川西地区安宁河断层古地震行为及其与则木河断层的比较

安宁河断层与则木河断层是青藏高原东南川滇地块东边界断裂带的重要组成部分,晚第四纪以来变形样式主要以左旋走滑运动为主。安宁河断层走向近SN向,以冕宁为界分为南北两段,北段古地震复发周期500~700a,全新世以来左旋平均位移速率约4mm/a。南段的古地震研究程度较低,通过在月华一带开挖探槽及大量14C测年限定其大地震平均复发间隔为600~800a。则木河断层北接安宁河断层,全新世以来平均左旋位移速率为2.4~3.6mm/a,大地震复发周期约2 300a。对比安宁河断层与则木河断层的古地震行为,发现安宁河断层大地震复发间隔相对较短,平均左旋位移速率稍大,存在着古地震行为的不协调性。安宁河断层与则木河断层走向不一致、螺髻山的快速隆升以及安宁河断层南侧SN向展布的走滑断层系统等可能是造成安宁河-则木河断层古地震行为差异的原因。     

龙陵-瑞丽断裂(南支)北段晚第四纪活动性特征

遥感影像解译和野外地质地貌调查表明,龙陵-瑞丽断裂(南支)北段是以左旋走滑为主兼张性正断的区域性活动断裂。根据一些断错地貌点的大比例尺填图、实地测量及其年代学分析,确定了该断裂为全新世活动断裂,断裂晚更新世以来的平均水平滑动速率为2.2mm/a,平均垂直滑动速率为0.6mm/a;全新世以来的平均水平滑动速率为1.8～3.0mm/a,平均垂直滑动速率为0.5mm/a。断裂晚更新世以来的滑动速率在不同的时间尺度上变化不大,反映了该断裂晚更新世以来的活动强度比较平稳     

HOLOCENE LEFT-LATERAL SLIP RATE OF THE LENGLONGLING FAULT,NORTHEASTERN MARGIN OF THE TIBETAN PLATEAU

The Lenglongling Fault(LLLF) is a major active left-lateral strike-slip fault along the northeastern margin of the Tibetan plateau. Fault slip rate is of great significance for researching the dynamics of tectonic deformation in NE Tibetan plateau and understanding the activity and seismic risk of the fault. However, slip rate of the LLLF, which remains controversial, is limited within~3~24mm/a, a relatively broad range. Taking Niutougou site(37.440 2°N, 102.094 0°E)and Chailong site(37.447 3°N, 102.063 0°E) in the upstream of Talihua gully in Menyuan County, Qinghai Province as the research objects, where faulted landform is typical, we analyzed the displacement evolution model and measured the slip amounts by back-slip of the faulted landform using high-resolution DEM from Terrestrial LiDAR and high-precision satellite images of Google Earth, and by collecting and testing samples from stratigraphic pit excavated in the faulted landform surface and stripping fresh stratigraphic section, we determined the abandonment age of the surface. Holocene slip rate obtained from Niutougou site and Chailong site is(6.4±0.7)mm/a and(6.6±0.3)mm/a, respectively, which have a good consistency. Taking into account the error range of the slip rate, the left-lateral slip rate of the LLLF is(6.6±0.8)mm/a since Holocene, which is between the previons results from geological method, also within the slip rate range of 4.2~8mm/a from InSAR, but slightly larger than that from GPS((4.0±1.0)mm/a). Late Quaternary slip rate of Qilian-Haiyuan fault zone, which displays an arc-shape distribution, turns to be the largest in LLLF region. The most intensive uplift in the LLLF region of the NE Tibetan plateau confirms the important role of the LLLF in accommodating the eastward component of movement of Tibetan plateau relative to the Gobi-Ala Shan block from one side.     

东昆仑活动断裂带东段全新世滑动速率研究

文中通过对东昆仑活动断裂带托索湖至玛曲段的实际野外测量,获得了该段上的1组断裂位错实测数据和14C及TL测年样品。通过室内分析研究,发现大体以阿尼玛卿山玛积主峰为界,东昆仑活动断裂带托索湖至玛曲段可再分为花石峡段和玛沁段2个在几何上不连续的段落,花石峡段的全新世水平滑动速率(115±11)mm/a明显高于玛沁段(70±06)mm/a。此外,由于断裂而引起的断裂两侧的差异垂直隆升速率,花石峡段自4kaBP以来约为(21±03)mm/a,玛沁段自10kaBP以来约为055mm/a。这种差异垂直隆升速率的明显变化,一方面反映了东昆仑活动断裂带不同段落上活动的差异,另一方面也可能反映了研究区内全新世以来的快速隆升     

口泉断裂中段晚第四纪以来断错地貌及滑动速率确定

通过口泉断裂1/5万地质填图,调查了口泉断裂中段(上神泉至杨家窑段)晚第四纪以来断错地貌特征.从山麓麓原面到山间沟谷河床一共可以划分出5级层状地貌面,最顶部(第5级地貌面)为山麓剥蚀面,推测为形成于新近纪的唐县期夷平面;第4级地貌面由大河间T3阶地以及山麓地带发育的同期洪积台地组合而成,形成于中更新世末、晚更新世初;第...     

安宁河断裂带北段的最新地面活断层与地震潜在能力研究

从最新地面活断层的不连续性,断层滑动速率以及古地震研究的角度讨论安宁河断裂带北段的地震潜在能力,认为不连续的活断层可能成为各自独立的地震破裂单元,从而决定了地震的潜在能力,其中,野鸡洞破裂段的潜在地震能力最强,可达7级。上次地震至今的平静时间已接近古地震的平均重现间隔,因而具有高度的地震危险性     

宗务隆山南缘断裂构造地貌特征与晚第四纪滑动速率

宗务隆山南缘断裂位于柴达木盆地东北缘,是祁连山南缘与柴达木盆地的边界逆断裂,对其晚第四纪活动性进行研究对于理解祁连山地区应变分配模式以及该地区断裂向柴达木盆地内部的挤压扩展过程具有重要意义。文中通过遥感影像解译和野外地质调查,结合GPS地形剖面测量以及宇宙成因核素与光释光定年,对宗务隆山南缘断裂拜京图和蓄集乡等段落开展了详细的研究。综合分析拜京图和蓄集乡地区不同期次洪积扇的垂直位错以及相应地貌面的年龄,得到宗务隆山南缘断裂晚第四纪以来的平均垂直滑动速率为(0. 41±0. 05) mm/a,水平缩短速率为0. 47～0. 80mm/a,约占祁连山地区地壳缩短速率的10%。这些结果有助于进一步理解祁连山地区的应变分配模式以及柴达木盆地北缘地区的构造变形机制。     

GEOMORPHIC FEATURES AND LATE QUATERNARY SLIP RATE OF THE SOUTHERN ZONGWULONG SHAN FAULT

With the continuous collision of the India and Eurasia plate in Cenozoic, the Qilian Shan began to uplift strongly from 12Ma to 10Ma. Nowadays, Qilian Shan is still uplifting and expanding. In the northern part of Qilian Shan, tectonic activity extends to Hexi Corridor Basin, and has affected Alashan area. In the southern part of Qilian Shan, tectonic activity extends to Qaidam Basin, forming a series of thrust faults in the northern margin of Qaidam Basin and a series of fold deformations in the basin. The southern Zongwulong Shan Fault is located in the northeastern margin of Qaidam Basin, it is the boundary thrust fault between the southern margin of Qilian Shan and Qaidam Basin. GPS studies show that the total crustal shortening rate across the Qilian Shan is 5~8mm/a, which absorbs 20% of the convergence rate of the Indian-Eurasian plate. Concerning how the strain is distributed on individual fault in the Qilian Shan, previous studies mainly focused on the northern margin of the Qilian Shan and the Hexi Corridor Basin, while the study on the southern margin of the Qilian Shan was relatively weak. Therefore, the study of late Quaternary activity of southern Zongwulong Shan Fault in southern margin of Qilian Shan is of great significance to understand the strain distribution pattern in Qilian Shan and the propagation of the fault to the interior of Qaidam Basin. At the same time, because of the strong tectonic activity, the northern margin of Qaidam Basin is also a seismic-prone area. Determining the fault slip rate is also helpful to better understand the movement behaviors of faults and seismic risk assessment.Through remote sensing image interpretation and field geological survey, combined with GPS topographic profiling, cosmogenic nuclides and optically stimulated luminescence dating, we carried out a detailed study at Baijingtu site and Xujixiang site on the southern Zongwulong Shan Fault. The results show that the southern Zongwulong Shan Fault is a Holocene reverse fault, which faulted a series of piedmont alluvial fans and formed a series of fault scarps.The 43ka, 20ka and 11ka ages of the alluvial fan surfaces in this area can be well compared with the ages of terraces and alluvial fan surfaces in the northeastern margin of Tibetan Plateau, and its formation is mainly controlled by climatic factors. Based on the vertical dislocations of the alluvial fans in different periods in Baijingtu and Xujixiang areas, the average vertical slip rate of the southern Zongwulong Shan Fault since late Quaternary is(0.41±0.05)mm/a, and the average horizontal shortening rate is 0.47~0.80mm/a, accounting for about 10% of the crustal shortening in Qilian Shan. These results are helpful to further understand the strain distribution model in Qilian Shan and the tectonic deformation mechanism in the northern margin of Qaidam Basin. The deformation mechanism of the northern Qaidam Basin fault zone, which is composed of the southern Zongwulong Shan Fault, is rather complicated, and it is not a simple piggy-back thrusting style. These faults jointly control the tectonic activity characteristics of the northern Qaidam Basin.     

THE HOLOCENE ACTIVITY AND STRIKE-SLIP RATE OF THE SOUTHERN SEGMENT OF XIAOJIANG FAULT IN THE SOUTHEASTERN YUNNAN REGION,CHINA

The southern segment of the Xiaojiang Fault (SSXF) is located at the intersection of the Xianshuihe-Xiaojiang Fault and Red River-Ailao Shan fault systems in the southeast margin of the Tibetan plateau. Based on the interpretation of remote sensing image, the SSXF clearly shows the linear feature and continuous distribution as a single, penetrating fault. It has a total length of about 70km, trends generally about 20° to the northeast and protrudes slightly in the middle to the east. A typically geomorphologic phenomenon about the synchronous left-lateral dislocation of ridges and gullies can be found at Liangchahe, Longtan Village along the SSXF. The distribution of faults, the sedimentary features, attitude variance and the primary dating results of the offset strata in the trench section across fault sag ponds reveal three paleoseismic events rupturing obviously the surface, which demonstrates that the SSXF has the ability of recurrence of strong earthquakes. High-precision topographic map about two gullies and the platform between them with synchronous dislocation is acquired by using the Trimble 5800 GPS real-time difference measurement system. The dislocation is (18.3±0.5)m. As the top geomorphologic surface between the above two gullies and their adjacent area, the terrace surface T₂ stopped accepting deposits at ~2606a, based on the linear regression analysis of three dating data. According to the geological method, a sinistral strike-slip rate of (7.02±0.20)mm/a on the SSXF in the Holocene is obtained, which has a good consistency with the results provided by using GPS data. The preliminary results about the Holocene activity and slip rate of the SSXF demonstrate that the southward or south-southeast motion of the Sichuan-Yunnan block in the SE Yunnan region has not been absorbed by the possible shortening deformation and the sinistral strike-slip rate of the SSXF has not been drastically reduced. The SSXF is a Holocene fault with obvious activity. This preliminary understanding provides some basic geological data for the seismic risk evaluation of the SSXF in the future, and for the establishment and inspection of the seismotectonic model about the Sichuan-Yunnan block.     

NEW ACTIVITY CHARACTERISTICS AND SLIP RATE OF THE EBOMIAO FAULT IN THE SOUTHERN MARGIN OF BEISHAN,GANSU PROVINCE

The Ebomiao Fault is a newly discovered active fault near the block boundary between the Tibetan plateau and the Alashan Block. This fault locates in the southern margin of the Beishan Mountain, which is generally considered to be a tectonically inactive zone, and active fault and earthquake are never expected to emerge, so the discovery of this active fault challenges the traditional thoughts. As a result, studying the new activity of this fault would shed new light on the neotectonic evolution of the Beishan Mountain and tectonic interaction effects between the Tibetan plateau and the Alashan Block. Based on some mature and traditional research methods of active tectonics such as satellite image interpretation, trenches excavation, differential GPS measurement, Unmanned Aircraft Vehicle Photogrammetry(UAVP), and Optical Stimulated Luminescence(OSL)dating, we quantitatively study the new activity features of the Ebomiao Fault.
Through this study, we complete the fault geometry of the Ebomiao Fault and extend the fault eastward by 25km on the basis of the 20km-fault trace identified previously, the total length of the fault is extened to 45km, which is capable of generating magnitude 7 earthquake calculated from the empirical relationships between earthquake magnitude and fault length. The Ebomiao Fault is manifested as several segments of linear scarps on the land surface, the scarps are characterized by poor continuity because of seasonal flood erosion. Linear scarps are either north- or south-facing scarps that emerge intermittently. Fourteen differential GPS profiles show that the height of the north-facing scarps ranges from (0.22±0.02)m to (1.32±0.1)m, and seven differential GPS profiles show the height of south-facing scarps ranging from (0.33±0.1)m to (0.64±0.1)m. To clarify the causes of the linear scarps with opposite-facing directions, we dug seven trenches across these scarps, the trench profiles show that the south-dipping reverse faults dominate the north-facing scarps, the dipping angles range from 23° to 86°. However, the south-facing scarps are controlled by south-dipping normal faults with dipping angles spanning from 60° to 81°.
The Ebomiao Fault is dominated by left-lateral strike-slip activity, with a small amount of vertical-slip component. From the submeter-resolution digital elevation models(DEM)constructed by UAVP, the measured left-lateral displacement of 19 gullies in the western segment of the Ebomiao Fault are(3.8±0.5)~(105±25)m, while the height of the north-facing scarps on this segment are(0.22±0.02)~(1.32±0.10)m(L₃-L₇), the left-lateral displacement is much larger than the scarp height. In this segment, there are three gullies preserving typical left-lateral offsets, one gully among them preserves two levels of alluvial terraces, the terrace riser between the upper terrace and the lower terrace is clear and shows horizontal offset. Based on high-resolution DEM interpretation and displacement restoration by LaDiCaoz software, the left-lateral displacement of the terrace riser is measured to be(16.7±0.5)m. The formation time of the terrace riser is approximated by the OSL age of the upper terrace, which is (11.2±1.5)ka BP at (0.68±0.03)m beneath the surface, and(11.4±0.6)ka at (0.89±0.03)m beneath the surface, the OSL age (11.2±1.5)ka BP at (0.68±0.03)m beneath the surface is more close to the formation time of the upper terrace because of a nearer distance to sediment contact between alluvial fan and eolian sand silt. Taking the (16.7±0.5)m left-lateral displacement of the terrace riser and the upper terrace age (11.2±1.5)ka, we calculate a left-lateral strike-slip rate of(1.52±0.25)mm/a for the Ebomiao Fault. The main source for the slip rate error is that the terrace risers on both walls of the fault are not definitely corresponded. The north wall of the fault is covered by eolian sand, we can only presume the location of terrace riser by geomorphic analysis. In addition, the samples used to calculate slip rate before were collected from the aeolian sand deposits on the north side of the fault, they are not sediments of the fan terraces, so they could not accurately define the formation age of the upper terrace. This study dates the upper terrace directly on the south wall of the fault.
Since the late Cenozoic, the new activity of the Ebomiao Fault may have responded to the shear component of the relative movement between the Tibetan plateau and the Alashan Block under the macroscopic geological background of the northeastern-expanding of the Tibetan plateau. The north-facing fault scarps are dominated by south-dipping low-angle reverse faults, the emergence of this kind of faults(faults overthrusting from the Jinta Basin to the Beishan Mountain)suggests the far-field effect of block convergence between Tibetan plateau and Alashan Block, which results in the relative compression and crustal shortening. As for whether the Ebomiao Fault and Qilianshan thrust system are connected in the deep, more work is needed.     

安宁河断裂带晚第四纪运动特征及模式的讨论

安宁河断裂带是中国西南地区一条重要的地震活动断层, 地方志记载公元1536年曾发生过震级大于7级的破坏性地震. 详细的断裂地貌航片解译和野外调查表明, 安宁河断裂带除具有主要的左旋走滑断层活动外,还兼有重要的逆冲运动分量. 根据冲沟和阶地面的位错量及其热释光测年结果估计,该断裂带晚更新世以来平均左旋走滑速率为3~7 mm/a. 根据滑移方向与断层走向的关系,推测跨安宁河断裂带东西向由于逆冲断层运动造成的挤压缩短速率约为1.7~4.0 mm/a; 简单分解鲜水河断裂带上的滑动速率,估计分配在大凉山断裂带上的滑动速率与安宁河断裂带上的大致相当,约为3~7 mm/a. 此外,根据野外调查结果,并结合最近青藏高原构造动力学研究的新认识, 建立了安宁河断裂带的动力学模型,认为安宁河断裂带是一条逆冲走滑断裂带. 其下盘（西盘）主动向南东方向下插,造成了上盘（东盘）向北西方向的上冲运动.      

LATE QUATERNARY PALEOEARTHQUAKES ON THE MIDDLE SEGMENT OF THE LIJIANG-XIAOJINHE FAULT,SOUTHEASTERN TIBET

More attention has been paid to the late Quaternary activity of the boundary fault of the Sichuan-Yunnan block in eastern Tibet. The Lijiang-Xiaojinhe Fault (LXF) locates along the boundary of the northwest Sichuan and central Yunnan sub-blocks in the Sichuan-Yunnan block. Clear displaced landforms show that the fault has undergone strong late-Quaternary activity. However there is no surface-rupturing earthquake occurring on the LXF in the historical record. The LXF crosses the city of Lijiang, one of the most important tourist cities in Southwest China. The rupture behavior on this fault remains unclear and it is hard to assess its seismic hazard in the future. In this study, on the base of the interpretation of high-resolution satellite imagery, we chose the middle segment of the LXF and dug three trenches at Muzhuda, Hongxing, and Gantangzi sites to constrain the ages of paleoearthquakes combined with radiocarbon dating and OxCal modeling. The Muzhuda trench shows that at least three events occurred on the middle segment of the LXF at 7 940~6 540a BP, 4 740~4 050a BP and 1 830~420a BP, respectively. The Hongxing trench indicates that the LXF underwent two events at 5 120~3 200a BP and 2 100~1 220a BP. The Gantangzi trench reveals at least three paleoearthquakes at 44 980~17 660a BP, 7 210~3 810a BP and 2 540~1 540a BP, respectively. The events in the Gantangzi trench might be incomplete because of stratigraphic gap. These three trenches indicate that three events occurred on the middle segment of the LXF in the Holocene at 7 940~7 210a BP, 4 740~4 050a BP and 1 830~1 540a BP, respectively. Large earthquakes on the middle segment of the LXF appear to fit the quasi-periodic model with the mean recurrence interval of~3 000a and the estimated magnitude 7.5. Given the strong late-Quaternary activity of the middle segment of the LXF and a long elapsed time, we propose that the middle segment of the LXF might have a high seismic hazard potential in the near future.     

阿尔金断裂带东段第四纪以来的水系位错与滑动速率

从阿克塞西红崖子向东经肃北至红柳峡口长约 150km的范围内 ,通过沟、脊位错的分级与相关阶地年龄测试分析 ,将第四纪以来的水系位错量分为 8级 ,并分别给出其形成年龄 ,得到各时段的断裂滑动速率介于 4 .7～ 6.7mm/a ,平均值 6.0mm /a,局部段落某个时段内最高滑动速率值7.7mm/a。位错量与滑动速率的空间分布有中间大、两头小的特点 ,这可能表明破裂从中间向两端发展的过程 ;在时间上 ,上新世以来的滑动速率比其它各个时段都大 ,这可能与青藏地块在距今 5Ma以来的快速隆升及大规模挤出运动相关。资料表明 ,断裂破裂有从主体断裂某一段落扩展到邻近地带 ,最后又回到主体断裂其它段落的时空演化过程     

THE LATE QUATERNARY ACTIVITY FEATURES AND SLIP RATE OF THE YANGGAO-TIANZHEN FAULT

The Shanxi Graben System is one of the intracontinental graben systems developed around the Ordos Block in North China since the Cenozoic, and it provides a unique natural laboratory for studying the long-term tectonic history of active intracontinental normal faults in an extensional environment. Comparing with the dense strong earthquakes in its central part, no strong earthquakes with magnitudes over 7 have been recorded historically in the Jin-Ji-Meng Basin-and-Range Province of the northern Shanxi Graben System. However, this area is located at the conjunction area of several active-tectonic blocks(e.g. the Ordos, Yan Shan and North China Plain blocks), thus it has the tectonic conditions for strong earthquakes. Studying the active tectonics in the northern Shanxi Graben System will thus be of great significance to the seismic hazard assessment. Based on high-resolution remote sensing image interpretations and field investigations, combined with the UAV photogrammetry and OSL dating, we studied the late Quaternary activity and slip rate of the relatively poorly-researched Yanggao-Tianzhen Fault(YTF)in the Jin-Ji-Meng Basin-and-Range Province and got the followings: 1)The YTF extends for more than 75km from Dashagou, Fengzhen, Inner Mongolia in the west to Yiqingpo, Tianzhen, Shanxi Province in the east. In most cases, the YTF lies in the contact zone between the bedrock mountain and the sediments in the basin, but the fault grows into the basin where the fault geometry is irregular. At the vicinity of the Erdun Village, Shijiudun Village, and Yulinkou Village, the faults are not only distributed at the basin-mountain boundary, we have also found evidence of late Quaternary fault activity in the alluvial fans that is far away from the basin-mountain boundary. The overall strike of the fault is N78°E, but the strike gradually changes from ENE to NE, then to NWW from the west to the east, with dips ranging from 30° to 80°. 2)Based on field surveys of tectonic landforms and analysis of fault kinematics in outcrops, we have found that the sense of motion of the YTF changes along its strikes: the NEE and NE-striking segments are mainly normal dip-slip faults, while the left-laterally displaced gullies on the NWW segment and the occurrence characteristics of striations in the fault outcrop indicate that the NWW-striking segment is normal fault with minor sinistral strike-slip component. The sense of motion of the YTF determined by geologic and geomorphic evidences is consistent with the relationship between the regional NNW-SSE extension regime and the fault geometry. 3)By measuring and dating the displaced geologic markers and geomorphic surfaces, such as terraces and alluvial fans at three sites along the western segment of the YTF, we estimated that the fault slip rates are 0.12~0.20mm/a over the late Pleistocene. In order to compare the slip rate determined by geological method with extension rate constrained by geodetic measurement, the vertical slip rates were converted into horizontal slip rate using the dip angles of the fault planes measured in the field. At Zhuanlou Village, the T₂ terrace was vertically displaced for(2.5±0.4)m, the abandonment age of the T₂ was constrained to be(12.5±1.6)ka, so we determined a vertical slip rate of(0.2±0.04)mm/a using the deformed T₂ terrace and its OSL age. For a 50°dipping fault, it corresponds to extension rate of(0.17±0.03)mm/a. At Pingshan Village, the vertical displacement of the late Pleistocene alluvial fan is measured to be(5.38±0.83)m, the abandonment age of the alluvial fan is(29.7±2.5)ka, thus we estimated the vertical slip rate of the YTF to(0.18±0.02)mm/a. For a 65° dipping fault, it corresponds to an extension rate of(0.09±0.01)mm/a. Ultimately, the corresponding extensional rates were determined to be between 0.09mm/a and 0.17mm/a. Geological and geodetic researches have shown that the northern Shanxi Graben System are extending in NNW-SSE direction with slip rates of 1~2mm/a. Our data suggests that the YTF accounts for about 10% of the crustal extension rate in the northern Shanxi Graben System.     

钻探揭示的黄河断裂北段活动性和滑动速率

黄河断裂是银川盆地内展布最长、切割最深的一条深大断裂,也是银川盆地的东边界。由于其北段呈隐伏状,因此,该段的活动性和滑动速率长期未知,影响了对盆地演化和地震危险性的认识。文中选择具有石油地震勘探基础的陶乐镇为研究场点,以人工浅层地震勘探结果为依据,在黄河断裂北段布设了一排钻孔联合剖面,并对标志层进行年代测试,获得了断裂的活动时代和滑动速率。结果表明,黄河断裂北段在晚更新世末期或全新世有过活动,在（28.16±0.12）ka BP 以来的累积位移为0.96m,晚第四纪以来的平均滑动速率为0.04mm/a,该值明显低于南段灵武断层（0.24mm/a）;尽管向下切割了莫霍面,黄河断裂晚第四纪活动强度和发震能力均要低于切割相对浅的贺兰山东麓断裂;黄河断裂可能在新生代之前已经强烈活动并深切莫霍面,新生代以来,银川盆地的构造活动迁移分解到以贺兰山东麓断裂为主的多条断裂之上,地壳双层伸展模型可解释银川盆地现今深浅部构造活动间的联系。     

大凉山断裂带南段滑动速率估计

大凉山断裂带是川滇活动块体东边界的重要组成部分,其活动速率的估计不仅对评价青藏高原东南边缘的地壳运动和变形模型具有重要理论意义,还对大凉山地区的地震危险性评价和地震中长期预测具有重要的应用价值。通过对大凉山断裂带南段交际河断裂和布拖断裂的详细野外调查、典型构造地貌GPS精细测量以及断错地貌的时间约束,获得大凉山断裂带南段全新世以来的滑动速率为2.5～4.5mm/a,交际河断裂平均滑动速率略大于布拖断裂的滑动速率。对比滑动速率发现,大凉山断裂带南段与鲜水河-小江断裂系中段西支的安宁河、则木河断裂带的水平滑动速率相当,表明大凉山断裂带活动强度不低于安宁河和则木河断裂带,随着大凉山断裂带逐渐取代安宁河和则木河断裂在鲜水河-小江断裂系中的作用,大凉山断裂带的活动强度将增强。     

THE SLIP RATE AND PALEOEARTHQUAKES OF THE YUMEN FAULT IN THE NORTHERN QILIAN MOUNTAINS SINCE THE LATE PLEISTOCENE

The Yumen Fault lies on the west segment of the north Qilian Fault belt and adjacent to the Altyn-Tagh Fault,in the north margin of the Tibet Plateau.The tectonic location of the Yumen fault is special,and the fault is the evidence of recent activity of the northward growth of Tibetan plateau.In recent twenty years,many researches show the activity of the Yumen Fault became stronger from the early Pleistocene to the Holocene.Because the Yumen Fault is a new active fault and fold belt in the Qilian orogenic belt in the north margin of the Tibet Plateau,it is important to ascertain its slip rate and the recurrence interval of paleoearthquakes since the Late Pleistocene.Using the satellite image interpretation of the Beida river terrace,the GPS measurement of alluvial fans in front of the Yumen Fault and the trench excavation on the fault scarps,two conclusions are obtained in this paper.(1) The vertical slip rate of the Yumen Fault is about 0.41~0.48mm/a in the Holocene and about 0.24~0.30mm/a in the last stage of the late Pleistocene.(2) Since the Holocene epoch,four paleoearthquakes,which happened respectively in 6.12~10.53ka,3.6~5.38ka,1.64~1.93ka and 0.63~1.64ka,ruptured the surface scarps of the Yumen Fault.Overall,the recurrence interval of the paleoseismic events shortens gradually and the activity of the Yumen Fault becomes stronger since the Holocene.Anther characteristic is that every paleoearthquake probably ruptured multiple fault scarps at the same time.     

FAULTED LANDFORM AND SLIP RATE OF THE JINGHE SECTION OF THE BOLOKENU-AQIKEKUDUKE FAULT SINCE THE LATE PLEISTOCENE

The Bolokonu-Aqikekuduke fault zone(Bo-A Fault)is the plate convergence boundary between the middle and the northern Tianshan. Bo-A Fault is an inherited right-lateral strike-slip active fault and obliquely cuts the Tianshan Mountains to the northwest. Accurately constrained fault activity and slip rate is crucial for understanding the tectonic deformation mechanism, strain rate distribution and regional seismic hazard. Based on the interpretation of satellite remote sensing images and topographic surveys, this paper divides the alluvial fans in the southeast of Jinghe River into four phases, Fan1, Fan2, Fan3 and Fan4 by geomorphological elevation, water density, depth of cut, etc. This paper interprets gullies and terrace scarps by high-resolution LiDAR topographic data. Right-laterally offset gullies, fault scarps and terrace scarps are distributed in Fan1, Fan2b and Fan3. We have identified a total of 30 right-laterally offset gullies and terrace scarps. Minimum right-lateral displacement is about 6m and the maximum right-lateral displacements are(414±10)m, (91±5)m and(39±1)m on Fan2b, Fan3a and Fan3b. The landform scarp dividing Fan2b and Fan3a is offset right-laterally by (212±11)m. Combining the work done by the predecessors in the northern foothills of the Tianshan Mountains with Guliya ice core climate curve, this paper concludes that the undercut age of alluvial fan are 56~64ka, 35~41ka, 10~14ka in the Tianshan Mountains. The slip rate of Bo-A Fault since the formation of the Fan2b, Fan3a and Fan3b of the alluvial-proluvial fan is 3.3~3.7mm/a, 2.2~2.6mm/a and 2.7~3.9mm/a. The right-lateral strike-slip rate since the late Pleistocene is obtained to be 3.1±0.3mm/a based on high-resolution LiDAR topographic data and Monte Carlo analysis.     

安宁河-则木河断裂带过渡段及其附近新发现的历史大地震破裂遗迹

在近些年的野外调查中,我们在安宁河、则木河2断裂带的过渡段(礼州至西昌之间)及其附近的3个场地发现了未知年代的地表破裂。通过分析这些地表破裂的特征以及在本区历史地震重破坏区中的位置,我们认为位于杨福山村以北与大坪子村以西2个场地的破裂应是1536年大地震地表破裂带的遗迹。这不仅反映了1536年大地震破裂带的南段沿安宁河与则木河断裂带的过渡段产生,而且反映了该破裂带的南端很可能到达了或者很接近于西昌。位于西昌略北李金堡村以东的破裂应属于1850年大地震地表破裂带的遗迹,它进一步证明了1850年大地震地表破裂带的西北端可能到达西昌以北至少数千米处。因而,由文中的证据可推断西昌附近的主干活动断裂在1536年和1850年大地震时均发生了破裂     

安宁河断裂带小相岭段古地震的新证据及最晚事件的年代

沿安宁河断裂带小相岭段发现了古地震的地表破裂遗迹。在两个场地开挖了横跨主断裂的探槽 ,以研究这里的晚全新世古地震。结果表明 ,在最近的大约 2 30 0a中 ,该断裂段至少发生过 4次伴有地表破裂的古地震事件 ,平均复发间隔为 6 0 0～ 70 0a。这里的最晚事件很可能发生在公元 15世纪 ,并且有可能发生在公元 14 80年。最晚事件沿地表断层产生了 3m的平均左旋位错 ,这相当于一次矩震级为 7 5± 0 3的走滑型大地震的同震平均位错量