地球化学在工程地震中的应用：瘦狗岭活动断裂探测

场地地震安全性评价中的近场区活动断裂评价是确定近场区地震活动水平的重要一环。实践证明,地球化学方法探测隐伏活动断裂效果很好。本文利用地球化学方法确定了瘦狗岭断裂东段的具体位置。     

郑州市断裂最大潜在地震发震概率评价

根据“郑州市城市活断层探测与地震危险性评价（二期）”综合目标区断层最大潜在地震判定结果,郑州市近东西向断裂有老鸦陈断裂和上街断裂等。老鸦陈断裂第四纪不活动,上街断裂等可能具有发生5—5.5级地震的能力。为了得到最大地震的发震概率,划分了统计区及潜在震源区,得到了地震活动性参数及空间分布函数。最终得出了郑州市断裂未来50年发生1次5级以上地震的概率为6%,未来100年发生1次5级以上地震的概率为11%。     

郑州市断裂最大潜在地震发震概率评价

根据“郑州市城市活断层探测与地震危险性评价(二期)”综合目标区断层最大潜在地震判定结果,郑州市近东西向断裂有老鸦陈断裂和上街断裂等.老鸦陈断裂第四纪不活动,上街断裂等可能具有发生5-5.5级地震的能力.为了得到最大地震的发震概率,划分了统计区及潜在震源区,得到了地震活动性参数及空间分布函数.最终得出了郑州市断裂未来50年发生1次5级以上地震的概率为6％,未来100年发生1次5级以上地震的概率为11％.     

鄂豫皖交界地区地震地质背景与中强地震复发特征的研究

鄂豫皖交界地区位于东大别山西部，历史中强地震(M≥43/4)主要发生在土地岭-落儿岭及商城-麻城断裂带上，且“互动”和“连动”的特征较为显著。根据这一特征，在研究东大别山区域地质、地壳结构、断裂活动及地震构造应力场特征的基础上，可将鄂豫皖交界地区的中强地震作为秦岭-大别山活动地块中的次级地块的整体活动来看待。该区历史地震活动整体表现为丛集特征，而主要发震断层(土地岭-落儿岭断裂)的历史地震活动则具有相对较好的准周期性。地震复发周期研究提示，该地块近期发生M≥5．0左右地震的危险性较大，而霍山-六安地区为未来发生中强地震的主要危险区。     

论广州地区的地震构造及其发震危险性

广州的主要断裂构造是北北东向的广州—从化断裂带与近东西向的瘦狗岭断裂带与广州—三水断裂带。在北西西—南东东向区域构造应力场作用下,上述两条近东西向的断裂带组成右行左阶排列,导致岩桥区出现近东西向的附加挤压应力场,酿成广州—从化断裂带广州段内发生右行剪切运动,它是广州地区历史上数十次地震的发生带,是广州地区的主要发震构造;而右行左阶排列的近东西向断裂带的活动则是蕴育广州地震的原因。由于广州地区之主要发震构造规模不大,地震最大强度将以中强震为主,其极震区之地震烈度一般为六度,少数情况下可能接近七度。     

广州地区活动断裂的特征及其与工程抗震的关系

根据第四纪地质、地球化学、地壳形变和地震活动资料,论述了晚第四纪广州地区主要断裂的活动特征。认晚更新世以来,广从断裂、清泉街断裂、瘦狗岭断裂和文冲断裂发生过拉张式活动,但活动较弱,对工程地震未构成较严重危害,但在这些断裂所通过的地了在砂土液化、淤泥塌陷等潜在地质灾害。     

罐罐岭断裂带最新活动特征

断层的最新活动时代以及分段特征一直在重大工程安全性评价中具有特别重要的意义。在解决黄河黑山峡地震地质问题时,通过对罐罐岭断裂带的航片解译、野外追踪调查、地形地貌测量和古地震槽探资料研究,从而确定了该断裂带的活动时代以及分段特征。该断裂带发育在青藏块体东北缘,是中卫-同心弧形活动构造带的一部分,总体走向近EW,长约60km,分为5条不连续的次级断层,各段成左阶羽列,晚第四纪以来表现出强烈的左旋走滑兼挤压逆冲活动特征。断层错断了一系列山脊、小冲沟和阶地等,发育醒目的断层陡坎。研究发现,罐罐岭断裂最新一次地震破裂发生在距今700～1200a之间,最大同震位移位于罐罐岭附近,全新世以来水平左旋最大错距达6m     

安丘-莒县断裂北段几何结构与最新活动特征

安丘-莒县断裂是沂沭断裂带的主要分支之一,也是最主要的一条活动断裂。通过断裂活动性调查和地质填图,查明了安丘-莒县断裂北段的空间展布、几何结构以及最新活动特征。在莒县至昌邑一带,安丘-莒县断裂自北向南大致可划分为昌邑—南流段、安丘—孟疃段、青峰岭段和孟堰段等4个段落。它们以左阶斜列形式展布,而每个断层段又由更次一级的段落以右阶斜列的形式组成。昌邑—南流断层段的最新活动时代为全新世中晚期,除右旋走滑断层活动外,还观察到逆冲和正断运动分量,其中正断运动分量的发生时代较新。安丘—孟疃和青峰岭2个断层段以右旋走滑运动为主,兼有逆冲运动分量,最新活动时代分别为晚更新世和全新世早期。孟堰断层段也以右旋为主兼具逆冲分量,最新活动时代为全新世早期。安丘—孟疃断层段公元前70年曾发生过安丘7级地震,结合断层活动性质和最新活动时代综合判断,山东莒县以北的安丘-莒县断裂的未来地震危险性较大,在今后的地震灾害防御和地震预测工作中应予以重视。     

珠江三角洲断裂构造最新活动性研究

根据在珠江三角洲及其周围地区测得的热释光年龄和第四系沉积物的分布等资料，分析讨论了断裂的最新活动性。自晚更新世以来，陈三角洲外围几条主要的北东向断裂的局部地段以外，基本上处于比较稳定的状态。晚更新世一全新世早期有过明显活动的断裂有狮子洋东西两侧的北西向断裂，近南北向的崖门断裂和北东向的古劳－广州断裂。近东西向的瘦狗岭断裂新世亦有过活动。     

银川地区M_L4级地震活动特征研究

1970年以来银川地区ML4级地震在时间上丛集发生,分别从主震震前小震与震后余震分布特征、余震序列参数计算和震源机制解的角度,研究了以上地震的活动特征。结果显示:每次地震的发生均具有一定的独立性;可计算余震参数的地震序列为非前兆震群,这一点与实际相符;震源机制解显示几次地震的发震断层主要属于银川隐伏断裂,并可能与该断裂附近的一系列次级断裂有关。分析认为几次地震的发生可能是局部应力调整的结果,与未来该区域是否发生大震关系不大,同时可以推测未来该区域依旧可能发生类似震级的有感地震。     

珠江三角洲地区新构造运动

概述了珠江三角洲地区新构造运动的基本特征：晚第三纪以来的构造运动经历了由强逐渐减弱，晚更新世（约50－30Ka B.P)又重新增强的演变。重点估算了晚第四纪珠江三角洲断块垂直构造运动速率，定量分析了分割断块的断裂构造的活动性。认为斗门断块区和广州－番禺断块区这两个次级断块构造以及围限它们的广州－从化断裂，三水－罗浮断裂，西江断裂，白坭－沙湾断裂的活动性相对较强。从区域地震构造而言 ，珠江三角洲新构造运动远弱于日本－琉球－台湾岛弧，也弱于奥东潮汕和桂东南灵山等强震危险区。但由于其震源浅及松软土层较厚，加上本区经济发达，人口稠密，因此地震造成的破坏和损失仍不可低估，必须加强抗震减灾工作。     

试论地质学者的地震理念

地质学者认为断层是震源在地表的表现。在这一理念的基础上,文中讨论了如何通过活断层定量研究开展强震预测。强震地点预测的依据是断层活动性调查。在这方面强调航片判读和野外断层地形学的调查,由此获取断裂带的最新活动时期。对于确认的晚第四纪以来活动的断裂带,认为其将来具有发生强震的潜势。强震的活动强度从调查活断层的长度和同震位移入手。全球大量的历史地震和现今地震表明,断层长度与地震震级之间、以及同震位移与地震震级之间存在正比例关系。有关强震时间的预测,需要获知各条断裂带的强震间隔和最新活动的离逝时间。尽管通过断层的活动速率和同震位移的比值可获取断裂带的强震平均间隔,但通过探槽调查获取古地震活动的年代对分辨各条断裂带强震活动的个性特征仍十分重要。文中多处引用了日本活断层研究的资料和松田?彦教授的认识。最后简要回顾了中国活断层研究过程中的几个重要事件     

Late Quaternary surface deformation and rupture behavior of strong earthquake on the segment north of Mianning of the Anninghe fault

The Anninghe fault is an important active fault along the eastern boundary of Sichuan-Yunnan active tectonic block, and the study of its surface deformation and rupture behavior during strong earthquake in the late Quaternary is of fundamental importance for understanding the future seismic risk of the fault zone or even the entire western Sichuan region. Using the methods of detailed geomorphic and geological survey, digital image analysis, total station instrument survey, excavation of combined trench and dating, we analyze the geomorphologic sequences of the offset strata at several sites where the late Quaternary deformation remnants are fairly well preserved and obtain some new results as follows: Strong earthquake events with left-lateral displacements of about 3 m occurred at the two sites of Zimakua and Yejitong at 1634-1811, 1030-1050 and 280-550 a BP, respectively, and the recurrence interval is 520-660 a; The youngest event in the area of Dahaizi-Ganhaizi should be the earthquake of 1536, other events are at 1768-1826, 2755-4108 and 4108-6593 a BP, respectively, with a recurrence interval of 1300-1900 a. The strong earthquake activity shows a clustering character. The possibility of occurrence of a strong earthquake exists on the north segment of the Anninghe fault sometime in the future.     

北京黄庄-高丽营断层、八宝山断层现今活动追踪研究

综合分析了控制黄庄—高丽营断层、八宝山断层活动性的形变、重力及地磁资料，认为断层的活动以永定河断层与良乡断层之间最为显著；其活动与强震的发生密切相关；断层所在地段是地震活动引起应力场变化的敏感地区。是大同及张北地震后应力转移集中的地区。转移集中的部分应力可能以断层蠕动的形式得到缓慢释放。     

THE ACTIVITY FEATURES OF XIADIAN FAULT ZONE REVEALED BY RONGJIABAO TRENCH AND ITS PROBABILISTIC SEISMIC HAZARD EVALUATION

The time-dependent probabilistic seismic hazard assessment of the active faults based on the quantitative study of seismo-geology has the vital practical significance for the earthquake prevention and disaster management because it describes the seismic risk of active faults by the probability of an earthquake that increases with time and the predicted magnitude. The Poisson model used in the traditional probabilistic method contradicts with the activity characteristics of the fault, so it cannot be used directly to the potential earthquake risk evaluation of the active fault where the time elapsing from the last great earthquake is relatively short. That is to say, the present Poisson model might overestimate the potential earthquake risk of the Xiadian active fault zone in North China because the elapsed time after the historical M8 earthquake that occurred in 1679 is only 341a. Thus, based on paleoearthquake study and geomorphology survey in the field, as well as integrating the data provided by the previous scientists, this paper reveals two paleo-events occurring on the Xiadian active fault zone. The first event E₁ occurred in 1679 with magnitude M8 and ruptured the surface from Sanhe City of Hebei Province to Pinggu District of Beijing at about 341a BP, and the other happened in (4.89±0.68)ka BP(E₂). Our research also found that the average co-seismic displacement is ~(1.4±0.1)m, and the predicted maximum magnitude of the potential earthquake is 8.0. In addition, the probabilistic seismic hazard analysis of great earthquakes for Xiadian active fault zone in the forthcoming 30a is performed based on Poisson model, Brownian time passage model(BPT), stochastic characteristic-slip model(SCS)and NB model to describe time-dependent features of the fault rupture source and its characteristic behavior. The research shows that the probability of strong earthquake in the forthcoming 30a along the Xiadian active fault zone is lower than previously thought, and the seismic hazard level estimated by Poisson model might be overestimated. This result is also helpful for the scientific earthquake potential estimation and earthquake disaster protection of the Xiadian active fault zone, and for the discussion on how to better apply the time-dependent probabilistic methods to the earthquake potential evaluation of active faults in eastern China.     

广从断裂飞来岭-象岗山段最新活动性研究

本文采用野外地质地貌调查、联合钻孔探测、浅层地震勘探、14C测年和ESR测年等技术方法,对广从断裂飞来岭-象岗山段最新活动性进行了综合研究。结果表明:广从断裂飞来岭-象岗山段最新一次活动发生在中更新世晚期。晚更新世以来,该段基本上处于比较稳定的状态。     

由现今地震活动分析鲜水河断裂带中-南段活动习性与强震危险地段

利用最近25年的区域台网地震资料, 基于沿鲜水河断裂带中-南段的b值分布以及多个地震活动参数值的不同组合, 结合震源深度分布、 历史强震背景等, 分析了不同断裂段落的现今活动习性, 进而初步判别该断裂带潜在的强震危险地段。 结果表明, 鲜水河断裂带中-南段目前存在6个不同活动习性的段落。 其中, 道孚段自1981年强震后已再次趋于闭锁, 原因可能与断层面存在“凹凸体”有关, 但应变可能还会进一步积累; 八美段目前处于中偏高应力下的相对静止状态, 推测其断面正处于新的应力积累阶段; 塔公段已有255~300年的无强震期, 目前正处于高应力下的相对闭锁状态, 震源深度剖面上的小震空白区显示出闭锁断层面的轮廓, 应属于未来最可能发生强震的危险地段; 康定、 磨西二个段落表现出中偏低应力下的稀疏小震滑动及较频繁小震滑动的状态, 意味着最晚的一次大地震破裂后断层面尚未重新耦合; 石棉段表现出偏高应力下的频繁中-小地震活动与该段的多条断裂交汇有关。     

An Inhomogeneous Distribution Model of Strong Earthquakes along Strike-Slip Active Fault Segments on the Chinese Continent and Its Implication in Engineering Seismology

Through the statistical analysis of earthquake distribution along 51 strike-slip active fault segments on the Chinese continent, we found that strong earthquake distribution along the seismogenic fault segments is inhomogeneons and the distribution probability density p (K) canbe stated as p(K)=1.1206e^3.947k^2 in which K = S/(L/2), S refers to the distance from earthquake epicenter to the center of a fault segment, L is the length of the fault segment. The above model can be utilized to modify the probability density of earthquake occurrence of the maximum magnitude interval in apotential earth quake source. Nevertheless, it is only suitable for thosepotential earthquake sources delineated along a single seismogenic fault. This inhomogeneons model has certain effects on seismic risk assessment, especially for those potential earthquake sources with higher earthquakerates of the maximum magnitude interval. In general, higher reoccurrence rate of the maximum magnitude interval and lower exceeding probability level may bring larger difference of the results in seismic risk analysis by adopting the inhomogeneons model, the PGA values increase inner the potential earthquake source, but reduce near the vicinity and out of the potential earthquake source. Taking the Tangyin potential earthquake source as an example, with exceeding probability of 10% and 2% in 50 years, the difference of the PGA values between inhomogeneons model and homogenous models can reach 12 %.     

福建政和-海丰断裂带地震活动特征分析

通过对1971年以来福建政和-海丰断裂地震活动特征分析,认为政和-海丰断裂的地震活动是:在主体北东向政和-海丰断裂带和次级北西向永安-晋江断裂带相互交汇的构造格局下,形成了4～5级中强地震反复发生的潜在震源区.     

Expulsion of a geopressured hydrothermal system associated with destructive earthquakes and buried active faults in the Shinanogawa Seismic Belt, Japan

Abstract   The Shinanogawa Seismic Belt in the Northern Fossa Magna, Honshu Island, Japan, extends along the Shinano River, bounding the Eurasian Plate and the Okhotsk Plate. The geopressured hydrothermal system occurs widely in the Northern Fossa Magna region. Many destructive earthquakes are related to the activity of this system in the Shinanogawa Seismic Belt. Expulsion of a geopressured hydrothermal system and rising from depth along an active fault triggers the occurrence of an earthquake and opens the fault as a pathway. Anomalous areas in temperature, electrical conductivity and Cl^– concentration of groundwater trend north–east in a linear distribution, and convincingly demonstrate the presence of a buried active fault at the epicentral area of the destructive earthquake in the Shinanogawa Seismic Belt. The distribution of the major axis of the anomalous area in groundwater temperature shows a strong positive relationship with earthquake magnitude, which means that the distribution of this area may indicate the scale of earthquake fault. The linearly anomalous areas in groundwater temperature, resulting from the percolation of a geopressured hydrothermal system, that have no record of previous destructive earthquake are predicted to be areas where destructive earthquakes could occur in the future. Four potential earthquake areas are proposed and discussed in this paper, based on re-examination of active faults and seismicity in the Shinanogawa Seismic Belt.