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1.
A model is proposed for studying the mechanical behaviour of faults during their interseismic periods. The model considers a plane fault surface in an elastic medium, subject to a uniform shear stress which increases slowly with time. A1-D friction distribution is assumed on the fault, characterized by asperities and a weaker zone. The traction vector on the fault plane has an arbitrary orientation: in particular, it can be nonperpendicular to the asperity borders. Aseismic fault slip takes place when the applied stress exceeds the frictional resistance: slip starts in weak zones and is confined by asperities, where it propagates at increasing velocity. Propagation into asperities is characterized by a dislocation front, advancing perpendicularly to the asperity border. Fault slip does not take prate in the direction of traction, except when traction is perpendicular or parallel to the asperity border. The propagation of such aseismic dislocations produces a stress redistribution along the fault and can play a key role in determining the conditions which give rise to earthquakes.  相似文献   

2.
The Jiashian earthquake (ML 6.4) occurred on 4 March 2010. It was the largest inland event in southern Taiwan of 2010. The mainshock location was unexpected since it occurred in an area with relatively low background seismicity. In addition, reports of earthquake focal mechanisms do not fit with any known active fault geometry. In order to understand the origin of this earthquake, especially its rupture process, we perform a joint source inversion by using teleseismic body wave, GPS coseismic displacements and near field ground motion data. In this study, we considered a northwest–southeast trending fault with a northeast dip retrieved from GPS coseismic data and aftershocks distribution. To analyze the detailed slip distribution in space and time, we used near field 3D Green’s functions provided by spectral-element method and a full time–space inversion technique. We find a complex rupture process with several slip patches distributed inside two main asperities. The slip map reveals a mean slip of 12.9 cm for a maximum slip of 27.3 cm leading to a Mw 6.47 for this event. The rupture initiates in the deepest portion of the fault at 20 km depth, and propagated upward up to 2 km depth to form the two asperities. The source time function of this event revealed two pulses corresponding to the two asperities, for a total duration time of about 16 s. Most aftershocks occurred near the upper boundary of the deepest asperity while no aftershocks are located close to the shallowest one. We infer that the locations of these slip patches are related to the surrounding fault systems that may have restricted the rupture propagation during the earthquake.  相似文献   

3.
近断层强地震动预测中的有限断层震源模型   总被引：1，自引：0，他引：1  
提出了近断层强地震动预测中建立活断层上设定地震有限断层震源模型的方法和步骤.首先,根据地震地质和地震活动性调查以及地球物理勘探等资料,确定活断层的空间方位和滑动类型; 然后,根据地震定标律确定活断层的宏观震源参数; 第三,将高强体模型与k平方滑动模型相结合,产生断层破裂面上的混合滑动分布.在此基础上,预测了与1994年Northridge地震断层类型、矩震级(Mw6.7)基本一致的设定地震的有限断层震源模型.最后,将预测的有限断层震源模型与基于地震学的、使用动力学拐角频率的地震动随机合成方法相结合,预测了1994年Northridge地震近断层12个基岩台站的加速度时程,并和实际记录进行了对比.结果表明,用上述方法和步骤建立的有限断层震源模型是可行、实用的.   相似文献   

4.
基于实验结果讨论断层破裂与强震物理过程的若干问题   总被引：9，自引：0，他引：9  
基于断层摩擦滑动实验、含凹凸体断层的变形破坏实验、断层撕裂扩展的实验、交叉断层的变形实验等多种实验结果并结合前人的工作 ,讨论了与断层破裂与强震物理过程相关的若干问题。研究表明 ,断层的整体滑动引起其两侧块体弹性应变的释放 ,是强震发生的原因 ,因此构造活动区具有较大尺度、结构连续且简单、介质均匀的断层 (或断层段 )是产生强震必备的构造条件 ,深部新生断层(盲断层 )向上撕裂扩展产生强震 ,尚需“弱层”提供“解耦”条件以便断层发生整体滑动。强震孕育过程中包含着凹凸体的破裂 ,断层面上凹凸体的尺度、强度及数量决定着前震活动的特征、强震动态破裂过程以及前兆现象。由断层分割的块体通过边界断层的交替滑动、以“框动”的方式运动 ,因此块体周边的断层上强震活动具有交替性。  相似文献   

5.
Analysis of vertical crustal deformation data in the southwestern part of Shikoku, southwest Japan, suggests that the Nankaido earthquake of 1946 (Mw = 8.1), which is a principal interplate thrust earthquake, was accompanied by subsidiary faulting on a splay fault adjacent to the coast of Shikoku. Discarding crustal movement resulting from the main thrusting of the Nankaido earthquake, local leveling data are explained by slip on a simple rectangular thrust fault located just offshore of Shikoku. Although it is difficult to constrain the fault location, a possible result is a high-angle thrust dipping landward at an angle of about 70°, with a dislocation of about 1.5 m, and source dimensions of 30 × 13 km along strike and dip. respectively. This result indicates that the fault may be one of the steeply dipping subsidiary faults branching from the main low-angle thrust, as was the case in the Alaska earthquake of 1964. Although several lines of evidence suggest that this faulting occurred as slow aseismic slip, its discrimination from the main seismic event is extremely difficult. This kind of high-angle thrusting just offshore of the coast would play an important role for the formation of the marine terraces during the late Quaternary period.  相似文献   

6.
Seismic coupling and uncoupling at subduction zones   总被引：1，自引：0，他引：1  
Seismic coupling has been used as a qualitative measure of the “interaction” between the two plates at subduction zones. Kanamori (1971) introduced seismic coupling after noting that the characteristic size of earthquakes varies systematically for the northern Pacific subduction zones. A quantitative global comparison of many subduction zones reveals a strong correlation of earthquake size with two other variables: age of the subducting lithosphere and convergence rate. The largest earthquakes occur in zones with young lithosphere and fast convergence rates, while zones with old lithosphere and slow rates are relatively aseismic for large earthquakes. Results from a study of the rupture process of three great earthquakes indicate that maximum earthquake size is directly related to the asperity distribution on the fault plane (asperities are strong regions that resist the motion between the two plates). The zones with the largest earthquakes have very large asperities, while the zones with smaller earthquakes have small scattered asperities. This observation can be translated into a simple model of seismic coupling, where the horizontal compressive stress between the two plates is proportional to the ratio of the summed asperity area to the total area of the contact surface. While the variation in asperity size is used to establish a connection between earthquake size and tectonic stress, it also implies that plate age and rate affect the asperity distribution. Plate age and rate can control asperity distribution directly by use of the horizontal compressive stress associated with the “preferred trajectory” (i.e. the vertical and horizontal velocities of subducting slabs are determined by the plate age and convergence velocity). Indirect influences are many, including oceanic plate topography and the amount of subducted sediments.All subduction zones are apparently uncoupled below a depth of about 40 km, and we propose that the basalt to eclogite phase change in the down-going oceanic crust may be largely responsible. This phase change should start at a depth of 30–35 km, and could at least partially uncouple the plates by superplastic deformation throughout the oceanic crust during the phase change.  相似文献   

7.
Oil from the 1989 Exxon Valdez oil spill persists in many gravel beaches in Prince William Sound (Alaska, USA), despite great remedial efforts. A tracer study using lithium at a gravel beach on Knight Island, Prince William Sound, during the summer of 2008 is reported. The tracer injection and transport along a transect were simulated using the two-dimensional numerical model MARUN. Model results successfully reproduced the tracer concentrations observed at wells along the transect. A sensitivity analysis revealed that the estimated parameters are well determined. The simulated spatial distribution of tracer indicated that nutrients applied along the transect for bioremediation purposes would be washed to the sea very quickly (within a semi-diurnal tidal cycle) by virtue of the combination of the two-layered beach structure, the tidal fluctuation and the freshwater flow from inland. Thus, pore-water samples in the transect were found to be clean due to factors other than bioremediation. This may explain why the oil did not persist within the transect.  相似文献   

8.
The 2002 earthquake sequence of October 31 and November 1 (main shocks Mw = 5.7) struck an area of the Molise region in Southern Italy. In this paper we analyzed the co-seismic deformation related to the Molise seismic sequence, inferred from GPS data collected before and after the earthquake, that ruptured a rather deep portion of crust releasing a moderate amount of seismic energy with no surface rupture. The GPS data have been reduced using two different processing strategies and softwares (Bernese and GIPSY) to have an increased control over the result accuracy, since the expected surface displacements induced by the Molise earthquake are in the order of the GPS reliability. The surface deformations obtained from the two approaches are statistically equivalent and show a displacement field consistent with the expected deformation mechanism and with no rupture at the surface. In order to relate this observation with the seismic source, an elastic modeling of fault dislocation rupture has been performed using seismological parameters as constraints to the model input and comparing calculated surface displacements with the observed ones. The sum of the seismic moments (8.9 × 1017 Nm) of the two main events have been used as a constraint for the size and amount of slip on the model fault while its geometry has been constrained using the focal mechanisms and aftershocks locations. Since the two main shocks exhibit the same fault parameters (strike of the plane, dip and co-seismic slip), we modelled a single square fault, size of 15 km × 15 km, assumed to accommodate the whole rupture of both events of the seismic sequence. A vertical E–W trending fault (strike = 266°) has been modeled, with a horizontal slip of 120 mm. Sensitivity tests have been performed to infer the slip distribution at depth. The comparison between GPS observations and displacement vectors predicted by the dislocation model is consistent with a source fault placed between 5 and 20 km of depth with a constant pure right-lateral strike-slip in agreement with fault slip distribution analyses using seismological information. The GPS strain field obtained doesn't require a geodetic moment release larger than the one inferred from the seismological information ruling out significant post-seismic deformation or geodetic deformation released at frequencies not detectable by seismic instruments. The Molise sequence has a critical seismotectonic significance because it occurred in an area where no historical seismicity or seismogenic faults are reported. The focal location of the sequence and the strike-slip kinematics of main shocks allow to distinguish it from the shallower and extensional seismicity of the southern Apennines being more likely related to the decoupling of the southern Adriatic block from the northern one.  相似文献   

9.
On December 26, 2004 the world's fourth largest earthquake since 1900 and the largest since the 1964 Prince William Sound, Alaska earthquake, occurred off the west coast of northern Sumatra with a magnitude of 9.3. On March 28, 2005 another event of magnitude 8.7 took place in the same region. The December 26, 2004 earthquake has prompted scientists to investigate possible electromagnetic signatures of this event, using ground magnetic observations. Iyemori et al. [Iyemori, T. et al., 2005. Geomagnetic pulsations caused by the Sumatra earthquake on December 26, 2004. Geophys. Res. Lett., 32, L20807, doi:10.1029/2005GL024083.] have suggested that a 3.6 min long geomagnetic pulsation, observed shortly after this event, was generated by the earthquake. They have speculated that a 30 s magnetic pulsation was also caused by the earthquake. Here for the first time, CHAMP satellite magnetic and electron density data are examined to find out if electromagnetic signatures which are possibly related to these recent megathrust earthquakes are observed in satellite magnetic data. We have shown that some specific features are observed after the two earthquakes, with periods of about 16 and 30 s. Our results favor an external source origin for the 30 s pulsation. Moreover, after more than 1 h, CHAMP magnetic data indicate the existence of a feature characterized by the same parameters (duration, amplitude, and frequency content), which could be associated with each earthquake, respectively. Further investigations are required in order to answer the question of whether these signals can be associated with earthquakes and to assign their possible usefulness with respect to earthquake development.  相似文献   

10.
利用华北地区1999～2007、2013～2017两期GPS水平运动速度场数据,采用块体负位错模型,分别反演了郯庐断裂带中南段不同段的断层闭锁程度和滑动亏损速率分布;结合地表应变结果,综合分析了郯庐断裂带前后两期的变形差异特征,并探讨了其与日本3·11地震间的可能关系。研究结果表明:日本地震后,郯庐断裂带中南段郯城以北的段落闭锁程度有所减弱,中南段东部地区主张应变率增强,处于拉张状态;日本大地震的发生对郯庐断裂带中南段的应变积累起到一定的缓解作用。2013～2017最新一期反演结果显示莒县以北断层闭锁程度仍较高,闭锁深度较深,为右旋挤压亏损,是1668年郯城地震的未破裂段;莒县以南到泗洪附近断层闭锁程度较低,无滑动亏损积累;泗洪以南到嘉山段断层闭锁程度较高,是历史地震的未破裂段,同时该地区小震不活跃,易于应力积累,地震危险性值得关注。  相似文献   

11.
马宗晋  叶洪 《地学前缘》2005,12(1):281-287
2004年12月26日在印度尼西亚苏门答腊岛西侧海域发生的地震是自1964 年阿拉斯加大地震以来最大的地震,震级达到9级或9级以上。它是由印度洋板块向缅甸微板块底下俯冲过程中的逆断层作用造成的。印度洋板块以每年6~7 cm的速率向北北东方向运动,与南亚板块发生斜向聚敛俯冲,此运动在该地区解耦为印度洋板块沿巽他海沟的正向俯冲及缅甸微板块东侧的右旋走向平移运动。主震破裂模型研究的结果表明,破裂是由南向北传播的,地震破裂带长达1 200余km,宽度约100 km,最大位移约为20 m,地震断层向上穿透海沟底面,估计约有10 m左右的错距。这次大地震的同震效应导致地球自转轴摆动、地球自转加速,日长缩短。据目前统计,地震引发的大海啸造成305 276人死亡,被此次海啸夺走生命的人数超过了有史以来历次大海啸灾难中死亡人数的总和。  相似文献   

12.
To investigate the relation between the rock friction and the fractal electromagnetic radiation before the main-shock of earthquakes, we conducted a friction experiment simulating the motion of an asperity on a fault plane, and observed photon emissions due to electric discharge by dielectric breakdown of ambient gases from friction contacts between rock minerals. This indicates that frictional discharges (plasma generations) could occur locally at microscopic asperities on fault surfaces. From concepts on the fractal size-distribution and temporal evolution of fault asperities, the frictional discharge occurring at asperities on the fault plane can be one of origins of the fractal electromagnetic radiation (Benioff electromagnetic radiation) prior to earthquakes.  相似文献   

13.
Teleseismic and strong-motion data are inverted to determine the rupture process during the November 1999 Düzce earthquake in NW Turkey. The fault geometry, rise time and rupture velocity are determined from the aftershock distribution and preliminary inversions of the teleseismic data. Joint inversion of the teleseismic and strong-motion data is then carried out for the slip distribution. We obtain the strike 264°, dip 64°, rake −172°, seismic moment 5.0×1019 N m (Mw 7.1), and average stress drop 7 MPa. This earthquake was characterized by bilateral fault rupture and asymmetric slip distribution. Two asperities (areas of large slip) are identified, the eastern one being 1.5 times larger than the western one. The derived slip distribution is consistent with the aftershock distribution, surface rupture and damage. The point of rupture initiation in this Düzce earthquake coincided with the eastern tip of the aftershock distribution of the August 1999 Izmit earthquake.  相似文献   

14.
Surface sediments from the Outer Continental Shelf of Alaska were analyzed for hydrocarbons as part of an environmental survey sponsored by NOAA/BLM. Sediments were collected from the proposed oil lease areas of Beaufort Sea, southeastern Bering Sea, Norton Sound, Navarin Basin, Gulf of Alaska, Kodiak Shelf and lower Cook Inlet. Data on normal and branched alkanes and di- and triterpenoids from capillary gas chromatography (GC) and gas chromatography-mass spectrometry (GC/ MS) indicate that the area displays little evidence of petroleum hydrocarbons (i.e., seeps) except at a few isolated stations. Beaufort Sea sediments have the highest hydrocarbon budget, whereas Kodiak Shelf sediments have the lowest. The molecular markers of the hydrocarbons are of a mixed marine autochthonous and terrestrial allochthonous origin. Norton Sound and Cook Inlet sediments contain the highest levels of terrigenous lipids and Kodiak Shelf the lowest. The abundance of alkenes implies that relatively low oxidizing conditions exist in some of the depositional areas studied, suggesting that extraneous petroleum hydrocarbons introduced into these sediments would be expected to have a relatively long residence time. The distribution of polynuclear aromatic hydrocarbons (PAH) is complex and shows a pyrolytic origin. The data on perylene strongly favor the hypothesis that it is “performed” from terrigenous precursors and transported into the marine environment with no apparent in situ generation. Polynuclear aromatic hydrocarbons of diagenetic origin are probably dominant in Gulf of Alaska and Kodiak Shelf sediments.Two stations, north of Kalgin Island, in lower Cook Inlet and one in southeastern Bering Sea show typical weathered petroleum distribution of n-alkanes and triterpenoids. Probable pathways of transport and fate of petroleum hydrocarbons in case of an oil spill are also briefly discussed.  相似文献   

15.
N. Pulido  T. Kubo   《Tectonophysics》2004,390(1-4):177-192
The October 6/2000 Tottori earthquake that occurred in central Japan was an intermediate size strike-slip event that produced a very large number of near field strong motion recordings. The large amount of recorded data provides a unique opportunity for investigating a source asperity model of the Tottori earthquake that, combined with a hybrid strong motion simulation technique, is able to reproduce the observed broadband frequency near-fault ground motion.

We investigated the optimum source asperity parameters of the Tottori earthquake, by applying a Genetic Algorithm (GA) inversion scheme to optimise the fitting between simulated and observed response spectra and Peak Ground Acceleration (PGA) values. We constrained the initial model of our inversion by using the heterogeneous slip distribution obtained from a kinematic inversion of the source of previous studies. We used all the observed near-fault ground motions (−100 m) from the borehole strong motion network of Japan (KiK-Net), which are little affected by surficial geology (site effects).

The calculation of broadband frequency strong ground motion (0.1–10 Hz) is achieved by applying a hybrid technique that combines a deterministic simulation of the wave propagation for the low frequencies and a semi-stochastic modelling approach for the high frequencies. For the simulation of the high frequencies, we introduce a frequency-dependent radiation pattern model that efficiently removes the dependence of the pattern coefficient on the azimuth and take-off angle as the frequency increases. The good agreement between the observed and simulated broadband ground motions shows that our inversion procedure is successful in estimating the optimum asperity parameters of the Tottori earthquake and provides a good test for the strong ground motion simulation technique.

The ratio of background stress drop to average asperity stress drop from our inversion is nearly 50%, in agreement with the theoretical asperity model of Das and Kostrov [Das, S., Kostrov, B.V., 1986. Fracture of a single asperity on a finite fault: a model for weak earthquakes? Earthquake Source Mechanics, AGU, pp. 91–96.], and an empirical ratio of asperities to rupture area [Seismol. Res. Lett. 70 (1999) 59–80.].

The simulated radiation pattern is very complex for epicentral distances within half the fault length, but it approaches the radiation of a double-couple point source for larger distances.

The rupture velocity and rise time have a significant influence on the Peak Ground Velocity (PGV) distribution around the fault. An increase in rupture velocity produces a similar effect on the ground motion as a reduction in rise time.  相似文献   


16.
This paper presents the computation of time series of the 22 July 2007 M 4.9 Kharsali earthquake. It occurred close to the Main Central Thrust (MCT) where seismic gap exists. The main shock and 17 aftershocks were located by closely spaced eleven seismograph stations in a network that involved VSAT based real-time seismic monitoring. The largest aftershock of M 3.5 and other aftershocks occurred within a small volume of 4 × 4 km horizontal extent and between depths of 10 and 14 km. The values of seismic moment (M ∘) determined using P-wave spectra and Brune’s model based on f 2 spectral shape ranges from 1018 to 1023 dyne-cm. The initial aftershocks occurred at greater depth compared to the later aftershocks. The time series of ground motion have been computed for recording sites using geometric ray theory and Green’s function approach. The method for computing time series consists in integrating the far-field contributions of Green’s function for a number of distributed point source. The generated waveforms have been compared with the observed ones. It has been inferred that the Kharsali earthquake occurred due to a northerly dipping low angle thrust fault at a depth of 14 km taking strike N279°E, dip 14° and rake 117°. There are two regions on the fault surface which have larger slip amplitudes (asperities) and the rupture which has been considered as circular in nature initiated from the asperity at a greater depth shifting gradually upwards. The two asperities cover only 10% of the total area of the causative fault plane. However, detailed seismic imaging of these two asperities can be corroborated with structural heterogeneities associated with causative fault to understand how seismogenesis is influenced by strong or weak structural barriers in the region.  相似文献   

17.
Use of tsunami waveforms for earthquake source study   总被引：1，自引：0，他引：1  
Tsunami waveforms recorded on tide gauges, like seismic waves recorded on seismograms, can be used to study earthquake source processes. The tsunami propagation can be accurately evaluated, since bathymetry is much better known than seismic velocity structure in the Earth. Using waveform inversion techniques, we can estimate the spatial distribution of coseismic slip on the fault plane from tsunami waveforms. This method has been applied to several earthquakes around Japan. Two recent earthquakes, the 1968 Tokachi-oki and 1983 Japan Sea earthquakes, are examined for calibration purposes. Both events show nonuniform slip distributions very similar to those obtained from seismic wave analyses. The use of tsunami waveforms is more useful for the study of unusual or old earthquakes. The 1984 Torishima earthquake caused unusually large tsunamis for its earthquake size. Waveform modeling of this event shows that part of the abnormal size of this tsunami is due to the propagation effect along the shallow ridge system. For old earthquakes, many tide gauge records exist with quality comparable to modern records, while there are only a few good quality seismic records. The 1944 Tonankai and 1946 Nankaido earthquakes are examined as examples of old events, and slip distributions are obtained. Such estimates are possible only using tsunami records. Since tide-gauge records are available as far back as the 1850s, use of them will provide unique and important information on long-term global seismicity.  相似文献   

18.
The kinematic rupture process of the 2011 Tohoku-Oki earthquake (Mw 9.0) was derived given apparent source time functions (ASTFs) retrieved from Rayleigh waves using a refined homomorphic deconvolution method. The total duration of the rupture process was about 165 s. Three slip-concentrated areas were identified based on images of static slip distribution. The largest asperity, located up-dip from the hypocenter with an area of 250 km × 110 km extending to the trench on the fault, had a maximum slip of about 54 m. The other asperities with smaller slip down-dip from the hypocenter were centered on the north and south of the hypocenter, respectively. The preferred average rupture expansion velocity was 1.2 km/s within 130 km from the hypocenter and up to 2.3 km/s over other areas on the fault. Thus, the region near the vicinity of the hypocenter with lower rupture velocity had higher slip amplitude, strongly suggesting brittle failure on a high friction fault. Based on ASTF results, our proposed method offers another way of directly detecting the kinematic source parameters of earthquakes.  相似文献   

19.
The epicentral tract of the great Assam earthquake of 1897 of magnitude 8·7 was monitored for about 6 months using an array of portable seismographs. The observed seismicity pattern shows several diversely-oriented linear trends, some of which either encompass or parallel known geological faults. A vast majority of the recorded micro-earthquakes had estimated focal depths between 8–14 km. The maximum estimated depth was 45 km. On the basis of a seismic velocity model for the region reported recently and these depth estimates we suggest that the rupture zone of the great 1897 earthquake had a depth of 11–12 km under the western half of the Shillong massif. Four composite fault plane solutions define the nature of dislocation in three of the seismic zones. Three of them show oblique thrusting while one shows pure dip slip reverse faulting. The fault plane solutions fit into a regional pattern of a belt of earthquakes extending in NW-SE direction across the north eastern corner of the Bengal basin. The maximum principle stress axis is approximately NS for all the solutions in conformity with the inferred direction of the Indian-EuroAsian plate convergence in the eastern Himalaya.  相似文献   

20.
郯庐断裂带是中国东部板内一条规模最大的强构造变形带与地震活动断裂带,其断裂结构与历史地震活动性具明显的分段活动性。文中通过沿郯庐断裂带中南段的历史地震活动性、精定位背景地震活动性与震源机制解分析,讨论了断裂带的深部几何结构与现今活动习性。现今地震活动在中段主要沿1668年郯城MS 8地震破裂带线性分布,线性条带在泗洪-诸城间延伸约340 km长,为1668年地震长期缓慢衰减的余震序列活动。大震地表破裂遗迹与精定位地震分布都揭示出郯庐断裂带中段的两条全新世活动断裂昌邑-大店断裂与安丘-莒县断裂以右阶斜列的形式共同参与了1668年郯城MS 8地震破裂。精定位震源剖面刻画出两条断裂结构面呈高角度相背而倾,其中昌邑-大店断裂倾向SE,安丘-莒县断裂倾向NW,两条断裂在深部没有合并汇聚。余震活动所代表的1668年地震震源破裂带是郯庐断裂带中现今尚未闭锁的安全段落,对应于高b值段。而未发生破裂的安丘以北段,小震活动不活跃,b值低,现今可能已成为应力积累的闭锁段。震源机制解揭示的断裂应力状态在中段以NE向主压应力为主,表现为右旋走滑活动性质,且存在少量正断分量,南段转为以NEE至近EW向为主,存在少量的逆冲分量。在中段与南段的转折处宿迁-嘉山段,主压应力方向垂直断裂带走向呈NWW向,反映出局部以挤压为主的应力特征,其中泗洪-嘉山段也是历史地震未破裂段,现今小震活动不活跃,因此该段可能更易于应力积累。精定位小震活动在郯庐断裂与北西向断裂相交汇处聚集,反映出北西向断裂的新活动性,以及郯庐断裂带现今的逆冲作用。在断裂带南端,精定位背景地震活动沿与其相交汇的襄樊-广济断裂带东段呈北西向线性分布,表明了该段的现今活动性。  相似文献   

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