中国活动构造基本特征

最近20年来我国活动构造研究进入了定量研究阶段, 并取得了很大的进展. 总结这些定量研究成果, 编制了1∶400万中国活动构造图, 尽可能详尽地表示了活动断裂、活动褶皱、活动盆地、活动块体、火山和地震等不同类型的活动构造及其运动学参数, 总结了中国活动构造的基本特征. 喜马拉雅和台湾为板块现代活动边界构造带, 活动强烈, 断裂滑动速率大于15 mm/a; 大陆板内地区构造活动以块体运动为特征, 可以划分出不同级别的地壳和岩石圈块体, 其中以青藏、新疆和华北断块区现代构造活动最为强烈; 各区200多条活动构造带的运动学特征表明, 板内构造活动是一种有限制的低速率块体运动, 块体边界构造带的水平滑动速率一般小于10 mm/a, 最大为10~15 mm/a, 因而不支持高速率滑动的逃逸理论.     

安徽淮河构造变形带及邻近块体现代构造应力场特征

针对安徽省较特殊的构造环境及历史地震分布特点，利用直达波最大振幅比和系统聚类分析方法，在对安徽淮河中游区1974年以来近百个中小地震震源机制反演、聚类及空间合成的基础上，分析了华北断块南缘的安徽淮河构造变形带及邻近块体震源断层滑动方式、构造应力场分布及块体运动方式、应力场随时间变化等。结果显示：淮河构造变形带及其邻近块体上震源断层总体上以近走滑型或斜滑型破裂为主，但倾滑型破裂也占一定比例；该地区构造应力以水平作用为主，但也存在一定的垂向作用。其中淮北和皖中块体仍可能分别向SWW和NEE方向运动，并在淮河构造变形带上产生左旋剪切作用，呈现一定的继承性活动特征；各块(带)上主压应力P轴走向随时间的变化在总体上较为一致，而各时段之间P轴方位存在一定差异，显示安徽淮河中游区受华北和华南应力场的共同作用，但其地震活动可能主要受控于华北应力场。     

福建地壳运动与地震关系初探

基于福建省2005~2009年的GPS观测资料研究福建地区地块运动的时空变化特征。结合福建地区地质构造、区域构造变形资料,分析了福建块体的时间序列、计算了小区域内一固定不动点下各GPS观测点运动速率,探讨福建地区活动地块边界带的运动及块体内部变形的规律。     

滇缅活动地块构造应力场研究

本文收集了1976—2017年滇缅活动地块98个M_W 4.8—7.0地震的震源机制解,分析震源机制解和震源深度的空间分布特征,探讨了其构造动力学背景。结果表明:①滇缅活动地块震源深度优势分布范围为10—30km,90%以上的地震震源深度小于30km,结合研究区统计时段内地震震源深度、优势度、众数等参数,推断滇缅活动地块及周边震源深度的下界为30km,脆性多震层位于10—30km,且主要位于15km附近;②滇缅活动块体不同断裂带、块体内部各次级块体之间、块体内外表现出不同的震源机制解,在空间上存在着明显的分区性特征,揭示出位于青藏高原东南缘的滇缅活动块体及周边地区应力场的非均匀性;③滇缅活动地块区域构造应力场明显受周边板块作用的控制,活动地块内部由于构造格局及其运动的差异,应力状态具有明显的区域特征。根据研究区各主要断裂带所反映的与构造背景作用一致的震源机制分布特征,可以将滇缅活动地块初步分为3个应力区。     

汉中与安康盆地地震活动特征

根据块体内地震受块体边缘地震影响的观点,对汉中与安康盆地的历史及现代地震活动特点、规律进行了讨论和分析。得到这样结果：(1)块体内断陷盆地的地震活动水平将小于块体边界上的地震活动水平;(2)块体内盆地的地震活动,主要受块体边缘较大地震活动的影响,反映块体边界较大地震发生前后其附近构造的调整运动;(3)当与块体内盆地较近的块体交界带上发生大地震时,应注意盆地的地震危险。     

从胶南地区断裂与地震活动关系研究胶南块体稳定性

通过搜集资料和野外地质调查,对胶南块体周边及内部主要断裂的最新活动进行了判定,结合研究区的地震活动情况进行分析,得出了该区构造活动较弱、与地震活动情况较为一致的结论,据前人研究,胶南块体隶属于苏鲁造山带,其周边断裂都具有一定的新活动迹象,而内部断裂活动性弱,证明胶南块体内部相对稳定。     

由GPS观测结果推断中国大陆活动构造边界

利用“中国地壳运动观测网络”基本网1998年和2000年两期观测数据,得到分布在全国各构造块体上的79个GPS观测站速度场，对中国大陆主要活动构造块体间的相对运动显著性进行了分析和检验. 分析结果表明，西部活动构造块体的边界有较明显的相对运动，而东部运动不明显. 根据分析得到的活动边界，将中国大陆归并为11个活动块体，逐一计算了这些块体边界的活动量大小，确定了它们最新活动的方式.     

华北北部GPS观测(195～1996)及其结果解释

利用１９９５和１９９６年华北地区两期ＧＰＳ复测资料,计算研究了该区现阶段的构造块体运动。结果说明,该区现阶段的构造运动可用鄂尔多斯块体、晋冀鲁块体、胶辽块体和阴山 燕山块体４块体运动模型进行描述和分析。鄂尔多斯块体与晋冀鲁块体之间差异活动较强烈,阴山 燕山块体与晋冀鲁块体之间较弱,郯庐断裂带居中。结果还表明渤海可能仍有一定的扩张活动。若以鄂尔多斯块体为本区参照,其东部各块体均向东移动     

相对于一组稳定点的位移的确定方法

在分析地壳变形时,除了要确定各构造块体间的相对运动外,常常还需要确定各构造块体本身的变形状态,为此介绍了确定某一个构造块体内的变形监测点相对于该块 内一 相对稳定点位移的几种方法,并用一个例子证明这些方法可得到基本相同的结果,因而可根据资料处理不同的需要加以选用。得到的这种位移可作为各块体变形分析的基础。     

中国大陆活动地块边界带与强震活动

本文在前人对中国大陆及周边活动地块研究和划分的基础上，系统研究了6个Ⅰ级活动地块区和22个Ⅱ级活动地块之间共26个活动边界带的构造变形与强震活动，包括强震分布与活动边界带的关系，边界带构造活动速率与地震活动水平及强震复发期等的关系. 给出了边界带强震活动水平与构造活动速率之间的线性关系和强震复发期长短与构造活动速率的反向变化关系. 从而进一步揭示了中国大陆活动地块构造及其块体运动特征，以及块体边界带的构造变形对强震的控制作用.     

现今区域活动块体划分方法研究

本文提出的将拟准检定法与DDA正分析方法相结合进行区域活动块体的划分，改善了观测资料缺乏区域的活动块体划分结果，为完整地研究区域活动块体运动变形提供了一种思路。另外，以川滇地区为实例，对该方法的具体实施作了简单的介绍。     

青藏高原东部构造块体的运动学及形变特征分析

通过分析青藏高原东部的活动断裂资料和GPS速度场数据,试图阐述活动地块的几何学、运动学和形变特征。初步认为:(1)第四纪特别是晚更新世以来的活动地块边界带与早期的构造单元边界密切相关,但也具有明显的新生性;(2)根据两种资料推导出的各个活动地块的运动学特征基本上是吻合的,其中鲜水河-玉树-玛尼断裂带是一条重要的分界线,其南、北部活动地块的运动方式差异明显;(3)除了活动地块的边界带强烈活动外,各个地块内部也显示出很强的变形;(4)晚更新世以来,青藏高原地壳的运动学和形变特征表现为在印度板块挤压力作用下,活动地块在向NE方向的运动过程中遇到稳定地块阻挡,调节方式是地壳增厚以及南、北部地块分别向SE-SSE和NWW-W方向的构造软弱部位水平侧向迁移。     

Active blocks and strong seismic activity in North China region

The active North China block consists of three second-order blocks: Ordos, North China Plain, and East Shandong-Huanghai Sea blocks. Two active tectonic zones, the Anyang-Heze- Linyi and Tangshan-Cixian zones, exist in the active North China Plain block and have separated the active block into 3 third-order active blocks, Taihangshan, Hebei-Shandong, and Henan-Huai blocks. The 3 third-order active blocks are characterized by their entire motion and are clearly different in their Cenozoic structures and deep structures. The active boundary tectonic zones between the third-order active blocks are less than those between the first- and second-order active blocks in their movement strength, extent, and seismic activity. The density of M ≥ 6 earthquakes in the boundary zones between active blocks is higher than that within the blocks by 9-22 times in the North China region, up to one order of magnitude on average. M ≥ 7 earthquakes occurred basically in the boundary zones between active blocks. The difference is not occasional, but reflects the nature of intraplate movement and the characteristics of strong seismic activity and is the powerful evidence for hypothesis of active blocks.     

Active blocks and strong seismic activity in North China region

The active North China block consists of three second-order blocks: Ordos, North China Plain, and East Shandong-Huanghai Sea blocks. Two active tectonic zones, the Anyang-Heze-Linyi and Tangshan-Cixian zones, exist in the active North China Plain block and have separated the active block into 3 third-order active blocks, Taihangshan, Hebei-Shandong, and Henan-Huai blocks. The 3 third-order active blocks are characterized by their entire motion and are clearly different in their Cenozoic structures and deep structures. The active boundary tectonic zones between the third-order active blocks are less than those between the first- and second-order active blocks in their movement strength, extent, and seismic activity. The density of M· ·6 earthquakes in the boundary zones between active blocks is higher than that within the blocks by 9–22 times in the North China region, up to one order of magnitude on average. M· · 7 earthquakes occurred basically in the boundary zones between active blocks. The difference is not occasional, but reflects the nature of intraplate movement and the characteristics of strong seismic activity and is the powerful evidence for hypothesis of active blocks.     

Experiment of Dividing the Active Blocks Based on Horizontal Crustal Movement Observed by GPS

In this paper, the discrepancy between the movements of intraplate blocks and plates isdiscussed, and the method to divide the intraplate active blocks is presented by selecting Bursaformula as the kinematic model for the intraplate blocks. Based on the data of three GPScampaigns in North-China network in l995, 1996 and l999, respectively, the northern area inNorth China is divided into eight small blocks with the mathematical model and methodpresented in this paper. The divided blocks based on tbe horizontal and vertical crustalmovements in the paper are consistent or approximate with each other in the area as a whole.The divided blocks in the paper is also basically accordant with the neotectonic movement,which indicates that the current movement of active blocks in this area is the succession anddevelopment of neotectonic movement. Moreover, some new activity characteristics in the areahave been revealed by the tectonic units divided with the horizontal crustal movement.     

Movement and strain conditions of active blocks in the Chinese mainland

The definition of active block is given from the angles of crustal deformation and strain. The movement and strain parameters of active blocks are estimated according to the unified velocity field composed of the velocities at 1598 GPS stations obtained from GPS measurements carried out in the past years in the Chinese mainland and the surrounding areas. The movement and strain conditions of the blocks are analyzed. The active blocks in the Chinese mainland have a consistent E-trending movement component, but its N and S components are not consistent. The blocks in the western part have a consistent N-trending movement and the blocks in the eastern part have a consistent S-trending movement. In the area to the east of 90°E, that is the area from Himalayas block towards NE, the movement direction of the blocks rotates clockwisely and the movement rates of the blocks are different. Generally, the movement rate is large in the west and south and small in the east and north with a difference of 3 to 4 times between the rates in the west and east. The distributions of principal compressive strain directions of the blocks are also different. The principal strain of the blocks located to the west of 90oE is basically in the SN direction, the principal compressive strain of the blocks in the northeastern part of Qingzang plateau is roughly in the NE direction and the direction of principal compressive strain of the blocks in the southeastern part of Qingzang plateau rounds clockwisely the east end of Himalayas structure. In addition, the principal strain and shear strain rates of the blocks are also different. The Himalayas and Tianshan blocks have the largest principal compressive strain and the maximum shear strain rate. Then, Lhasa, Qiangtang, Southwest Yunnan (SW Yunnan), Qilian and Sichuan-Yunan (Chuan-Dian) blocks followed. The strain rate of the blocks in the eastern part is smaller. The estimation based on the stain condition indicates that Himalayas block is still the area with the most intensive tectonic activity and it shortens in the NS direction at the rate of 15.2±1.5 mm/a. Tianshan block ranks the second and it shortens in the NS direction at the rate of 10.1±0.9 mm/a. At present, the two blocks are still uprising. It can be seen from superficial strain that the Chinese mainland is predominated by superficial expansion. Almost the total area in the eastern part of the Chinese mainland is expanded, while in the western part, the superficial compression and expansion are alternatively distributed from the south to the north. In the Chinese mainland, most EW-trending or proximate EW-trending faults have the left-lateral or left-lateral strike-slip relative movements along both sides, and most NS-trending faults have the right-lateral or right-lateral strike-slip relative movements along both sides. According to the data from GPS measurements the left-lateral strike-slip rate is 4.8±1.3 mm/a in the central part of Altun fault and 9.8±2.2 mm/a on Xianshuihe fault. The movement of the fault along the block boundary has provided the condition for block movement, so the movements of the block and its boundary are consistent, but the movement levels of the blocks are different. The statistic results indicate that the relative movement between most blocks is quite significant, which proves that active blocks exist. Himalayas, Tianshan, Qiangtang and SW Yunnan blocks have the most intensive movement; China-Mongolia, China-Korea (China-Korea), Alxa and South China blocks are rather stable. The mutual action of India, Pacific and Philippine Sea plates versus Eurasia plate is the principal driving force to the block movement in the Chinese mainland. Under the NNE-trending intensive press from India plate, the crustal matter of Qingzang plateau moves to the NNE and NE directions, then is hindered by the blocks located in the northern, northeastern and eastern parts. The crustal matter moves towards the Indian Ocean by the southeastern part of the plateau.     

北京地区上地壳三维细结构层析成像

利用三维不分块地震层析成像技术对北京东北部地区的三维人工地震莫霍反射波走时数据进行反演,得到了该区上地壳的三维P波、S波慢度及波速比结构图像,三种结构不同深度的切片图像揭示出慢度和波速比分布有呈北东向和北西向展布的特征.断裂活动引起沉积不均匀造成现今的速度分布,地震大多分布在波速比较低的块体内,说明地震不仅与断裂活动有关,有可能还与物质结构和性质相关;北京地区上地壳速度结构、断裂活动和物质性质三者之间存在密切关系.     

Movement and strain conditions of active blocks in the Chinese mainland

The definition of active block is given from the angles of crustal deformation and strain. The movement and strain parameters of active blocks are estimated according to the unified velocity field composed of the velocities at 1598 GPS stations obtained from GPS measurements carried out in the past years in the Chinese mainland and the surrounding areas. The movement and strain conditions of the blocks are analyzed. The active blocks in the Chinese mainland have a consistent E-trending movement component, but its N and S components are not consistent. The blocks in the western part have a consistent N-trending movement and the blocks in the eastern part have a consistent S-trending movement. In the area to the east of 90°E, that is the area from Himalayas block towards NE, the movement direction of the blocks rotates clockwisely and the movement rates of the blocks are different. Generally, the movement rate is large in the west and south and small in the east and north with a difference of 3 to 4 times between the rates in the west and east. The distributions of principal compressive strain directions of the blocks are also different. The principal strain of the blocks located to the west of 90°E is basically in the SN direction, the principal compressive strain of the blocks in the northeastern part of Qingzang plateau is roughly in the NE direction and the direction of principal compressive strain of the blocks in the southeastern part of Qingzang plateau rounds clockwisely the east end of Himalayas structure. In addition, the principal strain and shear strain rates of the blocks are also different. The Himalayas and Tianshan blocks have the largest principal compressive strain and the maximum shear strain rate. Then, Lhasa, Qiangtang, Southwest Yunnan (SW Yunnan), Qilian and Sichuan-Yunan (Chuan-Dian) blocks followed. The strain rate of the blocks in the eastern part is smaller. The estimation based on the stain condition indicates that Himalayas block is still the area with the most intensive tectonic activity and it shortens in the NS direction at the rate of 15.2 ± 1.5 mm/a. Tianshan block ranks the second and it shortens in the NS direction at the rate of 10.1 ± 0.9 mm/a. At present, the two blocks are still uprising. It can be seen from superficial strain that the Chinese mainland is predominated by superficial expansion. Almost the total area in the eastern part of the Chinese mainland is expanded, while in the western part, the superficial compression and expansion are alternatively distributed from the south to the north. In the Chinese mainland, most EW-trending or proximate EW-trending faults have the left-lateral or left-lateral strike-slip relative movements along both sides, and most NS-trending faults have the right-lateral or right-lateral strike-slip relative movements along both sides. According to the data from GPS measurements the left-lateral strike-slip rate is 4.8 ± 1.3 mm/a in the central part of Altun fault and 9.8 ± 2.2 mm/a on Xianshuihe fault. The movement of the fault along the block boundary has provided the condition for block movement, so the movements of the block and its boundary are consistent, but the movement levels of the blocks are different. The statistic results indicate that the relative movement between most blocks is quite significant, which proves that active blocks exist. Himalayas, Tianshan, Qiangtang and SW Yunnan blocks have the most intensive movement; China-Mongolia, China-Korea (China-Korea), Alxa and South China blocks are rather stable. The mutual action of India, Pacific and Philippine Sea plates versus Eurasia plate is the principal driving force to the block movement in the Chinese mainland. Under the NNE-trending intensive press from India plate, the crustal matter of Qingzang plateau moves to the NNE and NE directions, then is hindered by the blocks located in the northern, northeastern and eastern parts. The crustal matter moves towards the Indian Ocean by the southeastern part of the plateau.     

Research on the Dividing Method for Present-Day Regional Active Block

INTRODUCTIONThe constant accumulation of large-range ,high-accuracy GPS observation data makes it possibleto studythe crustal movement in a range as large as possible .The demarcation of crustal blocks withdifferent deformation trends in the studied area and the elimination of the abnormal deformationinformation withinthe blocks ,are prerequisites to gain a correct acquisition of all parameters of theblock movement .The methods of dividing active blocks mainlyinclude 2 classes :one is ba…     

华北块体中等地震活动平静特征

采用累计频度方法,对华北活动地块Ms≥5．5地震前中等地震聚集活动区的地震做了时空扫描,并对平静现象进行了定量分析,结果表明：对各Ⅱ级活动地块采用不同的扫描方法．在强震前都表现出明显的增强、平静过程,平静的时间长短与所给定的构造区域有关。本文给出了华北3个Ⅱ级活动地块的发震模式。对各活动地块分别进行了R值检验,表明3个活动地块采用不同的发震模式均具有较高的预报效能。