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1.
四川省大邑地区地处龙门山南段,是有名的地震多发地区。文章基于现代构造地质学理论,通过地震解释及构造几何分析、断层相关褶皱原理与几何分析方法、运动学正演模拟方法,开展了对大邑地区断裂带活动多期性研究,结果表明大邑地区断裂带活动具有多期性的特点。自印支期以来主要经历了两期三次构造活动:印支晚期的低角度逆冲推覆过程,须家河组四段(T3x4)中上部形成生长地层;喜马拉雅期Ⅰ幕,隐伏断层再次活动,造成侏罗系与下伏三叠系的变形差异;喜马拉雅期Ⅱ幕,龙门山构造带区域应力场向前传递,大邑地区形成高角度逆冲断层,断层沿深部滑脱层在大邑地区向上逆冲直至地表,早期隐伏断层被错断,伴随次级断层、反冲断层产生。  相似文献   

2.
Graphite in fault zones has received little attention even though it is a well-known solid lubricant that could affect frictional properties of faults dramatically. This paper reports the presence of abundant graphite in fault zones of the Atotsugawa fault system, central Japan. Mesoscopic and microscopic observations of fault rocks revealed two processes of carbon enrichment in fault zones. One is a pressure solution process or diffusive mass transfer in general which removes water-soluble minerals such as quartz and carbonates from rocks, resulting in the enrichment of insoluble minerals including carbon. The other process is precipitation of graphite from a high-temperature carbon-rich fluid, forming graphite filling fractures within cataclasitic fault zones. The two processes have led to the concentration, up to 12 wt% of graphite, in the Atotsugawa fault zones, compared to 0 to 3 wt% of carbonaceous materials in the host rocks. This concentration is high enough for graphite to affect frictional properties at wide range of slip rates. The presence of graphite may provide an explanation for the low resistivity, the patterns of microearthquakes and fault creep along the western part of the Atotsugawa fault system. Graphite should receive more attention as a weakening and stabilizing agent of faults.  相似文献   

3.
The historical seismicity of the last ten centuries and the instrumental data that occurred in the Gulf of Aqaba region during the period 1982–2008 are evaluated. It is found that 12 historical earthquakes have occurred with average recurrence periods 70–90 and 333–500 years for M?≥?6.0 and 7.0, respectively. Those with M?≤?6.5 appear to be incomplete and require further investigation. More than 98 % of the instrumental data has occurred in the form of swarms and sequences. The first have released about 32 % of the total energy and are most likely related to subsurface volcanic activities. Their epicentral distribution indicates that all regional faults of the gulf area are active in the present, but with clear concentration within the area bound by latitudes 28.2°–29.8° and longitudes 34.4°–35.2°. Regional strike-slip faults of the northern two basins appear to be as twice active as the normal, or more. An appreciable level of seismic hazard is envisaged as the “a” value is 6.0–6.2 while the “b” value shows a temporal variation, mostly in the range 0.8–1.05. More than 95 % of the seismic energy was released from earthquakes shallower than 22 km. This indicates a brittle upper crust and a ductile lower crust and upper mantle. Tectonic movements at depths?>?22 km appear to be aseismic. The epicentral distribution of the five swarms indicates that the lengths of the causative faults varied in the range 45–70 km. The maximum expected magnitude is Mw?=?6.8–7.2. This implies a seismic slip rate of about 0.54–0.8 Cm/year and some 20–30 % of aseismic tectonic movements. This and the sequence nature of the seismicity of this region result in a noticeable hazard reduction. Combining the seismicity data of the Gulf of Aqaba region with other geophysical, geological, tectonic, and environmental data, clearly indicate that the seismicity of this region is as old as the initiation of the gulf itself. No apparent southward or northward migration of activity is observed.  相似文献   

4.
The internal structure and permeability of the Neodani fault, which was last activated at the time of the 1891 Nobi earthquake (M8.0), were examined through field survey and experiments. A new exposure of the fault at a road construction site reveals a highly localized feature of the past fault deformation within a narrow fault core zone. The fault of the area consists of three zone units towards the fault core: (a) protolith rocks; (b) 15 to 30 m of fault breccia, and (c) 200 mm green to black fault gouge. Within the fault breccia zone, cataclastic foliation oblique to the fault has developed in a fine-grained 2-m-wide zone adjacent to the fault. Foliation is defined by subparallel alignment of intact lozenge shaped clasts, or by elongated aggregates of fine-grained chert fragments. The mean angle of 20°, between the foliation and the fault plane suggests that the foliated breccia accommodated a shear strain of γ<5 assuming simple shear for the rotation of the cataclastic foliation. Previous trench surveys have revealed that the fault has undergone at least 70 m of fault displacement within the last 20,000 years in this locality. The observed fault geometry suggests that past fault displacements have been localized into the 200-mm-wide gouge zone. Gas permeability analysis of the gouges gives low values of the order of 10−20 m2. Water permeability as low as 10−20 m2 is therefore expected for the fault gouge zone, which is two orders of magnitude lower than the critical permeability suggested for a fault to cause thermal pressurization during a fault slip.  相似文献   

5.
磨西断裂变形与运动学特征研究   总被引:1,自引:0,他引:1       下载免费PDF全文
磨西断裂位于鲜水河活动断裂带的东南侧,北段为松潘-甘孜地槽褶皱系与扬子陆块的分界,南段则伸入扬子地台内部,成为扬子地台西缘拗褶带与康滇地轴的分界,是扬子西缘不同构造单元的控制性断裂构造。通过宏观分析地层分布,磨西断裂北段磨西磨子沟(新近崩塌出露),中段湾东剖面和南段新民腊树岗剖面的构造变形、几何学与运动学特征,收集整理擦痕资料,再结合糜棱岩微观石英C轴组构特征,认为磨西断裂曾经历5次强烈活动:早期为正断性质,西低东高,控制两侧沉积分异(晋宁期);中期为韧性逆冲(印支期),形成糜棱岩;晚期新近纪中新世又一次韧性逆冲,之后又经历了脆性左旋逆冲、脆性左旋逆冲平移两次强烈活动(喜马拉雅期)。  相似文献   

6.
The current contribution presents aspects of the structural style and fault kinematics of the Rus Formation that expose at Jabal Hafit, Al Ain, United Arab Emirates. Although the major structure of Jabal Hafit is an anticlinal fold, fractures (joints and faults) are the prominent structure of the study area. The fractures can be interpreted as the distributed effect of deep-seated basement fault reactivation or to be as reactivation of deep-seated basement faults. These fractures were created during two main tectonic stress regimes. The first is a WNW–ESE S Hmax strike-slip stress regime, responsible for producing E–W to ESE–WNW joints and E–W dextral strike-slip and NNE–SSW reverse faults. This stress is interpreted to be post-Early Eocene in age and related to the second phase of thrusting in the Oman Mountains in the Miocene. The second stress regime is a NNE–SSW S Hmax transtensional (strike-slip extensive) stress regime that was responsible for N–S to NNE–SSW striking joints and NE–SW sinistral strike-slip and N–S normal faults. This regime is interpreted to be post-Middle Eocene in age. This stress was the response to the collision of the Arabian–Eurasian Plates which began during the Late Eocene and continues to the present day.  相似文献   

7.
红3井东侧断层的成因与中拐凸起的形成与演化密切相关,解析其构造几何学与运动学特征对于揭示中拐凸起自晚古生代以来的构造变形具有积极作用,并对于研究区的油气勘探具有重要意义。本文利用断层相关褶皱理论,不整合面识别及平衡剖面的方法,对红3井东侧断层进行精细的构造解析、建模与构造复原。中拐凸起发育白垩系-侏罗系、侏罗系-三叠系、三叠系-上乌尔禾组、上乌尔禾组底界及佳木河组-石炭系5个区域不整合面。研究认为,红3井东侧断层为一断层传播褶皱模型,发育生长三角,平面上分为北段、中段和南段。受海西晚期及燕山期的区域挤压作用的影响,红3井东侧断层在早二叠世末期(P1f末期)至中二叠世晚期(P2w)及早侏罗世晚期(J1s)至晚侏罗世发生两期传播活动,并在中段发生分支,分支断层的断距较小。早期的断层活动在中段最强,南段其次,北段最弱。中-下二叠统被抬升,遭受大面积剥蚀,地层缩短量约为3.8 km。晚期的断层活动微弱,且只发生在中段和北段,地层缩短量约为200 m。红3井东侧断层自北东向南西方向的传播、推覆作用控制了中拐凸起的主体构造形态,整体具有“南北分段、早晚期构造叠加”的特征。  相似文献   

8.
The global carbon cycle, one of the important biogeochemical cycles controlling the surface environment of the Earth, has been greatly affected by human activity. Anthropogenic nutrient loading from urban sewage and agricultural runoff has caused eutrophication of aquatic systems. The impact of this eutrophication and consequent photosynthetic activity on CO2 exchange between freshwater systems and the atmosphere is unclear. In this study, we focused on how nutrient loading to lakes affects their carbonate system. Here, we report results of surveys of lakes in Japan at different stages of eutrophication. Alkalization due to photosynthetic activity and decreases in PCO2 had occurred in eutrophic lakes (e.g., Lake Kasumigaura), whereas in an acidotrophic lake (Lake Inawashiro) that was impacted by volcanic hot springs, nutrient loading was changing the pH and carbon cycling. When the influence of volcanic activity was stronger in the past in Lake Inawashiro, precipitation of volcanic-derived iron and aluminum had removed nutrients by co-precipitation. During the last three decades, volcanic activity has weakened and the lake water has become alkalized. We inferred that this rapid alkalization did not result just from the reduction in acid inputs but was also strongly affected by increased photosynthetic activity during this period. Human activities affect many lakes in the world. These lakes may play an important part in the global carbon cycle through their influence on CO2 exchange between freshwater and the atmosphere. Biogeochemical changes and processes in these systems have important implications for future changes in aquatic carbonate systems on land.  相似文献   

9.
《Comptes Rendus Geoscience》2018,350(8):464-475
Seismicity induced by fluid perturbations became an important societal concern since felt earthquakes (Mw up to 6) occurred after anthropogenic activities. In order to mitigate the risks associated with undesired seismicity, as well as to be able to use the micro-seismicity as a probe for in-depth investigation of fluid-driven processes, it is of crucial importance to understand the links between seismicity, fluid pressure and flow. We have developed a series of in-situ, decameter-scale experiments of fault zone reactivation by controlled fluid injection, in order to improve the near-source geophysical and hydromechanical observations. The deployed geophysical monitoring close to the injection allows one to cover the full frequency range of the fault responses from the static deformation to the very high-frequency seismic emissions (up to 4 kHz). Here, we focus on the microseismicity (Mw  –4 to –3) recorded during two fluid injection experiments in low-permeable shale and highly-fractured limestone formations. In both experiments, the spatio-temporal distribution of the seismic events, the energy balance, and the seismic velocity changes of the fractured medium show that most of the deformation does not actually emit seismic signals. The induced deformation is mainly aseismic. Based on these high-resolution multiparametric observations in the near-field, we therefore proposed a new model for injection-induced seismicity: the seismicity is not directly induced by the increasing fluid pressure, but it is rather triggered by the stress perturbations transferred from the aseismic motion caused by the injection.  相似文献   

10.
A 1 km square regular grid system created on the Universal Transverse Mercator zone 54 projected coordinate system is used to work with volcanism related data for Sengan region. The following geologic variables were determined as the most important for identifying volcanism: geothermal gradient, groundwater temperature, heat discharge, groundwater pH value, presence of volcanic rocks and presence of hydrothermal alteration. Data available for each of these important geologic variables were used to perform directional variogram modeling and kriging to estimate geologic variable vectors at each of the 23949 centers of the chosen 1 km cell grid system. Cluster analysis was performed on the 23949 complete variable vectors to classify each center of 1 km cell into one of five different statistically homogeneous groups with respect to potential volcanism spanning from lowest possible volcanism to highest possible volcanism with increasing group number. A discriminant analysis incorporating Bayes’ theorem was performed to construct maps showing the probability of group membership for each of the volcanism groups. The said maps showed good comparisons with the recorded locations of volcanism within the Sengan region. No volcanic data were found to exist in the group 1 region. The high probability areas within group 1 have the chance of being the no volcanism region. Entropy of classification is calculated to assess the uncertainty of the allocation process of each 1 km cell center location based on the calculated probabilities. The recorded volcanism data are also plotted on the entropy map to examine the uncertainty level of the estimations at the locations where volcanism exists. The volcanic data cell locations that are in the high volcanism regions (groups 4 and 5) showed relatively low mapping estimation uncertainty. On the other hand, the volcanic data cell locations that are in the low volcanism region (group 2) showed relatively high mapping estimation uncertainty. The volcanic data cell locations that are in the medium volcanism region (group 3) showed relatively moderate mapping estimation uncertainty. Areas of high uncertainty provide locations where additional site characterization resources can be spent most effectively. The new data collected can be added to the existing database to perform future regionalized mapping and reduce the uncertainty level of the existing estimations.  相似文献   

11.
《Engineering Geology》2002,63(1-2):169-185
Heavy rainfall from 26 to 31 August 1998 triggered many landslides in Nishigo Village of southern Fukushima Prefecture, Japan. The Hiegaesi landslide, a long-runout landslide with travel angle of 11°, which occurred in loamy volcanic-ash/pumice layer and was deposited in a nearby rice paddy, was investigated. In an observation pit dug in the middle part of the landslide deposit, the sliding zone just above the deflected rice plants was observed, and it was confirmed that grain crushing occurred in the sliding zone. The triggering and sliding mechanisms of this landslide then were investigated by ring-shear tests in laboratory. For the triggering mechanism, one saturated naturally drained test (test A: torque-controlled test) and one saturated undrained test (test B: speed-controlled test) were conducted on the samples taken from the source area of the landslide. Even in the naturally drained test opening the upper drain valve of the shear box, a temporary liquefaction occurred. In the undrained test, excess pore-pressure was generated along with shearing, and “sliding-surface liquefaction” phenomenon was observed. The effective stress and shear resistance finally decreased to near zero. These results can explain the observed phenomenon of small friction resistance like a flow of liquid when the sliding mass slid out of the source area. For the sliding mechanism of the landslide in the rice paddy, saturated undrained test (test C: speed-controlled test) was performed on soil sample above the deflected rice plants. The apparent friction angle obtained in this test was 8°. In addition, the residual friction angle measured after test B and test C was the same value of 41°. Combining with the observation on the shear zone in the ring-shear box after test C, it is concluded that, during the sliding in rice paddy, the undrained shear strength of the soil layer itself mainly influenced the high mobility of the landslide, probably because the friction between rice plants and soils is greater than the undrained shear strength inside the soil mass.  相似文献   

12.
Transecting the Los Angeles metropolitan area in a general E-W direction are major north-dipping reverse faults comprising the Santa Monica—Raymond Hill fault zone, a segment of the frontal fault system separating the Transverse Ranges from the Peninsular Ranges geomorphic provinces of southern California. Pleistocene or Holocene movement is evident along some segments of these faults, but urban development precludes accurate location and assessment of Quaternary movement by conventional mapping techniques. At present no conclusive evidence of Holocene surface rupture has been found onshore west of the Raymond Hill segment of the fault zone, but the geologic conditions and urban development in the area are such that the possibility of Holocene movement cannot be excluded at this time. Groundwater barriers in Pleistocene sediments are indicative of Quaternary faulting on the Santa Monica fault segment west of the Newport—Inglewood fault zone. Most literature indicates that movement along the Beverly Hills—Hollywood segment east of the Newport—Inglewood fault zone terminated in Late Miocene or Pliocene time, and there is no general agreement on the location of faults in this segment. However, recent work by the Division of Mines and Geology, by Geotechnical Consultants, Inc., and others suggests that the Santa Monica fault transecting the Hollywood area is associated with a zone of differential subsidence that varies from 100 to 400 m wide, depending on the resolution of repeated leveling survey data and with a groundwater barrier determined from analysis of oil-well and water-well data. Additional exploration is essential to test our present geologic model and to evaluate the earthquake hazard and seismic risk of faults in the area.  相似文献   

13.
The pattern of local seismicity (110 events) and the source parameters of 26 local events (1.0?≤?Mw?≤?2.5) that occurred during May 2008 to April 2009 in Bilaspur region of Himachal Lesser Himalaya were determined. The digital records available from one station have been used to compute the source parameters and f max based on the Brune source model (1970) and a high-frequency diminution factor (Boore 1983) above f max. The epicentral distribution of events within 30 km of local network is broadly divided into three clusters of seismic activity: (1) a cluster located to the south of the Jamthal (JAMT) station and falls to the north of the Main Boundary Thrust (MBT) which seems to reflect the contemporary local seismicity of the segment of the MBT, (2) an elongated zone of local seismicity NE–SW trending, delineated NE of JAMT station that falls in the Lesser Himalaya between the MBT and the Main Central Thrust, and (3) NE–SW trending zone of local seismic activity located at about 10 km east of NHRI station and about 15 km northeast of NERI station and extending over a distance of about 20 km. Majority of events occur at shallow depths up to 20 km, and the maximum number of events occurs in the focal depth range between 10 and 15 km. The entire seismic activity is confined to the crust between 5 and 45 km. The average values of these source parameters range from 3.29?×?1017 to 3.73?×?1019?dyne-cm for seismic moment, 0.1 to 9.7 bars for stress drops, and 111.78 to 558.92 m for source radii. The average value of f max for these events varies from 7 to 18 Hz and seems to be source dependent.  相似文献   

14.
We conducted a seismic tomographic analysis to estimate the crustal structure beneath the Shikoku and Chugoku regions in Japan. The Philippine Sea slab (PHS slab) subducts continuously in a SE–NW direction beneath this region, and the crustal structure is complex. Furthermore, the Median Tectonic Line (MTL), one of the longest and most active arc-parallel fault systems in Japan (hereafter, the MTL active fault system), is located in this area, and the right-lateral strike–slip movement of this fault system is related to the oblique subduction of the PHS slab. The MTL active fault system has ruptured repeatedly during the last 10 000 years, and has high seismic potential. Our tomographic analysis clarified the heterogeneous crustal structure along the MTL active fault system. This fault system in Shikoku can be divided into two segments, an east segment and a west segment, on the basis of the velocity structure. This segmentation model is consistent with other such models that have been determined from geological and geomorphological data such as fault geometry, slip rate, and faulting history. This consistency suggests that the surface characteristics of the MTL active fault system are related to structural properties of the crust. In particular, a prominent low-velocity (low-V) zone is present in the lower crust beneath the east segment. Our tomographic images show that the lower crust structure beneath the east segment is obviously different from that of the other segment. Furthermore, this low-V zone may indicate the presence of fluid, possibly related to dehydration of the PHS slab. As the presence of fluid in the lower crust affects the activity of the fault, stress accumulation and the fault failure mechanism may differ between the two segments of the MTL active fault system.  相似文献   

15.
The Hirabayashi borehole (Awaji Island, Japan) was drilled by the Geological Survey of Japan (GSJ) 1 year after the Hyogo-ken Nanbu (Kobe) earthquake (1995, MJMA=7.2). This has enabled scientists to study the complete sequence of deformation across the active Nojima fault, from undeformed granodiorite to the fault core. In the fault core, different types of gouge and fractures have been observed and can be interpreted in terms of a complex history of faulting and fluid circulation. Above the fault core and within the hanging wall, compacted cataclasites and gouge are cut by fractures which show high apparent porosity and are filled by 5–50 μm euhedral and zoned siderite and ankerite crystals. These carbonate-filled fractures have been observed within a 5.5-m-wide zone above the fault, but are especially abundant in the vicinity (1 m) of the fault. The log-normal crystal size distributions of the siderite and ankerite suggest that they originated by decaying-rate nucleation accompanied by surface-controlled growth in a fluid saturated with respect to these carbonates. These carbonate-filled fractures are interpreted as the result of co-seismic hydraulic fracturing and upward circulation of fluids in the hanging wall of the fault, with the fast nucleation of carbonates attributed to a sudden fluid or CO2 partial pressure drop due to fracturing. The fractures cut almost all visible structures at a thin section scale, although in some places, the original idiomorphic shape of carbonates is modified by a pressure-solution mechanism or the carbonate-filled fractures are cut and brecciated by very thin gouge zones; these features are attributed to low and high strain-rate mechanisms, respectively. The composition of the present-day groundwater is at near equilibrium or slightly oversaturated with respect to the siderite, calcite, dolomite and rhodochrosite. Taken together, this suggests that these fractures formed very late in the evolution of the fault zone, and may be induced by co-seismic hydraulic fracturing and circulation of a fluid with a similar composition to the present-day groundwater. They are therefore potentially related to recent earthquake activity (<1.2 Ma) on the Nojima fault.  相似文献   

16.
胡波  李泊洋  张明  张兰玲 《世界地质》2011,30(4):585-592
地质剖面测量和区域构造解析方法研究表明,嘉黎断裂是一条多期活动并在不同时期显示不同性质的、有着长期发展历史的深大断裂。在晚三叠世-侏罗纪时期,班公湖-怒江洋盆南侧比如弧后盆地发生裂解,此时的嘉黎断裂应是北倾的正断层,控制着弧后盆地的沉积。晚侏罗世-早白垩世时期,伴随着盆地的消亡,出现一系列由南向北的逆冲断裂和蛇绿岩的就位。中新世至第四纪,嘉黎断裂带表现为伸展构造体系,局部出现右旋走滑,形成机理是青藏高原隆升导致构造块体不均匀运动和塌陷所致。  相似文献   

17.
Comparative evaluation of landslide susceptibility in Minamata area, Japan   总被引:6,自引:0,他引:6  
Landslides are unpredictable; however, the susceptibility of landslide occurrence can be assessed using qualitative and quantitative methods based on the technology of the Geographic Information Systems (GIS). A map of landslide inventory was obtained from the previous work in the Minamata area, the interpretation from aerial photographs taken in 1999 and 2002. A total of 160 landslides was identified in four periods. Following the construction of geospatial databases, including lithology, topography, soil deposits, land use, etc., the study documents the relationship between landslide hazard and the factors that affect the occurrence of landslides. Different methods, namely the logistic regression analysis and the information value model, were then adopted to produce susceptibility maps of landslide occurrence. After the application of each method, two resultant maps categorize the four classes of susceptibility as high, medium, low and very low. Both of them generated acceptable results as both classify the majority of the cells with landslide occurrence in high or medium susceptibility classes, which could be believed to be a success. By combining the hazard maps generated from both methods, the susceptibility was classified as high–medium and low–very low levels, in which the classification of high susceptibility level covers 6.5% of the area, while the areas predicted to be unstable, which are 50.5% of the total area, are classified as the low susceptibility level. However, comparing the results from both the approaches, 43% of the areas were misclassified, either from high–medium to low–very low or low–very low to high–medium classes. Due to the misclassification, 8% and 3.28% of all the areas, which should be stable or free of landsliding, were evaluated as high–medium susceptibility using the logistic regression analysis and the information value model, respectively. Moreover, in the case of the class rank change from high–medium susceptibility to low–very low, 35% and 39.72% of all mapping areas were predicted as stable using both the approaches, respectively, but in these areas landslides were likely to occur or were actually recognized.  相似文献   

18.
克拉通内古隆起的构造变形是探究板块内部变形行为与大陆流变构造学的理想场所,断裂研究则是其主要突破口。本文基于新的地球物理与钻探资料,对塔里木盆地北部隆起的断裂系统尤其是其北部边界断裂的几何学与运动学开展研究。分析表明,温宿北—野云沟断裂系在重磁场与反射地震剖面上具有清楚的反映,为塔北隆起的北部边界断裂,长达600 km,自西向东由温宿北断裂、温巴什断裂和野云沟断裂三段构成。该断裂系是在早奥陶世末沿基底软弱带自南向北逆冲形成的大型断层相关褶皱带基础上在前翼发生突破而形成的,加里东末期形成雏形,二叠纪末期,受南天山洋关闭的影响由北向南的强烈挤压形成自北而南的逆冲构造系统。该逆冲系统迁就原加里东期的滑脱面发育,并对原来的逆冲系统进行叠加、改造,形成一系列小断块叠加的大型背冲断裂系统,使得该断裂带基本定型。喜马拉雅期塔北隆起轴部发育张扭性断裂构造系统,该断裂系遭受左旋压扭,断裂的活动时序自东向西趋晚,具有长期演化、多期发育、继承、叠加与复合的特征。活动强度呈古生代强烈、中生代—新生代早期弱化、新生代晚期趋强的"强-弱-强"的演化趋势,在横向上呈西段强烈、东段略弱的特征。其成因主要与早奥陶世末期北昆仑洋关闭、二叠纪末期南天山洋关闭、古近纪新特提斯洋关闭引起的周缘地体与塔里木地块的碰撞拼合相关,表现出周缘板块构造事件对板内变形的强烈影响。该断裂系是重要的油气富集带。研究其成因与演化有助于该带油气勘探的拓展,例如西秋断裂带的油气发现。  相似文献   

19.
The results of seismic monitoring in the area of the Franz Victoria and Orla trenches in 2011–2013 are discussed in the paper. A seismic catalog of recorded earthquakes with calculated source parameters is given, and the spatial distribution of these earthquakes is characterized. The results of monitoring are compared with the data on historical earthquakes. A cumulative graph of recurrence has been constructed.  相似文献   

20.
塔中低凸起位于塔里木盆地中央隆起的中段,发育4组不同方向的断裂,以北西向的塔中Ⅰ号断裂带为主干断裂,其南的近北西向断裂和近东西向断裂与之组成"入"字形构造,向西撒开;剖面上则因塔中Ⅰ号断裂带活动强度自东向西减弱而出现不同的断裂组合样式。基于地层记录和区域演化分析了该区断裂系统的活动时期和活动方式,两次重大的挤压—剪切事件分别发生在奥陶纪末和晚志留-中泥盆世,因而塔里木盆地中央隆起可能是晋宁期山体在后期重新活动形成的加里东期陆内造山带。北西向断裂是二叠纪岩浆侵入或玄武岩喷溢的通道,之后全区断裂基本处于平静状态。结合塔里木周边造山带的演化,认为古生代—三叠纪时塔中地区的盆地发育主要受西昆仑造山带演化制约,同时叠加有古阿尔金剪切造山带的影响,这是为塔中地区特殊的构造位置决定的。侏罗纪—新近纪,该地的盆地主要与阿尔金断裂的剪切造山作用耦合发育,仅早白垩世时与塔北—库车地区同属南天山的"盆""山"系统。断裂的运动学特征取决于其动力学背景,实际上受制于邻侧的造山带发育。断裂系统的发育是塔中地区能形成复式油气田的关键条件之一,本文的研究对推进复式油气成藏的机理研究、明确近期的重点勘探靶区等有积极意义。  相似文献   

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