祁连山—海原断裂带跨断层形变近期异常特征研究及机理初探

分析了祁连山—海原断裂带跨断层形变近期异常变化特点,给出了该断层形变区域特征异常量,认为断层形变不但能够显示局部构造活动,而且可以反映大范围地壳形变波的空间传播与演化,从而为利用跨断层观测资料进行地震跟踪预报提供了一定的物理背景     

深地震反射剖面揭示的海原断裂带深部几何形态与地壳形变

由于活动的青藏高原不断的隆升和推挤作用,在西南向东北的推挤作用和周缘块体的阻挡以及东北缘内部块体挤压形变的作用下,形成了多个走向不同的青藏高原东北缘构造体系.新生代构造变形和地震活动强烈,区内分布多条大型深断裂带.海原断裂是青藏高原东北缘发育的弧形活动断裂带中规模最大、活动最为强烈的一条左旋走滑型断裂带,是重要的大地构造区边界,也是控制现今强震活动的活断层.本文利用2009年完成的高分辨率深地震反射剖面的北段资料,对其进行初步构造解释,揭示出海原断裂带的深部几何形态和其两侧地壳上地幔细结构.结果显示海原断裂并不是简单的陡立或者较缓,其几何形态随着深度变化.在海原断裂之下的Moho并未错断的反射特征显示海原断裂并不是直接错断莫霍面的超壳断裂.海原断裂带及两侧岩石圈结构和构造样式的研究为探讨青藏高原东北缘岩石圈变形机制提供地震学依据.     

用GPS数据反演分析海原断裂带分段活动特征

首先应用1999-2007年的GPS观测资料分析海原断裂带的运动特征,看出期间该断裂带GPS站点运动速度由南向北逐渐衰减,在NWW和NE走向断层两盘的运动差异较为明显,断层的活动以走滑运动为主.然后依据地质、地球物理等资料给出反演参数初值,利用水平形变资料对断裂三段的走滑速率及断层下界深度进行反演.结果为从西到东断裂带各段走滑速率分别为8.25 mm/a、5.49 mm/a和5.97 mm/a,断层底部深度依次为22.8 km;13.3 km;11.1 km.综合分析认为毛毛山-老虎山断裂运动速度明显高于海原断裂速度,在速度变化梯度较大的毛毛山断裂存在6级以上地震空区,推测具有发生强震的危险性.     

基于PS-InSAR技术的海原断裂带地壳形变观测研究

基于单像对的常规D-InSAR技术在形变量较大的地震同震形变场探测中已取得成功应用,但由于其受时间、空间失相干和大气影响的严重制约,难以应用于长期缓慢微小地壳形变的观测研究中.近几年发展起来的PS-InSAR(Permanent scatterer InSAR)技术是对常规D-InSAR的创新性发展,它通过将干涉处理对象集中在SAR图象中散射特性稳定的高相干点集上(人工建筑物或巨石、山峰等自然地物),避开非相干象元可能带来的各种复杂问题,从而间接克服了相位失相关和大气延迟的局限性,极大地提高了干涉测量的精度和可靠性,使基于InSAR技术的mm级微小地壳形变的遥感观测得以实现.     

基于地壳变形观测资料分析广义海原断裂运动状态

广义海原断裂包括冷龙岭断裂、 金强河断裂、 毛毛山断裂、 老虎山断裂、 海原断裂等几段, 地震地质研究认为该断裂不同断层段处于不同的孕震阶段。 利用大地测量观测的地壳运动速率做约束, 通过反演确定现今上述各断层的运动状态。 首先基于黏弹性地震周期变形模型计算广义海原断裂不同断层带的位移累积速率, 然后根据获得的结果与海原大地震的同震位移进行对比分析, 最后讨论该区域断裂带上不同孕震阶段的活动特征和运动状态。 反演结果表明, 1920年海原8.5级地震发震断层闭锁程度整体较低; “天祝空段”的闭锁程度较高, 断层累积速率较小; 1888年景泰7级地震发震断层的闭锁程度也相对较高; 1990年景泰—天祝6.2级地震发震断层的闭锁程度相对较低; 广义海原断裂的整体速率由西向东呈阶段性分布, 位移累积速率与大地震的发震地区呈对应关系。     

基于GPS观测的张家口-渤海断裂带活动性

文中基于1999年、2007年、2009年、2011年、2013年以及2015年6期GPS区域站观测资料,计算得到了5个相邻时段中张家口-渤海断裂带的水平形变速率和应变率,据此研究了该断裂带的活动性演化特征。结果表明,在5个时段中,张家口-渤海断裂带的总体形变速率平均为1. 74mm/a,左旋走滑速率平均为1. 59mm/a,压缩速率平均为-0. 59mm/a。张家口-渤海断裂带各时段的左旋走滑速率均大于压缩速率,说明其活动性以左旋走滑活动为主,兼有压缩运动。在5个时段中最小主应变率均小于0,为压性,最大主应变率>0,为张性。张家口-渤海断裂带的主压应力方向均为NEE-SWW向,主张应力方向NNW-SSE向;正应变率均为负数,为压性;断裂带的剪应变率值相对于正应变率较大,表明剪应力较强,各时段均以左旋剪切应力作用为主。张家口-渤海断裂带的构造活动具有继承性,在日本3·11大地震后,其构造活动性呈现逐步减小的趋势。     

郯庐断裂带中南段重磁综合剖面探测研究

郯庐断裂中南段在第四纪以来活断层最发育,历史上曾发生过多次中强以上地震,是中国目前主要地震活动区域之一。汶川8.0级地震发生后,地下流体观测井多测项震后效应在郯庐断裂带中南段部分地区一直持续存在,同时速度结构研究表明该区域存     

西-海-固地区垂直形变分析及地震趋势研究

通过对西（吉）-海（原）-固（原）地区垂直形变场的演化分析表明:①90年代以来,垂直形变场升降差异运动减弱;②现今青藏亚板块对鄂尔多斯地块西南缘（西-海-固地区） 的 NE 方向挤压应力有所减弱,华北亚板块 SW 方向挤压应力有所加强;③鄂尔多斯块体周缘小震出现的活跃状态,可能是由于青藏亚板块挤压应力的减弱而造成鄂尔多斯块体水平挤压应力场的“失稳”,以及华北亚板块挤压应力相对增强的结果。     

青藏高原东北缘马衔山断裂带构造属性的综合研究

左旋走滑的马衔山断裂带位于青藏高原东北缘陇中盆地内部,呈北西-南东向伸展.宽约8~10 km,长约115 km.马衔山断裂带表面虽然局部已被黄土覆盖,但并不代表它的活动性不强.1125年的兰州M_S7.0地震就发生在马衔山断裂带北缘的西侧.前人对马衔山断裂带的研究基本上多依靠于地表地质和地球化学数据分析进行一般性讨论,而缺少对马衔山断裂带深部构造伸展的清晰认识.本文中,我们主要依靠一条横跨马衔山断裂带的深地震反射剖面数据资料进行地壳尺度的构造解释.在此基础之上,对研究区所获得的重力数据进行相应的处理分析.最后辅助于马衔山断裂带两侧野外地表形变的观察和前人研究所获得的地球化学数据分析,我们的研究认为马衔山断裂带为一不同块体间的边界断裂带.它可能形成于早古生代祁连造山带东缘北部马里亚纳式岛弧和南部日本式岛弧的相互拼贴作用.该边界断裂带在随后的青藏高原东北缘物质逃逸过程中被激活,并且目前仍处于构造活动活跃期.

     

地质观测、地震剖面和重力测量的综合方法在前陆褶皱冲断带的应用:以天山北麓呼图壁河剖面为例

褶皱逆冲带的几何学研究是造山带研究的热点,但是无论是传统构造地质学方法还是地球物理学方法都在研究褶皱逆冲带几何特征时存在多解性.为了制约这种多解性,本文以天山北麓的呼图壁河剖面为列,介绍一种地质与地球物理相结合的研究方法.该方法首先沿呼图壁河剖面进行详细的地表观测,获取地表的构造地质数据形成初步的地质模型,其次结合地表构造和钻井分层数据,对收集到的石油地震剖面进行重新解释.然而,地震反射数据只分布在盆地内部,在盆山结合带缺失或者不清晰,因此对该剖面进行了重力测量并计算出布格重力异常.结合盆地各沉积地层和基底密度值,用重力正演方法模拟呼图壁河剖面的密度结构.研究结果显示沿呼图壁河剖面并不存在天山北缘断裂,盆地的沉积盖层可以从准噶尔盆地连续过度到天山内部并不整合覆盖在天山古生代基底之上.这一结果与西段金钩河剖面的天山基底逆冲到准噶尔盆地显然不同,说明了天山北缘盆山结合带构造的多样性.利用平衡剖面技术,恢复的呼图壁河平衡剖面缩短量约为4.8km,对比前人研究,说明了天山北缘的缩短量沿东西方向存在显著的不均一性.本研究也说明这种构造地质与地震及非震地球物理相结合的方法可以广泛地被应用于褶皱逆冲带.     

Spatiotemporal patterns of fault slip rates across the Central Sierra Nevada frontal fault zone

Patterns in fault slip rates through time and space are examined across the transition from the Sierra Nevada to the Eastern California Shear Zone–Walker Lane belt. At each of four sites along the eastern Sierra Nevada frontal fault zone between 38 and 39° N latitude, geomorphic markers, such as glacial moraines and outwash terraces, are displaced by a suite of range-front normal faults. Using geomorphic mapping, surveying, and ¹⁰Be surface exposure dating, mean fault slip rates are defined, and by utilizing markers of different ages (generally, ~ 20 ka and ~ 150 ka), rates through time and interactions among multiple faults are examined over 10⁴–10⁵ year timescales.At each site for which data are available for the last ~ 150 ky, mean slip rates across the Sierra Nevada frontal fault zone have probably not varied by more than a factor of two over time spans equal to half of the total time interval (~ 20 ky and ~ 150 ky timescales): 0.3 ± 0.1 mm year^? 1 (mode and 95% CI) at both Buckeye Creek in the Bridgeport basin and Sonora Junction; and 0.4 + 0.3/?0.1 mm year^? 1 along the West Fork of the Carson River at Woodfords. Data permit rates that are relatively constant over the time scales examined. In contrast, slip rates are highly variable in space over the last ~ 20 ky. Slip rates decrease by a factor of 3–5 northward over a distance of ~ 20 km between the northern Mono Basin (1.3 + 0.6/?0.3 mm year^? 1 at Lundy Canyon site) to the Bridgeport Basin (0.3 ± 0.1 mm year^? 1). The 3-fold decrease in the slip rate on the Sierra Nevada frontal fault zone northward from Mono Basin is indicative of a change in the character of faulting north of the Mina Deflection as extension is transferred eastward onto normal faults between the Sierra Nevada and Walker Lane belt.A compilation of regional deformation rates reveals that the spatial pattern of extension rates changes along strike of the Eastern California Shear Zone-Walker Lane belt. South of the Mina Deflection, extension is accommodated within a diffuse zone of normal and oblique faults, with extension rates increasing northward on the Fish Lake Valley fault. Where faults of the Eastern California Shear Zone terminate northward into the Mina Deflection, extension rates increase northward along the Sierra Nevada frontal fault zone to ~ 0.7 mm year^? 1 in northern Mono Basin. This spatial pattern suggests that extension is transferred from more easterly fault systems, e.g., Fish Lake Valley fault, and localized on the Sierra Nevada frontal fault zone as the Eastern California Shear Zone–Walker Lane belt faulting is transferred through the Mina Deflection.     

Research on paleoearthquakes in Jiuxian trenches across Nankou-Sunhe fault zone in Changping County of Beijing plain

An abundance of the phenomena of tectonic deformation and paleoseismic events of different times and their recurrent interval, as well as coseismic vertical displacements is exposed in Jiuxian trenches across the Nankou-Sunhe fault zone in Changping County. The research result shows three paleoearthquakes occurring during the Holocene. They were dated as 10643 ± 250 a B.P.-9706 ± 1235 a B.P., 7894±150 a B.P.-7640 ± 650 a B.P., and 3987±100 a B.P.-3670 ± 310 a B.P., respectively. The coseismic vertical displacements are 1.0 m, 2.0 m, and 2.0 m, respectively. From a statistical formula of relation between historic earthquake magnitudes and surface seismic dislocations in North China, the magnitudes of these paleoearthquakes are inferred to be in a range from M 7.7 to M 7.9. The research shows that the Holocene fault activity in the plain can be traced in the trenches according to the micro-geomorphic features. Many micro-structural phenomena are also found in these trenches. Identification of the paleoearthquakes in the Nankou-Sunhe fault zone during the Holocene time is of significance for assessment of future seismic risk in Beijing area.     

Active fault survey on the Tanlu fault zone in Laizhou Bay

Introduction The Tanlu fault zone, the largest active structure in the eastern region of China, is character-ized by right lateral strike-slip movement with dip-slip component in the Quaternary; it shows great significance for the modern seismicity (FANG et al, 1976; Institute of Geophysics, China Earthquake Administration, 1987; GAO et al, 1980; MA, 1987; LI, 1989; CHAO et al, 1995). The Tanlu fault zone is the boundary between the Jiaoliao block and the North China Plain block of …     

基于GPS连续站观测资料的鲜水河断裂运动特征研究

鲜水河断裂GPS连续站监测网由七美、瓦日、牦牛、塔工4个站组成,于2006年2月建成并开始运行。本文利用该监测网2006年2月至8月期间的观测资料,计算出6条基线长变化的时间序列,在此基础上,分析了鲜水河断裂的运动特征。结果表明,在测区范围内,鲜水河断裂以12.3±1.2 mm/a的速率左旋滑动,测区北端有明显张性,而南端则没有明显的张性或压性特征。最后,通过与以前对鲜水河断裂运动状态进行观测的各种手段和结果的比较,本文认为GPS连续运行参考站监测网在活动断裂的监测方面具有明显优势。     

基于多参数组合分析海原—六盘山—宝鸡断裂带地震危险性

1 研究背景 近年来,易桂喜等(2006,2007)、武敏捷等(2013)利用以b值为主的地震活动性参数空间分布,结合历史及现今地震活动背景,分析活动断裂带现今活动习性,综合判断处于相对高应力和闭锁状态下活动断裂带的强震危险性.这种组合分析方法比单个活动性参数值能更好地反映断裂现今活动习性,且对地震样本需求不高,适用于...     

政和-海丰断裂带b值空间扫描分析

应用b值空间扫描方法,分析福建地区政和-海丰断裂带上发生的ML≥4.5中强地震前b值空间扫描图像.分析结果表明:在此断裂带上发生中强地震前,均存在b值空间扫描异常现象,且震中皆在异常区域内.b值空间扫描方法,对政和-海丰断裂带ML≥4.5中强地震发生的时间、地点映震效果明显,对该断裂带上发生的中强地震进行中短期预测有一定效果.     

A recent paleoearthquake on Qingfengling seismic fault of Tanlu fault zone

Introduction The Tanlu fault zone lies in the eastern China, which is an important huge active fault with a long history. It has experienced a complex generation and evolution process and affects significantly the regional structure, paleogeography, magma activity, minerogenesis and earthquake activity in the area. With a length of 2 400 km, the fault zone consists of 2-4 or more parallel faults of 10-40 km in width, cutting through different geotectonic elements in the eastern China （FANG et al, 1986）. On July 25 in 1668, an extraordinarily large earthquake of M=8.5 occurred on the Changyi-Dadian fault （F1） that is an embranchment of Tanlu fault zone, resulting in a surface rupture with a total length of 130 km （LI et al, 1994; CHAO et al, 1995）. The paleoseismic study reveals that 3 events with a magnitude equal to 8 occurred on the Changyi-Dadian fault. The recent event occurred 3 500 a ago and the reoccurrence interval is about 3 500 a （LIN and GAO, 1987）. During the Tancheng earthquake （on July 25, 1668）, the Anqiu-Juxian fault was not ruptured, which was a Late Pleistocene active fault （ZHENG et al, 1988; GAO et al, 1988; CHAO et al, 1994） and was doubted as the seismogenic fault of the M=7.0 Anqiu earthquake occurred in 70 BC by certain geologists （CHAO et al, 1994）.     

Deformational behaviour of continental lithosphere deduced from block rotations across the North Anatolian fault zone in Turkey

Theoretical considerations of lithosphere deformation across transform plate boundaries predict an expression in terms of 3istributed deformation. The magnitude of rotation is expected to diminish away from the fault zone in a way which depends on the length of the fault, the amount of displacement, and the ductility of the lithosphere. Palaeomagnetic studies across the North Anatolian transform fault zone, which separates the Eurasian Plate and Anatolian Block in northern Turkey, show that clockwise rotations predicted from the sense of dextral motion are indeed present and have attained finite rotations of up to 270° during the 5 Ma history of Neotectonic deformation. Such rotations are, however, confined to narrow ( 10 km wide) zones between system-bounding faults and appear to have resulted from rotation in ball-bearing fashion of equidimensional blocks a few kilometres in size. Outside of this zone only anticlockwise rotations are observed; these are unrelated to deformation across the fault zone and record regional anticlockwise rotation of Turkey which is complementing clockwise rotation of Greece and accompanying Neogene opening of the Aegean Sea. The observed behaviour of continental lithosphere satisfies no plausible value of power law behaviour. We therefore conclude that relative motion across this transform boundary occurs as a discrete zone of intense deformation within a brittle layer comprising the seismogenic upper crust. This is presumed to be detached from a continuum deformation response to shearing in the lower crust and mantle beneath.     

区域地电场观测数据分析研究

在对地电场观测方法进行了概要介绍的基础上,利用自己编写的不同台站之间观测数据的相关分析软件和MAPSIS中的谱分析功能,对“首都圈”地区部分台站地电场观测数据进行了分析研究,包括相关性研究和频谱特性研究等。研究结果表明：①在正常观测条件下,小区域地电场台网观测数据有一定的相关性,频谱特性具有一定的相似性;地电场台站之间的观测数据的相关性,似乎与台距有一定的关系;②通过多个台站的相关性分析和频谱特性分析,可以对地电场数据的变化情况如干扰,漂移等进行初步评判和辐助研究。     

库尔勒体应变观测资料可靠性分析

剔除库尔勒体应变观测资料中地震波、仪器标定及明确原因的干扰数据,计算应变潮汐因子、高频信息和非潮汐速率,结果显示：O1波、半日波潮汐因子在轮台5.4级、新源-和静交界6.6级地震前存在明显的异常反应,潮汐因子曲线形态、周期均发生明显的异常变化,异常结束后2-3个月内发震.总结体应变观测资料的异常特征,可有效捕捉前兆异常变化信息,有助于提高台站的地震短临预报水平.