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| 1 | The Holocene Activity Evidence of the Yema River-Daxue Mountain Fault in Western Qilian Mountain显示文摘Altyn Tagh fault controls the deformation characteristics of the northern margin of the Qinghai-Tibet Plateau.The sinistral slip rate of the eastern segment of the fault reduces gradually where the reduction transforms into the deformation within Qilian Mountain,forming a series of thrust faults and strike-slip faults.Among them,the Yema River-Daxue Mountain fault is one of the important structural transform faults in the study area.Based on the differences of the geometrical characteristics and activities,the fault is divided into four segments,the Yema River segment,the Shibandun segment,the Liushapo segment and the Baishitougou segment,among which the former three are Holocene active faults,and the Baishitougou segment belongs to late Pleistocene fault.The excavated trenches imply a total of 6paleoearthquake events,and at least 4 events have occurred during Holocene,whose occurrence times are 8300±700 yr BP,6605±140 yr BP,4540±350 yr BP,2098±47 yr BP,respectively.The recurrence interval is 2600±600 yr BP that is close to the lapsed time of the last one,2098±47 yr BP,which suggests that the Yema River-Daxue Mountain fault is in a high risk of major earthquakes in the future.The vertical coseismic displacements of the four Holocene paleoearthquake events are 100 cm,42 cm,40 cm and 50 cm,respectively,the horizontal coseismic displacements are 5 m,4.5–5.5 m,5–8 m and 4–5.5 m,separately,and then the reference magnitude of the paleoearthquake events is conjectured to be M7.6±0.1. | LUO Hao HE Wengui YUAN Daoyang SHAOYanxiu | 2013 | Acta Geologica Sinica(English Edition)2013，87，6： | 7 |
| 2 | Slip Rate of Yema River–Daxue Mountain Fault since the Late Pleistocene and Its Implications on the Deformation of the Northeastern Margin of the Tibetan Plateau显示文摘The slip rate of Yema River–Daxue Mountain fault in the western segment of Qilian Mountains was determined by the dated offset of river risers or gullies. Results indicate that the left-lateral fault slip rate is 2.82 ± 0.20 mm/a at Dazangdele site,2.00 ± 0.24 mm/a at Shibandun site,and 0.50 ± 0.36 and 2.80 ± 0.33 mm/a at two sites in Zhazihu. The ideal average slip rate of the whole fault is 2.81 ± 0.32 mm/a. The lower slip rate confirms part of the displacement of Altyn Tagh fault was transformed into an uplifting of the strap mountains in the western segment of Qilian Mountains,whereas another part transformed into sinistral displacement of Haiyuan fault. This study illustrates that the slip of large strike-slip faults in the northeastern margin of the plateau transforms into crust thickening at the tip of the fault without large-scale propagation to the outer parts of the plateau. | LUO Hao HE Wengui YUAN Daoyang SHAO Yanxiu | 2015 | Acta Geologica Sinica(English Edition)2015，89，2： | 5 |
| 3 | Crustal Motion Characteristics in the Eastern Margin of the Tibetan Plateau and Adjacent Regions after the Wenchuan Earthquake显示文摘The Wenchuan earthquake has altered the crustal motion characteristics in the eastern margin of the Tibetan Plateau and adjacent regions.Using discontinuous GPS survey data for 2008–2012, the velocity field for the Eurasia reference framework has been obtained, and the general trend of contemporary crustal motion after the occurrence of the Wenchuan earthquake has been studied.In addition, using the velocity field, the block movement velocity has been estimated by least-squares fitting.Furthermore, the properties and displacement rates of main faults have been obtained from the differences in velocity vectors of the blocks on both sides of the faults.The results reveal that there are no obvious changes in the general characteristics of crustal motion in this area after the Wenchuan earthquake.The earthquake mainly changed the rate of the movement of the Chuan-Qing block and caused variation in the movement direction of the South China block.The effect of the earthquake on faults is mainly reflected in variations in fault displacement velocity; there is no fundamental change in the properties of fault activity.The displacement rates of the Xianshuihe fault decreased by 3–4 mm/a, the Longmenshan fault increased by 9–10 mm/a, and the northern segment of the Anninghe fault increased by approximately 9 mm/a.Furthermore, the displacement rates of the Minjiang, Xueshan, Huya, Longquanshan, and Xinjin faults increased by 2–3 mm/a.This implies that the effects of the Wenchuan earthquake on crustal movement can mainly be observed in the Chuan-Qing, South China, and N-Chuan-Dian blocks and their internal faults, as well as the Xianshuihe and Longmenshan faults and the northern section of the Anninghe fault.The reason for this is that the Wenchuan earthquake disturbed the kinematic and dynamic balance in the region. | TANG Wenqing ZHANG Qingzhi PAN Zhongxi LI Jun YANG Cheng | 2015 | Acta Geologica Sinica(English Edition)2015，89，5： | 5 |
| 4 | Geochronology and Geochemistry of the Tinggong Porphyry Copper Ore Deposit, Tibet显示文摘We have determined the ages of the ore-bearing Tinggong porphyries and the Eocene granites using the LA-ICPMS zircon U-Pb method. Zircons from one adamellite porphyry and two diorite porphyries yield ages of 15.54±0.28 Ma, 15.02±0.25 Ma and 14.74±0.22 Ma, respectively. The ages of two granites are 50.48±0.71 Ma and 50.16±0.48 Ma. Light Rare Earth Elements(LREE) are enriched in the ore-bearing adamellite porphyries, which are high-K calc-alkaline and metaluminous, while Heavy Rare Earth Elements(HREE) and Y are strongly depleted, indicating an adakitic affinity. The Large Ion Lithophile Elements(LILE) of the adamellite porphyries are highly enriched, whereas some High Field Strength Elements(HFSE) are depleted. The diorite porphyry in this study is chemically similar to the adamellite porphyries, except that the Mg# of the diorite porphyry is a little higher, demonstrating more mantle contamination. Four samples from different rocks are selected for in situ zircon Hf isotopic analyses. The samples show positive εHf(t) values and young Hf model ages, indicating their derivation from juvenile crust. However, the adamellite porphyry and diorite porphyry formed in the Miocene exhibit more heterogeneous Hf isotopic ratios, with lower εHf(t) values than the granites formed in the Eocene, suggesting the involvement of old Indian continent crust in their petrogenesis. The geochronology and geochemistry of the adamellite porphyries and the diorite porphyries indicate that they formed from the same source region in a post-collisional environment, but contaminated by crust and mantle materials in different ratios. The metallic minerals formed mainly during the older adamellite porphyry stage, but they were recycled and reactivated by the diorite porphyry intrusion. | CHEN Rui LIU Yulin GUO Lishuang WANG Zhenghua LIU Hongfei XU Kaifeng ZHANG Jinshu | 2014 | Acta Geologica Sinica(English Edition)2014，88，3： | 4 |
| 5 | Magmatic Processes of Ashi Volcano, Western Kunlun Mountains, China显示文摘The Ashikule volcanic cluster(AVC) in western Kunlun Mountains is located in a graben region at the convergence of the Altun and Kangxiwa fault zones, and consists of more than 10 main volcanoes and dozens of volcanelloes. The Ashi volcano lies in the central part of the volcanic cluster. The lithology, chemical composition and texture of Ashi volcanic rocks were studied in detail, and their implication in magmatic processes was discussed. The phenocrysts in Ashi volcanic rocks consist mainly of plagioclase and pyroxene, and the statistical results of phenocryst contents show that the rocks can be subdivided into two groups. In group A, the content of pyroxene phenocrysts is generally higher than that of plagioclase phenocrysts, but an inverse relation occurs in group B. In TAS diagram, the compositions of both groups fall into the trachyandensite field, but they are obviously concentrated into two clusters. The two clusters exist also in the oxide diagrams. The pyroxene phenocrysts comprise augite, bronzite and hypersthene, and their Mg# histogram shows two peaks. Plagioclase phenocrysts with reaction rim are observed in rocks of both groups. The An values of the core are generally 30–40, and those of the rim are 44–48, which are closer to those of euhedral plagioclases. The bronzites are in equilibrium with the melt, and two sets of magma depths, i.e., 18–25 km and 13–18 km, can be estimated by using thermobarometer proposed by Putirka. The hypersthenes are not in equilibrium with the melt, and can be assigned to xenocrysts. The crystal size distribution(CSD) curves of plagioclase appear as kinked lines indicative of magma mixing. The above analyses show that two magma pockets might exist beneath the Ashi volcano. It is likely that they are connected with each other. The one has more evolved and contains more acidic magma, and the other is a trachyandensite magma pocket characterized by layering. The magma from the upper part of the trachyandensite magma pocket might mix with more acidic magma, resulting in a magma that is more acidic than the magma from the lower part. | YU Hongmei XU Jiandong ZHAO Bo SHEN Huanhuan LIN Chuanyong | 2014 | Acta Geologica Sinica(English Edition)2014，88，2： | 3 |
| 6 | 2015年尼泊尔地震三维发震构造及地震危险性研究显示文摘2015年4月25日尼泊尔M_W7.8地震发生在喜马拉雅造山带上,人们普遍认为该地震不足以释放该造山带上累积的能量,但对该地区后续地震危险性评价多基于二维或是假三维的形变反演计算结果.本研究从2015年尼泊尔地震主震与其最大余震M_W7.3地震之间的关系出发,着重分析讨论了尼泊尔地震的时间和空间的非均匀性,结合震源机制解、地壳速度结构、精定位后的余震分布及InSAR反演结果,建立了三维发震构造模型,利用非线性摩擦有限元方法,对一个地震周期内断层摩擦行为和块体变形进行了模拟,将计算结果和地表同震形变、形变反演的同震破裂、历史地震时空演化进行对比,在确认该三维模型可靠性的基础上,讨论了该地区后续地震的可能位置,认为在1934年比哈—尼泊尔M_W^8.1地震以东区域,还存在发生大地震的可能,在最大余震M_W7.3地震东南部位,还存在发生中大地震的可能. | 姚琪 徐锡伟 邢会林 程佳 江国焰 马未宇 刘杰 杨文 | 2018 | 地球物理学报2018，61，6： | 2 |
| 7 | 利用非线性摩擦有限元方法计算大凉山次级块体及其周边地区地震危险性显示文摘大部分地震是在复杂的物性条件下,应力不均匀加载作用下断层活动的结果,还受到断层结构和断层相互作用的影响,导致地震中长期预测研究中常用的'地震空区'理论出现误差。断层的摩擦行为可以体现断层的不均匀破裂过程,文中尝试将非线性摩擦有限元方法应用到区域地震危险性评价中,模拟计算了大凉山次级块体及周边地区主要断层的摩擦行为,将断层节点破裂与7级以上历史地震的时空演化进行对比。结果表明,模拟所得的断层破裂与历史地震对应较好,且在地震震级、地震破裂顺序上都有良好表现。模拟结果还显示,小江断裂和则木河断裂有可能是后续地震危险性较强的地区,在更长的时间内,大凉山断裂和安宁河断裂具有发生中等强度地震的可能,鲜水河断裂的北段可能发生较大地震。 | 姚琪 邢会林 徐锡伟 张微 刘杰 | 2018 | 地震地质2018，40，1： | 2 |
| 8 | Preface to the special issue on the M_(S)6.4 Yangbi (Yunnan) and M_(S)7.4 Maduo (Qinghai) earthquakes显示文摘The Tibetan Plateau and the Himalayas,which are the highest mountains in the world,were created by the collision of the Indian and Eurasian plates.Earthquakes pose significant hazards in these mountainous regions as demonstrated by recent large earthquakes,including the M_(S)6.4/M_(W)6.1 Yangbi earthquake in Yunnan province on May 21,2021 and the M_(S)7.4/M_(W)7.4 Maduo earthquake in Qinghai province on May 22,2021.The Yangbi earthquake occurred near the northwestern extension of the Red River fault in the southeastern part of the Tibetan Plateau whereas the Maduo earthquake occurred in the Bayan Har block in the northeastern part of the plateau.Both earthquakes are related to strike-slip faults and provide unique opportunities to learn more about the lateral extrusion and escape of the southeastern edge of the Tibetan Plateau. | Ling Bai Lihua Fang | 2021 | Earthquake Science2021，34，5： | 0 |
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