of high seismicity, due to the shortness of historic catalogues. This uncertainty increases greatly with decreasing seismic activity. Uncertainty is dependent on the length of the catalogue as well as the fitting method used (least squares vs. maximum likelihood). Examination of 90th percentile recurrence rates reveals that epistemic uncertainty in the true parameters may cause recurrence rates determined from historic catalogues to be uncertain by a factor greater than 50. 相似文献
7.
为研究中国地震分布的时空特征,采用时空联合的单键群（ＳＬＣ）方法,计算了１９７０－１９９８年３月间该区域发生的４级和４级以上地震的时空ＳＬＣ构架．对时空ＳＬＣ构架所做的统计分析表明：①截止键长Ｄ在 ５０－８０ｋｍ范围内时,地震集团的个数 Ｔ（ｎ）与集团的大小 ｎ（所含地震个数）之间是自相似分布．在６５ ｋｍ附近,ｌｇＴ（ｎ）与 ｌｇｎ之间的线性相关性最好;②构架的累计键长符合Ｗｅｉｂｕｌｌ分布;③在删除前震和余震之后,构架的累计键数也服从Ｗｅｉｂｕｌｌ分布． 相似文献
8.
历史地震目录修订问题 总被引：1，自引：1，他引：0
中国地震目录历经四次大规模的修订,已渐趋完善,然而,由于资料的不足和认识的差异,对地震目录中,特别是历史地震目录中一些参数的确定,甚至地震的增删,还存在不同看法和外议,给实际使用造成一定困难。本文针对目前历史地震目录确定中存在的多观点状态,提出四个方面的问题,希望引起历史地震工作者讨论,以期共同制定一个能为大家接受的历史地震参数确定方法的规约。 相似文献
9.
Real-time envelope cross-correlation detector: application to induced seismicity in the Insheim and Landau deep geothermal reservoirs 总被引：1，自引：0，他引：1
Margarete Vasterling Ulrich Wegler Jan Becker Andrea Brüstle Monika Bischoff 《Journal of Seismology》2017,21(1):193-208
We develop and test a real-time envelope cross-correlation detector for use in seismic response plans to mitigate hazard of induced seismicity. The incoming seismological data are cross-correlated in real-time with a set of previously recorded master events. For robustness against small changes in the earthquake source locations or in the focal mechanisms we cross-correlate the envelopes of the seismograms rather than the seismograms themselves. Two sequenced detection conditions are implemented: After passing a single trace cross-correlation condition, a network cross-correlation is calculated taking amplitude ratios between stations into account. Besides detecting the earthquake and assigning it to the respective reservoir, real-time magnitudes are important for seismic response plans. We estimate the magnitudes of induced microseismicity using the relative amplitudes between master event and detected event. The real-time detector is implemented as a SeisComP3 module. We carry out offline and online performance tests using seismic monitoring data of the Insheim and Landau geothermal power plants (Upper Rhine Graben, Germany), also including blasts from a nearby quarry. The comparison of the automatic real-time catalogue with a manually processed catalogue shows, that with the implemented parameters events are always correctly assigned to the respective reservoir (4 km distance between reservoirs) or the quarry (8 km and 10 km distance, respectively, from the reservoirs). The real-time catalogue achieves a magnitude of completeness around 0.0. Four per cent of the events assigned to the Insheim reservoir and zero per cent of the Landau events are misdetections. All wrong detections are local tectonic events, whereas none are caused by seismic noise. 相似文献
10.
The EEPAS (Every Earthquake a Precursor According to Scale) model is a method of forecasting earthquakes based on the notion that the precursory scale increase () phenomenon occurs at all scales in the seismogenic process. The rate density of future earthquake occurrence is computed directly from past earthquakes in the catalogue. The EEPAS model has previously been fitted to the New Zealand earthquake catalogue and successfully tested on the California catalogue.Here we describe a further test of the EEPAS model in the Japan region spanning 1965–2001, initially on earthquakes with magnitudes exceeding the threshold value 6.75. A baseline model and the Gutenberg-Richter b-value were fitted to the JMA catalogue over the learning period 1926–1964. The performance of EEPAS, with the key parameters unchanged from the New Zealand values, was compared with that of the baseline model over the testing period, using a likelihood ratio criterion. The EEPAS model proved superior. A sensitivity analysis shows that this result is not sensitive to the choice of the learning period or b-value, but that the advantage of EEPAS over the baseline model diminishes as the magnitude threshold is lowered. When key model parameters are optimised for the Japan catalogue, the advantage of EEPAS over the baseline model is consistent for all magnitudes above 6.25, although less than in the New Zealand and California regions.These results add strength to the proposition that the EEPAS model is effective at a variety of scales and in a variety of seismically active regions. 相似文献
11.
The construction of 3-D basin velocity structures is ongoing in many regions of Japan. The structure models are constructed
mainly for the prediction of long-period ground motions from future large earthquakes. In this paper, we validate the 3-D
velocity structure model of the Tokachi basin, a deep sedimentary basin located in eastern Hokkaido, Japan, based on 3-D simulation
of long-period (2–20 s) ground motions from three nearby intermediate-depth earthquakes; this model was constructed by the
National Research Institute for Earth Science and Disaster Prevention (NIED). We make comparisons between the observed and
synthetic long-period ground motions for the basin-induced surface waves as well as the direct S-wave. We also try to revise
the 3-D velocity structure in the western part of the Tokachi basin based on 1-D velocity structures estimated using long-period
S-wave modeling and the microtremor survey method. We then perform the 3-D simulation again to validate the revised model.
Based on quantitative comparisons of the long-period ground motions from these simulations with those observed, we conclude
that the NIED and revised velocity structure models are generally good at the central basin sites, but that both models require
modification at the basin edges to explain the details of the observed basin-induced surface waves. 相似文献
12.
In this study, 3-D Lattice Solid Model (LSMearth or LSM) was extended by introducing particle-scale rotation. In the new model,
for each 3-D particle, we introduce six degrees of freedom: Three for translational motion, and three for orientation. Six
kinds of relative motions are permitted between two neighboring particles, and six interactions are transferred, i.e., radial,
two shearing forces, twisting and two bending torques. By using quaternion algebra, relative rotation between two particles
is decomposed into two sequence-independent rotations such that all interactions due to the relative motions between interactive
rigid bodies can be uniquely decided. After incorporating this mechanism and introducing bond breaking under torsion and bending
into the LSM, several tests on 2-D and 3-D rock failure under uni-axial compression are carried out. Compared with the simulations
without the single particle rotational mechanism, the new simulation results match more closely experimental results of rock
fracture and hence, are encouraging. Since more parameters are introduced, an approach for choosing the new parameters is
presented. 相似文献
13.
Probabilistic analysis by Monte Carlo Simulation method (MCSM) is a computationally prohibitive task for a reactive solute transport involving coupled PDEs with nonlinear source/sink terms in 3-D heterogeneous porous media. The perturbation based stochastic finite element method (SFEM) is an attractive alternative method to MCSM as it is computationally efficient and accurate. In the present study SFEM is developed for solving nonlinear reactive solute transport problem in a 3-D heterogeneous medium. Here the solution of the biodegradation problem involving a single solute by a single class of microorganisms coupled with dynamic microbial growth is attempted using this method. The SFEM here produces a second-order accurate solution for the mean and a first-order accurate solution for the standard deviation of concentrations. In this study both the physical parameters (hydraulic conductivity, porosity, dispersivity and diffusion coefficient) and the biological parameters (maximum substrate utilization rate and the coefficient of cell decay) are considered as spatially varying random fields. A comparison between the MCSM and SFEM for the mean and standard deviation of concentration is made for 1-D and 3-D problem. The effects of heterogeneity on the degradation of substrate and growth of biomass concentrations for a range of variances of input parameters are discussed for both 1-D and 3-D problems. 相似文献
14.
In earthquake early warning systems, real-time shake prediction through wave propagation simulation is a promising approach. Compared with traditional methods, it does not suffer from the inaccurate estimation of source parameters. For computation efficiency, wave direction is assumed to propagate on the 2-D surface of the earth in these methods. In fact, since the seismic wave propagates in the 3-D sphere of the earth, the 2-D space modeling of wave direction results in inaccurate wave estimation. In this paper, we propose a 3-D space numerical shake prediction method, which simulates the wave propagation in 3-D space using radiative transfer theory, and incorporate data assimilation technique to estimate the distribution of wave energy. 2011 Tohoku earthquake is studied as an example to show the validity of the proposed model. 2-D space model and 3-D space model are compared in this article, and the prediction results show that numerical shake prediction based on 3-D space model can estimate the real-time ground motion precisely, and overprediction is alleviated when using 3-D space model. 相似文献
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16.
A. V. Kuvshinov 《Surveys in Geophysics》2008,29(2):139-186
Electromagnetic induction in the Earth’s interior is an important contributor to the near-Earth magnetic and electric fields.
The oceans play a special role in this induction due to their relatively high conductivity which leads to large lateral variability
in surface conductance. Electric currents that generate secondary fields are induced in the oceans by two different processes:
(a) by time varying external magnetic fields, and (b) by the motion of the conducting ocean water through the Earth’s main
magnetic field. Significant progress in accurate and detailed predictions of the electric and magnetic fields induced by these
sources has been achieved during the last few years, via realistic three-dimensional (3-D) conductivity models of the oceans,
crust and mantle along with realistic source models. In this review a summary is given of the results of recent 3-D modeling
studies in which estimates are obtained for the magnetic and electric signals at both the ground and satellite altitudes induced
by a variety of natural current sources. 3-D induction effects due to magnetospheric currents (magnetic storms), ionospheric
currents (Sq, polar and equatorial electrojets), ocean tides, global ocean circulation and tsunami are considered. These modeling
studies demonstrate that the 3-D induction (ocean) effect and motionally-induced signals from the oceans contribute significantly
(in the range from a few to tens nanotesla) to the near-Earth magnetic field. A 3-D numerical solution based on an integral
equation approach is shown to predict these induction effects with the accuracy and spatial detail required to explain observations
both on the ground and at satellite altitudes.
On leave from Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation, Russian Academy of Sciences, 142190
Troitsk, Moscow region, Russia. 相似文献
17.
Proper stacking of three-dimensional seismic CDP-data generally requires the knowledge of normal moveout velocities in all source-receiver directions contributing to a CDP-gather. The azimuthal variation of the stacking velocities mainly depends on the dip of the seismic interfaces. For a single dipping plane a simple relation exists between the dip and the azimuthal variation of NMO-velocity. Varying strike and dip of subsequent reflectors, however, result in a complex dependency of the seismic parameters. Reliable information on the spatial distribution of the normal moveout (NMO)-velocity can be derived from a wavefront curvature estimation using a 3-D ray-tracing technique. These procedures require additional information, e.g. reflection time gradients or depth maps to show interval velocities between leading interfaces. Moreover, their application to an extended 3-D data volume is restricted by high costs. The need for a routine 3-D procedure resulted in a special data selection to create pseudo 2-D profiles and to apply existing velocity estimation routines to these profiles. At least three estimates in different directions are necessary to derive the full azimuthal velocity variation, characterized by the large and the small main axis and the orientation of the velocity ellipse. Errors are estimated by means of computer models. Stacking velocities obtained by mathematical routines (least-squares fit) and by seismic standard routines (NMO-correction and correlation) are compared. Finally, a general 3-D velocity procedure using cross-correlation of preliminarily NMO-corrected traces is proposed. 相似文献
18.
三维波动方程叠前深度偏移是复杂介质中进行构造成像、弹性参数反演的重要环节．由于其技术实现不仅涉及波场延拓理论的创新,而且需要大规模计算,因而研究难度较大．本文以实验效果的取得为目的,完整地实现了SEG／EAEG盐丘和推覆体模型的三维波动方程辛几何算法的叠前深度偏移成像计算．文中详细考察了所研制的波动方程三维叠前深度偏移软件系统及其对复杂地质构造的成像能力,具体包括：1)对于盐丘模型,文中讨论了成像参数的选择、地震子波对成像精度的影响、完成二维及三维叠前深度偏移的比较;2)对推覆体模型,文中进行了脉冲响应测试;3)由两个模型的成像结果可见本文的波动方程三维叠前深度偏移软件系统已具有适应强速度横向变化、复杂构造的成像能力。 相似文献
19.