低温热年代学数据对龙门山推覆构造带南段新生代构造活动的约束   总被引：3，自引：2，他引：1  

谭锡斌  李元希  徐锡伟  陈玟禹  许冲  于贵华 《地震地质》2013,35(3)

龙门山位于青藏高原东边缘,地形陡变,剥蚀作用强烈.近年来先后经历了2008年汶川MW7.9地震和2013年芦山MS7.0地震,多位学者对龙门山地区做了大量的低温热年代学研究.文中在研究程度相对薄弱的龙门山南段补充了4个锆石裂变径迹年龄和4个磷灰石裂变径迹年龄,结合前人的低温热年代学数据结果得出,宝兴杂岩从新生代早期开始快速冷却,降温幅度超过225℃,而龙门山中段的彭灌杂岩降温幅度为185 ～225℃.宝兴杂岩的4个裂变径迹年龄分布在2.7 ～5Ma,相对彭灌杂岩较年轻,表明晚新生代以来宝兴杂岩的冷却速率要高于彭灌杂岩.在地表温度为15℃和古地温梯度为30℃/km的假设下,宝兴杂岩距今3～5Ma以来的平均剥露速率为0.63 ～ 1.17mm/a.低温热年代学数据揭示出龙门山中段的差异剥蚀集中在北川-映秀断裂和江油-灌县断裂上,而南段的差异剥蚀分散在更宽范围内的双石-大川断裂(南、北2个分支)及其东侧的断层和褶皱.  相似文献   

2013年芦山7.0级地震一年尺度预测的回顾性研究——基于三性法、静中动和垂震底继模式          下载免费PDF全文

郭安宁  李鑫  赵乘程  张炜超 《地震工程学报》2013,35(2):257-265

对2013年中期地震预测的研究结果(一年尺度)进行了阐述与分析。该预测综合了三性法判据、静中动判据和垂震底继模式,给出了2013年左右在鲜水河断裂带上发生7级以上大震的可能性很大的结论。重点预测了两个具体发生的区域,预测的区域与2013年4月20日芦山7.0级地震的震源区相差70～80km左右。预测结果震级与时间吻合,但地点上发生了偏离。文中重点回顾研究了基于三性法,静中动、垂震底继方法的预测过程。  相似文献   

芦山地震中校舍建筑的震害特点与分析     

王涛  雷远德  张永群  孔子昂 《地震工程与工程振动》2013,33(3)

本文对芦山地震中的校舍建筑震害进行调查和分析.调查发现,汶川地震后重建的框架结构,由于按照新的抗震规范进行设防,大多数没有出现结构性损伤,震害集中在填充墙等非结构构件上.建于汶川地震前的框架结构,当不符合规范的强制条文时,破坏严重,特别是单跨框架,个别发生首层柱端破坏.砖混结构校舍中的宿舍楼,由于开间小,横墙多,多设置了构造措施,虽有结构破坏,但均可修复.砖混结构教学楼采用砖墙-框架柱混合承重的结构体系,大多在汶川地震后得到加固,未加固的教学楼有严重的结构破坏,而加固后的校舍建筑则表现较好,但是这些结构体系多采用预制空心板,整体性较差,已经被规范禁止用于校舍建筑.场地对结构震害有重要的影响,密实的持力层、妥善的地基处理和整体性好的基础形式,可以大幅度减轻结构的震害.本文建议:应加强校舍建筑基于性能设计的研究,进一步明确其设防目标;研究填充墙与框架的相互作用,设计新型的填充墙体系以实现校舍建筑在不同地震水平下的功能要求.  相似文献   

fmax and fault zone property of Lushan earthquake of 20 April 2013, Sichuan,China     

Jian Wen  Xiaofei Chen 《地震学报(英文版)》2013,(3):179-183

In this study, we determined fnax from near- field accelerograms of the Lushan earthquake of April 20, 2013 through spectra analysis. The result shows that the values of fmax derived from five different seismography stations are very close though these stations roughly span about 100 km along the strike. This implies that the cause offmax is mainly the seismic source process rather than the site effect. Moreover, according to the source-cause model of Papageorgiou and Aki （Bull Seism Soc Am 73：693-722, 1983）, we infer that the cohesive zone width of the rupture of the Lushan earthquake is about 204 with an uncertainty of 13 m. We also find that there is a significant bulge between 30 and 45 Hz in the amplitude spectra of accel- erograms of stations 51YAL and 51QLY, and we confirm that it is due to seismic waves＇ reverberation of the sedi- mentary soil layer beneath these stations.  相似文献   

Preliminary results of strong ground motion simulation for the Lushan earthquake of 20 April 2013, China     

Gengshang Zhu  Zhenguo Zhang  Jian Wen  Wei Zhang  Xiaofei Chen 《地震学报(英文版)》2013,(3):191-197

The earthquake occurred in Lushan County on 20 April, 2013 caused heavy casualty and economic loss. In order to understand how the seismic energy propagates during this earthquake and how it causes the seismic haz- ard, we simulated the strong ground motions from a rep- resentative kinematic source model by Zhang et al. （Chin J Geophys 56（4）：1408-1411, 2013） for this earthquake. To include the topographic effects, we used the curved grids finite difference method by Zhang and Chen （Geophys J Int 167（1）：337-353, 2006）, Zhang et al. （Geophys J Int 190（1）：358-378, 2012） to implement the simulations. Our results indicated that the majority of seismic energy con- centrated in the epicentral area and the vicinal Sichuan Basin, causing the XI and VII degree intensity. Due to the strong topographic effects of the mountain, the seismic intensity in the border area across the northeastern of Boxing County to the Lushan County also reached IX degree. Moreover, the strong influence of topography caused the amplifications of ground shaking at the moun- tain ridge, which is easy to cause landslides. These results are quite similar to those observed in the Wenchuan earthquake of 2008 occurred also in a strong topographic mountain area.  相似文献   

Co- and post-seismic surface deformation and gravity changes of Ms7.0 Lushan,earthquake     

Kai Wang  Chengli Liu  Xiong Xiong  Yong Zheng 《地震学报(英文版)》2013,(3):207-212

On April 20, 2013, an earthquake with mag- nitude 7.0 occurred in the southwest of the Longmenshan fault system in and around Lushan County, Sichuan Province, China. This devastating earthquake killed hun- dreds of people, injured 10 thousand others, and collapsed countless buildings. In order to analyze the potential risk of this big earthquake, we calculate the co- and post-seismic surface deformation and gravity changes of this event. In this work, a multilayered crustal model is designed, and the elastic dislocation theory is utilized to calculate the co- and post-seismic deformations and gravity changes. During the process, a rupture model obtained by seismic waveform inversion （Liu et al. Sci China Earth Sci 56（7）： 1187-1192, 2013） is applied. The time-dependent relaxation results show that the influences on Lushan and its surrounding areas caused by the Ms7.0 Lushan earthquake will last as long as 10 years. The maximum horizontal displacement, vertical uplift, and settlement are about 5 cm, 21.24 cm, and 0.16 m, respectively; the maximal positive and nega- tive values of gravity changes are 45 and -0.47 μGal, respectively. These results may be applied to evaluate the long-term potential risk caused by this earthquake and to provide necessary information for post-earthquake reconstruction.  相似文献   

Did the Ms7.0 Lushan earthquake dynamically trigger earthquakes in the Datong volcanic region （Shanxi Province）？     

Meiqin Song  Yong Zheng  Rui Fu  Xiangjun Li-ang  Xia Wang  Li Li  Bin Li 《地震学报(英文版)》2013,(3):229-239

Immediately following the Ms7.0 Lushan earthquake on April 20, 2013, using high-pass and low- pass filtering on the digital seismic stations in the Shanxi Province, located about 870-1,452 km from the earthquake epicenter, we detected some earthquakes at a time corre- sponding to the first arrival of surface waves in high-pass filtering waveform. The earthquakes were especially noticed at stations in Youyu （YUY）, Shanzizao （SZZ）, Shanghuangzhuang （SHZ）, and Zhenchuan （ZCH）, which are located in a volcanic region in the Shanxi Province,but they were not listed in the Shanxi seismic observation report. These earthquakes occurred 4-50 rain after the passage of the maximum amplitude Rayleigh wave, and the periods of the surface waves were mainly between 15 and 20 s following. The Coulomb stresses caused by the Ray- leigh waves that acted on the four stations was about 0.001 MPa, which is a little lower than the threshold value of dynamic triggering, therefore, we may conclude that the Datong volcanic region is more sensitive to the Coulomb stress change. To verify, if the similar phenomena are widespread, we used the same filtering to observecontrastively continuous waveform data before, and 5 h after, the Ms7.0 Lushan earthquake and Ms9.0 Tohoku earthquake in 2011. The results show that the similar phenomena occur before the earthquakes, but the seis- micity rates after the earthquakes are remarkably increased. Since these weak earthquakes are quite small, it is hard to get clear phase arrival time from three or more stations to locate them. In addition, the travel time differences between P waves and S waves （S-P） are all less than 4 s, that means the events should occur in 34 km around the stations in the volcanic region. The stress of initial dynamic triggering of the Ms9.0 Tohoku earthquake was about 0.09 MPa, which is much higher than the threshold value of dynamic triggering stress. The earthquakes after the Ms9.0 Tohoku earthquake are related to dynamic triggering stress, but the events before the earthquake cannot be linked to seismic events, but may be related to the back- ground seismicity or from other kinds of local sources, such as anthropogenic sources （i.e., explosions）. Using two teleseismic filtering, the small background earthquakes in the Datong volcanic region occur frequently, thus we postulate that previous catalog does not apply bandpass filter to pick out the weak earthquakes, and some of the observed weak events were not triggered by changes in the dynamic stress field.  相似文献   

山东鲁山混合岩表面发现第四纪冰川剥蚀的直接证据——颤痕   总被引：1，自引：0，他引：1  

吕洪波  徐兴永  易亮  李萍 《地质学报》2012,86(3):514-521

本文首次报道了在山东鲁山南坡山谷发现混合岩表面的颤痕。颤痕是冰川底部携带的岩石碎块在下伏基岩表面刮凿而形成的一系列弧形裂隙,颤痕的弧形突出方向与冰川运动方向一致,而裂隙也是向下游方向深入基岩内部,其中突出的中间部位裂隙最深,向两端逐渐变浅直至消失。作者探讨了颤痕的形成机理,认为:颤痕相当于主剪切面上的伴生构造——R剪切面,在剖面上看就是一系列雁列式排列的R面,它不仅是冰川在基岩上运动留下的重要证据,而且还能指示冰体的运动方向。除了颤痕之外,在鲁山山麓还分布着大量的冰碛地貌:巨漂砾、冰碛堤等,在鲁山山脊上还见有典型的壶穴、冲刷槽等冰川融水侵蚀标志。这些标志与颤痕一起构成了强大的证据群,揭示了中国东部曾经发育过第四纪冰川的历史。中国东部是否发育过第四纪冰川?地学界已经争论了80多年,而颤痕的发现为进一步肯定中国东部存在第四纪冰川活动提供了最直接的证据。  相似文献   

地震预测:从芦山地震到大陆地震   总被引：5，自引：0，他引：5       下载免费PDF全文

李德威  陈桂凡  陈继乐  郝海健 《地学前缘》2013,20(3):1-10

自从1990年以来,通过对青藏高原的调查和研究,认识到下地壳流动同步形成盆地和造山带,并受控于相关洋盆地幔软流圈向大陆的顺层流动和底辟作用。下地壳不均匀流动通过韧脆性中地壳热能-应变能转换孕育地震,部分发震能量通过上地壳脆性断层释放。在地震孕育过程中通常会伴生跨年度干旱和异常降雨,构成热灾害链。近5年内青藏高原东部连续发生汶川、玉树、芦山大地震,形成于从亚东流经羊八井、安多、玉树并分支流向汶川和芦山—康定的下地壳"热河"的仰冲式和侧冲式撞击作用。从2008年9月以来连续发表5篇论文,根据地壳热构造和热灾害链的时空结构对芦山地震的三要素进行了长期和中期预测。2008年9月预测从2013年开始可能发生大地震,2012年9月将鲜水河—安宁河—小江异常热流构造带5年内将发生多个7级地震的首个大震锁定在芦山或西昌。芦山地震只释放了亚东—羊八井—安多—玉树—鲜水河—安宁河—小江"热河"剩余热能中的一小部分,在西昌—会理—昭通地区、道孚—康定地区、通海—石屏地区近5年内很可能发生4个7级左右的地震。此外,华北典型的热灾害链结构表明震情严峻,环渤海地区近3年内很可能发生大地震。从地震热流体撞击机理与地震异常之间的关联性出发,提出了动态立体监测及短临预测地震的思路和方法。  相似文献   

芦山地震：一个成功的中期预测案例   总被引：1，自引：0，他引：1       下载免费PDF全文

曾佐勋  王杰 《地学前缘》2013,20(3):21-24

2013年4月20日MS 7.0级芦山地震是2008年汶川地震以后龙门山断裂带的又一个灾难性的地质事件。文中回顾了对芦山地震的成功中期预测并给出了预测的依据。2012年11月25日上午,中国地球物理学会天灾预测专业委员会讨论中国西南地区中期地震预测问题。专业委员会主任耿庆国回顾了2012年4月作出的中期预测,认为2012年5月至2013年5月期间,在我国西南地区可能存在MS 7~8级地震。参加会议的委员们同意这一时间预测和震级预测,但是在震中位置预测方面存在不同意见。文章第一作者在会上作了一个报告,并展示了确切的震中预测位置图,即位于四川省雅安与康定连线的中间位置。这一预测的依据主要有两个方面：一方面,雅安西侧与汶川两地,具有两个特征相同的独立的卫星重力局部高异常;二是汶川(5·12)大震只是释放了龙门山断裂带北东段的能量和应力,这导致能量和应力在龙门山断裂带南西段,特别是南西端与重力异常突变叠加区(即中上地壳密度突变区)的加速积累和集中。芦山地震震中位于雅安芦山,与预测震中位置仅相差80 km,发震时间在2013年5月前。芦山地震中期预测的成功给予我们很多启示。作为一种地质过程,地震应该有其自身的规律可循;成功的地震预测需要多方面观测信息的综合分析,正是基于此,目前迫切需要国家的或者国际的具有综合分析经验的专家组和有效的前兆信息平台;卫星重力异常数据的处理和更新将有助于缩小强震预测的包围圈。  相似文献