南海东北部陆坡天然气水合物区的滑塌和泥火山活动

本文研究了南海东北部陆坡天然气水合物区滑塌和泥火山活动的特征及表现形式,探讨了滑塌和泥火山活动对天然气水合物成藏的影响,提出了滑塌主导和滑塌、泥火山共同作用两种控制模式。根据地震数据、浅层剖面和海底地形数据解释,将研究区划分为规则滑塌区和泥火山活动影响区,并识别出泥火山、泥火山脊、凹槽、凹坑等特征地形。滑塌和泥火山活动是陆坡天然气水合物发育区重要的地形控制因素,两种活动共同作用产生复杂的地形特征。综合多条地震测线中似海底反射层(BSR)形态、连续性和滑塌、泥火山活动的关系,认为滑塌控制的区域,BSR连续,天然气水合物储藏较完整,泥火山活动区天然气水合物储藏也仅受到局部破坏。同时指出滑塌和泥火山活动对研究区长期天然气渗漏活动具有重要作用。     

昆仑山与汶川强烈地震对青藏块体东北缘地壳运动及应变积累的影响

充分应用GPS、区域水准、跨断层等地形变观测资料, 借助非震负位错反演, 结合地震活动, 综合研究2001年11月14日昆仑山Ms8.1级地震对青藏块体东北缘地壳运动与应变积累的影响。通过分析笔者认为, 青藏块体内部Ms8.1级巨大地震能量释放产生的扰动应力场对NE向主压背景应力场的调制作用, 导致块体边界构造区域地壳差异运动和应力应变状态发生变化。其中, 对阿尔金断裂东段与祁连山断裂带西段的应变积累状态反映减缓为主的影响, 而对祁连山断裂带中东段则反映促进应变积累为主的影响。这种影响是一定时期、一定程度的。近期青藏块体东北缘区域应力场处于昆仑山、玉门、民乐等地震后的恢复状态。而由2008年5月12日汶川Ms8.0地震后有限的GPS、跨断层短水准观测资料, 可推测汶川地震对甘川交界东段-甘川陕交界区应变积累状况一定程度促进影响。     

Crustal structure of northeastern Tibet inferred from receiver function analysis

Sponsored by National Science & Technology Committee, the cooperation between China Academy of Geoscience and Institute of Geophysics and Tectonics, University Joseph, France conducted a lithospherical experiment using 40 Minititan 3-component and 13 CEIS 1-component seismometers along the road from Gonghe to Yushu in Qinghai Province during 5 months after June, 1998. The interested area is on the north of Bangong- Nujiang fault, the east of Qaidam basin, the south of Center Qilian fault and the west of Longmenshan fault. And the profile across most tectonic parts of Eastern Tibet such as Southern Qilian, Eastern Kunlun fault, Bayan Har terrane, Jinshajiang suture (Figure 1), which is the first seismological profile across Eastern Tibet (Qinghai-Tibet) and will be beneficial on the comparison with the results of its center parts, especially on the understanding of the effect of the thousands-kilometer-faraway collision between Eurasia Plate and Indian Plate on the uplifting of south and north part of Eastern Kunlun fault, and on the thickening of crust and the feature of deep structure of Qilian mountain on the north of Tibet Plateau.     

Characteristics of the mantle source region of sodium lamprophyres and petrogenetic tectonic setting in northeastern Hunan,China

~~Characteristics of the mantle source region of sodium lamprophyres and petrogenetic tectonic setting in northeastern Hunan,China~~     

Estimates of coda Q attenuation in the João Câmara area (Northeastern Brazil)

S coda wave of seventy-four local earthquakes recorded in a network of ten seismic stations were used to calculate coda Q attenuation (Q_c) in the João Câmara area (northeastern Brazil). The estimates show Q_c as a strong function of frequency in the range from 6.0 to 20.0 Hz. We found out that Q_c in João Câmara has a functional form given by Q_c= Q₀ f, where Q₀= 151 ± 99 and = 0.98 ± 0.05. If the standard deviations are taken into account,we conclude that there are no relevant changes in both Q₀ and values from one station to another. The estimated Q₀ values at the different stations suggest that the Samambaia fault is a boundary between two different seismic attenuation zones. In one side of the fault (left), where stations were installed in Pre-Cambrian terrain and thick sedimentary layer, the seismic attenuation is stronger than in the other side (stations installed in thin sedimentary layer and limestone outcrop).The anomalous Q₀ values in the left side of the Samambaia fault can be explained due to the presence of a shallow conductive layer in the upper crust( 10 km), such as proposed by Padilha et al. (1992). According to our results, if there is a conductive layer in the area, it probably spreads over João Câmara city and surrounding regions.However, more detailed investigation either with seismic methods (seismic attenuation,3D tomography with P and/or S wave velocities) or with other geophysical methods is needed to interpret the observed differences in Q₀ values between the two sides of the Samambaia fault.     

塔里木东北地区盆山耦合及其对油气成藏的控制

震旦纪一寒武纪库鲁克塔格、英吉苏地区为陆内裂谷盆地。加里东末期与早海西运动造成塔东地区的普遍抬升剥蚀，孔雀河斜坡、罗布庄凸起开始形成，早二叠世，塔里木板块与中天山地块、哈萨克斯坦一准噶尔板块最终碰撞拼贴，古天山造山带相继形成。燕山晚期，受中特提斯洋关闭影响。塔里木盆地基底随造山带的构造抬升而部分抬升，喜马拉雅期开始，在南北向挤压力作用下，收缩、隆升的山体侧向扩张，向沉积盆地逆冲形成型逆冲推覆构造。造山带和盆地的共同演化不仅形成了多套烃源岩，而且控制了古生界和中新生界两套不同的油气成藏系统。元古界地层由北向南推覆，可能预示着在库鲁克塔格南缘西段山前前寒武纪地层下部保存有古生代和中新生代烃源岩建造，如果配有有利的油气储盖组合和圈闭，有望在山前获得突破。     

Gravity evolution and earthquake activities of the northeastern edge of Qinghai-Xizang block

Introduction Earthquake is closely tied up with gravity on the basis of crustal deformation and crustaldensity change. With the accumulation of stress around the epicenter, the spatial position ofground point and density crustal medium will change with strain during the seismogenic processof an earthquake. All these factors will bring about the change of gravity field. Since the Xingtaiearthquake in China in 1966, mobile gravity measurements in a large scale and the studies ongravity var…     

Geomorphologic evidence of phased uplift of the northeastern Qinghai-Tibet Plateau since 14 million years ago

~~Geomorphologic evidence of phased uplift of the northeastern Qinghai-Tibet Plateau since 14 million years ago~~     

On the Age of the Ophiolitic Complexes in Northeastern Jiangxi:A Micropaleontological Analysis

The age assignment of cherts from ophiolitic/metamorphic complexes in northeastern Jiangxi is widely regarded as one of the crucial issues in the tectonic interpretation of South China. The ophiolitic and metamorphic complexes in northeastern Jiangxi have been traditionally regarded as part of the Proterozoic “Banxi (=Penhsi) Group” of the Jiangnan Uplift. However, recent reports of Late Paleozoic radiolarians from the rock complexes have caused some researchers to question the traditional interpretation of the tectonic and paleogeographic framework in the region; but other workers are suspicious about these findings. In order to test the validity of the putative radiolarians, we, an interdisciplinary study group including micropaleontologists, tectonic specialists and regional geologists, conducted field investigations and multiple re-samplings of the localities where the reported fossils were collected. Our comprehensive study shows that the chert of the ophiolitic complex and the associated low-grade metamorphic slate yield Mesoproterozoic and Neoproterozoic acritarchs, confirming the traditional view of their age assignment (Proterozoic); on the other hand, no recognizable radiolarian fossils have been discovered therein, thus raising questions about the recently published result of Paleozoic radiolarian findings. Probable causes for the putative radiolarian findings are thus discussed herein. Geochemical characteristics indicate that the chert sedimentation most probably occurred under a continental margin setting.     

Gravity evolution and earthquake activities of the northeastern edge of Qinghai-Xizang block

The relationship between temporal-spatial evolution of gravity and earthquake activity during 1992–2001 has been analyzed systematically by integrally adjusting the gravity observation data of the northeastern edge of Qinghai-Xizang (Qingzang) block. The result shows that the gravity observation data of the northeastern edge of Qingzang block obtained by using the uniform starting datum can completely reflect the precursory gravity information appearing during the seismogenic process. In the genesis stage of an earthquake, regional gravity anomaly appears in a large area, resulting in related local gravity anomaly. The dynamic image of gravity field can clearly reflect the orderly evolution and earthquake activity. Foundation item: Key Project of China Earthquake Administration during the tenth Five-year Plan (100501-05-05).