Stable inversions for complete moment tensors   总被引：5，自引：0，他引：5  

Sarah E. Minson  Douglas S. Dreger 《Geophysical Journal International》2008,174(2):585-592

The seismic moment tensors for certain types of sources, such as volcanic earthquakes and nuclear explosions are expected to contain an isotropic component. Some earlier efforts to calculate the isotropic component of these sources are flawed due to an error in the method of Jost & Herrmann. We corrected the method after Herrmann & Hutchensen and found great improvement in the recovery of non-double-couple moment tensors that include an isotropic component. Tests with synthetic data demonstrate the stability of the corrected linear inversion method, and we recalculate the moment tensor solutions reported in Dreger et al. for Long Valley caldera events and Dreger & Woods for Nevada Test Site nuclear explosions. We confirm the findings of Dreger et al. that the Long Valley volcanic sources contain large statistically significant isotropic components. The nuclear explosions have strikingly anomalous source mechanisms, which contain very large isotropic components, making it evident that these events are not tectonic in origin. This indicates that moment tensor inversions could be an important tool for nuclear monitoring.  相似文献   

Coulomb stress evolution in Northeastern Caribbean over the past 250 years due to coseismic, postseismic and interseismic deformation   总被引：5，自引：0，他引：5  

Syed Tabrez Ali  rew M. Freed  Eric Calais  David M. Manaker  William R. McCann 《Geophysical Journal International》2008,174(3):904-918

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Seismic radiation from dynamic coalescence, and the reconstruction of dynamic source parameters on a planar fault     

Nobuki Kame  Koji Uchida 《Geophysical Journal International》2008,174(2):696-706

The dynamic coalescence of two mode II cracks on a planar fault is simulated here using the elastodynamic boundary integral equation method. We focus on the complexity of the resultant slip rate and seismic radiation in the crack coalescence model (CCM) and on the reconstruction of a single crack model (SCM) that can reproduce the CCM waveforms from heterogeneous source parameters rather than coalescence. Simulation results reveal that localized higher slip rates are generated by coalescence as a result of stress interaction between the approaching crack tips. The synthesized seismic radiation exhibits a distinct coalescence phase that has striking similarities to stopping phases in the radiation and propagation properties. The corresponding SCM yields a singular increase in the stress drop distribution, which is accompanied by a sudden decrease in it across the point of coalescence in the CCM. This implies that the generation of high-frequency radiation is more efficient from coalescence than from stopping, although both phenomena exhibit the same strong  ω⁻²  -type displacement spectra.  相似文献   

Statistical identification of seismicity phases     

A. Pievatolo  R. Rotondi 《Geophysical Journal International》2008,173(3):942-957

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Earthquake prediction: probabilistic aspect     

G. Molchan  V. Keilis-Borok 《Geophysical Journal International》2008,173(3):1012-1017

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Retrieving earthquake signature in grace gravity solutions   总被引：2，自引：0，他引：2  

O. de Viron  I. Panet  V. Mikhailov  M. Van Camp  M. Diament 《Geophysical Journal International》2008,174(1):14-20

The GRACE satellites have been orbiting the Earth since 2002, monitoring the time variable gravity field. Some of the observed fluctuations are due to geodynamic causes, but they are often hidden in the complex signal, composed of hydrology, ocean, atmosphere, and geodynamics, the signal of geodynamic origin being usually the smallest. In addition, dealiasing residuals and noise make the separation of the signal from the different causes more difficult. We proposed a method based on the Empirical Orthogonal Function decomposition to extract the signal of physical origin, under the hypothesis that the physical signal is spatially more consistent than the noise and aliasing incomplete correction. We used synthetic geoid variations associated with earthquakes located at nearly 2000 positions at the Earth surface, based on several examples of large actual subduction events. We show that, with the present day accuracy, we can retrieve the geoid variations associated with more than 98 per cent of the earthquakes of magnitude 9 or above, around 60 per cent for magnitude 8.8, 40 per cent for magnitude 8.6 and 33 per cent for magnitude 8.3. Some events, with the right properties and location, can be detected with magnitude as low as 8. We then applied the method to the GRACE solutions, and retrieved the Hokkaido event (2003) and the Sumatra event (2004), which is in agreement with the retrieval rates mentioned here above.  相似文献   

我国东部沿海省区城镇化水平影响因素的空间差异   总被引：5，自引：2，他引：3  

曹广忠  王纯洁  齐元静 《地理研究》2008,27(6):1399-1406

本文利用2000年截面数据,用因子分析法考察了我国东部沿海省区人口城镇化影响因素的差异、特征和类型。分析结果表明,沿海省区的城镇化水平受到多种因素不同程度的影响,各省区城镇化水平的影响因素及其影响作用呈现出明显的差异化特征,既有明显受到转型期要素流动影响的省份如广东省;也有综合经济实力提高推动城镇化的区域如沪苏和浙江省;还有表现为典型的工业化带动城镇化的传统模式的省份如山东省等。省区间差异化的城镇化影响因素表明,我国沿海省区的城镇化具有明显的个性化特征。  相似文献   

城市植被覆盖变化可预测性及其空间格局的定量递归分析——以深圳市为例   总被引：3，自引：0，他引：3  

李双成  赵志强  高阳  王仰麟 《地理研究》2008,27(6):1243-1252

由于人口的快速增加和经济要素的大量聚集,城市是下垫面性质改变最为显著的区域。本文应用定量递归分析技术对1999~2006年逐旬的1km SPOT-VEGETATION NDVI数据进行分析,以期揭示NDVI时间系列的非线性动态特征及其空间格局。研究结果表明,深圳市的NDVI时间系列的RQA特征值居于随机系列和确定性系列之间,属于含有随机成分的确定性系列。不同覆被类型下NDVI系列的特性不同,林地区的NDVI系列规则性最高,农地区次之,建设用地区最差,表明人类活动作为一种噪声对于NDVI系列性质的扰动。用二阶Rényi熵作为NDVI系列的可预测性指标,其空间格局表现为海拔高、坡度大、林地分布集中的西北和东南部可预测性高,而海拔相对低、建设用地相对集中的中南部地区可预测性低。  相似文献   

1959-2008 年黄土高原地区年内降水集中度和集中期时空变化特征   总被引：2，自引：0，他引：2  

刘宪锋  任志远  张翀  林志慧 《地理科学进展》2012,31(9):1157-1163

本文基于黄土高原地区1959-2008 年51 个地面气象台站的逐日降水资料, 计算了降水集中度(PCD)和集中期(PCP), 并结合EOF、趋势分析以及相关分析等方法对我国黄土高原地区年内降水不均匀性特征及其趋势进行了分析。结果表明:①黄土高原地区PCD在0.53~0.75 之间, 自东南向西北逐渐增加, 而PCP变化不大, 主要集中在7 月中旬和下旬;②近50a 黄土高原地区PCD主要以南北反向型分布为主;③从变化趋势来看, PCD增加趋势较明显的区域主要分布在宁夏的同心和山西的五台山等地, PCD减小比较明显的区域主要分布在山西的阳泉以及青海的门源等地区;而PCP整体上呈现提前趋势, 只有青海的门源站附近有小幅推迟趋势;④年降水量与PCD有较好的相关性, 大部分地区都通过了显著水平为0.05 的检验;而年降水量与PCP的相关性并不显著, 通过显著水平0.05 检验的区域仅分布在山西的兴县、陕西的洛川以及宁夏的固原等地。  相似文献   

沂沭断裂带构造区光弹实验与地震危险区判定研究     

黄兴  胡宏玖  王华林  黄大卫  王纪强  陈平  胡超  刘军  刘红欣 《中国地震》2015,31(3):529-543

在对沂沭断裂带的地质构造环境、断裂带分布特征进行详细分析的基础上,采用聚碳酸酯材料制成沂沭断裂带构造区域的地质模型,分别运用集中、2点和均布等加载方式,使用光弹实验方法模拟特定构造框架下应力、应变场的变化特征。通过对光弹实验数据的分析,在对比不同加载方式下应力积累区域和地震危险区的基础上判定沂沭断裂带构造区中的地震危险区域。  相似文献