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1.
We investigate the late Quaternary active deformation along the Jordan Valley segment of the left-lateral Dead Sea Fault and provide new insights on the behaviour of major continental faults. The 110-km-long fault segment shows systematic offsets of drainage systems surveyed at three sites along its southern section. The isotopic dating of six paleoclimatic events yields a precise chronology for the onset of six generations of gully incisions at 47.5 ka BP, 37.5 ka BP, 13 ka BP, 9 ka BP, 7 ka BP, and 5 ka BP. Additionally, detailed mapping and reconstructions provide cumulative displacements for 20 dated incisions along the fault trace. The individual amounts of cumulative slip consistently fall into six distinct classes. This yields: i) an average constant slip rate of 4.7 to 5.1 mm/yr for the last 47.5 kyr and ii) a variable slip rate ranging from 3.5 mm/yr to 11 mm/yr over 2-kyr- to 24-kyr-long intervals. Taking into account that the last large earthquake occurred in AD 1033, we infer 3.5 to 5 m of present-day slip deficit which corresponds to a Mw  7.4 earthquake along the Jordan Valley fault segment. The timing of cumulative offsets reveals slip rate variations critical to our understanding of the slip deficit and seismic cycle along major continental faults.  相似文献   

2.
The archaeological site of Qasr Tilah, in the Wadi Araba, Jordan is located on the northern Wadi Araba fault segment of the Dead Sea Transform. The site contains a Roman-period fort, a late Byzantine–Early Umayyad birkeh (water reservoir) and aqueduct, and agricultural fields. The birkeh and aqueduct are left-laterally offset by coseismic slip across the northern Wadi Araba fault. Using paleoseismic and archaeological evidence collected from a trench excavated across the fault zone, we identified evidence for four ground-rupturing earthquakes. Radiocarbon dating from key stratigraphic horizons and relative dating using potsherds constrains the dates of the four earthquakes from the sixth to the nineteenth centuries. Individual earthquakes were dated to the seventh, ninth and eleventh centuries. The fault strand that slipped during the most recent event (MRE) extends to just below the modern ground surface and juxtaposes alluvial-fan sediments that lack in datable material with the modern ground surface, thus preventing us from dating the MRE except to constrain the event to post-eleventh century. These data suggest that the historical earthquakes of 634 or 659/660, 873, 1068, and 1546 probably ruptured this fault segment.  相似文献   

3.
如何准确测定断裂滑动速率是近年来活动构造研究的前沿与热点.随着高精度地形数据获取手段与第四纪测年方法的不断进步,位错量和地貌面年龄的精度均得到大大提高.在进行滑动速率计算时还要考虑地质过程是否合理,蒙特卡洛方法为获取更加符合地质过程的滑动速率提供了重要工具.本文以滑动速率研究程度较低的海原断裂带老虎山段为例,基于LiDAR高精度地形数据,测得T1—T4阶地面年龄分别为1~3 ka,9~11 ka,15~17 ka,40~45 ka,陡坎前缘的位错分别为7~14 m,28~36 m,59~66 m,180~190 m.综合多地点的左旋走滑位错量及不同时代的地貌面年龄数据,并考虑滑动历史,利用蒙特卡洛模拟方法,将位错-时间两个参数的不确定性定量化,限定老虎山断裂45 ka以来平均滑动速率为4.3±0.16 mm·a-1,17ka以来的平均滑动速率为4.0±0.15 mm·a-1,与前人研究得到的狭义海原断裂滑动速率4.5±1.0 mm·a-1基本一致.综合整个海原断裂带滑动速率,本文结果更支持低滑动速率变化趋势,即海原断裂带整体滑动速率趋于稳定,向东至六盘山断裂,滑动速率开始降低,推测海原断裂带的左旋走滑在尾端主要为马东山—六盘山隆起所吸收.结合老虎山断裂历史地震资料和深部锁闭浅部蠕滑的动力学特征,推测老虎山断裂具备与相邻断裂一起触发强震的能力.  相似文献   

4.
The Tian Shan Mountains is an active orogen in the continent. Previous studies on its tectonic deformation focus on the expanding fronts to basins on either side, while little work has been done on its interiors. This work studied the north-edge fault of the Yanqi Basin on the southeastern flank of Tian Shan. Typical offset landforms, and lineaments of scarps on the eastern segment of this fault were used to constrain the vertical displacement and shortening rates. Geological and geomorphic mapping in conjunction with high-resolution GPS differential measurement reveals that the vertical offsets can be divided into three groups of 1.9m, 2.4m and 3.0m, and the coseismic vertical offset was estimated as 0.5~0.6m. In situ 10Be terrestrial cosmogenic nuclide dating of three big boulders capping the regional geomorphic surface that preserved 3.0m vertical offset suggests that the surfaces were exposed at~5ka. Meanwhile, the lacustrine sediments from Bosten Lake within the Yanqi Basin suggest climate change during cooling-warming transitions was also at~5ka. The climate, therefore, controlled creation and abandonment of geomorphic surfaces in southern piedmont of Tian Shan. Combining the exposure ages and vertical offsets, we inferred that the east section of the north-edge fault in the Yanqi Basin has a dip slip rate 0.6~0.7mm/a,~0.5mm/a of vertical slip and~0.4mm/a of shortening since 5ka. Based on calculation of earthquake moment, we estimated that this fault is capable of generating M7.5 earthquakes in the future. This study provides new data for further understanding tectonic deformation of Tian Shan and is useful in seismic hazard assessment of this area.  相似文献   

5.
In the interior of the Tibetan Plateau, the active tectonics are primarily marked by conjugate strike slip faults and north-trending rifts, which represent the E-W extension since late Cenozoic of the plateau. The conjugate faults are mainly composed of NE-trending left-lateral strike-slip faults in Qiangtang terrane and NW-trending right-lateral strike-slip faults in Lhasa terrane. While, the rifts mainly strike N, NNW and NNE within southern Tibet. However, it is still a debate on the deformational style and specific adjustment mechanism of E-W extension. One of key reasons causing this debate is the lack of detailed investigation of these active faults, especially within the northwestern plateau. Recently, we found a 20km long, NNW-trending active fault at Bero Zeco in northwestern Tibet. This fault is presented as fault sag ponds, channel offsets and fault scarps. Displacement of channels and geomorphic features suggested that the Bero Zeco Fault(BZF)is a dextral strike-slip fault with a small amount of normal slip component, which may result from the E-W extensional deformation in the interior of Tibet. BZF strikes N330°~340°W, as shown on the satellite image. The main Quaternary strata in the studied area are two stages alluvial fans around the Bero Zeco. From the satellite images, the old alluvial fans were cut by the lake shoreline leaving many of lake terraces. And the young fans cut across the lake terraces and the old fans. By contrasting to the "Paleo-Qiangtang Huge Lake" since late Quaternary, these old alluvial fans could be late Pleistocene with age ranging from 40ka to 50ka. And the young fans could be Holocene. The sag ponds along the BZF are distributed in the late Pleistocene alluvial fans. Also, the BZF displaced the late Pleistocene fans without traces within Holocene fans, suggesting that the BZF is a late Pleistocene active fault. The fault scarps are gentler with the slope angle of around 10° and the vertical offset is about 2m by field measurement. Reconstruction of the offset of channels suggested that the accumulated dextral offset could be about 44m on the late Pleistocene alluvial fans. Therefore, we infer that the dextral slip-rate could be around 1mm/a showing a low-rate deformation characteristic. The angle between the strike of BZF and principal compressive stress axis(σ1)is around 30°, which is significantly different to the other faults within the conjugate strike-slip fault zones that is 60°~75°. Now, the deformation mechanisms on these conjugate faults are mainly proposed in the studies of obtuse angle between the faults and σ1, which is likely not applicable for the BZF. We infer that the BZF could be the northward prolongation of the north-trending rifts based on the geometry. This difference suggests that the conjugate strike-slip faults may be formed by two different groups:one is obtuse angle, which is related to block extrusion or shear zones in Lhasa and Qiangtang terranes possibly; the other is acute angle, which may represent the characteristics of new-born fractures. And more studies are needed on their deformation mechanisms.  相似文献   

6.
The question of whether millennial‐scale geological slip rates are consistent with decade‐scale geodetic slip rates is of great importance in evaluating the nature of continental deformation within the Tibetan Plateau. We determined the time‐averaged slip rate of the Sulu He segment of the Altyn Tagh Fault, near Changma in Gansu Province, China, based on geomorphic analysis, remote sensing data, and cosmogenic 10Be surface‐exposure age dating. Quaternary alluvial fan deposits in the study area (Qf1, Qf2, Qf3) are displaced by left‐lateral movement along the Altyn Tagh Fault. Because of the large accumulated displacement of these fans, some of them have become disconnected from the fan apexes that are directly linked to the debris‐source areas in the piedmont of the Qilian Shan to the south. The total minimum offsets are estimated to be about 429 ± 41 m for Qf1, about 130 ± 10 m for Qf2, and 32 ± 1 m for Qf3. The 10Be surface‐exposure ages obtained for Qf1 and Qf2 are 100–112 ka and 31–43 ka, respectively. Accordingly, the slip rate since the period of Qf1 and Qf2 depositions is calculated to have been about 3.7 mm/yr.  相似文献   

7.
In this paper, we present optically and infrared stimulated luminescence (OSL and IRSL) ages for four samples from alluvial fan surfaces in the Astaneh Valley. This valley is located in the north-east part of the Alborz range in Iran. Our morphologic interpretations recognize at least three generations of fans in the study area, all of which have been displaced along the left-lateral strike-slip Astaneh fault. Because of the dry, loose, and sometimes complex juxtaposition of the target sediments, we collected the samples in total darkness beneath dark plastic layers placed atop the pit openings. Luminescence ages of the fans are ～55 ka, ～32 ka and ～16 ka. These ages are concurrent with periods of loess deposition and wet climatic conditions previously recorded in the Arabia-Iranian region. They allow estimation of a horizontal slip rate of ～2 mm/yr along the Astaneh fault, which is consistent with additional slip rates determined for the Holocene period along faults further west of the Astaneh fault.  相似文献   

8.
Although the precise boundaries and kinematics of the Sinai subplate are still doubtful, it has a significant role in the tectonic evolution of the northern Red Sea region. On the basis of earthquake distribution, the Sinai region can be considered as a subplate partially separated from the African plate by the Suez rift. The relative motion between Africa, Sinai and Arabia is the main source generating the present-day earthquake activity in the Gulf of Suez and the Gulf of Aqaba regions.According to geological observations, the southern segment of the Dead Sea fault system can be characterized by a left-lateral displacement of about 107km since the Middle Miocene, in contrast to the northern segment where only 25 to 35km offset can be inferred. We think that along the southern segment the total displacement was 72km until the late Miocene (10Ma). The earthquake activity is strongly reduced along the northern segment of the Dead Sea fault segment. Therefore, we suggest that the northern part (Yammouneh fault) evolves through initial cracking of the crust due to build-up of stress since the Pliocene time (5Ma) and propagates northward into Lebanon and Syria. This last 5 million years is the period when the southern and northern segments became linked and formed a single fault system with a new displacement of 35km.According to the proposed model the predicted opening pole of the Red Sea is near 34.0oN, 22.0oE with an angle of total rotation of 3.4o since the early miocene, providing a 0.82cm/a opening rate in the northern Red Sea. We suggest that the Dead Sea strike-slip fault was active since Middle Miocene time (15Ma) with a slip rate of 0.72cm/a to provide a total displacement of about 107km. This strike slip motion occured about an Euler pole near 33.0oN, 21.0oE with a rotation angle of about 3.0o. It can be inferred from the proximity of the pole and angle of rotations for the Red Sea and Dead Sea fault that more than 85% of the motion has been accommodated on the Gulf of Aqaba and the Dead Sea fault and less than 15% in the Gulf of Suez.This model predicts a normal extensional motion in the Gulf of Suez with a minor left-lateral strike-slip component. We expect the pole of this motion to be at 31.0oN, 29.0oE, offshore of Alamein city about 320 km west of the Nile Delta. The rate of motion through the last 15Ma (Middle Miocene) is about 0.1 cm/a and the angle of rotation is 0.9o. During this period the total opening of the Suez rift is 15 km while the rest of the motion (45 km) occured mainly through the first phase of the development before the Middle Miocene.  相似文献   

9.
由于南华山北麓断裂带的新活动,使得南华山北麓菜园—乱堆子16公里范围内的21条冲沟发生明显断错,显示出左旋位移指向。本文研究了这些断错冲沟的地质地貌表征、断错冲沟的发育过程和断错量,并根据晚更新世以来沉积物的~(14)C年龄和区域冲沟的溯源侵蚀速率,计算出晚更新世以来南华山北麓断裂带的平均滑动速率为4.3毫米/年;同时,量测出1920年海原8.5级地震震中区地震断层的最位移量为6.9米。根据以上资料,估算出南华山北麓断裂带8.5级强震的重复率约为1600年  相似文献   

10.
The Pollino Range area represents the mostprominent gap in seismicity within thesouthern Apennines. Geomorphic andtrenching investigations along theCastrovillari fault indicate that thisnormal fault is a major seismogenic faultwithin the southern part of this gap. Atleast four surface-faulting earthquakeshave occurred on this fault since latePleistocene age. Radiocarbon dating coupledwith historical consideration set thetime of the most recent earthquake as mostlikely to be between 530 A.D. and 900 A.D.,with the possible widest interval of530–1100 A.D. No evidence for this eventhas been found in the historical records,although its age interval falls within thetime spanned by the seismic catalogues.Slip per event ranges between 0.5 and1.6 m, with a minimum rupture length of13 km. These values suggest a M 6.5–7.0 forthe paleoearthquakes. The minimum long-termvertical slip rate obtained from displacedgeomorphic features is of 0.2–0.5 mm/yr. Avertical slip-rate of about 1 mm/yr is alsoinferred from trenching data. Theinter-event interval obtained from trenchdata ranges between 940 and 7760 years(with the young part of the intervalpossibly more representative; roughly940–3000 years). The time elapsed since themost recent earthquake ranges between aminimum of 900–1100 and a maximum of 1470years. The seismic behavior of this faultappears to be consistent with that of othermajor seismogenic faults of thecentral-southern Apennines. The Pollinocase highlights the fact thatgeological investigations represent apotentially useful technique tocharacterize the seismic hazard of `silent' areas for which adequate historical andseismological data record are notavailable.  相似文献   

11.
The 150-km-long Itoigawa-Shizuoka tectonic line active fault system (ISTL)in central Japan is one of the most active Quaternary fault systems inJapan. Estimated slip-rates on the fault system are as large as 10 m/ka, butthe historic seismicity has been low since 841 A.D. with no largeearthquakes recorded. The high slip rates contrast with the long time sincethe last major earthquake on the ITSL and indicates the high potential of a largeearthquake from the ISTL. Based on slip-rate estimates, more than 10 mof potential slip may have accumulated on the fault system since the 841A.D. earthquake. Recent paleoseismolgical studies on the middle andnorthern parts of the ISTL have determined that the average recurrenceinterval of surface-faulting earthquakes on the middle ISTL is 680 to 825years (Gofukuji fault) and 1258 to 1510 years in the northern ISTL. These data suggest the most recent event on both northern and middleISTL occurred in 841 A.D. The results highlight the high seismic potentialof the ISTL. Additional studies of the entire ISTL are needed to define theextent of the next rupture.  相似文献   

12.
Clastic dikes are formed either by passive deposition of clastic material into pre-existing fissures (depositional dikes), or by fracturing and injection of clastics during earthquakes (injection dikes). We proposed to use optically stimulated luminescence (OSL) dating to distinguish between the two modes of formation and hypothesized that (1) depositional dikes filled from above show OSL ages younger than the host rock; and (2) injection dikes filled from below show the same OSL ages as that of the host rock. We studied the mechanisms of clastic-dike formation and their ages within the seismically active Dead Sea basin, where hundreds of dikes crosscut the late Pleistocene (70–15 ka) lacustrine sediments of the Lisan Formation. Field observations and analysis of magnetic tensors show unequivocally that most of these dikes were emplaced by injection, inferred to be due to seismically triggered fluidization–liquefaction during earthquakes. Twenty-eight samples were collected from the Lisan source material and dikes that, based on field observations, are unmistakably either depositional dikes or injection dikes.

Quartz single aliquot OSL ages of the source Lisan layers are between 43 and 34 ka, and are typical for the Lisan Formation. The ages of both depositional and injection dikes are between 15 and 17 ka, younger than the Lisan host rock. Depositional dikes show a highly scattered distribution of single grain ages, suggesting several episodes of infill. Single grain ages of injection dikes are of latest Pleistocene to Holocene, and do not contain recently bleached grains that infiltrated from above. These results imply that the OSL signals were reset at the time of fluidization–liquefaction and buildup of fluid pressure within the injection dikes. If this resetting mechanism has a physical ground, then OSL dating is an important tool for constraining the ages of earthquake-induced injection dikes and recovering paleoseismic data from them.  相似文献   


13.
On 15 July 1995, the Egion earthquake (Ms = 6.2) occurred in the vicinity of Egion, west-central Greece. Macroseismic observations along the 12 km long E-W trending Egion fault represent short-term or earthquake-related deformation characterized by fairly straight E-W trending surface ruptures with small displacements that mimic the Egion fault geologic offsets and segmentation. Hanging wall converging slip vectors along the Egion fault are clearly related to fault motions at depth. Furthermore, peak accelerations of the built-up area of Egion amount to 0.54 g, that is double the estimated peak acceleration of the Egion coastal area, showing thus close relation between fault trace and attenuation of the ground motion.The Egion fault, with a total geological throw of 200 m and dips to the north at about 55 °, accommodating active tectonic deformation of the Egion area. Its morphotectonic expression reflects long-term deformation in competition with the 1995 earthquake related deformation. The Egion fault is controlling the geomorphic evolution of the Egion area as follows: 1) The fault is defining the evolution of fan-deltas (offshore) and the Meganitas river alluvial plain (onshore). 2) The hanging-wall's greatest subsidence is observed, at the Egion bay, at the central portion of the fault. The Egion bay is located at the central part of the fault showing a strong relationship between the long term slip-rate ratio and the recent coastal morphology. The subsidence gradient or the tectonic activity along the fault is defined by the valley-floor width to valley height index (Vf) of small rivers draining the fault scarp. The Meganitas river course is tilted, when crosses the Egion fault trace, towards the area with the highest subsidence along the fault. 3) Stream incision is more important than slope recession at areas close to the fault trace.All these observations suggest that the Egion fault, which probably hosted the last earthquake, are geomorphically controlling the evolution of a 15 km-long by 5 km-wide zone, fairly similar in dimensions to the surface length of the fault.  相似文献   

14.
Paleoseismology, the study of past earthquakes based on their geological record in the stratigraphy and landscape, is a successful newly developing field of research. The application of fault trench studies in volcanic environments is one of the youngest branches of paleoseismology. In this paper, we present the results of the first exploratory trenches excavated at Mt. Etna in Sicily, the largest European volcano. Modern surface faulting at Etna is a very well known feature, which poses significant hazard to the local community, both in terms of ground displacement of essential lifelines and ground shacking from frequent damaging earthquakes. However, while the geomorphology and the seismicity of the active fault in the Etna region consistently show very high rates of tectonic activity, the Holocene cumulative throw and slip-rates, along with the nature (coseismic vs. creeping fault slip), dimension and timing of the displacement events, are still poorly constrained. For this purpose, we selected as a sample area the Moscarello fault, one of the most outstanding segment of the Timpe system of active normal faults in the volcano’s lower eastern flank. Displaced landforms and volcanic units at the Fondo Macchia basin, in the central sector of this fault, indicate some hundreds of meters of vertical offset in the last ca. 80 kyr, with a long-term slip-rate substantially higher than 1.5–2.0 mm/yr. According to the historical sources and instrumental observations, the Moscarello fault ruptured four times in the last 150 years during shallow (H < 5 km) and moderate magnitude (M < 4.8) earthquakes. These events were associated with severe damage in a narrow epicentral area (macroseismic intensities up to the IX–X grade of the MSK scale) and extensive surface faulting (end-to-end rupture length up to 6 km, vertical offsets up to 90 cm). This clearly indicates very high modern rates of deformation along this fault. We conducted trench investigations at the Fondo Macchia site, in a point where eyewitnesses observed ca. 20 cm of coseismic vertical displacement after the April 21, 1971, Ms=3.7, earthquake. The excavated sections provided direct stratigraphic evidence for a vertical slip-rate of 1.4–2.7 mm/yr in the last ca. 6 kyr. This should be regarded as a minimum slip-rate for the central section of the fault. We explored a single scarp at a single site, while we know from recent historical observations that several parallel scarps may rupture coseismically at Fondo Macchia. Thus, the relevant deformation rate documented for the modern period might be likely extended back in the past to a time-span of some thousands of years at least. As expected, for such a volcanic environment, the activity rates of the Moscarello fault are also significantly higher than for the Apennines normal faults, typically showing slip-rates lower than 1 mm/yr. The agriculturally reworked trench hangingwall stratigraphy did not allow to recognize individual displacement events. Nevertheless, the sedimentary structures observed in the trench footwall strongly suggest that, as for the last 150–200 years of detailed historical record, fault behavior at Fondo Macchia is governed by coseismic surface displacement rather than fault creep. This research confirms that paleoseismology techniques can be effectively applied also in active volcanic environments, typically characterized by rheology and, consequently, seismicity and fault dynamics very different from those of other tectonic environments in which paleoseismology has been firstly developed and is today extensively applied.  相似文献   

15.
The moment tensor solution, source time function and spatial-temporal rupture process of the MS6.4 earthquake, which occurred in Ning’er, Yunnan Province, are obtained by inverting the broadband waveform data of 20 global stations. The inverted result shows that the scalar seismic moment is 5.51×1018 Nm, which corresponds to a moment magnitude of MW 6.4. The correspondent best double couple solution results in two nodal planes of strike 152°/dip 54°/rake 166°, and strike 250°/dip 79°/ rake 37°, respectively...  相似文献   

16.
2008年5.12汶川大地震发生在中国大陆南北地震带中段.由于龙门山断裂带历史上只发生过3次6～61/2级强震,而且其晚第四纪构造活动速率很低,以至于对其潜在地震危险性认识不足.为什么在龙门山地区突发大地震,该地震具有哪些特征？其成因机制是什么？本文在地震地质科学考察的基础上,利用震前的GPS观测结果,试图对上述问题进行一些初步的思考和探讨.结果表明,5.12汶川大地震是龙门山断裂带的映秀—北川断裂突发错动的结果,地表上形成200多公里长的地表破裂带;灌县—江油断裂在地震中也发生了破裂,形成的地表破裂带长达60多公里.震前的GPS观测表明,横跨整个龙门山断裂带的滑动速率不超过～2 mm/yr,单条断裂的活动速率不超过～1 mm/yr,与地震地质研究结果和历史地震记录相一致.利用地震地质考察和地震波反演得到的最大同震位移可以获得相当于5.12汶川大地震的强震复发周期为2000～6000年.龙门山断裂带发育在破裂强度很大的变质杂岩体中,断裂带本身在剖面上呈“犁形”或“铲形”结构,有利于能量积累,形成破坏性巨大的地震.所以,5.12汶川大地震是一次低滑动速率、长复发周期和高破坏强度的巨大地震,是一种值得高度重视和深入研究的新的地震类型.  相似文献   

17.
The Litang fault zone (LFZ) is an important active fault within the northwestern Sichuan sub-block. To-gether with the Garzê-Yushu, Xianshuihe, and An-ninghe fault zones on its northern, eastern and south-eastern sides, the LFZ constitutes the lateral extrusion tectonic system in the southeastern part of the Qing-hai-Tibetan Plateau[1,2] (Fig. 1). According to instru-mental records, historical recordings and field investi- gation, an earthquake (Ms7.3) occurred on its middle to south se…  相似文献   

18.
王华林  侯珍清 《地震研究》1994,17(1):79-107
昌马断裂带是是青藏高原北部一条活动强烈的左旋走滑断裂带。它表现为重力、航磁、地壳厚度的综合异常梯度带，属于断面陡、切割深的超岩石圈断裂。昌马断裂带由１２条长４公里至１８公里不等的不连续的主断层和４条次级断层组成，可划分为东、中、西三大段落。断裂的水平位移和滑动速率具有分段性，全新世以来，东、中、西三段的左旋水平滑动速率分别为４．１毫米／年，２．６毫米／年和１．５毫米／年。北东东、北北西和北西西三个方向断层的位移具有分级特征，不同级别的位移具有良好的同步性。全新世以来北东东、北北西和北西西三个方向断层的水平滑动速率分别为４．１毫米／年、３．８毫米／年和２．７毫米／年。白垩纪以来，昌马断裂呈天平式运动，显示了枢纽断裂运动特征，枢纽轴位于断裂中段。昌马地震震源破裂性质及其反映的震源应力场与地震破裂带的破裂性质及其反映的构造应力场不一致。昌马地震震源机制解反映了北北西～南南东挤压，作用应力近于水平的震源应力场；昌马地震破裂带的变形组合反映了东北～南西挤压的构造应力场。昌马地震破裂带长１２０公里，分为东部正走滑段、中部逆走滑段和西部尾端破裂段，显示了多个水平位移峰值。全新世以来，沿昌马断裂发生了６次强震事件，强震复发  相似文献   

19.
小江西支断裂的滑动速率与强震重复周期   总被引：7，自引：3，他引：7       下载免费PDF全文
本文通过对各种断错地质地貌现象及被错体年龄的分析,估算出小江西支断裂在第四纪、晚更新世及全新世以来的滑动速率分别为6.7毫米/年、7.0毫米/年及6.4毫水/年。在此基础上,结合历史地震及古地震活动讨论了强震的重复周期和断裂的活动特征,结果表明小江西支断裂的活动以重复错动发生强烈地震为主要特征,强震在断裂带上同一地段的平均重复周期为900年左右,沿整个断裂带的重复周期大于330年  相似文献   

20.
2010年9月4日新西兰南岛Canterbury平原发生了Mw7.1地震,震源深度约为10 km.本次地震发生在一条震前不为人所知的断层上.我们利用覆盖整个震区的合成孔径雷达(SAR)观测资料,通过干涉处理分析获得雷达视线向(LOS)同震形变场;以此资料为约束反演了断层的几何参数以及同震破裂分布.结果显示,该地震造成四条相对独立断层的破裂.大部分的地震矩释放发生在Greendale断层(编号1-4),其错动以右旋走滑为主,最大破裂约为8.5 m.其它三条断层中,经过震源的逆冲断层最大破裂为5.1 m (编号6),位于Greendale断层以西的逆冲断层最大破裂为3.5 m (编号5),位于Greendale断层北面的走滑断层最大破裂为1.9 m(编号7).反演的Greendale断层地表滑动与地质调查得到的地表破裂在形态和数值上均吻合较好.本次地震释放的地震矩为5.0×1019N·m,矩震级为7.1.板块边界带形变场分析表明,Darfield地震的发生受边界带应变分配在该地区残留构造应力场控制,其复杂性体现了区域构造应力场的特点.地震对其周围地区的应力场影响较大,库仑应力增加区与余震分布有一定对应关系,并在2011年Christchurch 6.3级地震发震断层区域造成约0.1bar的库仑应力增加,对此地震有一定的触发作用.  相似文献   

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