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71.
Relationships between moment magnitude and fault parameters: theoretical and semi-empirical relationships 总被引:1,自引:0,他引:1
Fault parameters are important in earthquake hazard analysis. In this paper, theoretical relationships between moment magnitude and fault parameters including subsurface rupture length, downdip rupture width, rupture area, and average slip over the fault surface are deduced based on seismological theory. These theoretical relationships are further simplified by applying similarity conditions and an unique form is established. Then, combining thc simplified theoretical relationships between moment magnitude and fault parameters with seismic source data selected in this study, a practical semi-empirical relationship is established. The seismic source data selected is also to used to derive empirical relationships between moment magnitude and fault parameters by the ordinary least square regression method. Comparisons between semi-empirical relationships and empirical relationships show that the former depict distribution trends of data better than the latter. It is also observed that downdip rupture widths of strike slip faults are saturated when moment magnitude is more than 7.0, but downdip rupture widths of dip slip faults are not saturated in the moment magnitude ranges of this study. 相似文献
72.
用不变矩从机载激光扫描测高点云数据中重建规则房屋 总被引:4,自引:0,他引:4
介绍了不变矩的概念,结合实例,基于机载激光扫描测高的三雏点云数据,用不变矩实现了规则房屋的模型重建。对不变矩重建房屋模型的精度进行了讨论和分析.得出了一些有益的结论。 相似文献
73.
I. Markiewicz W. G. Strupczewski K. Kochanek V. P. Singh 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(6):391-405
Three dispersion measures of a random variable, i.e., the standard deviation, the mean deviation (MD) about the mean and the second L-moment, are analyzed in terms of their properties and mutual relationships. Emphasis is placed on the MD, as it is less recognized than two other dispersion measures. The relationships between the dispersion measures are derived for distributions commonly applied in flood frequency analysis (FFA). For distributions that are unbounded, there is a distribution-dependent constant value of the ratio of dispersion measures, or equivalently of respective coefficients of variation. For two-parameter distributions that are lower-bounded, the relationship between the coefficients of variation is also distribution dependent and is not linear. For lower-bounded three-parameter distributions, the dispersion measure ratios, or equivalently the ratios of coefficients of variation, depend on the coefficient of skewness and show a strong distributional dependence. For selected distributions, the three dispersion measures are compared both in terms of the robustness to the largest samples element and the accuracy of upper quantile estimation. The MD statistics may be highly competitive to the two other dispersion measure statistics if applied in FFA for parameters estimation. 相似文献
74.
The Harvard CMT catalogue contains 481 shallow earthquakes that occurred between 1 January 1977 and 30 November 2005 within
a broad region defined by the geographical latitude from 3°S to 14°N and by the longitude from 91°E to 102°E. There are 230
events that occurred before the great earthquake of 26 December 2004. Their surface distribution is not uniform and the source
area of the 2004 great event appears as an area of seismic quiescence with a radius of about 100 km. There are 186 events
that occurred between the two great earthquakes of 26 December 2004 and 28 March 2005. Practically all of them are located
to the northwest from the great earthquake of 2005, that in turn was followed by 63 events, mostly located to the southeast.
The cumulative seismic moment from earthquakes before the occurrence of the great event of 2004 increased rather regularly
with time, with sudden increase about twenty years and two years before the occurrence of the great event. The seismic moment
of earthquakes between the two great events increased rapidly during the first ten-fifteen days, then flattened out and increased
slowly with time. After the great event of 2005 the seismic moment shows quiet increase during some 115 days, then sudden
jump, followed by very small activity till the end of our observations. From the spatial distribution of seismic moment of
earthquakes that occurred before the great event of 2004 it follows that its largest release appeared to the southeast from
the great event, around the rupture area of the great earthquake of 2005. The largest release of seismic moment from earthquakes
between the two great events is observed in the vicinity of the 2004 event and further up to the north. The seismic moment
from earthquakes that occurred after the great event of 2005 was mostly released in its vicinity and further down to the south. 相似文献
75.
76.
鲜水河断裂带是四川西部一条晚第四纪强烈左旋走滑活动的构造带,历史上发生多次强震. 它与西北侧的甘孜—玉树断裂带一起,构成青藏高原东部的侧向滑移构造系统中的川滇活动地块的北边界——羌塘地块的东北边界. 鲜水河断裂带北西段可以分成4个段落,每一段落均可作为一个独立的基本破裂单元而发生地震破裂,亦有可能发生不同尺度的多段联合瞧裂. 对鲜水河断裂带北西段不同尺度破裂的震级及复发间隔进行研究. 根据该地区的地质、地球物理、测量及地震等方面的资料,结合我国强震复发的特点,分析了拉分盆地内部的滑动速率分布,以确定各段落的等效长度和倾向宽度,从而建立适合我国大陆走滑断裂的面波震级与断裂发震面积的关系式;进而运用地震矩方法,考虑断层之间的相互作用,结合专家意见建立了该段的矩平衡断裂破裂模型;最后,给出了鲜水河断裂带北西段各破裂源特征化地震的复发间隔、震级大小和不确定性,以及他与中小地震的联合震级分布. 结果表明,鲜水河断裂带北西段较易发生单段破裂,复发间隔在100~150年左右. 相似文献
77.
1994年9月16日台湾海峡7.3级地震震源过程的研究 总被引:1,自引:1,他引:0
采用数字化台网P波波形资料及台湾台网P波初动方向资料,研究了1994年9月16日台湾海峡73级地震及邻近地区(北纬21~26°,东经115~120°)ML≥58级共5次地震的矩张量解及震源参数。结果表明,这次73级地震的矩张量解以双力偶成分为主,是断层面接近NW走向的正断层。断层面的走向与大震前地震的条带分布走向及余震分布显示的破裂图象较相象,震源机制的张应力轴接近水平,近NE走向;压应力轴几乎垂直,近NWW走向,似乎表明这次地震是受菲律海板块向欧亚板块北西向挤压的力源控制。从P轴接近竖直而T轴接近水平来看,发震断层为强烈拉张性正断层,可能还同时存在垂直向上的应力作用。其它4个强震的震源机制解与73级大震的差别较大。这些地震震源机制解的复杂性,表明台湾海峡地震序列的发展过程比较复杂。 相似文献
78.
Applying genetic algorithm to inversion of seismic moment tensor solution and using the data of P waveform from digital network
and initial motion directions of P waves of Taiwan network stations, we studied the moment tensor solutions and focal parameters
of the earthquake of M=7.3 on 16 September of 1994 in Taiwan Strait and other four quakes of M
L≥5.8 in the near region (21°–26°N, 115°–120°E). Among the five earthquakes, the quake of M=7.3 on September 16, 1994 in Taiwan Strait is the strongest one in the southeastern coast area since Nan’ao earthquake of
M=7.3 in 1918. The results show that moment tensor solution of M=7.3 earthquake is mainly double-couple component, and is normal fault whose fault plane is near NW. The strike of the fault
plane resembles that of the distributive bands of earthquakes before the main event and fracture pattern shown by aftershocks.
The tension stress axis of focal mechanism is about horizontal, near in NE strike, the compressive stress axis is approximately
vertical, near in NWW strike. It seems that this quake is controlled by the force of Philippine plate’s pressing Eurasian
plate in NW direction. But from the viewpoint of P axis of near vertical and T axis of near horizontal, it is a normal fault of strong tensibility. There are relatively big difference between focal mechanism
solution of this quake and those of the four other strong quakes. The complexity of source mechanism solution of these quakes
represents the complexity of the process of the strait earthquake sequences.
Contribution No. 98A01001, Institute of Geophysics, State Seismological Bureau, China.
The subject is supported and helped by Academician Yun-Tai CHEN, Profs. Qing-Yao HONG, Zhen-Xing YAO, Tian-Yu ZHENG, Yao-Lin SHI, Ji-An XU, Bo-Shou HUANG and colleague Mei-Jian AN, Xue-Reng DING, Rui-Feng LIU. De-Chong ZHANG and Ming Li provided the digital data warm-heartedly. Lin-Ying WANG offered us the catalogue of earthquakes in southeastern coastal area in China. Xi-Li WANG and Tong-Xia BAI provided us the issued annual reports data. The authors would like to express their gratitude to all of these people.
This paper is sponsored by the National Natural Science Foundation of China and Scientific and Technological Commission of
Shantou, Guangdong Province. 相似文献
79.
Jorge A. Mendiguren 《Pure and Applied Geophysics》1980,118(2):1192-1208
It is shown, through numerical experiments, that the effect of ignoring ellipticity and rotation of the earth when inverting free oscillation data in moment tensor studies, is to introduce spurious spectral components in the solution. For numerical simulation of the data conditions of the 1970 deep Colombian event the spurious part has isotropic and deviatoric components, besides a distortion in the phase spectra which may lead to artificial precursive source in the solution. The magnitude of the artificial isotropic component is of the order of 10% of the real source moment tensor, depending on the data set used in the inversion. Measuring the excitation of each mode at each station using the technique of integrating over the spectral peaks does not cancel completely the effect of multiplet splitting, in particular that splitting due to rotation of the earth. The effect of lateral heterogeneities was simulated by introducing arbitrary splitting parameters which produced scattering in the eigenperiods compatible with those observed. For that splitting the inversion rendered additional isotropic components.We conclude that the observed implosive precursor the the 1970 Colombian event could have been artificially introduced by ignoring rotation, ellipticity and lateral heterogeneities of the earth.A procedure to invert free oscillation data for an elliptical rotating earth is proposed. It could be applied to a laterally inhomogeneous earth if the excitation for that model could be computed. Its application to real data for the deep Colombian event indicates that we will need to improve our knowledge on the effect of rotation, ellipticity, lateral heterogeneities and anelasticity on free oscillation and their excitation in order to solve accurately for the six components of the moment tensor independently. 相似文献
80.
华北地区一次中尺度对流系统上方的Sprite放电现象及其对应的雷达回波和闪电特征 总被引:3,自引:3,他引:0
利用低光度相机首次观测到了2013年7月31日华北地区一次中尺度对流系统(MCS)上空产生的中高层Sprite放电现象。结合闪电定位、天气雷达等同步观测, 对一次MCS诱发的Sprite的形态学特征及其对应的母体闪电和雷暴系统的雷达回波特征等进行了详细分析。研究除发现了2例圆柱型、3例胡萝卜型和1例舞蹈型 Sprite外, 还发现了2例发光主体发育不完全的Y字型Sprite。估算的Sprite的底部平均高度低于61.8±3.5 km, 顶部平均高度为84.3±6.8 km。Sprite持续时间算术平均值为25.7±9.8 ms, 几何平均值为24.4 ms。Sprite的母体闪电均为正地闪, 峰值电流在+62.5~+106.2 kA之间, 算术平均值为+77.1±22.2 kA, 是本次MCS所有正地闪平均峰值电流的1.4倍。Sprite母体闪电的脉冲电荷矩变化(iCMC)在+475~+922 C km之间, 几何平均值为+571.0 C km。Sprite母体闪电发生在MCS雷达回波25~35 dBZ的层状云降水区, 弱回波(<30 dBZ)面积的突然增加对Sprite的产生有重要指示作用。Sprite易发生在MCS成熟—消散阶段正地闪比例(POP)显著增加的时段。在本次MCS消散阶段中, 有两个时间段可能有利于产生Sprite。在Sprite集中发生时间段, 北京闪电综合探测网(BLNET)探测到的正地闪比例为54.2%, 正地闪连续电流比例70.24%, 连续电流持续时间为58.17±50.31 ms, 有利于Sprite的产生。 相似文献