Tectonic deformation buildup in folded mountain terrains in the October 23, 2004, Mid-Niigata earthquake

The October 23, 2004, Mid-Niigata Earthquake jolted central Japan, causing serious damage in a mountainous region of Pliocene sedimentary rocks. Though aftershocks distribution showed a diffused pattern, it indicated that a blind-thrust fault having a NE–SW strike and inclined towards NW was the most causative. Tectonic deformation caused by this faulting was considered to be one of the causes of flooding that occurred about 8 months after the earthquake. Precise digital elevation models (DEMs) before and after the earthquake were obtained with stereoscopy for aerial photographs and laser imaging detection and ranging technology (LIDAR), respectively, and then compared to detect elevation changes and translations. Lastly, the changes of landforms due to landslides are excluded from the estimated deformations to obtain only the components of tectonic deformations of the ground surface.     

汶川地震中绵阳市梓潼县水库土坝震害调查与分析

5·12汶川特大地震对绵阳市梓潼县170座水库造成了不同程度的破坏和严重的经济损失.依据绵阳市梓潼县水库地震灾害的现场科学考察资料,对绵阳市梓潼县48座高危以上险情水库土坝的震损情况做了初步总结和分析.典型震害现象包括裂缝、渗漏以及泄水建筑物和附属设施的损毁等;以梓潼县3座典型震损水库土坝为例,总结了震损水库的特点和经验教训,给出了一些建设性结论.     

地震动参数与地震灾害相关性分析——以汶川震区地震滑坡灾害为例

本文以汶川地震滑坡震害为例, 设计一种方法, 对几个反映不同地震动特性的地震动参数与地震滑坡灾害的相关性进行了分析比较.结果表明: Arias强度参数与地表破坏的相关性最好, 该参数比较适合小区域范围的震害预测评估; 峰值加速度与地表破坏的相关性较好, 但更适合作为较大区域的震害评估参数; 与持时和频率有关的参数对于具体场地的震害机理分析具有辅助作用; 垂向地震动对滑坡震害的作用不容忽视. 本文结论对于其它震害相关研究中评估因子的选取具有参考意义.      

Numerical modeling of vibrations induced by railway traffic in tunnels: From the source to the nearby buildings

In this paper, a numerical approach for the prediction of vibrations induced in buildings due to railway traffic in tunnel is proposed. The numerical method is based on a sub-structuring approach, where the train is simulated by a multi-body model; the track–tunnel–ground system is modeled by a 2.5D FEM–PML approach; and the building by resource to a 3D FEM method. The coupling of the building to the ground is established taking into account the soil–structure-interaction (SSI). The methodology proposed allows dealing with the three-dimensional characteristics of the problem with a reasonable computational effort. Using the proposed model, a numerical study is developed in order to better discern the impact of the use of floating slabs systems for the isolation of vibrations in the tunnel on the dynamic response of a building located in the surrounding of the tunnel. The comparison between isolated and non-isolated scenarios allowed concluding that the mats stiffness is a key parameter on the efficiency of floating slab systems. Furthermore, it was found that the selection of the stiffness of the mats should be performed carefully in order to avoid amplification of vertical vibrations of the slabs of the building.     

Observations of damage due to the Kashmir earthquake of October 8, 2005 and study of current seismic provisions for buildings in Pakistan

On October 8, 2005 an earthquake of magnitude 7.6 (M _w) struck the Kashmir region of Pakistan causing widespread damage to buildings and infrastructure. This paper summarizes field observations of building damage made by the Earthquake Engineering Field Investigation Team (EEFIT) after the event, where the performance of residential, commercial and government buildings was investigated. A study of the seismic design provisions currently in place in Pakistan is presented and compared with seismic provisions of EC8 (1998) and UBC (1997). Several problems are identified for the implementation of the Pakistan seismic code in its current form and recommendations are made for its improvement in order to be used for the reconstruction of affected areas.     

同震重力变化对震源滑动参数的敏感性研究：以2004年苏门答腊地震为例

在地震孕育和发生过程中,常伴有地表重力变化.通过同震重力变化反演震源参数,可以为认识地震活动特征奠定基础.为了有效提高同震重力变化反演滑动参数的精度,本文设计了一套定量化表征同震重力变化对震源不同滑动参数敏感性的方法.首先,基于位错理论,通过正演得到震源不同滑动参数下的同震重力变化;随后,利用无量纲化的敏感性分析方法,计算同震重力变化对不同滑动参数的敏感度因子.以2004年苏门答腊地震的断层模型为参考,定量评估了该地震同震重力变化对断层深度、断层倾角、滑移量和滑动角四个独立震源滑动参数的敏感性.评估结果显示,2004年苏门答腊地震同震重力变化对滑移量、滑动角、断层深度和断层倾角这四个独立震源滑动参数的敏感性依次降低.因对滑移量的敏感性远高于对断层倾角的敏感性,滑移量较小的反演偏差可以造成断层倾角较大的反演偏差.所以,在反演过程中,需要更加重视排序靠前的滑移量和滑动角.本文设计的方法虽然适用于其他震例,但在不同震例中,同震重力变化对各滑动参数的敏感性将有所差别.

     

Fault induced permanent ground deformations: Experimental verification of wet and dry soil, numerical findings’ relation to field observations of tunnel damage and implications for design

Few building codes contains provisions fault surface ruptures and accompanying soil deformations which constitutes a great risk to human lives, buildings and infrastructure. A numerical and experimental comparison show a fair agreement of result. Analysis of “real” scale show the how water increases the incompressibility of wet soil causing shear deformations to become larger and conjugate ruptures to appear for reverse faults. Field observations and numerical analysis indicates that horizontal compression of soil surrounding underground structures should be taken into account in design.     

构造"稳定"区强震长期预测的简便途径--以张北地震为例

作为强震长期预测基础的地震带、潜在震源区的划分,仍然依据地震构造类比和地震活动重复两原则。现有的强震长期预测方法在构造“稳定”区,即没有活动构造、没有历史地震(包括古地震)资料的条件下,无能为力。通过张北地震资料的分析,高精度地震定位并结合波形数据反演震源机制的结果表明：在稳定而统一的构造应力场的作用下,沿其最大剪切应力方向上的小地震集中成带,并且持续活动、震源机制的优势取向与应力场吻合,小震带便可以看作属于现今活动的震源断层,在地震长期预测工作中可以作为划分潜在震源区的依据。构造“稳定”区发生的强震属于新破裂。     

历史地震参数校订方法探讨——以北京延庆公元294年地震为例

随着应用、研究的广泛和深入,对历史地震参数精度有了更高的要求.因此,有必要探讨历史地震参数校订的新思路和新方法.公元294年（晋惠帝元康四年）记载了北京延庆的一次强震事件.由于年代久远,史料简略,对史料的理解及对此次地震的参数存在分歧.通过系统收集、整理原有研究成果,详细分析其异同,并通过细读原始资料,实地考察以及定量分析1970年以来的中小地震时空分布特征与强震的关系等多个方面,对此次地震参数进行了校订.校订后的结果是：地震名称应为北京延庆海坨山地震,发震时间为公元294 年9月,震级为6级,震中位置为115.85deg;E、40.59deg;N,震中误差为Ⅱ类.并以此为例,探讨了历史地震参数校订的一般原则和方法.     

变质岩区地震波速度的特点及其影响因素--以中国大陆科学钻探孔区为例

地震波速度是地震勘探中最重要的一个参数，而VSP测量是一种比较直接且行之有效的获取地震波速度的方法。文中结合中国大陆科学钻探工程预先导孔和先导孔的VSP速度分析成果，总结超高压变质岩地区地震波速度的主要特征；探讨影响变质岩地震波速度的因素。认为除密度和岩性外，变质作用的类型和强度是决定性因素，而变质期后和／或后期的各种构造地质作用对变质岩地震波速度的影响是显著的，但范围常常又是局部的。     

Rock magnetic analyses as a tool to investigate diversity of drift pumice clasts: An example from Japan's 2021 Fukutoku-Oka-no-Ba (FOB) eruption

The crystallization of nanolites within magma chambers has recently raised a strong interest due to their impact on increasing melt viscosity and triggering magmatic eruptions. In 2021, the Fukutoku-Oka-no-Ba (FOB) underwater eruption produced large quantities of pumices that eventually formed rafts drifting at the surface of the ocean to the East coasts of Japan. Pumices collected along the shore shortly after grounding show various colors, microscopic and Raman analyses made by Yoshida et al. (Island Arc, 31, 1, 2022) revealed the presence of magnetite nanolites in some of them. In this study, we explore the magnetic properties of a batch of pumices of different colors from the FOB eruption, aiming to refine characterization of iron oxide nanolites. We used various analytical techniques such as SEM and FEG-SEM observations, EDS-X analyses, and rock magnetic experiments, including thermomagnetic analyses, hysteresis curves, coercivity analyses and FORC measurements. Our findings reveal that the iron oxides present in the FOB samples are Ti-magnetite, with minor amounts of Mg and Al. The magnetic crystals show a wide range of sizes, from extra small iron oxide nanolites (ESION) in the pumices with the lighter colors, to more bulky grains reaching the micrometer size in some of the dark color samples, significant diffusion is inferred in that case. Consequently, the magnetic characterization of iron oxide crystals within the Fukutoku-Oka-no-Ba pumices reveals varying stages of nucleation, dissolution, growth, and diffusion processes, providing evidences for the heterogeneous state of the magma during the eruption.     

建(构)筑物地震破坏等级划分标准有关问题研究

我国国家标准《建(构)筑物地震破坏等级划分》GB/T24335-2009已于2009年7月16日发布,2009年12月1日开始实施。为了更好地了解该标准,本文介绍了该标准制定过程中一些有关问题的研究情况,主要回顾了我国建(构)筑物地震破坏等级划分的发展历史,总结了国内外现有建(构)筑物地震破坏等级的划分方法,并对其优缺点进行了评述。在此基础上,对标准制定过程中存在的问题进行了讨论,给出了相应的解决办法。     

Influence of earthquake ground‐motion duration on damage estimation: application to steel moment resisting frames

This paper presents an analytical study evaluating the influence of ground motion duration on structural damage of 3‐story, 9‐story, and 20‐story SAC steel moment resisting frame buildings designed for downtown Seattle, WA, USA, using pre‐Northridge codes. Two‐dimensional nonlinear finite element models of the buildings are used to estimate the damage induced by the ground motions. A set of 44 ground motions is used to study the combined effect of spectral acceleration and ground motion significant duration on drift and damage measures. In addition, 10 spectrally equivalent short‐duration shallow crustal ground motions and long‐duration subduction zone records are selected to isolate duration effect and assess its effect on the response. For each ground motion pair, incremental dynamic analyses are performed at at least 20 intensity levels and response measures such as peak interstory drift ratio and energy dissipated are tracked. These response measures are combined into two damage metrics that account for the ductility and energy dissipation. Results indicate that the duration of the ground motion influences, above all, the combined damage measures, although some effect on drift‐based response measures is also observed for larger levels of drift. These results indicate that because the current assessment methodologies do not capture the effects of ground motion duration, both performance‐based and code‐based assessment methodologies should be revised to consider damage measures that are sensitive to duration. Copyright © 2016 John Wiley & Sons, Ltd     

2016年M6.2呼图壁地震发震构造及其对天山构造带隆升的启示:来自中近场钻孔应变观测的证据

天山山脉在新生代经历了强烈的构造隆升和地壳缩短作用,其周缘发生的地震活动是了解这一构造模式的窗口.对2016年呼图壁地震的发震构造有两种解读：向南倾斜的低角度逆断层和向北倾斜的高角度逆断层.中近场四台钻孔应变仪记录到了本次地震的同震响应,本文采用均质模型对IGP-CEA和USGS震源机制解进行模拟,结果显示发震断层为向北陡倾的反冲断层,15个原始方位和8个N-S、E-W方位观测值全部与预测值一致.对比天山北缘常见的低角度逆冲断层,反冲断层对构造隆升的贡献更有效,以断层倾角70°和19°计算,二者对隆升和缩短贡献比例分别为2.89：1和1：2.76.这一结果表明天山构造带内部的反冲构造同样具有单独发震的可能性,它们对天山现今的隆升高度同样起着不可忽视的作用.

     

礼县—罗家堡断裂晚第四纪活动特征:兼论1654年礼县8级地震孕震机制

1654年7月21日甘肃省礼县8级地震发生在南北地震带的中北段, 该地区的构造变形和构造活动与青藏高原向北东方向的扩展密切相关, 复杂的构造几何特征主要受控于东昆仑断裂、西秦岭北缘断裂和一系列北东向断裂. 礼县—罗家堡断裂为一条北东东向的左旋走滑活动断裂, 错断了含有仰韶文化红色陶瓷片的一级阶地堆积物, 阶地面上断层陡坎高约1.5 m. 沿断裂带发现冲沟的左旋位错量为3~10 m, 晚更新世黄土中残留的断层陡坎高4.5~8 m. 其中两条冲沟中发现裂点, 高3.5~3.9 m, 距断层陡坎的距离为16 m. 礼县—盐关—罗家堡—天水镇一带发育大量的滑坡, 长轴走向与礼县—罗家堡断裂一致, 滑坡体后缘、侧壁陡峭, 出露晚第四纪黄土, 鲜有植被覆盖. 礼县—罗家堡断裂为1654年8级地震的发震断裂.综合分析认为, 受青藏高原向北东方向的扩展, 被西秦岭北缘断裂、礼县—罗家堡断裂和岷县—宕昌断裂围限的礼县次级地块向南东滑动可能导致了1654年礼县8级地震的发生. 断裂北、南两侧地壳电性结构的差异为强震的孕育提供了深部构造条件.     

基于随机森林算法的陆相沉积烃源岩定量地震刻画:以东海盆地长江坳陷为例

烃源岩的定量地震刻画对于勘探开发区块的优选、盆地油气资源量的估算都具有重要意义.陆相沉积环境下的浅湖或半深湖相的烃源岩横向变化快,其空间展布需要依靠钻井约束下的反射地震进行刻画,但是其地震弹性特征与岩性和有机质含量的映射关系呈现高度非线性化,因而很难利用传统基于地震岩石物理模型驱动的烃源岩地震预测方法进行有效刻画.本文以低勘探区的东海盆地长江坳陷为例,提出了一种在数据驱动的机器学习框架下,综合利用地质约束、钻井录井、测井、地球化学和叠前地震数据进行烃源岩的定量地震刻画的工作流程.其核心思想是利用随机森林集成学习算法对小样本数据表现优异的特征,以井位处的测井弹性数据（纵波速度和密度）、岩性、地球化学标定的总有机碳含量（TOC）为样本标签数据,在地质导向约束下通过随机森林算法生成学习网络,并将该网络与叠前地震反演结果相结合,采取先预测泥岩再预测总有机碳含量的"两步走"策略,完成对烃源岩空间分布及其非均质性的定量地震刻画,并对预测结果的不确定性进行评价.测试结果显示,随机森林算法相较于其他的机器学习算法能够更准确的识别陆相沉积地层的泥岩,并比传统的利用阻抗转化方法获得更可靠的总有机碳含量预测结果.     

Study on relationship between features of strain anomaly obtained by borehole strain meter at Wushi station in Xinjiang and strong earthquake: Taking Jiashi MS = 6.8 earthquake as an example

Introduction According to the Seismograph Network of China, an earthquake of MS=6.8 occurred at10:03:42 on February 24, 2003 in Jiashi county, Xinjiang (39.55°N, 77.15°E) with the focal depthof 25.2 km. The macroseismic epicenter located at the boundary of Bachu and Jiashi counties,Xinjiang Uygur Autonomous Region. 248 persons died and 4 853 ones were injured (2 058 ofthem were heavily injured) in the earthquake. 49 656 households (about 205 079 persons) losttheir houses. The Dis…     

数字科普馆建设对防震减灾科普宣传的启示——以海南省地震局防震减灾数字科普馆为例

随着数字化技术的发展和互联网的普及,互联网+防震减灾科普已成为实现防震减灾科普社会化的最有效途径。数字地震科普馆作为计算机技术发展的产物,在更深更广的时空范围内进行地震知识的普及,能够极大地提高地震科普宣传的质量和效率。本文以海南省地震局防震减灾数字科普馆为例,介绍其构建及实现技术,说明其应用情况,探讨了数字科普馆对防震减灾科普宣传的启示及其对未来宣传防震减灾科学知识的促进作用。     

基于数值模拟和地震活动性统计的混合地震预测: 在中国地震科学实验场的应用

地震数值预测是近年来最为前沿的科学研究问题之一,但是大部分地震数值预测的探索都受困于数值模拟步长的问题.本文引入混合预测方法,探索了较短预测时长的地震数值预测方法,并在中国地震科学实验场区中进行应用.该混合预测方法主要建立在活动块体理论和构造力学分析的基础上,利用数值模拟推测未来长时间的应力变化量,并引入上一次7级地震之后数十年间,中等强度地震同震应力的影响,最后通过重分类和加权,在应力变化量上叠加年尺度小地震活动异常的统计,从而实现区域地震危险程度的混合评估.基于该方法,我们将地震数值预测的预测时间尺度缩短到年尺度,以年为单位滚动预测了中国地震科学实验场自2021—2030年或更长时间段内可能出现中强地震的区域.2022年芦山6.1级地震、2021年漾濞6.4级地震、2021年泸州6.0级地震和2022年泸定6.8级地震均发生在危险性较高的区域,而2022年马尔康6.0级地震则不在预测区域内.本文展示的混合预测尝试为地震数值预测研究提供了一个可供参考的例证,也为解决数值预测步长控制难的问题提供了一个可能的探索途径.

     

1997年玛尼地震对青藏川滇地区构造块体系统稳定性影响的三维DDA+FEM方法数值模拟

本文用三维非连续变形与有限元相结合（DDA+FEM）的方法,在青藏川滇地区三维构造块体相互制约的大背景中,通过用GPS资料做位移速率边界约束和震源机制约束,计算得到研究区的初始位移场和应力场与该地区GPS测量结果和震源机制分布结果基本一致.在此基础上进一步数值模拟1997年玛尼7.9级大震的发生过程,研究大震引起研究区各块体边界断层应力状态变化的特征.（1）发震断层两侧发生左旋走滑错动,最大水平位错大约7 m;（2）深部位错面上位错分布与用地震波资料震源反演的结果类似;（3）最大差应力变化等值线图与由星载D\|INSAR技术获取的地表形变场图像相似;（4）地表垂直位移表明地震断层面略向北逆冲.计算模拟得到了玛尼地震发生引起青藏川滇地区构造块体系统各边界断层上库仑破裂应力变化的分布,表明玛尼大震的发生除了使其发震断层的两端库仑破裂应力增大,应力进一步集中外,位于上地壳层上东昆仑断裂中段的2001年昆仑山8.1大震（H=11 km）发震断层段的库仑破裂应力增加约2 MPa,位于中地壳层上喀拉昆仑断裂带中的2008年改则6.9级地震（H=30 km）发震断层段的库仑破裂应力也增加约0.7 MPa,可见这两个已接近破裂强度地段的失稳对发生大震起了一定促进作用.研究结果也表明：作者发展的三维DDA+FEM方法能有效地用于大震活动与各构造块体相互作用关系的研究.