Resolving co- and early post-seismic slip variations of the 2021 MW 7.4 Madoi earthquake in east Bayan Har block with a block-wide distributed deformation mode from satellite synthetic aperture radar data

On 21 May 2021(UTC),an MW 7.4 earthquake jolted the east Bayan Har block in the Tibetan Plateau.The earthquake received widespread attention as it is the largest event in the Tibetan Plateau and its surroundings since the 2008 Wenchuan earthquake,and especially in proximity to the seismic gaps on the east Kunlun fault.Here we use satellite interferometric synthetic aperture radar data and subpixel offset observations along the range directions to characterize the coseismic deformation of the earthquake.Range offset displacements depict clear surface ruptures with a total length of~170 km involving two possible activated fault segments in the earthquake.Coseismic modeling results indicate that the earthquake was dominated by left-lateral strike-slip motions of up to 7 m within the top 12 km of the crust.The well-resolved slip variations are characterized by five major slip patches along strike and 64%of shallow slip deficit,suggesting a young seismogenic structure.Spatial-temporal changes of the postseismic deformation are mapped from early 6-day and 24-day InSAR observations,and are well explained by time-dependent afterslip models.Analysis of Global Navigation Satellite System(GNSS)velocity profiles and strain rates suggests that the eastward extrusion of plateau is diffusely distributed across the east Bayan Har block,but exhibits significant lateral heterogeneities,as evidenced by magnetotelluric observations.The block-wide distributed deformation of the east Bayan Har block along with the significant co-and post-seismic stress loadings from the Madoi earthquake imply high seismic risks along regional faults,especially the Tuosuo Lake and Maqên-Maqu segments of the Kunlun fault that are known as seismic gaps.

An Overview of Formation Mechanism and Disaster Characteristics of Post-seismic Debris Flows Triggered by Subsequent Rainstorms in Wenchuan Earthquake Extremely Stricken Areas

The Wenchuan earthquake induced large amounts of debris flows and catastrophic incidents triggered by subsequent rainstorms occurred frequently in the past 6 rainy seasons, and thus resulted in serious casualties, huge economic loss and long-term impact. In this paper, post-seismic debris flows distributed in 10 Wenchuan earthquake extremely stricken counties were verified and debris flow database consisting of 609 debris flows was established based on detailed investigation organized by Land and Resources Department of Sichuan Province. Combined with database and related studies, the impact of Wenchuan earthquake on debris flows was analyzed. And then variation of formation conditions including rainfall threshold and landform condition was analyzed by contrasting pre-seismic and post-seismic debris flows. Followed are some typical viewpoints on initiation mechanism of post-seismic debris flows. In the end of this paper, characteristics of postseismic debris flows triggered by subsequent rainstorms were comprehensively summarized, such as regional group occurrence, high frequency, high viscosity, chain effect, huge dynamics, large scale and long duration. We hope this paper will be helpful in understanding the formation mechanism, disaster characteristics and prevention countermeasures of post-seismic debris flows in Wenchuan earthquake extremely stricken areas.

Co- and post-seismic vertical displacements of Wenchuan Ms8.0 earthquake near Beichuan

Co- and post-seismic vertical displacements of the Wenchuan earthquake derived from two measurements in 2008 and 2010 along two partly-damaged leveling lines near the epicenter show the following features： Co-seismic displacement at Beichuan-Yingxiu fault was as large as 4. 711 m near Beichuan, where the maximum observed fault offset was 5.1 m. In contrast, the observed co-seismic offset of the Qingchuan fault in Pingwu County was only 0. 064 m. During 2008 - 2010, the post-seismic displacement rate was 5 - 27 mm/a near Beichuan-Yingxiu fault in Beichuan area, 20.6 mrn/a at Jiangyou-Guangyuan fault near Dakang, and only 0.2 - 1.3 mm/a at Qingehuan fault near Gucheng.

Co- and post-seismic slip analysis of the 2017 M_(W)7.3 Sarpol Zahab earthquake using Sentinel-1 data

The M_(w)7.3 Sarpol Zahab earthquake that occurred in the Zagros Fold-Thrust Belt(ZFTB) of Iran on November 12,2017 is the largest earthquake instrumentally recorded in the region.This earthquake provides an opportunity to investigate the slip behaviour and frictional properties of the fault,which is significant for assessing future seismic potential.In this study,we use Sentinel-1 images to map the coand post-seismic deformation to invert for the fault slip.The result indicates that most of the coseismic slip is buried in the depth range of 11-17 km,and the maximum slip is about 3.8 m at a depth of 15 km.The coseismic slip induces an increase of Coulomb stress in the unruptured area of the seismogenic fault plane,driving the afterslip.Based on the stress-driven afterslip,we obtain a frictional parameter of(ab)=(0.001-0.002) for the updip afterslip zone and(a-b)=0.0002 for the downdip afterslip zone in the framework of rate-and-state friction.The constitutive parameter(a-b) of the fault is very small,suggesting that the fault segments are close to velocity-neutral and may experience coseismic rupture.

Numerical simulation of influences of the earth medium's lateral heterogeneity on co- and post-seismic deformation

Many studies revealed that the Earth medium＇s lateral heterogeneity can cause considerable effects on the co- and post-seismic deformation field. In this study, the threedimensional finite element numerical method are adopted to quantify the effects of lateral heterogeneity caused by material parameters and fault dip angle on the co- and postseismic deformation in the near- and far-field. Our results show that： 1） the medium＇s lateral heterogeneity does affect the co-seismic deformation, with the effects increasing with the medium＇s lateral heterogeneity caused by material parameters; 2） the Lame parameters play a more dominant role than density in the effects caused by lateral heterogeneity; 3） when a fault＇s dip angle is smaller than 90, the effects of the medium＇s lateral heterogeneity on the hanging wall are greater than on the footwall; 4） the impact of lateral heterogeneity caused by the viscosity coefficient on the post-seismic deformation can affect a large area, including the near- and far-field.

Post-seismic relaxation from geodetic and seismic data

We have examined the aftershock sequence and the post-seismic deformation process of the Parkfield earthquake （2004, M = 6, California, USA） source area using GPS data. This event was chosen because of the possibility of joint analysis of data from the rather dense local GPS network （from SOPAC Internet archive） and of the availability of the rather detailed aftershock sequence data （http：]/www.ncedc.org[ ncedc[catalog-search.html）. The relaxation process of post-seismic deformation prolongs about the same 400 days as the seismic aftershock process does. Thus, the aftershock process and the relaxation process in deformation could be the different sides of the same process. It should be noted that the ratio of the released seismic energy and of the GPS obtained deformation is quite different for the main shock and for the aftershock stage. The ratio of the released seismic energy to the deformation value decreases essentially for the post-shock process. The similar change in the seismic energy[deformation value ratio is valid in a few other strong earthquakes. Thus, this decrease seems typical of aftershock sequences testifying for decrease of ratio of elastic to inelastic deformation in the process of post-shock relaxation when the source area appears to be mostly fractured after the main shock occurs, but the healing process had no yet sufficient time to develop.

Post-seismic relaxation process and vertical deformation following the 2008 Ms8.0 Wenchuan earthquake, China

The post-seismic horizontal and vertical deformations following the 2008 Ms8.0 Wenchuan earth- quake are inferred from GPS and precise leveling data. The post-seismic relaxation process is measured using GPS data from campaign stations located around the Longmenshan fault, and the derived decay time constant is 12 days. The evolution of the post-seismic vertical deformation is obtained from precise leveling data measured near the surface rupture. The results demonstrate that the hanging wall is uplifting and the foot wall is subsi- ding. The amplitude of the post-seismic deformation is lower than that of the co-seismic deformation. The re- gion with the largest post-seismic displacement is located on the leveling route between Maoxian and Beichuan on the hanging wall.

Time-space characteristics of viscoelastic post-seismic deformations corresponding to different rheology models

On a long time(>1 a)scale,the viscoelastic properties of mantle media significantly affect post-seismic deformation.The stress field disturbance in viscoelastic medium caused by fault slip gradually relax,and the relaxation process and its temporal-spatial characteristics are determined by the viscoelastic model.In this paper,we assume that the mantle media are types of common linear rheological models,i.e.,the Burgers body,the standard linear solid,and the Maxell body,and we calculate the dislocation Love number and Green function for a spherically symmetric,non-rotating,viscoelastic,and isotropic(SNRVEI)Earth model.The characteristics of the post-seismic relaxation deformations corresponding to the different models are compared.Our results show that for a short time period,the Burgers body and standard linear solid are similar;while for the long time period,the Burgers body and Maxwell body are similar.This suggests that the observations of post-seismic deformation on the surface have a great potential for the inversion of underground viscoelastic structures.However,the potential of using surface displacement to distinguish different rheological models is limited when the observation period is not long enough.

Studying the viscosity of lower crust of Qinghai-Tibet Plateau according to post-seismic deformation

The viscosity of lower crust of Qinghai-Tibet Plateau on earth should be determined. It has become a predominant problem in quantitative research on geodynamics. Its order of magnitude will have a great influence on the results of quantitative modeling. To obtain the viscosity of lower crust of Qinghai-Tibet Plateau, this parameter was calculated by three methods. The first is based on the estimation on the temperature state of Qinghai-Tibet Plateau in the deep part, and the viscosity of lower crust of northern Plateau was recomputed with strain rate derived from rheology law and GPS observation. Effective viscosity of middle crust in Kunlun region is between 1020 and 1022 Pa·s, and that of lower crust is be- tween 1019 and 1021 Pa·s; the second is based on three kinds of rheological models used to fit the post-seismic deformation recorded by cross-over fault GPS sites set after Ms8.1 Kunlun earthquake in 2001. The viscosity of lower crust obtained by this method is of 1017 Pa·s order of magnitude. However, higher viscosity is required to fit the data of south fault better, and the lower one is required to fit the data of north fault better. The viscosity of lower crust, which was obtained by fitting the cross-over fault post-seismic deformation after Ms7.6 Luhuo earthquake in 1973, is of 1019 Pa·s order of magnitude. Non-linear relationship between effective viscosity and strain rate is ignored in the former research of effective viscosity. This research shows the difference of effective viscosity obtained from laboratory experiment, and shorter and longer time post-seismic deformation after large earthquakes can be explained in phase.

海底震后形变多基站联合估计模型

海底基准站坐标时序可用于海底震后形变监测,但受观测条件和观测成本所限,海底基准站定位精度相对较低,难以获取高时间分辨率海底基准站坐标时序.针对小样本、非连续海底观测时序分析问题,本文提出将站速度、震后形变参数作为多个邻近基准站的公共参数进行联合估计,并将N-E方向震后形变弛豫因子也作为公共参数;提出了求解站坐标、站速度等线性参数与震后形变非线性参数进行混合非线性估计的“一步法”.试验表明,相对单站估计模型,本文提出的多站联合估计模型可克服海底基准站坐标时序样本有限和精度受限等问题,且相对于站速率和震后形变参数分离估计的“两步法”,“一步法”更为严密,可获得更为有效的震后形变参数估计.

新型带可更换耗能装置预制混凝土梁-柱节点抗震性能分析

该文提出了一种新型的带可更换耗能装置的预制混凝土梁柱节点。该装置主要由上下削弱钢板和开孔削弱H型钢板组成。设计了一个带有可更换耗能装置的试件和一个现浇整体试件,对其开展了梁端循环往复试验研究,探究了该节点的滞回响应、梁纵筋应变、极限承载能力、耗能能力、残余转角和震后可恢复性。试验结果表明,带可更换耗能装置的试件能够将塑性区域从梁柱的核心部分转移到耗能装置上,实现耗能装置耗能;在耗能装置屈服破坏时,梁柱仍为弹性状态;相比于现浇试件其耗能能力高出20%,该装置具有良好的耗能能力和震后可恢复性。

考虑地震动空间变化的区域公路网连通可靠性研究

区域公路网是社会交通大动脉和地震灾害救援生命线,连通可靠性反映了地震灾害发生后公路网的通行能力,地震动受震源位置及震中距的影响而具有显著的空间变化,对公路网的震后破坏状态具有重要影响。以邯郸地区公路网为研究对象,通过设定震源位置与震级,研究地震动空间变化影响下的区域公路网连通可靠性。首先,设定邯郸市1830年磁县大地震及一个虚拟地震为地震情景,分别设置震级为M6.0、6.5、7.0和7.5,基于地震动衰减关系表达地震动空间变化,得到公路单元对应的PGA。然后,结合地震易损性模型分析公路单元震后通行概率。最后,针对区域公路网空间范围大的典型特征,优化城市道路所用的最大可能状态算法,对邯郸地区公路网进行连通可靠性评估。结果表明,区域尺度下公路网络单元和节点数量多、空间展布复杂,其抗震连通可靠性与既有公路分布、区域城市位置等因素密切相关,地震动空间变化显著影响公路单元的震后破坏状态和通行概率,研究成果可为区域尺度公路网地震灾害评估及抗震韧性研究提供参考。

2008年M_(W)7.9汶川地震早期余震频度衰减速率空间分布特征分析

深入认识余震频度衰减及其影响因素对理解余震触发机理和震后应急救援具有重要意义.然而,由于强震后余震数量庞大,波形相互叠加导致了目录中余震缺失,进而影响了余震频度衰减速率的估计.本研究采用模板匹配技术对2008年M_(W)7.9汶川地震后约50天内连续数据进行扫描,检测余震数量约为模板地震数量的5倍,完备震级由M3.0降低到M2.3.根据余震沿映秀—北川断裂走向优势深度分布的变化,以映秀、汶川、茂县、北川、南坝为界,余震活动大致可分为6个区域.本研究利用最大似然法分别计算了各个区域的余震频度衰减速率,结果显示:以茂县、青川为界,余震频度衰减速率表现出映秀—北川断裂西南段较快、中间段居中、东北段较慢的特征.将余震频度衰减速率和余震空间分布、断裂类型、震后形变、同震形变等进行对比分析,本研究得到以下结论:1、余震频度衰减速率分区与断裂类型分区吻合.其中,映秀—北川断裂西南段余震频度较快衰减速率区域断裂以逆冲为主,中间段为经过各种震源机制类型交替出现的过渡带,映秀—北川断裂东北段余震频度较慢衰减速率区域断裂以右旋走滑为主;2、余震频度衰减速率西南段较快、东北段较慢的空间分布特征与震后形变特征相一致;3、余震频度衰减速率与同震形变相关性不强.结合本研究观测到的同震滑移量较大区域余震分布较少、部分区域余震数目和震后形变空间分布一致性等特征,我们推测汶川地震早期余震可能主要与震后余滑相关,余震频度衰减速率的空间分布差异主要与不同类型断裂震间滑移速率不同相关,震间滑移速率较快的区域余震频度衰减速率较快及震后形变较大.

集装箱式边缘数据中心震后功能概率评价方法

集装箱式边缘数据中心是5G通信网络中的一类重要节点,准确评价其在不同强度地震作用下的功能水平是5G通信网络震后功能评价的基础。该文以一个典型集装箱式边缘数据中心为研究对象,提出了该类数据中心震后功能的概率评价方法。详细分析了典型数据中心5个子系统的基本部件构成和各基本部件间的功能逻辑关系,建立了子系统的故障树模型和数据中心的状态树模型;通过数值模拟和文献调研,给出了数据中心各基本部件的地震易损性参数;将状态树和蒙特卡洛模拟相结合,计算出了典型数据中心的地震功能易损性曲线和参数。研究表明:空调内机、蓄电池柜和空调外机是集装箱式边缘数据中心的薄弱环节,改善这些薄弱环节可显著提升集装箱式边缘数据中心震后功能水平。

大庆SN油田东部过渡带油水边界综合确定

为确定大庆SN油田东部过渡带油水界面,综合钻井、测井、地震资料,结合岩心含油产状分析和老井油水层二次解释,基于双相介质理论的叠后属性油气检测以及基于叠前地震波形指示反演的流体识别等技术,探讨构造油气藏外扩区油水边界的综合确定方法。研究区油水边界具有以下特征:岩心含油产状为油斑以上;测井解释外推为油层或油水同层;叠后属性低高频能量比大于0.85;叠前反演预测含水饱和度小于75%。因此,以“井点定深度、地震定边界、动态来验证”为原则,从“点—线—面—空”,经过综合分析,确定最终油水边界位置。研究成果有效指导了研究区外扩评价部署,对同类型构造油田油水边界研究具有参考意义。

具有屈服后硬化刚度减震结构等效速度谱研究

具有屈服后硬化刚度减震结构的输入能计算中,等效速度谱一般通过改变结构阻尼比获得,这与实际不符,而不同的反应谱对输入能的计算精度影响较大。本文旨在构建综合考虑结构参数、场地类别和地震类型的等效速度谱,为相关减震结构能量设计提供参考。基于此,首先,建立了考虑屈服后硬化刚度影响的能量平衡方程及其运动方程,并构建了具有屈服后硬化刚度单自由度(single degree of freedom,SDOF)体系等效速度谱计算程序;其次,选取了不同场地类别和地震类型的120条地震记录,利用上述程序分析了屈服后硬化刚度、阻尼比、延性系数、场地类别和地震类型等五种因素对等效速度的影响规律;最后,利用数据拟合工具提出了综合考虑多因素影响的等效速度谱计算公式并与程序计算结果对比。研究表明:等效速度随硬化刚度系数的增大呈减小趋势,但对等效速度谱的下降段影响较小,同时,等效速度随延性系数和阻尼比增大也有减小趋势,但阻尼比影响更为显著。

基于叠后地震几何属性融合的煤层大尺度裂缝预测

煤层大尺度裂缝是导致煤矿瓦斯突出和矿井突水的主要因素之一,准确预测煤层中的大尺度裂缝对于煤层气开发和矿井水害治理至关重要。本文以叠后地震数据为基础,提取能够反映目标层位裂缝几何特征和分布信息的叠后地震几何属性;为避免单一地震几何属性在预测煤层大尺度裂缝时出现的多解性或不确定性问题,通过PCA(Principal Component Analysis)-BP(Back Propagation)神经网络(主成分分析与反向传播神经网络相结合)模型对相干、曲率、倾角、方差等地震几何属性进行融合,预测得到目标煤层大尺度裂缝分布特征。通过对比预测结果与实际揭露情况,90%的断层位置与大尺度裂缝发育区相一致,融合结果与构造解释结果吻合较好。表明基于地震几何属性融合的预测方法具有一定的效果,能在一定程度上刻画煤层大尺度裂缝的特征。

后锚固锚栓的抗震性能设计

后锚固锚栓即通过在混凝土、钢材等材料表面钻孔,并利用锚固技术将被连接件与之紧密连接的技术,可细分为机械锚固以及化学锚固两部分。在地震作用下,后锚固锚栓可以提供附加的抗震能力,提升结构的安全性。文中通过设计试验,对后锚固锚栓抗震性能进行了检验。

±800 kV换流站典型电气回路抗震性能研究

依托±800 kV布拖换流站一期工程,对直流场电气设备耦联回路进行有限元抗震分析。采用振型分解反应谱法和时程分析法对支柱绝缘子回路和直流滤波器回路进行抗震分析,研究了设备在地震作用下的应力和位移,为电气金具设计提供数据支撑。

预应力摇摆双层桥梁框架墩结构体系地震反应分析

为了提升双层桥梁结构震后功能的可恢复性,本文提出一种预应力摇摆双层桥梁框架墩结构体系。采用拉格朗日方程和动量矩守恒定理建立该类摇摆双层桥梁框架墩的动力反应分析模型,进行了结构地震反应的分析,给出了预应力束参数对体系地震反应的影响,并对Ricker小波作用下结构的抗倒塌能力进行了分析。研究结果表明:采用实际工程尺寸的预应力摇摆双层桥梁框架墩在E2地震作用下的残余位移小,结构基本无塑性损伤;增大初始预应力参数ρ_(t0)可以减小上层墩柱的位移反应,但下层墩柱的反应呈现一定程度的增大;在一定频率范围内预应力设计参数的增大可以提升结构的抗倒塌能力,但在另外一些频率范围内则存在负效果。