强震对大地震发生率的影响研究及在鲜水河断裂带的应用

根据弹性回跳理论,有些断层上的大地震复发具有准周期性.强震的发生会对断层上大地震的复发周期产生影响.利用布朗过程时间（BPT）模型能够定量计算出一次强震对同一断层上大地震复发的延后时间.本文对断层上的强震对大地震发生率的改变量进行了研究,并以鲜水河断裂的几次地震为例,将由BPT模型计算的强震对大地震发生率的改变量与由库仑破裂应力计算的结果进行了比较.本文的研究表明,对于强震对大地震发生时间的延后幅度,使用BPT模型和库仑破裂模型计算的结果差别不大.周边强震对断层状态的加载使大地震复发时间的提前幅度可由BPT模型和库仑破裂模型计算,模型计算结果与现实震例相符.2014年11月22日康定M6.3级和M5.8级地震使鲜水河断裂带乾宁-康定段的大地震复发期望时间延后了36年,使磨西断裂的大地震复发期望时间提前了9年,从公元2086年提前至公元2077年.     

LATE-QUATERNARY ACTIVITY OF THE YALAHE FAULT OF THE XIANSHUIHE FAULT ZONE,EASTERN MARGIN OF THE TIBET PLATEAU

Complex geometrical structures on strike-slip faults would likely affect fault behavior such as strain accumulation and distribution, seismic rupture process, etc. The Xianshuihe Fault has been considered to be a Holocene active strike-slip fault with a high horizontal slip rate along the eastern margin of the Tibetan plateau. During the past 300 years, the Xianshuihe Fault produced 8 earthquakes with magnitude≥7 along the whole fault and showed strong activities of large earthquakes. Taking the Huiyuansi Basin as a structure boundary, the northwestern and southeastern segments of the Xianshuihe Fault show different characteristics. The northwestern segment, consisting of the Luhuo, Daofu and Qianning sections, shows a left-stepping en echelon pattern by simple fault strands. However, the southeastern segment(Huiyuansi-Kangding segment)has a complex structure and is divided into three sub-faults: the Yalahe, Selaha and Zheduotang Faults. To the south of Kangding County, the Moxi segment of the Xianshuihe Fault shows a simple structure. The previous studies suggest that the three sub-faults(the Yalahe, Selaha and Zheduotang Faults of the Huiyuansi-Kangding segment)unevenly distribute the strain of the northwestern segment of the Xianshuihe Fault. However, the disagreement of the new activity of the Yalahe Fault limits the understanding of the strain distribution model of the Huiyuansi-Kangding segment. Most scholars believed that the Yalahe Fault is a Holocene active fault. However, Zhang et al.(2017)used low-temperature thermochronology to study the cooling history of the Gongga rock mass, and suggested that the Yalahe Fault is now inactive and the latest activity of the Xianshuihe Fault has moved westward over the Selaha Fault. The Yalahe Fault is the only segment of the Xianshuihe Fault that lacks records of the strong historical earthquakes. Moreover, the Yalahe Fault is located in the alpine valley area, and the previous traffic conditions were very bad. Thus, the previous research on fault activity of the fault relied mainly on the interpretation of remote sensing, and the uncertainty was relatively large. Through remote sensing and field investigation, we found the geological and geomorphological evidence for Holocene activity of the Yalahe Fault. Moreover, we found a well-preserved seismic surface rupture zone with a length of about 10km near the Yariacuo and the co-seismic offsets of the earthquake are about 2.5~3.5m. In addition, we also advance the new active fault track of the Yalahe Fault to Yala Town near Kangding County. In Wangmu and Yala Town, we found the geological evidence for the latest fault activity that the Holocene alluvial fans were dislocated by the fault. These evidences suggest that the Yalahe Fault is a Holocene active fault, and has the seismogenic tectonic condition to produce a large earthquake, just like the Selaha and Zheduotang Faults. These also provide seismic geological evidence for the strain distribution model of the Kangding-Huiyuansi segment of the Xianshuihe Fault.     

川滇菱形块体东边界库仑应力演化及强震发生概率估算

本研究基于分层黏弹介质模型,考虑强震或大地震同震位错、震后黏滞松弛及主断层段震间构造应力加载三方面效应,给出1480年以来,川滇菱形块体东边界鲜水河断裂带、安宁河断裂带、则木河断裂带和小江断裂带共20个断层段由三方面效应引起的累积库仑应力变化随时间的演化,分析强震间相互作用和强震发生的应力累积背景,定性分析各断层段的地震危险性.同时,分别采用现今台网地震目录和川滇菱形块体东边界各断层段强震复发间隔两种资料,定量计算2030年各断层段的强震发生概率;并基于摩擦本构理论,将周边强震引起的库仑应力变化量作为应力扰动,修正强震发生概率的计算结果.各断层段累积库仑应力演化的结果表明,鲜水河断裂带中部八美段、色拉哈段及南部磨西段、安宁河断裂带冕宁-西昌段、小江断裂带北部巧家-东川段和南部建水段的累积库仑应力显著增加.修正的强震发生概率计算结果显示,鲜水河断裂带中部八美-色拉哈-康定一带、安宁河断裂带冕宁-西昌段、小江断裂带南部华宁-建水一带强震发生概率较高,地震危险性值得关注.本研究基于库仑应力演化计算定性分析强震危险性的同时,基于摩擦本构律理论,结合地震引起的应力扰动和强震发生背景,定量计算修正的强震发生概率,为川滇菱形块体东边界强震危险地点及中长期发震紧迫程度判定提供方法和依据.

     

FEATURES OF EARTHQUAKE CLUSTERING FROM CALCULATION OF COULOMB STRESS AROUND THE BAYAN HAR BLOCK,TIBETAN PLATEAU

Since 1997, several major earthquakes occurred around the Bayan Har block in the Tibetan plateau, providing an opportunity to further understanding the mechanism of intraplate earthquakes. What is the effect of interactions among these events on the earthquake occurrence pattern is an issue to be addressed. In this article, we use the visco-elastic Coulomb stress changes model to calculate the stress interactions among the historical events close to or large than M_S7.0 since 1893 in the Bayan Har block. We apply the relationships between the slip rate and stress accumulation rate to transform the Coulomb stress changes into the influenced time. Then we remove such influence time from the occurrence years, and analyze the effects of the earthquake interactions on the clustering patterns of the historical earthquakes in the Bayan Har block. The results show that the major earthquakes in the Bayan Har block are characterized by a quasi-period of about 16 years from 1893 to 1973 and a clustering occurrence time period from 1997 to present following a relatively long quiescence period. The Bayan Har block is still in the active period with high probabilities of major quakes. We calculate the conditional probabilities of the rupture segments that did not rupture since 1893 of the boundary faults of the Bayan Har block in the next 30 years. The following faults or fault sections seem to be of major risk:The Maqin segment and the Maqu fault of the East Kunlun fault zone, the Awanang fault, the Luocha segment of the Tazhong fault, the Moxi segment of the Xianshuihe fault, and the Dangjiang fault. Other Fault segments in the Bayan Har block without seismic events since 1893 probably also have hazard of M_S7 earthquakes in the future.     

大凉山断裂带北段石棉断裂的古地震

大凉山断裂带是大型走滑断裂鲜水河-小江断裂系的重要组成部分,其活动性是认识和探讨青藏高原东南缘现今地震活动和构造变形机制的重要基础资料.相较于中段和南段,关于大凉山断裂带北段活动性的相关研究成果,尤其是古地震资料非常缺乏.文中基于野外地质地貌调查,在石棉断裂联合村处开挖了一组(2个)探槽,揭露出断裂全新世活动的直接证据...     

中国陆区活动地块边界带主要断层10年尺度强震发生概率

中国陆区孕震环境具有“垂向分层,横向分块”的特征,活动地块边界带对中国陆区的强震具有控制作用,针对活动地块边界带主要断层开展10年尺度强震危险性定量研究对抗震设防工作有重要意义.本文综合不同区域断层离逝率样本建立了中国陆区通用强震复发模型,在此基础上,对各断层段强震概率进行预测.由于中国陆区幅员辽阔,不同断层的研究程度有较大差距,部分断层由于缺乏计算离逝率的资料而无法获得强震概率.因此本文使用不同方法对相关资料进行了补充.针对缺乏强震复发周期记录的断层段,通过统计断层运动速率与强震复发周期的经验关系,使用地震地质资料或大地测量资料给出的断层运动速率计算强震复发周期;针对缺乏强震离逝时间记录的断层段,根据地震目录完整时间给出强震离逝时间的分布.在此基础上,获得了中国陆区活动地块边界带主要断层的391个断层段未来10年的强震累积概率和条件概率.由于相对预测时长对条件概率的影响较大,而中国陆区不同断层段的强震复发周期有较大差别,本文主要依据累积概率分析强震危险性.结果表明,未来10年强震危险性较高的断层段主要集中于川滇菱形地块东边界、青藏高原东北缘、鄂尔多斯地块东边界与西北边界、天山地区和喜马拉雅弧等区域.

     

STUDY OF THE INFLUENCE OF STRONG EARTHQUAKE ON THE RECURRENCE BEHAVIOR OF MAJOR EARTHQUAKE ON ACTIVE FAULT-TAKING THE MIDDLE-NORTH SECTION OF XIANSHUIHE FAULT AS AN EXAMPLE

It is of great significance to determine the factors and causes that affect the recurrence of major earthquakes. This paper introduces the influence of strong earthquake on the recurrence of major earthquakes according to elastic rebound theory, and then proposes to calculate the impact time Δt respectively from the effect of strong earthquakes on the same and surrounding faults on the major earthquake recurrence by using seismic moment release rate method and Coulomb stress change. In this paper, we studied the change amount of major earthquake recurrence by taking four earthquakes with magnitude greater than 6.5 occurring at different fracture sections of the Xianshuhe fault zone as an example, they occurred on Daofu, Changcu, Zhuwo Fault, respectively. We used seismic moment rate method to calculate the impact time Δt of strong earthquake on the recurrence of major earthquakes on the Daofu-Qianning Fault. We further discussed the effect of the Coulomb stress change due to the interaction between faults on the recurrence of subsequent major earthquakes. The co-seismic and post-seismic Coulomb stress changes caused by strong earthquake on the surrounding faults on the Ganzi-Luhuo Fault are calculated. With the fault interaction considered, the importance of the interaction between faults in the middle-north section of the Xianshuihe fault zone to change the recurrence of large earthquakes is retested and evaluated. The results indicate that the two strong earthquakes occurring along Xianshuihe Fault in 1904(M=7.0) and 1981(M=6.9) resulted in a delay of 80 years and 45 years of major earthquake recurrence on the Daofu-Qianning Fault respectively, and the M7.3 earthquake in 1923 and the M6.8 earthquake in 1967 resulted in an advance of 35 years of major earthquake recurrence on the Ganzi-Luhuo Fault.     

运用古地震数据评价东昆仑断裂带东段未来百年的强震危险性

通过收集、整理和分析青藏高原东北部22条断裂带上古地震定量数据,拟定了该区的地震复发概率密度函数.根据此函数对区内东昆仑断裂带东段不同段落上未来100年内强震原地复发的条件概率进行了初步研究.结果表明,该断裂带上自西向东的3个破裂段中,玛沁段和塔藏段未来20、50、100年的复发概率值介于0.76%~7.36%之间,玛曲段未来20、50年的复发概率值介于2.0%~5.26%,属于低概率事件;玛曲段未来100年的复发概率值为10.82%,属于中概率事件;整个段未来100年内至少发生一次7级以上强震的联合概率可达21.87%,属于中概率事件.考虑到概率模型的不确定性,进一步对各段进行了危险性的定性分类,综合评价认为玛沁段在未来百年内发生大震的危险性较低,玛曲段和塔藏段未来百年发生大震的危险性较高.最后将本文拟合的概率密度函数与传统通用函数计算的条件概率值进行比较,发现通用的复发概率函数随着自变量t/R的增大,因变量P的反映不如本文拟合函数的敏感.     

运用古地震数据评价东昆仑断裂带东段未来百年的强震危险性

通过收集、整理和分析青藏高原东北部22条断裂带上古地震定量数据,拟定了该区的地震复发概率密度函数.根据此函数对区内东昆仑断裂带东段不同段落上未来100年内强震原地复发的条件概率进行了初步研究.结果表明,该断裂带上自西向东的3个破裂段中,玛沁段和塔藏段未来20、50、100年的复发概率值介于0.76%~7.36%之间,玛曲段未来20、50年的复发概率值介于2.0%~5.26%,属于低概率事件;玛曲段未来100年的复发概率值为10.82%,属于中概率事件;整个段未来100年内至少发生一次7级以上强震的联合概率可达21.87%,属于中概率事件.考虑到概率模型的不确定性,进一步对各段进行了危险性的定性分类,综合评价认为玛沁段在未来百年内发生大震的危险性较低,玛曲段和塔藏段未来百年发生大震的危险性较高.最后将本文拟合的概率密度函数与传统通用函数计算的条件概率值进行比较,发现通用的复发概率函数随着自变量t/R的增大,因变量P的反映不如本文拟合函数的敏感.     

2013年芦山M_S7.0地震产生的静态库仑应力变化及其对余震空间分布的影响

2013年4月20日芦山MS7.0地震发生在龙门山断裂带的西南段,距2008年汶川MS8.0地震仅约85km,时间上仅相隔5年.首先计算了汶川地震的静态库仑应力变化对本次芦山地震的影响,得出芦山地震是由汶川地震触发造成的(库仑应力上升了0.012 MPa);进一步计算了芦山地震与汶川地震这两次大地震共同产生的静态库仑应力变化.结果表明,芦山地震的余震受前面两次大地震的共同影响,而不仅仅是芦山地震单独作用的结果,超过85%的余震发生在两次地震共同产生的静态库仑应力变化增大的地方,而芦山地震本身触发不了本次的余震序列(仅48.7%的余震位于主震所产生的应力加载区).此外,计算结果表明芦山地震本身对周边断层影响较小,仅龙门山断裂带的东北段受到一定的加载作用;而由于汶川地震的作用,安宁河断裂、大凉山断裂、马尔康断裂、岷江断裂和虎牙断裂呈卸载趋势,仅鲜水河断裂东南段和龙门山断裂中段受到加载作用,这均会加速断层上新地震的发生.     

2017年九寨沟地震所受历史地震黏弹性库仑应力作用及其后续对周边断层地震危险性的影响

首先对2017年九寨沟M_S7.0地震周边断裂活动和历史地震特征进行了阐述;然后利用黏弹性地壳模型,计算了1933年叠溪地震、1976年松潘震群和2008年汶川地震对2017年九寨沟地震的同震和震后库仑应力作用.该结果显示1933年叠溪地震对九寨沟地震具有延缓作用,而1976年松潘震群和2008年汶川地震对九寨沟地震的黏弹性库仑应力作用为正;随着下地壳和上地幔黏弹性物质的持续作用,前述几次地震总的黏弹性库仑应力在九寨沟地震破裂中心点处负的库仑应力逐渐减弱,而在破裂北段这些库仑应力逐渐转为正值,并促进了九寨沟地震的发生.本文也计算了九寨沟地震后对周边断层的库仑影响,并将此影响值转换为对断层能量积累的影响时间上,结果显示塔藏断裂带西段和中段在内的多条断裂带受到黏弹性库仑应力影响时间值超过10年.将库仑应力影响时间值加入到部分已知离逝时间的断层段上,也得到了这些断层段的未来30年特征地震发生概率.最终结果认为玛沁断裂带、玛曲断裂带、哈南—稻畦子断裂中段和西段等断层段的强震危险性需要重点关注.

     

Segmentation of Active Faults and Risk Probability Prediction of Strong Earthquakes in Sichuan Province

Based on geometric structure,active strength,and maximum seismic rupture length along the fault in the late Quaternary or Holocene,this paper presents the segmentation of main active faults in Sichuan Province and uses the recurrence probability model to predict the recurrence probabilities of strong earthquakes along each segment during next 30 years.The results indicate that earthquakes with M=7.0 or greater may happen along Qiajiao segment,Qianning segment,and Selaha segment of Xianshuihe fault zone,the segment from Xichang to Mianning and Yejidong segment of Anninghe fault zone; earthquakes with M=6.0 or greater may happen along the segment from Maowen to Caopuo of Longmenshan fault zone and Xiaoyanjing segment of Anninghe fault zone.     

2010年玉树地震的构造环境、历史地震活动及其复发周期估计

2010年4月14日青海省玉树发生了7.1级地震,造成了严重的人员伤亡和重大的经济损失。发生该地震的甘孜-玉树断裂是川滇菱形块体的边界断裂,晚第四纪左旋走滑运动强烈。震中所处的甘孜-玉树断裂中段,震前历史地震活动与东南段相比较弱。本文利用玉树地震的基本参数资料和地震破裂反演结果,综合历史地震法和地震矩率法估算出了玉树地震的复发周期约为200年。     

松原市扶余北隐伏活动断裂地震潜势研究

扶余肇东断裂带是松辽盆地中一条重要的隐伏发震断裂带,2006年和2014年在此断裂带上发生了多次近6级地震,地震活动主要集中在断裂的东北段和查干花段。在2012—2014年的松原市活断层探测工作中,探明扶余肇东断裂带东北段经过松原市区,该段呈近EW向,具有明显的分段性和独立性,将其命名为扶余北断裂。通过三维物探资料和浅层人工探测,确定了扶余北断裂的空间展布和剖面特征,并利用联排钻孔探测和光释光测年技术,确定该断裂存在晚更新世以来的活动;利用石油物探资料获得的基岩面破裂规模,对扶余北断裂的地震潜势进行了估计,并进行了概率性地震危险性研究。     

鲜水河断裂带的应力积累与释放

本文根据历史地震(Ms6.0)的资料,研究了鲜水河断裂带的地震活动性,并利用断层的位错模式进一步研究该断裂带的应力积累和释放过程.结果表明,该断裂带的强震活动大致以道孚为界,形成北西和南东两个活动地段,呈现南北交替活动的特征.地震能量的这种交替释放似具有准周期性质,Ms7.0级地震的平均复发周期为27.6年.给出该断裂带在三个不同时间段(1700-1811,1816-1967,1816-1982)强震断层作用引起的应力释放图象,讨论了前两个时间段地震应力场对其后发生的第一个大地震的重要影响.计算了1893年以来在断裂带南东段(相对闭锁段)的应力积累,示出相应的最大剪应力和流体静应力等值线图.最后,根据应力积累、附加应力变化、地震活动规律和应变释放曲线特征,估计了鲜水河断裂带的地震趋势.认为在本世纪末,在断裂带南东段的(1)康定-磨西段或(2)道孚-乾宁段或(3)乾宁-康定段将可能发生 Ms=7.40.3地震.     

Assessment of strong earthquake risk in the Chinese mainland from 2021 to 2030

The long-term earthquake prediction from 2021 to 2030 is carried out by researching the active tectonic block boundary zones in the Chinese mainland. Based on the strong earthquake recurrence model, the cumulative probability of each target fault in the next 10 years is given by the recurrence period and elapsed time of each fault, which are adopted from relevant studies such as seismological geology, geodesy, and historical earthquake records. Based on the long-term predictions of large earthquakes throughout the world, this paper proposes a comprehensive judgment scheme based on the fault segments with the seismic gap, motion strongly locked, sparse small-moderate earthquakes, and apparent Coulomb stress increase. This paper presents a comprehensive analysis of the relative risk for strong earthquakes that may occur in the coming 10 years on the major faults in the active tectonic block boundary zones in the Chinese mainland. The present loading rate of each fault is first constrained by geodetic observations; the cumulative displacement of each fault is then estimated by the elapsed time since the most recent strong earthquake.     

2001年昆仑山地震同震—震后效应与2021年玛多地震关系探讨

位于青藏高原中北部的巴颜喀拉地块是我国西部近年来的主体地震活动区,一系列M_W7.0以上强震均发生在该次级块体周边,而其北边界东昆仑断裂带是一条长达2000 km、规模最大、活动性最强的深大断裂带.2001年在东昆仑断裂带中段发生了M_W7.8昆仑山地震,2021年5月在其震中东南部大约450 km处巴颜喀拉块体内部一次级断裂上发生了M_W7.3玛多地震.玛多地震对人们以往认为强震更可能发生在巴颜喀拉块体边界断裂上的认识提出挑战,但是也为研究巴颜喀拉块体边界断裂与块体内部次级断裂活动关系、地震触发关系带来机遇.本文利用前期基于2001年昆仑山地震后积累的大量InSAR数据获得的震后大范围形变场时空演化图像和库仑应力变化模型,探讨昆仑山地震与玛多地震的关系.InSAR震后观测结果显示：昆仑山地震后沿东昆仑断裂带出现了长达500 km的大范围南北不对称震后形变场,其中南盘形变宽度和量级均明显大于北盘,南盘形变宽度达到250 km,断层近场相对平均形变速率达到＞20 mm·a^-1,而且南盘向南衰减梯度小,整体衰减缓慢,意味着震后形变对巴颜喀拉块体形成持续东向加载作用,并将分摊到块体内部的一系列次级断裂上,应力加载增加次级断层的地震危险性.2015—2020年InSAR震间应变率场则显示次级断裂——昆仑山口—江错断裂呈高剪切应变率特征.本文计算了昆仑山地震同震破裂和震后形变引起的玛多震区多条SE向次级断裂的累积库仑应力变化,结果显示昆仑山地震同震和震后形变对玛多地震发震断裂(昆仑山口—江错断裂)形成了一定的应力加载.本文认为昆仑山地震同震和长时间尺度震后形变加速了巴颜喀拉块体的东向运动,而断层本身运动学性质和区域应力扰动共同影响了玛多地震的发生.

     

Average slip rate,earthquake rupturing segmentation and recurrence behavior on the Litang fault zone,western Sichuan Province,China

The Litang fault zone (LFZ) is an important active fault within the northwestern Sichuan sub-block. To-gether with the Garzê-Yushu, Xianshuihe, and An-ninghe fault zones on its northern, eastern and south-eastern sides, the LFZ constitutes the lateral extrusion tectonic system in the southeastern part of the Qing-hai-Tibetan Plateau[1,2] (Fig. 1). According to instru-mental records, historical recordings and field investi- gation, an earthquake (Ms7.3) occurred on its middle to south se…     

云南红河断裂带北段断裂位错与地震重复发生的时间间隔

本文用地质方法确定了全新世以来红河断裂(北段)位错速率:狭谷段(定西岭)水平位错速率8毫米/年,垂直位错速率1.8毫米/年;宽谷段(大理)水平位错速率5毫米/年,垂直位错速率9毫米/年。据断裂位错参数计算,本区6.8级左右地震重复发生的时间间隔是178±29年;它与6—7级历史地震重复时间间隔150±50年在时间尺度上相当,这对地震中长期预报有参考价值     

东昆仑活动断裂带及其强震活动

本文在简述东昆仑活动断裂带的构造背景与演化历史的基础上，重点叙述了该活动断裂带的展布，几何结构，第四纪运动和强震活动等特征，指出，这是一条具有长期演化历史，深部构造背景和第四纪乃至全新强烈活动的断裂带。因而在我国大地构造演化，尤其在青藏高原隆起形成，占有重要地位，同时，它还是我国西部地区一条主要的强震活动构造带，根据现代强震活动记录和在全带新发现的多期全新世古地震及其地表破裂带，分析了大震在断裂带