龙门山断裂带南段地壳一维P波速度结构   总被引：2，自引：0，他引：2  

王小娜  于湘伟  章文波  王思琳 《地震研究》2015,38(1)

基于2009年1月1日至2013年5月6日四川地震台网、重庆地震台网记录的龙门山断裂带南段587个地震的5 012个P波到时数据,利用最小一维速度模型方法反演了龙门山断裂带南段地壳一维P波速度模型及台站校正值,并将其应用到龙门山地区地震重定位中。结果表明,台站校正值表征出龙门山断裂带南段地表速度结构的横向不均匀性,青藏高原的彭灌杂岩体及宝兴杂岩体在近地表表现为高速异常,而四川盆地的第四纪沉积表现为低速异常。重定位后地震震源在北西向的剖面上呈明显的条带状并向北西倾斜,该地震带与宝兴杂岩下方的滑脱带延伸趋势一致。此外,该地震带上方分布着一条反冲地震带,两地震带呈"y"型分布,这可能是宝兴杂岩上方的岩层为调节逆冲过程受阻而产生的反冲运动所致。  相似文献   

From outwash to coastal systems in the Portneuf–Forestville deltaic complex (Québec North Shore): Anatomy of a forced regressive deglacial sequence          下载免费PDF全文

Pierre Dietrich  Jean‐François Ghienne  Mathieu Schuster  Patrick Lajeunesse  Alexis Nutz  Rémy Deschamps  Claude Roquin  Philippe Duringer 《Sedimentology》2017,64(4):1044-1078

Deglacial sequences typically include backstepping grounding zone wedges and prevailing glaciomarine depositional facies. However, in coastal domains, deglacial sequences are dominated by depositional systems ranging from turbiditic to fluvial facies. Such deglacial sequences are strongly impacted by glacio‐isostatic rebound, the rate and amplitude of which commonly outpaces those of post‐glacial eustatic sea‐level rise. This results in a sustained relative sea‐level fall covering the entire depositional time interval. This paper examines a Late Quaternary, forced regressive, deglacial sequence located on the North Shore of the St. Lawrence Estuary (Portneuf Peninsula, Québec, Canada) and aims to decipher the main controls that governed its stratigraphic architecture. The forced regressive deglacial sequence forms a thick (>100 m) and extensive (>100 km²) multiphased deltaic complex emplaced after the retreat of the Laurentide Ice Sheet margin from the study area ca 12 500 years ago. The sedimentary succession is composed of ice‐contact, glaciomarine, turbiditic, deltaic, fluvial and coastal depositional units. A four‐stage development is recognized: (i) an early ice‐contact stage (esker, glaciomarine mud and outwash fan); (ii) an in‐valley progradational stage (fjord head or moraine‐dammed lacustrine deltas) fed by glacigenics; (iii) an open‐coast deltaic progradation, when proglacial depositional systems expanded beyond the valley outlets and merged together; and (iv) a final stage of river entrenchment and shallow marine reworking that affected the previously emplaced deltaic complex. Most of the sedimentary volume (10 to 15 km³) was emplaced during the three‐first stages over a ca 2 kyr interval. In spite of sustained high rates of relative sea‐level fall (50 to 30 mm·year^?1), delta plain accretion occurred up to the end of the proglacial open‐coast progradational stage. River entrenchment only occurred later, after a significant decrease in the relative sea‐level fall rates (<30 mm·year^?1), and was concurrent with the formation and preservation of extensive coastal deposits (raised beaches, spit platform and barrier sands). The turnaround from delta plain accretion to river entrenchment and coastal erosion is interpreted to be a consequence of the retreat of the ice margin from the river drainage basins that led to the drastic drop of sediment supply and the abrupt decrease in progradation rates. The main internal stratigraphic discontinuity within the forced regressive deglacial sequence does not reflect changes in relative sea‐level variations.  相似文献   

西南印度洋中脊三维地震探测中炮点与海底地震仪的位置校正   总被引：9，自引：3，他引：6       下载免费PDF全文

敖威  赵明辉  丘学林  李家彪  陈永顺  阮爱国  李守军  张佳政  吴振利  牛雄伟 《地球物理学报》2010,53(12):2982-2991

在海上实施三维地震探测过程中,人工震源枪阵中心与船上GPS的距离及地震探测作业中的船行方向造成炮点实际位置与预设位置有一定偏差;自由落体投放的OBS由于海流的影响会偏离原定设计位置(投放点),因此,炮点与海底地震仪(OBS)的位置校正是三维地震结构研究中的基本环节.本文利用艏向信息校正了炮点位置;采用蒙特卡洛和最小二乘法方法对海底地震仪的位置进行了校正,并探讨了直达水波曲线特征.结果表明 OBS位置一般偏离设计点1 km左右,其误差范围在20 m以内,校正后的OBS记录剖面展示了真实的记录情况.该研究结果为下一步西南印度洋的三维层析成像研究提供了坚实数据基础,同时为今后南海的三维深部地壳结构探测提供经验与借鉴.  相似文献   

Soil–structure interaction effects observed in the in situ forced vibration and pushover tests of school buildings in Taiwan and their modeling considering the foundation flexibility     

Yung‐Yen Ko  Cheng‐Hsing Chen 《地震工程与结构动力学》2010,39(9):945-966

In the conventional structural seismic analysis, the rigid base model is usually adopted without considering the flexibility of the ground, leading to inaccurate estimation of the vibration characteristics and the seismic response of the structure. In 2007, several in situ tests were conducted by the National Center for Research on Earthquake Engineering (NCREE) on the school buildings in the Guanmiao Elementary School in Tainan, Taiwan. For the study of soil–structure interaction (SSI) effects, the forced vibration test (FVT) was performed, and the deformation of the foundation system was measured during the pushover test. In this paper, the results of these in situ tests are presented and discussed, and the finite element models of the school buildings were generated for the simulation of the FVT and for the pushover analysis in order to investigate the difference between the rigid base model and the flexible base model. Results show that the mechanical properties of the structure and the foundation could be demonstrated in these in situ tests. Additionally, the introduction of the flexibility of the foundation has a considerable influence on the results of structural analysis. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

天然地基强迫振动测试与分析     

王岚  吕景权  朱文久  郑水明 《大地测量与地球动力学》2011,31(2):84-88

在试验块体分别为明置与埋置情形时,利用激振器对某工程场地天然地基分别进行竖向、水平回转及扭转稳态强迫振动试验。试验结果表明,埋置情形试验的动力特性参数值均大于明置情形试验相应值;同种试验情形下,地基第一振型共振频率竖向最大,水平回转向其次,扭转向最小;土的参振质量均远大于基础本身质量。  相似文献   

���������������¶�λ�������   总被引：3，自引：0，他引：3  

于湘伟  张怀  陈运泰 《大地测量与地球动力学》2010,30(2):29-33

????????λ???????????(111??120??E??35??42??N)1993??2004??6 771?ε???1.0??M??6.6???????λ???????λ???????????????????????????????????????????????;???o?????·???????????????????????????б???????????????????????????????????20 km????60 km???????25 km??34 km?????40 km;83%???????????λ??0??15 km??Χ?????????????λ???????????????(7??21 km)????????????????????????????????????????????????;???92%???????????λ??1??24 km??????24 km??????????????????????硣  相似文献   

Characteristics of Seismic Activity in a 3-Dimensional Space before the Wen'an Earthquake,Hebei Province by Relocation of Small Earthquakes in the China's Capital Area     

Xue Yan  Zhou Longquan  Ma Hongsheng  Liu Jie 《中国地震研究》2010,24(4):404-414

Characteristics of seismic activity before the M5.1 earthquake in Wen'an,Hebei Province on July 4,2006 are analyzed by relocation of small earthquakes in the China's capital area,and some results are obtained as follows:① The seismic activity of M L ≥3.0 in the middle part of the Hebei plain seismic belt displayed a feature of strengthening (lasting 43 months) quiescence (17 months) five years before the Wen'an earthquake.Simultaneously,the strain release curve showed a variation process of accelerating-flatting.② A seismogenic gap in a three-dimensional space,located at the depth of 15km ～ 20km,with 70km long in latitude direction and 90km long in longitude orientation,was formed by M≥2.0 earthquakes four years prior to the Wen'an earthquake.The initial rupture point of the Wen'an earthquake is situated at the bottom of the gap.③ The focal depths of earthquakes with M L ≥2.0 in the middle part of the Hebei plain seismic belt gradually increased from 10km to 30km during the period from April,2003 to October,2004.Meanwhile,the seismic activity obviously strengthened in the middle and lower crust (from 20km to 30km in depth).  相似文献   

RELOCATION OF MAIN SHOCK AND AFTERSHOCKS OF THE 2014 YINGJIANG M_S5.6 AND M_S6.1 EARTHQUAKES IN YUNNAN          下载免费PDF全文

YANG Ting  WU Jian-ping  FANG Li-hua  WANG Wei-lai 《地震地质》2016,38(4):1047-1057

Yingjiang area is located in the China-Burma border,the Sudian-Xima arc tectonic belt,which lies in the collision zone between the Indian and Eurasian plates.The Yingjiang earthquake occurring on May 30th,2014 is the only event above M_S6.0 in this region since seismicity can be recorded.In this study,we relocated the Yingjiang M_S5.6 and M_S6.1 earthquake sequences by using the double-difference method.The results show that two main shocks are located in the east of the Kachang-Dazhuzhai Fault,the northern segment of the Sudian-Xima Fault.Compared with the Yingjiang M_S5.6 earthquake,the Yingjiang M_S6.1 earthquake is nearer to the Kachang-Dazhuzhai Fault.The aftershocks of the two earthquakes are distributed along the strike direction of the Kachang-Dazhuzhai Fault (NNE).The rupture zone of the main shock of Yingjiang M_S6.1 earthquake extends northward approximately 5km.The aftershocks of two earthquakes are mainly located in the eastern side of the Kachang-Dazhuzhai Fault with a significant asymmetry along the fault,which differ from the characteristics of the aftershock distribution of the strike-slip earthquake.It may indicate that the Yingjiang earthquakes are conjugate rupture earthquakes.The non-double-couple components are relatively high in the moment tensor.We speculate that the Yingjiang earthquakes are related to the fractured zone caused by the long-term seismic activity and heat effect in the deep between Kachang-Dazhuzhai Fault and its neighboring secondary faults.Aftershock distribution of the Yingjiang M_S6.1 earthquake on the southern area crosses a secondary fault on the right of the Kachang-Dazhuzhai Fault,suggesting that the coseismic rupture of the secondary fault may be triggered by the dynamic stress of the main shock.  相似文献   

MECHANISM OF THE 2015 PISHAN,XINJIANG, M_S6.5 MAINSHOCK AND RELOCATION OF ITS AFTERSHOCK SEQUENCES          下载免费PDF全文

ZHANG Guang-wei  ZHANG Hong-yan  SUN Chang-qing 《地震地质》2016,38(3):711-720

Using the digital broadband seismic data recorded by Xinjiang network stations, we obtained focal mechanism of the July 3 Pishan, Xinjiang, M_S6.5 earthquake with generalized Cut and Paste(gCAP)inversion method. The strike, dip and rake of first nodal plane are 97°, 27°, 51°, and the second nodal plane are 318°, 70°, 107°. The centroid depth and moment magnitude are calculated to be 12km and 6.4. Combining with the distribution of aftershocks, we conclude that the first nodal plane is the seismogenic fault, and the main shock presents a thrust earthquake at low angle. We relocated 1014 earthquakes using the double-difference algorithm, and finally obtained 937 relocated events. Our results show that the earthquake sequences clearly demonstrate a unilateral extension about 50km nearly in NWW direction, and are mainly located above 25km depth, especially the small earthquakes are predominately located at the shallow parts. Furthermore, the focal depth profile shows a southwestward dipping fault plane at the main shock position, suggesting listric thrust faulting, which is consistent with the dip of the mainshock rupture plane. The spatial distribution of aftershocks represents that the Tarim block was thrust under the West Kunlun orogenic belt. In addition, the dip angle of the fault plane gradually increases along the NWW direction, possibly suggesting a gradual increase of strike-slip component during the NWW rupturing process. From above, we conclude that the Pishan M_S6.5 earthquake is the result of Tibet plateau pushing onto the Tarim block from south to north, which further confirms that the continuous collision of India plate and Eurasia plate has strong influence on the seismic activity in and around the Tibet plateau.  相似文献   

THE RESEARCH OF THE SEISMOGENIC STRUCTURE OF THE LUSHAN EARTHQUAKE BASED ON THE SYNTHESIS OF THE DEEP SEISMIC DATA AND THE SURFACE TECTONIC DEFORMATION          下载免费PDF全文

WANG Lin  ZHOU Qing-yun  WANG Jun  LI Wen-qiao  ZHOU Lian-qing  CHEN Han-lin  SU Peng  LIANG Peng 《地震地质》2016,38(2):458-476

The seismogenic structure of the Lushan earthquake has remained in suspensed until now. Several faults or tectonics, including basal slipping zone, unknown blind thrust fault and piedmont buried fault, etc, are all considered as the possible seismogenic structure. This paper tries to make some new insights into this unsolved problem. Firstly, based on the data collected from the dynamic seismic stations located on the southern segment of the Longmenshan fault deployed by the Institute of Earthquake Science from 2008 to 2009 and the result of the aftershock relocation and the location of the known faults on the surface, we analyze and interpret the deep structures. Secondly, based on the terrace deformation across the main earthquake zone obtained from the dirrerential GPS meaturement of topography along the Qingyijiang River, combining with the geological interpretation of the high resolution remote sensing image and the regional geological data, we analyze the surface tectonic deformation. Furthermore, we combined the data of the deep structure and the surface deformation above to construct tectonic deformation model and research the seismogenic structure of the Lushan earthquake. Preliminarily, we think that the deformation model of the Lushan earthquake is different from that of the northern thrust segment ruptured in the Wenchuan earthquake due to the dip angle of the fault plane. On the southern segment, the main deformation is the compression of the footwall due to the nearly vertical fault plane of the frontal fault, and the new active thrust faults formed in the footwall. While on the northern segment, the main deformation is the thrusting of the hanging wall due to the less steep fault plane of the central fault. An active anticline formed on the hanging wall of the new active thrust fault, and the terrace surface on this anticline have deformed evidently since the Quaterary, and the latest activity of this anticline caused the Lushan earthquake, so the newly formed active thrust fault is probably the seismogenic structure of the Lushan earthquake. Huge displacement or tectonic deformation has been accumulated on the fault segment curved towards southeast from the Daxi country to the Taiping town during a long time, and the release of the strain and the tectonic movement all concentrate on this fault segment. The Lushan earthquake is just one event during the whole process of tectonic evolution, and the newly formed active thrust faults in the footwall may still cause similar earthquake in the future.  相似文献