安宁河-则木河断裂带过渡段及其附近新发现的历史大地震破裂遗迹

在近些年的野外调查中,我们在安宁河、则木河2断裂带的过渡段(礼州至西昌之间)及其附近的3个场地发现了未知年代的地表破裂。通过分析这些地表破裂的特征以及在本区历史地震重破坏区中的位置,我们认为位于杨福山村以北与大坪子村以西2个场地的破裂应是1536年大地震地表破裂带的遗迹。这不仅反映了1536年大地震破裂带的南段沿安宁河与则木河断裂带的过渡段产生,而且反映了该破裂带的南端很可能到达了或者很接近于西昌。位于西昌略北李金堡村以东的破裂应属于1850年大地震地表破裂带的遗迹,它进一步证明了1850年大地震地表破裂带的西北端可能到达西昌以北至少数千米处。因而,由文中的证据可推断西昌附近的主干活动断裂在1536年和1850年大地震时均发生了破裂     

对东南沿海1067年和1574年两次地震的分析

地震目录给出的 1067年广东潮汕地震的参数不能合理解释历史记载中该地震的震害分布。文中将这次地震与 1918年南澳大地震在相同地点的震害记载进行了对比,发现几乎相同,进而论证了这两次地震属发生在同一震源的特征地震事件的可能性,认为 1067年地震的震中很可能位于南澎列岛西侧,其震级可达 71 /4。鉴于目前对 1574年福建东北沿海 53 /4级地震事件有不同的认识,文中重新分析了该地震的破坏区与有感区的分布,并与 1906年厦门海外地震进行了比较。结果认为, 1574年地震的震中更有可能位于福州—莆田以东的海域,且震级可能达到 61 /4。文中还认为:史料中有关 1574年浙江庆元地震的记述所指的可能不是发生在当地的破坏性地震,而更可能就是同年发生在福州—莆田以东海域的那次地震。1067年和 1574年地震可能都发生在NE向的滨海断裂带上     

鄂尔多斯块体周边正倾滑活动断裂历史强震地表破裂分段.

在近年活动断裂研究成果基础之上,分析了鄂尔多斯地块周边断陷系９次历史强震破裂的分段与活动构造之间的关系．结果表明,在个别具有较大不确定性参数不参加统计情况下,这些强震地表破裂参数与活动构造之间表现出较好的相关性,反映出强震的破裂强度及地表破裂的分段与活动构造之间的内在联系．同时,这些强震表现出特征型强震的稳定和非稳定的地表破裂边界,以及同一构造单元不同边界断裂存在的强震连续发生现象．     

THE CORRELATION BETWEEN GEOMETRIC FEATURE OF CO-SEISMIC RUPTURE AND CO-SEISMIC DISPLACEMENT

The existence of asperity has been confirmed by heterogeneously distributed seismic activities along the slipping surface associated with recent huge earthquakes, such as the M8.0 2008 Wenchuan earthquake and M9.0 2011 Tohoku-Oki earthquake. The location of asperity embedded in the seismogenic depth always corresponds to the area of high value of the co-seismic displacement and stress drop where the elastic energy is accumulated during the inter-seismic periods. Fault segmentation is an essential step for seismic hazard assessment. So far, the fault trace is dominantly segmented by considering its geometric features, such as bends and steps. But the connection between the asperity and geometric feature of the slipping surface is under dispute. Research on correlation between geometric feature of surface rupture and co-seismic displacement is of great significance to understand the relationship of seismicity distribution to geometric morphology of sliding surface. To scrutinize the correlation between the geometric feature and co-seismic displacement, we compiled 28 earthquake cases among which there are 19 strike-slip events and 9 dip-slip events. These cases are mainly collected from the published investigation reports and research papers after the earthquake occurred. All the earthquakes' magnitude is between M_W5.4~8.1 except for the M_W5.4 Ernablla earthquake. The range of the rupture length lies between 4.5~426km. Each case contains surface rupture trace mapped in detail with corresponding distribution of co-seismic displacement, but the rupture maps vary in projected coordinate system. So, in order to obtain uniform vector graphics for the following data processing, firstly, vectorization of the surface rupture traces associated with each case should be conducted, and secondly, the vector graphics are transformed into identical geographic coordinate system, i.e. WGS1984-UTM projected coordinate system, and detrended to adjust its fitted trend line into horizontal orientation. The geometric features of surface rupture trace are characterized from three aspects, i.e. strike change, step and roughness. Previous studies about the rupture geometry always describe the characteristics from the whole trace length, consequently, the interior change of the geometric characteristics of the rupture is overlooked. In order to solve this problem, a technique of moving window with a specified window size and moving step is performed to quantify the change of feature values along the fault strike. The selected window size would directly affect the quantified result of the geometric feature. There are two contrary effects, large window size would neglect the detail characteristics of the trace, and small window size would split the continuity of the target object and increase the noise component. So we tested a set of sizes on the Gobi-Altay case to select a proper value and choose 1/25 of the whole rupture length as a proper scaling. Here, we utilize the included angle value of the fitted line in the adjoining windows, Coefficient of variation and the intercept value of the PSD(Power Spectra Density)for characterizing the change of strike, step size and roughness. The rupture trace is extracted within every moving window to calculate the aforementioned feature values. Then we can obtain three sets of data from every rupture trace. The co-seismic displacement is averaged in piecewise with uniform interval and moving step along the fault strike. Then, the correlations between three kinds of feature value and the co-seismic displacement are calculated respectively, as well as the P-value of correlation coefficient significant test. We divided cases into two groups according to the slip mode, i.e. strike-slip group and dip-slip group, and contrast their results. In the correlation result list, there is an apparent discrepancy in correlation values between the two groups. The values of the strike-slip group mostly show negative, which indicates that geometric feature of the rupture trace is in inverse proportion to the displacement. In dip-slip group, the values distribute around zero, which suggests the geometric features is irrelevant to the displacement. Through the analysis of the correlation between the surface rupture and co-seismic displacement, the following conclusions can be reached:1)In comparison with the dip-slip earthquake type, the characteristics of surface rupture of strike-slip earthquakes have a higher-level of correlation with the distribution of the co-seismic displacement, which suggests that the geometric features of strike-slip active faults may have a higher reference value in the fault-segmentation research than the dip-slip type; 2)In most strike-slip events, there is a negative correlation between the geometric features and the co-seismic displacement, which implicates that the higher the feature values of the steps, strike change and roughness, the lower the corresponding co-seismic displacement is; 3)Among the three quantified features of the surface rupture trace, the ranking of relevancy between them and the co-seismic displacement is:step size > strike change > roughness.     

DISTRIBUTION OF 3 EARTHQUAKE RUPTURE ZONES IN ESATERN TIENSHAN AND ITS RELATIONSHIP WITH 2 HISTORICAL EARTHQUAKES

The distribution of earthquake rupture zone plays a very important role in determining location of epicenter and magnitude of historical earthquake. There is still argument about the seismogenic structure of the 1842 M7 Balikun earthquake and the 1914 M7 1/2 Balikun earthquake in the historical records in eastern Tienshan. Through field geological survey, we confirm that there exist 3 rupture zones in Eastern Tienshan. These rupture zones, Tazibulake rupture zone on the Jian Quanzi-Luo Baoquan Fault, north of Shanshan, Xiong Kuer rupture zone on the south Balikun Basin Fault and Yanchi rupture zone on the south Yiwu Basin Fault, are closely related to 2 historical earthquakes. Based on historical literature and current geological evidence analysis, we infer that Xiong Kuer rupture zone was produced by 1842 M7 earthquake and Yanchi rupture zone by 1914 M7 1/2 earthquake, while Tazibukale rupture zone may represent another unrecorded historical event. South Balikun Basin Fault disturbs Quaternary stratigraphy which has a ¹⁴C age of 3110±30 B.P in the south of Balikun County, ~100km to the east of Xiong Kuer rupture zone, therefore we can't preclude the possibility that Xiong Kuer rupture zone extends to the south of Balikun County. This region overlaps with the meizoseismal area based on the literature document, together with the fact that the impact of 1842 earthquake is no less than 1914 earthquake, we believe that the magnitude of 1842 earthquake is no less than that of the 1914 earthquake.     

TYPE AND DISPLACEMENT CHARACTERISTICS OF LINGSHAN M6¾ EARTHQUAKE SURFACE RUPTURE ZONE IN 1936, GUANGXI

On April 1, 1936, an M6¾ earthquake occurred on the Fangcheng-lingshan Fault. So far, the Lingshan M6¾ earthquake is the biggest one in South China. There are some reports about the Lingshan earthquake fissures, but its surface rupture hasn't been systemically studied. Based on the geological mapping and measurement of the right-lateral displacement and vertical offset, the surface rupture zone caused by the Lingshan M6¾ earthquake was found, which contains two secondary surface rupture zones in the east and west respectively, its strike varies from N55°E to N60°E with en echelon-like distribution along the north section of Lingshan Fault, and its total length is about 12.5km. The western surface rupture zone locates intermittently along Gaotang-Xiatang-Liumeng, about 9.4km in length, with a right-lateral displacement of 0.54~2.9m and a vertical offset of 0.23~1.02m; the other one appears between Jiaogenping and Hekou, about 3.1km in length, with a right-lateral displacement of 0.36~1.3m and a vertical offset of 0.15~0.57m. The maximum right-lateral displacement and vertical offset are 2.9m and 1.02m, appearing at the east of Xiatang reservoir. The types of surface rupture mainly contain earthquake fault, earthquake scarp, earthquake fissure, earthquake colluvial wedge, earthquake caused landslide and liquefaction of sand and so on. The earthquake fault develops at the east of Xiatang and Jiaogenping, earthquake scarp appears at Xiaoyilu and Xiatang, earthquake fissure locates at Xiatang, there are multiple earthquake landslides along the surface rupture zone, and the trench LSTC03 exposes the earthquake colluvial wedge. In order to further investigate the Lingshan earthquake surface rupture zones, the author compares the parameters of Lingshan M6¾ earthquake with the similar typical earthquakes in western China, the results show that the parameters of Lingshan earthquake are similar to the typical earthquakes in western China. The length of Lingshan earthquake surface rupture is shorter, but the dislocation is bigger. The author considers that this is mainly related with the parameters of Lingshan earthquake, site condition and structural environment of surface rupture zone, the symbols of dislocation measuring, human activity and weather condition and so on. The research of surface rupture zone features and analysis of Lingshan M6¾ earthquake provides important and basic data for exploring the seismogenic structure of Lingshan M6¾ earthquake, and it has important scientific significance.     

对1976年河北唐山MS7.8地震地表破裂带展布及位移特征的新认识

1976年河北唐山MS7.8地震发生之后,诸多资料报道了唐山市南侧展布的长8～11km的地震地表破裂带.该地表破裂带由10余条NE方向、具右旋走滑特征的地表破裂呈左阶形式组成,总体走向N30°E,最大右旋位移2.3m,多数地段的垂直位移为0.5 ～0.7m.近年有学者提出,在更大范围内出现的地表破坏现象.分辨这些地表破...     

根据烈度分布确定华北历史地震破裂区的经验准则及其应用

地震破裂区是地震时沿发震断裂带的同震错动面或破裂面在地表的垂直投影区域,指示了震源断层/破裂的位置与尺度。确定过去长期的强震/大地震破裂区是鉴别地震空区、研究与预测强震危险性的重要基础。对于现代强震,破裂区可运用多种现代技术方法确定,但对于历史强震,破裂区确定的方法需要探索与发展。以华北地区为例,研究利用烈度/等震线资料、结合地震构造与震区地表地质环境等信息确定历史强震破裂区的方法,并开展应用试验。结果表明:研究区现代地震破裂区延伸的烈度区间与极震区烈度、震区环境之间存在密切关系,基于这种关系建立了2条经验准则,可分别用于根据烈度分布确定华北2类震区环境(基岩区和厚层第四纪松散堆积覆盖区)历史强震破裂区的位置与延伸。文中还提出通过综合地震构造、现代小震/余震分布等信息,辅助确定历史强震破裂区横向宽度的思路与途径。作为应用试验,文中确定了5次历史地震的破裂区,结果表明本文发展的经验准则及相应方法适用于华北地区历史强震破裂区的确定。     

芦山县龙门乡芦山“4·20”7.0级强烈地震地表破裂迹象与讨论

在芦山县龙门乡发现芦山“4·20”7.0级强烈地震地表破裂的迹象,这些迹象点呈NE-SW向线状分布,总体走向N40°～50°E,长2～ 3km.根据水泥路面变形推断水平缩短量为8cm,垂直抬升量1 ～ 2em.地表未见走滑分量,运动学特征表现为由NW向SE的推挤作用.在地震地表破裂的力学性质方面,有斜向剪切裂缝,也有挤压对冲逆断层性质,但更多地表现为张性裂缝,这与拱曲顶部的局部张性应力场有关.虽然这些地表破裂组合特征不同,性质也有差异,但均反映了龙门乡一带受到NW-SE向挤压作用以及逆断层发震构造沿线近地表常见的拱曲作用.与大川-双石断裂(前山断裂)、大邑-名山断裂(山前断裂)相比,芦山-龙门隐伏推测断裂更有可能是此次地震的发震断裂,这一推论也与此次地震序列的精定位结果以及地震烈度分布特征相符.有关芦山“4·20”7.0级强烈地震发震断裂的认识,对研究此次地震的发震构造特征以及评价未来山前地带地震危险性具有重要意义.     

新疆及其邻近地区强震活动的时空分布特征

本文根据新疆及其邻近地区1880年以来Ms≥5.0的地震资料,研究了强震的时空分布特征。结果表明,研究区内应变能的释放逐步衰减,一百余年内地震活动呈现出一个较为完整的活动期。同时,活动期内地震活动又具有交替起伏变化的特点。因此,活动期又可分成五个活动幕和四个平静幕。分析讨论了各幕地震活动及研究区内强震活动。     

帕米尔高原1895年塔什库尔干地震地表多段同震破裂与发震构造

基于高分辨率卫星影像解译,通过野外地质地貌填图与差分GPS测量,初步获得了帕米尔高原1895年塔什库尔干地震地表破裂带的空间展布、破裂类型、位移及分布等基本参数,据此估算了可能的地震震级,讨论了其宏观震中及发震构造模型.塔什库尔干地震使得慕士塔格正断层南段的部分和整个塔合曼正断层发生破裂,形成了长约27km的地震地表破...     

DISCOVERY OF SURFACE RUPTURE ZONE IN JIUXI BASIN,GANSU PROVINCE

Qilian Shan-Hexi Corridor is located at the northeastern margin of Tibetan plateau. Series of late Quaternary active faults are developed in this region. A number of strong earthquakes even large earthquakes occurred in history and present-day. In the past, the study of active faults in the area was mostly concentrated in the northern margin fault zone of the Qilian Shan on the south side of the corridor, while the research on the interior and the north side of the corridor basin was relatively rare. We found a new fault scarp in the northern part of the Baiyanghe anticline in Jiuxi Basin in 2010. It is an earthquake surface rupture zone which has never been reported before. In this paper, we carried out palaeoearthquake trench analysis on the newly found earthquake surface rupture zone and textual research of relevant historical earthquakes data. According to the interpretation of aerial photo and satellite image and field investigation, we found the surface rupture has the length of about 5km. The rupture shows as an arc-shaped line and is preserved intact comparably. The lower terrace and the latest flood alluvial fan are offset in addition to modern gullies. By differential GPS measurement, the height of the scarp is about 0.5~0.7m in the latest alluvial fan and about 1.5m in the T₁ terrace. From the residual ruins along the earthquake rupture zone, we believe the surface rupture might be produced by an earthquake event occurring not long ago. In addition, the rupture zone locates in the area where the climate is dry and rainless and there are no human activities induced damages. These all provide an objective condition for the preservation of the rupture zone. The trench along the fault reveals that the surface rupture was formed about 1500 years ago, and another earthquake event might have happened before it. Based on the textural research on the historical earthquake data and the research degree in the area at present, we believe that the surface rupture is related to the Yumen earthquake in 365, Yumen Huihuipu earthquake in 1785 or another unrecorded historical earthquake event.     

汶川地震中的地表破裂与灾害

发生在龙门山断裂带上的汶川Ms8.0级地震引起的地表破裂主要分布在北川—映秀断裂带和江油—灌县断裂带上,尤其是沿前者发育了长达240 km的地表破裂带,造成了重大的人员与财产损失。灾害发生的原因是多方面的:地震的震级大;震中所处地区构造发育,地质环境极为脆弱;人口较为密集,城镇的场地普遍狭窄,空间有限等。但是,断层的作用是决定性的,且在不同地段表现出了明显的差异性,导致了不同类型的地震灾害。对于断层的避让与设防问题考虑不足,放大了本次地震的灾害效应。     

基于临汾2次强震史料与GIS技术对未来强震灾害预测评估

通过对临汾2次历史强震史料的研究,总结出其震害分布特征,对比各类衰减模型绘制的等震线图,确定了对该地区不同震级地震最适用的衰减关系模型和修正值;应用GIS技术的空间分析功能,实现了临汾地区更为直观的震害预测评估系统.再将临汾2次历史强震损失重建,从而预测出临汾地区现有经济社会情况下的地震灾害的损失情况,为其未来防震减灾...     

汶川地震小鱼洞地区的地表破裂和同震位移及其机制讨论

2008年5月12日在四川西部发生的汶川地震是一次以逆冲运动为主,兼有右旋走滑运动的斜滑型地震,形成了有史以来最长、最复杂的地表破裂之一.其中,很多复杂现象到目前为止还没有得到很好的解释或一致的认识,如小鱼洞地区出现的NW走向的小鱼洞断裂,在小鱼洞以北出现的2条相距llkm的平行断裂同时破裂的现象等.通过在小鱼洞地区的详细野外调查,获得了详细的地表破裂分布及同震位移分布,在此基础上对小鱼洞地区地表破裂的机制进行了分析.结果表明,造成上述复杂地表破裂的根本原因是汶川地震的主断层北川-映秀断裂的产状变化,即北川-映秀断裂在小鱼洞以北向NW偏移约3.5km.其破裂机制是:1)北川-映秀断裂的右旋走滑运动在小鱼洞西侧的左阶挤压阶区引起的挤压隆升形成前冲断层,即小鱼洞断裂;2)由于北川-映秀断裂在小鱼洞以北向NW偏移3.5km,导致其断层面倾角变大,逆冲运动引起的断层上盘对下盘的挤压方向变化,结合右旋走滑引起的上盘对下盘的侧向推挤,两者共同作用突破了彭灌断裂,从而形成了2条相距llkm的平行断裂同时错动的现象.另外,文中建议应该重视北川-映秀断裂右旋走滑运动分量、断层产状变化以及断层上、下盘的岩性差异对汶川地震地表破裂过程及地表破裂分布的影响.     

逆冲型断裂同震地表变形定量分析的几个问题——以汶川Ms 8.0地震为例

2008年5月12日四川汶川发生MS8.0地震,发震断裂在地表形成以逆断为主的破裂变形带。同震地表变形带的定量分析对理解地震的构造行为具有重要意义。文中以汶川地震典型调查点为例探讨了逆断型同震地表破裂变形带测量分析中值得重视并容易误解的几个问题,分析了地貌面标志和线性标志等测量数据与构造变形参数的几何关系,给出了变形参数的求解方法和相互关系。同时,就多观测点的定量数据在区域断裂几何结构变化和运动学分析中的运用进行了讨论     

2008年汶川Ms 8.0地震地表破裂变形定量分析——北川-映秀断裂地表破裂带

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