泥质砂岩激发极化弛豫时间谱的正则化反演

激发极化衰减谱是一系列单指数衰减的线性叠加,因此可以对衰减谱进行多指数反演,得到的弛豫时间谱可用于储层孔隙结构和渗透性评价,是一种非常有前途的技术。由于实际测井的信噪比相对较低,常规的奇异值分解方法难以获得合理的弛豫时间谱,为此,采用正则化约束,结合奇异值分解,对合成数据和实际测量的衰减谱进行反演,得到连续的弛豫时间谱;同时,讨论了弛豫时间谱的时间常数分布、正则化因子以及信噪比对反演结果的影响。研究结果表明:该方法适用于信噪比较低的实际测量结果的反演,弛豫时间常数的分布点数为32~64较为合适;随着正则化因子的增加,反演结果逐渐变得平滑,存在一个最优的正则化因子,用于获得最为合理的弛豫时间谱;在双对数图中,最优正则化因子随着信噪比的增加而线性降低,因此通过测量结果的信噪比,可以求取最优正则化因子,进而将该技术应用于实际。     

Seismic wave propagation in laterally inhomogeneous poroelastic media via BIEM

This work addresses in‐plane pressure P and vertically polarized shear SV seismic wave propagation in a finite, laterally inhomogeneous, multilayered poroelastic geological region resting on the homogeneous elastic half‐space. The particular approach followed here is based on a combination of the (i) viscoelastic approximation (isomorphism) to Biot's equations of dynamic poroelasticity and on the (ii) boundary integral equation method (BIEM) using frequency‐dependent fundamental solutions of the governing wave equations. The problem is formulated under plane strain conditions and time‐harmonic motions are assumed. Validation of the viscoelastic isomorphism and verification of the BIEM is done by solution of benchmark examples. These simulation studies reveal that the proposed methodology is able to depict a sensitivity of the seismic signals recovered to the following parameters: (i) poroelastic properties of fluid saturated layers; (ii) lateral geological inhomogeneity; (iii) surface topography and (iv) frequency content and direction of the incident wave. It is concluded that the combination of viscoelastic isomorphism with BIEM software provides an effective numerical tool for evaluating site‐effect phenomena in multilayered, fluid saturated geological regions with complex geometry. The numerical results obtained demonstrate that dynamic poroelasticity interacting with other physical peculiarities of the Earth's surface layers, such as lateral heterogeneity, material properties along the wave path, local geological profile and type of elastic wave, gives rise to complex seismic signals on the free surface at the site of interest. Copyright © 2010 John Wiley & Sons, Ltd.     

Klobuchar电离层延迟改正模型精化方法的研究

在GPS导航定位中,单频接收机利用导航电文发播的Klobuchar电离层改正模型对电离层误差进行改正,但改正效果不太理想,为了提高其改正精度,并利用它进行电离层实时预报,我们通过电离层电子含量实测数据,对其进行精化,以满足要求。本文在原有Klobuchar电离层改正模型精化的基础之上,提出了一种新的精化方法,并对两种方法进行了比较研究,结果表明这两种精化方法对电离层的改正均有很好地提高,且本文提出的方法更优良。     

1833年嵩明8.0级地震对周围断层的影响

应用粘弹性计算程序,计算1833年嵩明8.0级大地震产生的同震和震后应力场变化,并计算对附近的小江断裂带、安宁河断裂带、则木河断裂带及云南境内红河断裂带造成的同震和震后库仑应力变化。结果表明,嵩明8.0级大地震对滇中南地区应力分布产生较大影响,对周围断层的影响甚至持续数百年的时间。嵩明8.0级地震使震中附近的小江断裂中段、安宁河断裂南段和红河断裂带中段库仑应力减小,降低发震危险;而小江断裂带南北段、安宁河断裂北段、则木河断裂带和红河断裂带南北两段库仑应力增加,地震危险性增强。红河断裂带中段在数百年时间尺度内始终处于嵩明8.0级地震库仑应力的减小区域,该研究结果有助于解释此断裂段的地震平静现象。     

COULOMB STRESS EVOLUTION AND SEISMIC HAZARD ALONG THE EASTERN BOUNDARY OF THE SICHUAN-YUNNAN BLOCK

Using a more realistic model of multi-layered viscoelastic media, and considering the effects of the coseismic dislocation and the postseismic viscoelastic relaxation caused by the 34 great earthquakes occurring along the eastern boundary of the Sichuan-Yunnan block since 1480 and the interseismic stress accumulation caused by the tectonic loading generated by plate motions which were modeled by introducing "virtual negative displacements" along the major fault segment in the region under study, we calculated the evolution of the Coulomb stress change in each fault plane of 18 major fault segments along the eastern boundary caused by the coseismic, postseismic and interseismic effects. We studied the interactions of the Xianshuihe, Anninghe, Zemuhe and Xiaojiang fault zones on the eastern boundary of the Sichuan-Yunnan block. By evaluating if the previous earthquake could bring another earthquake closer to or farther from failure, we analyzed the interactions of the earthquakes which occurred in the different segments in the same fault zone, or in the different fault zones respectively. And further based on the calculation results of the Coulomb stress change on the fault planes, we analyzed the seismic hazard of each fault segment.The results show that the previous earthquake may trigger another earthquake which can occur in the same fault zone or in the different fault zone. And the calculation results on the evolution of the cumulative Coulomb stress change in the each fault segment show that, the Coulomb stress increases significantly in the middle section and the Moxi segment of the Xianshuihe fault zone, the Mianning-Xichang segment of the Anninghe fault zone, the Qiaojia-dongchuan segment and the Jianshui segment of the Xiaojiang fault zone, and the seismic hazard in these fault segments is worthy paying attention to.     

Study on Postseismic Impact of Wenchuan Earthquake on the Sichuan-Yunnan Region Based on Three-Dimensional Viscoelastic Finite Element Method

Based on the lateral segmentation and vertical stratification characteristics of the crustal medium in Sichuan-Yunnan region,and the asymmetry of the static dislocations on the coseismic fault plane of the Wenchuan M_S8. 0 earthquake,we built a three-dimensional viscoelastic finite element model of the crust in the Sichuan-Yunnan region. The postseismic impact of the Wenchuan M_S8. 0 earthquake on the Sichuan-Yunnan region was studied.The results show that:① The far-field horizontal deformation caused by the viscoelastic relaxation of the medium in the 10 years after the earthquake is about 0-20 mm within the Sichuan-Yunnan diamond-shaped block,which has a greater influence on north side and smaller on south side.② In the 10 years after the earthquake,the far-field vertical deformation caused by the viscoelastic relaxation effect of the medium is small,and it shows an increase of about 0-4 mm in most areas of the Sichuan-Yunnan diamond-shaped block.③ The Xianshuihe fault and the eastern segment of the East Kunlun fault,which are close to the seismogenic fault,show a high gradient on deformation fields after the earthquake.④ In order to compare with the strong earthquake activity in the SichuanYunnan region after the Wenchuan earthquake, the horizontal stress state and the Coulomb failure stress change of the active block boundary are also calculated. From the spatial distribution of the coseismic and postseismic displacement field,the fault activity characteristics reflected by the stress state and the stress loading of the fault layer reflected by the Coulomb failure stress change,there is a certain correlation with the spatial distribution of strong earthquake activity in this region.     

Experimental beyond design and residual performances of full-scale viscoelastic dampers and their empirical modeling

Most past researches relevant to viscoelastic (VE) dampers, regardless of analytical and experimental ones, aimed at their design (or pre-damage) performance. In reality, however, under maximum considered or greater shaking caused by earthquakes, the shear deformation of the VE dampers installed in a structure may exceed or is even much larger than their nominal design range, thus leading to damage to the VE material. Under this circumstance, the structural design might become not conservative when the viscoelastically damped structure is a retrofit design or is not a supplemental damping design. Therefore, in this study, the beyond design and residual performances of the full-scale VE dampers after suffering damage are experimentally probed and compared with their design (or pre-damage) performance tested before. To have more engineering sense in practice, some suitable and conservative empirical post-damage models through considering reduction factors in the Kelvin-Voigt model for assessing the beyond design and residual performances of the full-scale VE dampers after suffering damage are recommended.     

基于GPS观测研究中国东北地区现今地壳形变特征

基于中国东北和俄罗斯远东东南部2012—2017年的GPS观测数据, 利用包含年周期、 半年周期、 线性项和阶跃项的函数模型拟合GPS站坐标时间序列, 得到ITRF2014下的速度场, 并进一步转换到欧亚参考框架下得到相对欧亚板块的速度场。 基于多尺度球面小波方法解算应变率场, 并分析了其空间分布特征, 同时研究了各GPS站对2011年日本东北M_W9.0大地震的震后松弛响应特征和背景形变场特征。 结果表明: ① 若不扣除日本东北大地震的松弛效应, 相对欧亚板块中国东北主体上表现为东南方向运动, 在依兰—伊通断裂和嫩江断裂带之间, 地壳表现为逆时针旋转, 其他区域向东南方向运动, 方向一致性较好, 在敦化—密山断裂东侧速度大小明显增加。 敦化—密山断裂和依兰—伊通断裂两侧拉张量分别为3.96±0.04 mm/a和0.71±0.05 mm/a, 两条断裂的剪切运动不明显。 总体上, 面应变率显示出NW—SE向的拉张和NE—SW向的挤压, 面应变率显示出依兰—伊通断裂南端、 嫩江断裂带北端和俄罗斯远东东南部呈挤压状态。 在依兰—伊通断裂、 敦化—密山断裂南侧以及俄罗斯远东东南部最大剪应变率相对较大。 ② 各GPS测站对2011年日本东北M_W9.0大地震震后松弛的响应整体上表现为东南向运动, 松弛形变量随震中距增加而减小。 松弛效应的面应变率总体上表现为NW—SE向的拉张和NE—SW向的挤压, 面应变率显示出依兰—伊通、 敦化—密山断裂南端、 嫩江断裂带北端以及俄罗斯远东地区具有挤压特征, 其他地区表现为拉张特征。 中国与俄罗斯远东边界南端存在一个明显的最大剪应变率高值区。 ③ 扣除日本东北M_W9.0大地震引起的松弛变形后, 总体上面应变率仍然表现为NW—SE向的拉张和NE—SW向的挤压, 面应变率最大值仍然位于依兰—伊通断裂和敦化—密山断裂南端、 第二松花江断裂带以及俄罗斯远东和中国边界最南段。 在依兰—伊通断裂、 敦化—密山断裂南端, 中国与俄罗斯远东边界南端的最大剪应变率高值区仍然存在, 表明这些地区应变积累较快, 并且一直在持续。     

循环荷载作用下合成纤维系缆粘弹塑性应力应变关系

在循环载荷作用下,合成纤维系缆的应力应变关系表现出明显的非线性特性,直接影响系泊缆绳的动力响应。如何针对其在循环载荷作用下的应力应变关系进行准确的定量描述是有关绷紧式系泊系统设计的关键问题。国内外研究者之前的研究不能反映缆绳的载荷历史、蠕变特性以及刚度变化过程,因此提出一个粘弹性粘塑性模型来描述合成纤维系缆的应力应变关系。本模型能够反映合成纤维缆绳的时间变化特性以及在整个加载—卸载过程中的刚度变化。此外,提出了明确的参数确定方法及步骤,基于简单的蠕变实验可以确定模型的各个参数。将两种载荷条件下聚酯缆绳的实验结果与模型结果进行对比,二者吻合较好,证明了模型的有效性和可靠性。本研究对于绷紧式系泊系统的研发和工程应用具有重要意义。     

中国东西部地区震后形变有效松弛时间研究

顾及脆性转换带上的断层蠕动及其深部黏滞流对震后地表位移的影响,对5次大地震的震后垂直位移进行了最小二乘反演,并估计了有效松弛时间。反演结果表明,中国东、西部地震的有效松弛时间差异很大,其中唐山地震的有效松弛时间最长(10.3年),邢台地震次之(4.4年),而西部通海、炉霍、共和等3次地震的有效松弛时间则仅为2年多。究其原因,可能主要是由于中国东部和西部地区上地壳厚度不同以及下地壳、上地幔黏滞系数的差异所致。