Quantitative data about active tectonics and possible locations of strong earthquakes in the future in the northwestern Beijing

Deterministic, probabilistic and composite-grading methods are used to get the possible locations of strong earth-quakes in the future in Norwest Beijing and its vicinity based on the quantitative data and their accuracy about active tectonics in the research area and by ordering, some questions in the results are also discussed. It shows that the most dangerous fault segments for strong earthquakes in the future include: segments B and A of the southern boundary fault of the Yangyuan basin, the southern boundary fault of the Xuanhua basin, the east segment of the southern Huaian fault and the east segment of the northern YanggaoTianzhen fault. The most dangerous area is YangyuanShenjing basin, the second one is TianzhenHuaianXuanhua basin and the third dangerous areas are WanquanZhangjiakou and northeast of Yuxian to southwest of Fanshan.

2013年四川芦山M_(S)7.0地震仪器烈度与调查烈度对比分析

基于2013年四川芦山M_(S)7.0地震宏观调查点、调查烈度和强震仪记录数据,采用四川省地震局强震动监测技术组计算得到的各台仪器烈度值,绘制了芦山M_(S)7.0地震宏观调查点与调查烈度等震线和仪器烈度等值线分布图,分析了芦山M_(S)7.0地震的仪器烈度与调查烈度的对应关系。结果表明:仪器烈度与调查烈度有较好的对应关系,仪器烈度Ⅵ度点在调查烈度Ⅵ度以上区域总体占比为88.24%,仪器烈度Ⅶ度点在调查烈度Ⅶ度以上区域内总体占比为81.82%;仪器烈度的等值线高值范围可较好展示出地震灾害的程度;仪器烈度区的空间分布特征可表征芦山M_(S)7.0的发震断裂的控制作用,仪器烈度的等值线区总体呈现沿龙门山断裂带方向相对于垂直方向衰减慢;仪器烈度的等值线区发震断裂上盘影响范围相对发震断裂下盘影响范围大;仪器烈度分布与调查烈度分布既有对应关系又存在差异,这在震后短时间内灾区的震灾信息尚不清楚的情况下,能够快速对可能的震害涉及范围、人员伤亡分布、经济损失和生命线工程等损失作出预估,仪器烈度分布可以为应急救援决策、救灾方案制定和救灾力量部署等工作提供重要依据。

Upper crustal velocity and seismogenic environment of the M7.0 Jiuzhaigou earthquake region in Sichuan, China

On August 8,2017,a magnitude 7.0 earthquake occurred in Jiuzhaigou County,Sichuan Province,China.The deep seismogenic environment and potential seismic risk in the eastern margin of Tibetan Plateau have once again attracted the close attention of seismologists and scholars at home and abroad.The post-earthquake scientific investigation could not identify noticeable surface rupture zones in the affected area;the complex tectonic background and the reason(s)for the frequent seismicity in the Jiuzhaigou earthquake region are unclear.In order to reveal the characteristics of the deep medium and the seismogenic environment of the M7.0 Jiuzhaigou earthquake region,and to interpret the tectonic background and genesis of the seismicity comprehensively,in this paper,we have reviewed all available observation data recorded by the regional digital seismic networks and large-scale,dense mobile seismic array(China Array)for the northern section of the North-South Seismic Belt around Jiuzhaigou earthquake region.Using double-difference seismic tomography method to invert the three-dimensional P-wave velocity structure characteristics of the upper crust around the Jiuzhaigou earthquake region,we have analyzed and discussed such scientific questions as the relationship between the velocity structure characteristics and seismicity in the Jiuzhaigou earthquake region,its deep tectonic environment,and the ongoing seismic risk in this region.We report that:the P-wave velocity structure of the upper crust around the Jiuzhaigoug earthquake region exhibits obvious lateral inhomogeneity;the distribution characteristics of the shallow P-wave velocity structure are closely related to surface geological structure and formation lithology;the M7.0 Jiuzhaigou earthquake sequence is closely related to the velocity structure of the upper crust;the mainshock of the M7.0 earthquake occurred in the upper crust;the inhomogeneous variation of the velocity structure of the Jiuzhaigou earthquake area and its surrounding medium appears to be the deep structural factor controlling the spatial distribution of the mainshock and its sequence.The 3D P-wave velocity structure also suggests that the crustal low-velocity layer of northeastern SGB(Songpan-GarzêBlock)stretches into MSM(Minshan Mountain),and migrates to the northeast,but the tendency to emerge as a shallow layer is impeded by the high-velocity zone of Nanping Nappe tectonics and the Bikou Block.Our results reveal an uneven distribution of high-and low-velocity structures around the Tazang segment of the East Kunlun fault zone.Given that the rupture caused by the Jiuzhaigou earthquake has enhanced the stress fields at both ends of the seismogenic fault,it is very important to stay vigilant to possible seismic hazards in the large seismic gap at the Maqu-Maqên segment of the East Kunlun fault zone.

华北平原中南部聊城-兰考断裂的第四纪晚期活动性探测——兼论1937年菏泽7.0级地震发震机制

华北平原是中国人口最多、经济最为发达的地区之一,也是受地震灾害影响最为严重的地区之一。对于该地区断裂活动性和大地震发震机制的研究有利于探索板内地震的发震规律、减轻地震灾害所造成的损失。聊城-兰考断裂是华北平原中南部一条重要的隐伏深大断裂。结合浅层地震勘探、钻孔勘探和第四纪测年方法,对聊城-兰考断裂的活动性进行了精细的研究。坝城寺钻孔揭示聊城-兰考断裂南段错断了全新统底界,为全新世早期活动断裂,揭露出该断裂晚更新世以来造成了4次古地震事件,单次事件的垂直位错为1.2±0.2~3.7±0.2 m。根据钻孔揭示的地层落差计算出该断裂晚更新世早期的平均垂直滑动速率约为0.1±0.05 mm/a,晚更新世晚期—全新世中期的平均滑动速率为0.35±0.04 mm/a。根据1937年菏泽7.0级和6(3/4)级地震的等震线和地表破裂分布特征认为,小留-解元集断裂和东明-成武断裂为该地震的发震断裂;聊城-兰考断裂对于该地区应力的积累、地震的发生具有很好的控制和约束作用,为区域控震构造。

Intracontinental basins and strong earthquakes

The September 17, 1303 Hongtong M=8 earthquake occurred in Linfen basin of Shanxi down-faulted basin zone. It is the first recorded M=8 earthquake since the Chinese historical seismic records had started and is a great earth-quake occurring in the active intracontinental basin. We had held a Meeting of the 700th Anniversary of the 1303 Hongtong M=8 Earthquake in Shanxi and a Symposium on Intracontinental Basins and Strong Earthquakes in Taiyuan City of Shanxi Province on September 17~18, 2003. The articles presented on the symposium discussed the relationships between active intracontinental basins of different properties, developed in different regions, in-cluding tensional graben and semi-graben basins in tensile tectonic regions, compression-depression basins and foreland basins in compressive tectonic regions and pull-apart basins in strike-slip tectonic zones, and strong earth-quakes in China. In this article we make a brief summary of some problems. The articles published in this special issue are a part of the articles presented on the symposium.

Emergency Response to the MS7.0 Jiuzhaigou,Sichuan Earthquake,and Characteristics of Seismic Disasters in the Stricken Area in Gansu Province

This paper introduces the response process of the Gansu Earthquake Agency during the Jiuzhaigou M_S7.0 earthquake in Sichuan Province,including earthquake emergency disposal procedures,information reports,disaster investigation and intensity assessment,seismic monitoring and trend determination,and emergency dissemination. This paper reveals the characteristics of earthquake damage in the quake-hit areas of Gansu Province,draws some corresponding conclusions and summarizes the countermeasures for recovery and reconstruction in the quake-hit areas of Gansu Province.

Characteristics and Analysis of the Seismic Damage from the MS7.0 Jiuzhaigou Earthquake in the Area between Songpan and Jiuzhaigou

This paper expounds the features of the buildings and analyzes the seismic disaster characteristics of the Jiuzhaigou M_S7. 0 earthquake in the area between Songpan and Jiuzhaigou. New buildings (especially the frame structure) had good anti-seismic performance,but brick-wood structures and brick-concrete structures sustained large amounts of damage in the earthquake. By computing the seismic damage index,we found that the seismic damage index of the frame structure was far less than that of civil structures and brick-wood structures. The seismic damage index of frame structures were all zero in the Ⅵ area,and increased rapidly with the increase of intensity,but the increasing range was reduced. We also discussed how to evaluate the intensity in areas where there was a lack of buildings or there was only one structure type,which can be referenced in future field work.

Analysis of Digital Strong Motion Records of the M_S 8.0 Wenchuan Earthquake by the Network of Shaanxi Province

Records of the May 12, 2008 Ms8.0 Wenchuan, Sichuan, earthquake from 27 stations of Shaanxi Digital Strong Motion Network are processed and analyzed, including baseline adjustment of acceleration traces, filtering, and calculations of velocities, displacements and acceleration response spectra. The results show that direction energy radiation of the large earthquake and horizontal inhomogeneous medium along the wave traveling path might both have some effect on the scattering degree of the attenuation of PGAH, besides influence of local site conditions. For the same intensity, the ratios of PGA/PGV are commonly small, on average about 5, which indicates that long period components are rich in ground motion. Intensities for most sites of the stations are within V -VII. The larger one among PGAE-W and PGAN-S is quite close to their PGAH, which is less than 10 % in relative deviation. The dominated waves are surface waves. The thicker the soil overburden is, the stronger the surface wave will be and the longer the shaking will last. Local site conditions have strong effects on ground motion, especially those of thick sediment filled-in basins, as they can significantly amplify long-period components.

汶川M_(S) 8.0、芦山M_(S) 7.0地震晚期显著余震的“窗口”效应

1研究背景地震窗是一些频度较高、地震丛集的小区域,如一些大震的余震区、经常发生小震群的区域等。这些区域对构造应力场的变化比较敏感,其地震频度或应变能等的异常变化有可能反映周边区域的应力场变化,从而可用以提取周围区域发生中强地震的前兆信息(中国地震局监测预报司,2020)。早期研究发现华北邢台、海城、唐山3次强震的余震序列可作为监视华北地区中强以上地震孕育的“窗口”(王泽皋,1979;姜秀娥等,1982)。

2013年四川芦山M_S7.0地震强地面运动模拟

运用经验格林函数法模拟2013年4月20日芦山MS7.0地震的近场强地面运动.在拟合过程中,首先参考前人远场反演结果给出的滑动量分布特征和主震波形的包络线特征,确定强震动生成区的大致范围和数量;然后利用Somerville等提出的地震矩与凹凸体面积的经验关系式确定强震动生成区细小划分的初值,继而利用遗传优化算法确定以上二者的最优值及其它震源参数.将数值模拟波形与实际地震观测记录在时间域和频率域分别进行比较,结果显示,在所选取的30个观测台站中,多数台站的数值模拟结果与实际观测结果符合得很好,特别是大于1Hz的高频部分.断层面上有两个强震动生成区,其位置与前人反演的滑动量集中分布区相一致,而且强震动生成区规模比Somerville等获得的标度率估计值要小.

The GIS and analysis of earthquake damage distribution of the 1303 Hongtong M=8 earthquake

The geography information system of the 1303 Hongtong M=8 earthquake has been established. Using the spatial analysis function of GIS, the spatial distribution characteristics of damage and isoseismal of the earthquake are studied. By comparing with the standard earthquake intensity attenuation relationship, the abnormal damage dis-tribution of the earthquake is found, so the relationship of the abnormal distribution with tectonics, site condition and basin are analyzed. In this paper, the influence on the ground motion generated by earthquake source and the underground structures near source also are studied. The influence on seismic zonation, anti-earthquake design, earthquake prediction and earthquake emergency responding produced by the abnormal density distribution are discussed.

Study on the Genesis of the Yongsheng Earthquake with M_S6.0 on October 27, 2001

On October 27, 2001, a large earthquake with M S6.0, named the Yongsheng earthquake, occurred along the Jinshajiang segment of Chenghai fault in Yongsheng County, Yunnan Province. It is the largest event to occur along the Chenghai fault in the last 200 years. The seismo-geological survey shows that the seismogenic fault, which is the Jinshajiang segment of Chenghai fault, takes left-lateral strike-slip as its dominant movement pattern. According to differences in vertical motion, motion time, landforms and scales, the Chenhai fault can be divided into eight segments. The Jinshajiang segment has a vertical dislocation rate of 0.4 mm/a, far lower than the mean rate of the Chenghai fault, about 2.0 mm/a. It’s deduced that the two sides of Jinshajiang segment “stuck" tightly and hindered the strike-slip of the Chenghai fault. The strong earthquake distribution before this event shows that the Jinshajiang segment was in the seismic gap. The Chenghai fault, as a boundary of tectonic sub-blocks, makes the Northwest Yunnan block and the Middle Yunnan block move clockwise, and their margins move oppositely along the Chenghai fault. In the motion process of the Chenghai fault, structural hindrance and the seismic gap of strong earthquakes are propitious to the concentration and accumulation of structure stress. As a result, the Yongsheng M S6.0 earthquake occurred. The Sujiazhuang-Shangangfu segment is similar to the Jinshajiang segment with a low vertical motion rate of 0.3 mm/a and in the seismic gap. So it’s postulated that the segment may become a new structure hindrance, and the Yongsheng M S6.0 earthquake may trigger the occurrence of future large earthquakes along this segment.

九寨沟7.0级地震中典型非结构构件震害特征

九寨沟7.0地震给九寨沟地区建筑结构及非结构构件造成了严重破坏。本文主要涉及调查区域包括漳扎镇、甲藩古城、若尔盖县阿西茸乡、求吉乡及包座乡等。主要调查框架结构、砖混结构、大跨空间结构以及木结构的非结构构件震害。此次调查的结构多数是2000年以后建造,8度设防,在2008年汶川地震中主体结构和非结构构件均未受到影响。在此次地震中,非结构构件大量损坏,破坏主要以框架、砌体填充墙开裂或变形或局部倒塌、吊顶脱落、地板隆起、吊顶设备掉落、玻璃震碎等震害为主。调查结果表明,与以往地震不同,Ⅷ度区内仅有的三个大跨度结构均发生不同程度的破坏,其中一个结构出现节点破坏,此次地震中大跨空间结构非结构构件震损尤为明显,非结构构件设备损失最为严重。另一个不同于以往地震震害的是位于Ⅵ度区山坡上的木结构非结构震害明显比坡下要严重一些。

丽江7.0级地震丽江县城房屋震害分析

本文简述丽江７．０级地震造成的丽江县城钢筋砼框架、砖混结构和单层空旷房屋的震害，研究了房屋的震害特征，对震害的原因作了初步分析。

基于有限断层模型的芦山“4·20”7.0级强烈地震强地面运动特征

基于芦山地震的震源破裂过程反演结果,利用有限断层模型,以芦山地区三维地壳速率结构模型为基础,对芦山"4·20"7.0级强烈地震引起的强地面运动进行了模拟。对这次地震中由典型盲断层引起的强地面运动数值模拟结果反映了与实际震害相近的分布特征:断层上盘的宝盛、龙门及芦山以北位于极震区,也是强地面运动的高强度集中区,特别是垂向分量的速度、加速度峰值均在该地区达到了最大值,最能反映地表震害特征的竖向地震加速度在龙门一带达到了350gal,与极震区Ⅸ度的烈度相当,而在芦山以北龙门一带,瞬时竖向位移峰值高达110cm,这些特征与实际震害分布是非常相近的。综合分析认为,这次地震强地面运动表现出了明显的逆冲断层引起的强地面运动的分布特征,同时在强地震动传播过程中,由于高陡峭地形地貌特征及四川盆地内山间盆地的影响,地形地貌和盆地效应对地震波的反射和放大作用明显加强,也是该地区地震破坏强度增大的重要因素。

丽江7.0级地震的余震震源参数研究

本文从ＰＤＲ－２数字化近源（６２ｋｍ≤△≤４２ｋｍ）台网记录的丽江余震中初选了７４个地震，初定了震中位置，震中方位角。用相应的台网数据处理技术，研究了丽江地震序列的体波谱。对震级２５≤Ｍ≤５７、地震矩２１４０≤ｏｎｇＭＯ≤２３２８的地震，得出了丽江地区地震系列的震源参数；以及Ｐ波、Ｓ波的ｏｇＭＯ与Ｍｄ的关系式分别为：ｏｇＭＯｐ＝０６２Ｍｄ＋１９９３；ｏｇＭＯｓ＝０５９Ｍｄ＋１９６１。波谱拐角频率受地震辐射方向的调制，且与接受台站的场地响应有关。Ｐ波的拐角频率一般大于Ｓ波的拐角频率，平均拐角频率比为ｆＯ（ｐ）／ｆＯ（ｓ）＝１３。提出了归一化应力降的概念，给出了Ｗ（归一化应力降）随时间的分布。震源平均破袭尺度为４００多米。平均震源深度为９７ｋｍ。

丽江7.0级和唐山7.8级地震前形变场动态演化与异常特征

对１９９６年丽江７．０级和１９７６年唐山７．８级地震前的形变场动态演化过程做了对比分析，结果表明：①两次强震前形变场均存在大范围垂直差异运动增强以及与构造相关的形变高梯度带（区）；②震前数年（或更长）垂直形变场的趋势改变，并出现形变局部化。结合强震前区域地震活动，研究了这两次地震前垂直形变场动态演化与孕震形变的异常特征，认为与构造相关的强烈差异运动是孕震应变能积累的主要方式。

1996年2月3日云南丽江7.0级地震

１９９６年２月３日１９时１４分１８１秒，云南省丽江与中甸交界的丽江县境内（北纬２７°１８′，东经１００°１３′）发生７０级强烈地震。大震发生后，云南省地震局立即按《云南省破坏性地震应急预案》启动一类大震对策，成立地震前后方两个指挥部，全面开展震情现场监视、地震灾害损失评估、科学考察和宣传工作。准确地预报了２月５日６０级、２月６日５７级、２月７日５４级强余震，及时科学地完成了灾情调查和震害损失评估报告，为各级党委政府领导指挥地震应急抢险、恢复重建工作提供科学依据。对于丽江７０级地震的预测预报实践，经国家地震局及有关专家确认：①中期（１—３年）和中短期（１年尺度）预报较为准确；②震前短期预测向省政府打了一定招呼；③临震预报地点判断失误。本次地震由两次破裂构成，初始破裂从微观震中大具向东南方向扩展约１０余公里，以倾滑为主；主破裂方向偏转至近南北向，由北向南扩展近２０公里，其位置与方向与玉龙山东缘山前断裂基本一致，并在地表形成三段断续和长约３０公里的破裂带，总体走向Ｎ１０°—１５°Ｅ，具左旋斜滑特征。综合分析认为。

2020年1月19日新疆伽师MS6.4地震序列特征及后续趋势分析

介绍2020年1月18日新疆伽师M S5.4和1月19日M S6.4两次地震的基本参数、震源机制解、精定位等资料,分析伽师M S6.4地震序列类型、序列衰减特征和余震序列各项数字地震学资料,并就该序列与历史地震序列进行对比,提出震后趋势判定意见。分析认为,该序列为前—主—余型,余震序列衰减较为迅速。

起始破裂点位置对1932年昌马地震动的影响分析

起始破裂点位置是强地面运动模拟和预测的关键输入参数。为了进一步探究起始破裂点位置对强震模拟结果的影响,本文将非均匀凹凸体模型引入随机有限断层法,模拟了1932年昌马地震的强地面运动。结果显示:震中PGA随着起始破裂点位置的变化呈现明显的差异,产生高PGA值的起始破裂点大部分分布在断层左侧。起始破裂点对区域内PGA≥800 cm/s^(2)的空间分布影响有限,并且震中区PGA是整个区域内的最大值;对100~200 cm/s^(2)的PGA空间分布有较大影响;对其余范围PGA的空间分布影响较小。PGA衰减关系受起始破裂点位置的影响较大,起始破裂点位于断层中部和中下部偏右时,计算结果与第五代中国地震动参数区划图中的预测衰减关系较为符合。起始破裂点位置对反应谱影响的结果表明:震中的反应谱受到的影响有限。对不同周期反应谱空间分布的研究发现:反应谱值分布均呈现随周期增大而衰减的趋势。相较于其他部位的起始破裂点,起始破裂点位于断层底部时的反应谱值分布随周期的变化规律有明显不同。本文讨论了起始破裂点位置对昌马地震研究区域内PGA和反应谱的影响,研究结果可为地震动模拟时起始破裂点位置在断层上的选择提供参考。