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1.
Semiannual velocity variations around the 2008 M
w 7.9 Wenchuan Earthquake fault zone revealed by ambient noise and ACROSS active source data 
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下载免费PDF全文 We continuously monitor the long-term seismic velocity variation of one of the major ruptured faults of the devastating 2008 M w 7.9 Wenchuan earthquake in China from July 2009 to January 2012, jointly using accurately controlled routinely operated signal system active source and seismic noise-based monitoring technique. Our measurements show that the temporal velocity change is not homogeneous and highly localized in the damaged fault zone and the adjacent areas. Velocity variations from the active and passive methods are quite consistent, which both are characterized by ±0.2 % seasonal variation, with peak and trough at winter and summer, respectively. The periodic velocity variation within fault zone exhibits remarkably positive correlation with barometric pressure with stress sensitivity in the order of 10?6 Pa?1, suggesting that the plausible mechanism might be the crack density variation of the shallow subsurface medium of the damaged fault zone in response to the cyclic barometric pressure loading. 相似文献
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Yebang Xu 《地震科学（英文版）》1992,5(2):389-398
The research of the information dimension (D 1) in an active fault zone considers the contribution of each seismic event to information and reflects the characteristics of the temporal and spatial distributions of earthquakes from a new point of view, avoiding some short-comings of the research about the capacity dimension (D 0). The results of calculation show that the information dimension of the temporal distribution in Xianshuihe active fault zone before Luhuo large earthquake isD 1=0.1051. It is a consult creterion of large earthquakes in future in the fault zone. The information dimensions of the temporal distribution of the earthquakes in Anninghe active fault zone are respectivelyD 1(t N)=0.1363 (for the north section) andD 1(t S)=0.06710 (for the south section). The information dimensions of the spatial distribution are respectivelyD 1(K N)=1.053 (for the north section) andD 1(K S)=0.7758 (for the south section). The north section and the south section belong to two self-similar systems with different information dimensions respectively. The extent of the self-organization of seismic activity in the south section is higher than that in the north section. This is helpful for us to judge the major dangerous section in the key region of the seismic monitoring. The research about the information dimension of the temporal and the spatial distributions of earthquakes is significant for the exploration of active fault zones and seismic prediction. 相似文献
4.
Soil gas investigation is a useful tool to detect active faults. The sudden appearance of soil gas anomalies in zones of deep-reaching faults represents a promising potential precursor of earthquakes and volcanic eruptions. In volcanic areas the development of soil gas monitoring techniques is particularly important, as they can represent, together with remote sensing techniques, the only geochemical methods that can be safely applied during volcanic unrest, when it becomes impossible or too dangerous to sample crater fumaroles. A soil gas survey was carried out in June 1993 at the main island of Thera, in the Santorini volcanic complex. CO2 flux and CO2 and helium concentrations were measured at 50 cm depth for 76 points covering the entire island, with a spacing of 500 m or less. Several anomalous soil degassing sites have been detected. The main anomalies correspond to the Kolumbos line and to the Kameni line, two volcano-tectonic fault systems that controlled all the historic volcanic activity of Santorini. A third anomaly is related to a gas-leaking fault cutting the geothermal field of southern Thera. Soil gas data, together with geovolcanological and seismological evidence, indicate that the Kolumbos and Kameni lines are the most probable sites for future volcanic or seismic reactivation, and provide the basis for the establishment of a new geochemical monitoring technique at Thera. 相似文献
5.
郯庐断裂带宿迁段多年来一直被列为江苏地震重点关注区域。在该区域展开了多期活断层探测和工程地震安全性评价工作,地震监测已经建成了测震、形变、电磁、流体等多种手段。用气体地球化学方法开展相关研究,探索活动断层运动和地震发生之间的相互关系,是对该地区地震科学研究的一种补充,其有着十分重要的意义。沿郯庐断裂带宿迁段F5断裂布设土壤氡测线并获得相关数据,结合地质勘察、浅层人工地震等资料进行综合分析,结果表明该区域内土壤氡探测结果对断裂带的位置、断层类型和特征、断层活动性具有较好的指示性。土壤氡探测展示F5断裂两条分支断裂F5-1、F5-2的位置,氡浓度异常形态与断层特征存在一定的对应关系,并利用土壤氡浓度强度为指标,初步判断郯庐断裂带宿迁段F5断裂2条分支断裂的相对活动性。 相似文献
6.
Similarities between strike-slip faults at different scales and a simple age determining method for active faults 总被引：1，自引：0，他引：1
Abstract Several differently scaled strike‐slip faults were examined. The faults shared many geometric features, such as secondary fractures and linkage structures (damage zones). Differences in fault style were not related to specific scale ranges. However, it was recognized that differences in style may occur in different tectonic settings (e.g. dilational/contractional relays or wall/linkage/tip zones), different locations along the master fault or different fault evolution stages. Fractal dimensions were compared for two faults (Gozo and San Andreas), which supports the idea of self‐similarity. Fractal dimensions for traces of faults and fractures of damage zones were higher (D ～1.35) than for the main fault traces (D ～1.005) because of increased complexity due to secondary faults and fractures. Based on the statistical analysis of another fault evolution study, single event movements in earthquake faults typically have a maximum earthquake slip : rupture length ratio of approximately 10?4, although this has only been established for large earthquake faults because of limited data. Most geological faults have a much higher maximum cumulative displacement : fault length ratio; that is, approximately 10?2 to 10?1 (e.g. Gozo, ～10?2; San Andreas, ～10?1). The final cumulative displacement on a fault is produced by accumulation of slip along ruptures. Hence, using the available information from earthquake faults, such as earthquake slip, recurrence interval, maximum cumulative displacement and fault length, the approximate age of active faults can be estimated. The lower limit of estimated active fault age is expressed with maximum cumulative displacement, earthquake slip and recurrence interval as T ? (dmax /u) · I(M). 相似文献
7.
Yebang Xu 《地震学报(英文版)》1992,5(2):389-398
The research of the information dimension (D
1) in an active fault zone considers the contribution of each seismic event to information and reflects the characteristics
of the temporal and spatial distributions of earthquakes from a new point of view, avoiding some short-comings of the research
about the capacity dimension (D
0). The results of calculation show that the information dimension of the temporal distribution in Xianshuihe active fault
zone before Luhuo large earthquake isD
1=0.1051. It is a consult creterion of large earthquakes in future in the fault zone. The information dimensions of the temporal
distribution of the earthquakes in Anninghe active fault zone are respectivelyD
1(t
N)=0.1363 (for the north section) andD
1(t
S)=0.06710 (for the south section). The information dimensions of the spatial distribution are respectivelyD
1(K
N)=1.053 (for the north section) andD
1(K
S)=0.7758 (for the south section). The north section and the south section belong to two self-similar systems with different
information dimensions respectively. The extent of the self-organization of seismic activity in the south section is higher
than that in the north section. This is helpful for us to judge the major dangerous section in the key region of the seismic
monitoring. The research about the information dimension of the temporal and the spatial distributions of earthquakes is significant
for the exploration of active fault zones and seismic prediction.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 372–379, 1991.
This paper is sponsored by the Chinese Joint Seismological Science Foundation. The English version is improved by Zhenwen
An. 相似文献
8.
孟连断裂位于云南省西南部与缅甸交界地带,是川滇菱形块体南部一条规模较大的活动断裂带,总体呈NEE向延伸,长约90km,走向N70°E,倾向NW,倾角50°~60°,断裂晚第四纪活动较强烈,以左旋走滑为主,兼具有倾滑特征。通过卫星影像解译和野外调查发现,其断错地貌主要以线性断层崖为主,高度不等,其次为断层谷地、断层沟槽和断层垭口地貌,冲沟及阶地的水平位移多在几十米至几百米之间。在孟连县城西侧开挖的大型探槽中,揭露出多条断层,通过分析剖面和14C测年结果认为,孟连断裂晚第四纪发生过4次古地震事件,除最早一次年代较久远以外,其他3次均发生在全新世中晚期以来,最近一次古地震事件的年代为(1 860±30)~(1 090±30)a B.P.。 相似文献
9.
本文利用德国Wissel公司生产的新型穆斯堡尔谱仪(Bench-MB500)对山东龙口常庄子村北黄县弧形断裂断层剖面上的多种断层泥样品进行了穆斯堡尔谱测试分析,讨论了该断层剖面上铁元素地球化学分布特征及其地震地质意义。结果显示,该断裂中央部分比较年轻的断层泥相对富集para-Fe~(2+),而两侧较老的断层泥基本由para-Fe~(3+)组成;剖面断层泥样品中铁元素的地球化学特征与断层的活动演化历史密切相关,显示了断裂带内存在复杂的水岩相互作用。 相似文献
10.
James R. O'Neil 《Pure and Applied Geophysics》1984,122(2-4):440-446
Measurements were made of the amounts of D,18O, and H2O+ in fault gouge collected over a depth of 400 m in the San Andreas fault of California. The amounts and isotopic compositions of the pore fluids, also analyzed, suggest that formation waters from adjacent Franciscan rocks have migrated into the gouge and mixed with local meteoric water. Thus the gouge is an open system permeable to fluid flow. This permeability has important implications concerning heat flow along the fault zone.Analyses of the fault gouge itself give information on the amounts, timing, and conditions of formation of the clay minerals.Stable-isotope analyses of materials from fault zones are good indicators of water-rock interactions that bear importantly on processes taking place in seismically active regions. 相似文献
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Testing geomorphic signal of active normal faulting: The case of the Cittanova Fault (Calabria,southern Italy) 下载免费PDF全文
下载免费PDF全文 Edoardo Peronace Marta Della Seta Francesco Troiani Paolo Galli Biagio Giaccio Paolo Messina Paola Fredi 《地球表面变化过程与地形》2018,43(10):2256-2270
Extracting tectonic signals from the landscape is an important challenge for constraining the style and rate of deformation associated with active faults, especially where their displacement history cannot be independently determined. Based on previous paleoseismological data coupled with new geomorphological field work and 14C dating of geomorphic markers, we analysed the geomorphic signal of the along‐strike differential throw of the Cittanova Fault in southern Calabria (Italy), the recent activity of which is already well documented and constrained. Through DTM‐derived stream power law parameters (SL and χ), we provide evidence of drainage network disequilibrium and reorganization in response to fault growth and deformation style. Furthermore, a methodological test of the reliability of the χ metric as a proxy for the differential throw along the strike of active normal faults provided good preliminary results, consistent with a strong inverse linear correlation with fault throw. Copyright © 2018 John Wiley & Sons, Ltd. 相似文献
13.
Long-period strain seismogram recorded at Pasadena is used to determine the focal process of the 1960 Chilean earthquake. Synthetic seismograms computed for various fault models are matched with the observed strain seismogram to determine the fault parameters. A low-angle (～ 10°) thrust model with rupture length of 800 km and rupture velocity of 3.5 km/sec is consistent with the observed Rayleigh/Love wave ratio and the radiation asymmetry. A seismic moment of 2.7 · 1030 dyn · cm is obtained for the main shock. This value, together with the estimated fault area of 1.6 · 105 km2, gives an average dislocation of 24 m. The strain seismogram clearly shows unusually long-period (300–600 sec) wave arriving at the P time of a large foreshock which occurred about 15 minutes before the main shock, suggesting a large slow deformation in the epicentral area prior to the major failure. A simple dislocation model shows that a dislocation of 30 m, having a time constant of 300–600 sec, over a fault plane of 800 × 200 km2 is required to explain this precursory displacement. The entire focal process may be envisaged in terms of a large-scale deformation which started rather gradually and eventually triggered the foreshocks and the “main” shock. This mechanism may explain the large premonitory deformations documented, but not recorded instrumentally, for several Japanese earthquakes. The moments of the main shock and the precursor add to 6 · 1030 dyn · cm which is large enough to affect the earth's polar motion. 相似文献
14.
采用网格化布点野外流动观测的方法测量了汤阴地堑南部380个点的土壤 H2 浓度,分析其空间分布特征及其与构造的关系,并进一步揭示出气体地球化学特征与区域地质构造背景间的联系. 研究结果表明,汤阴地堑南部土壤 H2 浓度介于(0．26~175．50)×10-6,背景均值为(17．25±11．19)×10-6,异常阈值下限为57．30×10-6.在空间上,土壤 H2 呈现出西低东高的分布特征,受覆盖层厚度和地表沉积特征的影响,低于背景值的测点主要分布于研究区西部.高值异常测点主要集中在研究区东部并沿汤中、汤东断裂带分布,H2 浓度等值线高值中心点连线与断裂带走向基本一致,汤西断裂带虽没出现高值异常,但 H2 浓度相对高值仍然在断裂带及邻近区域,反映出构造对 H2 释放的控制作用.同时,土壤 H2 等值线空间分布也显示,在研究区存在一条北东-南西向的 H2 浓度高值异常条带,推测存在一条规模较大的隐伏断裂.研究区主要断裂带 H2 浓度表现为汤西断裂带显著低于汤中、汤东断裂带,而异常衬度表现为汤西断裂带、汤中断裂带小于汤东断裂带.结合研究区地球物理探测资料分析认为 H2 浓度及异常衬度是构造活动背景的反映,部分深部来源的 H2 通过深大断裂及有利的深浅构造组合向地表扩散迁移,在地壳浅部与浅源 H2 混合,并在断裂带上覆土壤层形成浓度高值异常条带.需进一步开展 H2 在汤阴地堑南部构造活动监测中的应用探索.同时也需要对研究区由北东-南西向 H2 浓度异常条带而推测出的隐伏断裂开展进一步深入研究. 相似文献
15.
活动断裂带中地震时空分布的信息维 D1避免了容量维 D0的缺陷,考虑了每一地震事件对信息所作的贡献,从新的角度反映了地震分布时空结构特征.计算表明,炉霍大震前鲜水河断裂带地震分布时间结构信息维 D1=0.1051,这是该区大震活动的一个参考性判据.安宁河断裂带十七年现今地震分布时间结构信息维:北段,D1（tN）=0.1363;南段,D1（tS）=0.06710.地震空间分布信息维:北段,D1（KN）=1.053;南段,D1（Ks）=0.7758.南北两段分属信息维维数不同的两个自相似系统.南段地震活动自组织程度较高.这有助于强震重点监测区内主要危险段的判定地震时空分布 D1特征探索对于活断层研究以及地震预报都有一定的意义. 相似文献
16.
Iain S. Stewart Callum R. Firth Derek J. Rust Philip E.F. Collins Judith A. Firth 《Journal of Seismology》2001,5(3):307-328
The Kinloch Hourn fault is the most prominent of a number of suspectedpostglacial faults in the western Scottish Highlands. These faults areinterpreted to have been reactivated by repeated large (M > 6)palaeoseismic events following deglaciation 10,000–13,000 years ago.Based on inferred deflections of drainage courses, previous studies of thefault have estimated 160 ± 40 m cumulative left-lateral displacementalong a 14 km long active segment during postglacial times. Reportedsoft-sediment deformation phenomena imply that activity on the KinlochHourn fault has persisted into the late Holocene, with the most recentmovement having been associated with a magnitude 5.5–6.0 surface-faultingevent between 3500 and 2400 years ago. The marked contrast betweensuch palaeoseismic activity and the present-day seismic quiescence ofwestern Scotland has stimulated this critical reappraisal of the KinlochHourn fault.This paper reassesses the key lines of evidence for postglacial fault activityand palaeoseismicty on the Kinloch Hourn fault, combining the analysis of1:15,000-scale air photos, field-based geomorphic mapping andpalaeoenvironmental investigations. Our reappraisal of inferred drainagedeflections across the fault contends that previous reports of significant(102 m) left-lateral slip on the fault during the Holocene arespurious. Instead, incidences of Holocene channel abandonment along thefault line are non-synchronous and probably reflect non-tectonic drainagechanges. The timing of soft-sediment deformation in the vicinity of the faultis revised to an early Holocene date (8990–8580 calendar years BP), whichis in accord with both the palaeoenvironmental history of the site andconsistent with published ages of earthquake-induced liquefactionphenomena documented elsewhere in western Scotland. An alleged recent(post-2400 radiocarbon years BP) ground rupture on the fault isquestioned in the light of uncertainty about both the nature of the faultedsoil deposit and the late Holocene age attributed to it.The study concludes that there is no convincing evidence for postglacialsurface rupture on the Kinloch Hourn fault and speculates that the casefor significant (101–102 m) postglacial movement on otherfaults in western Scotland may be similarly `unproven'. 相似文献
17.
Studies on40Ar/39Ar thermochronology of strike-slip time of the Tan-Lu fault zone and their tectonic implications 总被引：6，自引：0，他引：6
Samples of mylonite, ultramylonite and phyllonite were collected from 5 localities in the Anhui part of the Tan-Lu fault zone
for40Ar/39Ar chronological studies. Among them 4 samples from 3 localities on the eastern margin of the Dabie orogenic belt yielded40Ar/39Ar plateau ages of 128 —132 Ma; and 2 samples from the western margin of the Zhangbalin uplift and eastern margin of the Bengbu
uplift gave the same40Ar/39Ar plateau ages of 120 Ma. Isochron analyses and other lines of evidence suggest that the data are reliable. The data are
interpreted as cooling ages of sinistral strike-slip deformation of the Tan-Lu fault zone. The younger ages from the north
might be related to slower strike-slip rising. These results indicate that the large-scale left-lateral displacement in the
Tan-Lu fault zone took place in the Early Cretaceous, rather than in Late Triassic (Indosinian) as proposed by some geologists.
Therefore, this fault zone is an intracontinental wrench fault rather than a transform fault or suture line developed during
formation of the Dabie orogenic belt. 相似文献
18.
Yu. O. Kuzmin 《Izvestiya Physics of the Solid Earth》2013,49(5):626-642
The results of analyzing the long (20–50 years) time series of geodetic observations carried out in the regions with enhanced seismotectonic activity (Kopet Dag, Kamchatka, and California) are presented. It is established that recent vertical and horizontal displacements in the fault zones estimated by instrumental geodetic observations with increased spatiotemporal resolution indicate that the deformations in the fault zones paradoxically deviate from the movements inherited from the previous geological epochs. The paradoxes of high and low deformation rates in recent geodynamics lie in the reliably established empirical fact that extremely high local deformation rates (up to 10?5 per annum and higher) exist in the fault zones in the setting of weak regional deformations, whose annual rates are by two to three orders of magnitude lower. Very low annual average rates of relative horizontal deformations, which only measure 3–5 amplitudes of tidal deformations of the solid Earth, are revealed in the seismically active regions of Kopet Dag and Kamchatka as well as in the San Andreas Fault Zone in northern California. The fault-block dilemma arising in the interpretation of the observations of recent fault geodynamics is formulated. Either the role of active element, which forms the present anomalous deformations, is played by a block, while a fault plays the role of the passive element, or the fault zone itself is a source of anomalous movements, while the blocks are passive elements (hosting medium). It is shown that paradoxes of low and high deformation rates vanish if we assume that the recent anomalous geodynamics is formed by parametric excitation of the deformation processes in the fault zones in the conditions of quasi-static loading. 相似文献
19.
采用2014年10月22日至2019年4月11日之间的26景Sentinel-1升轨数据,基于PS-InSAR技术对蓟运河断裂这一隐伏断裂进行形变监测试验。结果表明：(1)研究区受地面沉降干扰强烈地区在南部宁河一带,向北地面沉降逐步减弱,在蓟运河断裂北段以北一带基本无地面沉降现象。(2)研究区北部的视向线形变速率在蓟运河断裂北段一带在0 mm·a-1左右,向北随远离断裂形变速率增大,表明研究区北部受近东西向燕山隆起控制,有向南掀斜运动的趋势。(3)蓟运河断裂北段活动方式为黏滑,其两盘的视线向相对形变速率差约为1.83 mm·a-1,蓟运河断裂南段两盘形变速率差小于2.96 mm·a,与2005—2012年的水准测量结果相近,表明蓟运河断裂2005年以来活动速率较为稳定。(4)在受到地面沉降影响下,隐伏断裂的InSAR形变场包含更多的非构造信息,无法获取断裂的具体形变速率。但断裂活动会导致断裂两盘含水层厚度不同,地下水超采造成的地面沉降幅度也不同,相应的其InSAR形变场在断裂两盘出现突变,对隐伏断裂的位置判定有一定意义。 相似文献
20.
Murat Utkucu 《Journal of Seismology》2013,17(2):783-805
The 23 October 2011 Van earthquake took place in the NE part of Lake Van area, surprisingly on a fault (the Van fault) that is not present in the current active fault map of Turkey. However, occurrence of such a large magnitude earthquake in the area is not surprising regarding the historical seismicity of the region. The comparison of the damage patterns suggests that the earthquake is much likely a recurrence of the 1715 Van earthquake. The finite fault modelling of the earthquake using teleseismic broadband body waveforms has shown that the earthquake rupture was unilateral toward SW, was mostly reverse faulting, confined to below the depth of 5 km, did not propagate offshore, and was dominated by a failure of a single asperity with a peak slip of about 5.5 m. The total seismic moment calculated for the model is 4.6?×?1019 Nm (M W ?≈?7.1). The finite fault model coincides with the field observations indicating blind faulting and the vertical displacements over the free surface estimated from it correlate well with the maximum reported uplift along the coast of Lake Van above the hanging wall. The possible offshore continuations of the Van fault and some other faults lying its south are also discussed by assessing a previous offshore seismic reflection study and the earthquake epicentres and focal mechanisms. 相似文献