2010 Vol. 16, No. 2

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THE SURFACE RUPTURES AND THE MACROSCOPICAL EPICENTER OF YUSHU MS7.1 EARTHQUAKE
MA Yin-sheng, ZHANG Yong-shuang, HU Dao-gong, YANG Nong, LONG Chang-xing, HOU Cun-tang, YAN Peng, WU Zhong-hai, YANG Zhen-yu, LEI Wen-zhi, TAN Cheng-xuan
2010, 16(2): 115-128.
Abstract (196) HTML (123) PDF (2183KB)(36)
Abstract:
At 7:49:40.7 on April 14, 2010, a MS 7.1 earthquake happened in Yushu County of Qinghai Province. In the field investigation two surface rupture zones were observed from west to east, Longbaotan surface rupture zone and Yushu surface rupture zone. They display NW trending and are respectively developed along hang wall of the Longbaotan active fault and Yushu active fault at an interval of 22km. The Longbaotan surface rupture zone, trending along 290° with a length of 21.5km, was sinistral strike-slip movement with a sinistral strike-slip displacement of about 1m. The Yushu surface rupture zone, trending 310° with a length of 23km, can be further divided into three sections. It shows sinistral strike-slip movement in western and middle segment, sinistral strike-slip and thrust in eastern segment. The maximum sinistral strike-slip displacement (2.4m) of the rupture zones appears near the Guoyangyansongduo. According to the displacement of the earthquake surface rupture and building destruction, the earthquake macroscopical epicenter can be considered in the Guoyangyansongduo near the macroscopical epicenter coordinates: at 33°03′11″N and 96°51′26″E.
D-INSAR OBSERVATION OF EARTH SURFACE DEFORMATION IN THE MS7.1 YUSHU EARTHQUAKE
YAO Xin, ZHANG Yong-shuang, YANG Nong, XIONG Tan-yu
2010, 16(2): 129-136.
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Abstract:
A "Two Paths+DEM" interferometric process was made for the PALSAR SAR data before (Jan. 15, 2010) and after (Apr. 17, 2010) the Yushu MS7.1 Earthquake, which yielded a high-quality co-seismic InSAR strip image and absolutely surface deformation. Based on the deformation scale, deformation magnitude and deformation gradient, in combination with tectonic setting of the area, the following conclusions can be drawn: (1) Yushu earthquake triggered a 70-km NWW-extending mutation belt, with a southern section Showing greater dislocation and deformation gradient, which will induce surface raptures, and No. 4 segment in northwestern part showing weaker deformation and no ruptures on the ground surface. (2) The SAR motive directions from both sides of mutation belt indicate a dominant sinistral movement of seisgenic faults. (3) The macro-epicenter is located on the mutation belt 16km northwest of Yushu County. The present InSAR interpretations match well with the seismic mechanics, field investigations and geomorphology features from the China Earthquake Networks Center, and can provide better support for rapid evaluation to earthquake hazard and accurately ing surface track of seismogenic fault.
NUMERICAL MODELING FOR MECHANISM OF YUSHU MS7.1 EARTHQUAKE
WANG Lian-jie, CUI Jun-wen, WANG Wei, QIAO Zi-jiang, SUN Dong-sheng, ZHAO Wei-Hua
2010, 16(2): 137-145.
Abstract (142) HTML (75) PDF (671KB)(7)
Abstract:
In this paper, strain softening model is used to establish the modeling for Yushu MS7.1 earthquake. The results shows that Yushu MS7.1 earthquake occurred as a combination of northward compressing of the Indian Plate and southeastward compressing of the Qinghai-Tibet Plateau. The stress drop, energy release amount, the magnitude of dislocation of fault, and earthquake recurrence intervals are given by the modeling. The modeling results show a good match with the geologic survey in the field.
FORMATION MECHANISM OF GEO-HAZARDS TRIGGERED BY WENCHUA MS8.0 EARTHQUAKE ALONG DUJIANGYAN-WENCHUAN HIGHWAY
GAN Jian-jun, HUANG Run-qiu, LI Qian-yin, YE Xiao-hua, GAO Wen-jun
2010, 16(2): 146-158.
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The geological hazards induced by the Wenchuan MS8.0 earthquake along the Dujiangyan-Wenchuan Highway are especially severe and have seriously affected the safe riding along the highway and the reconstructions. In order to prevent and reduce disasters effectively, main geo-hazard type, slope failure modes and its formation mechanism, and the tempo-spitial distribution in the area have been studied on the basis of the field investigations and statistic analysis of available data. The main damage types include debris flow to collapse, cataclastic rocks to collapse, and shatter-subduction type mudslides, oscillation high-speed sliding debris flows along the slope area. Born transformation induced by such disasters have intensive, systematic and subsection characteristic. Thegeologic hazards have many types and are notably divided into sectors; the high and steep rock deposits of complex origin become the main materials of geological hazards; intense earthquake effect and coupling of endogenic and exogenic forces are important factors for formation and occurrence of geological hazards in the area.
ESTIMATION OF MAJOR EARTHQUAKE CYCLE AND FUTURE TENDENCY IN HEXI CORRIDOR AND ITS ADJACENT AREA, NW CHINACHEN
CHEN Bai-lin, LIU Jian-sheng, ZHANG Yong-shuang, LIU Jian-min, DONG Cheng, WU Nai-fen
2010, 16(2): 159-175.
Abstract (206) HTML (57) PDF (951KB)(11)
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The Hexi corridor, with its particular geographical position, is an important line connecting middle and lower reaches of the Yellow River and NW China. Affected by the late Mesozoic-early Cenozoic collision between Indian Plate and Eurasian Plate and the continuous northward compression the Hexi corridor and its adjacent area occur as a strong Crustal movement zone, as marked by earthquakes. Since 1555AD, two active periods and two quiet periods have been recognized and now is in the second active period since 1920. The second active period in the past 100 years can be divide to five active stages and five quiet stagese, each lasting for 9~16 years, and now is in the last active stage since 2002. Study of major earthquake cycle indicates that the major earthquakes (MS=7.0~7.5) happen at the interval of 2000~3000 years in the study area. According to the state of every active fault in the recent earthquake, it can be predicted that in the coming 100 years the MS>7.0 earthquakes most likely appear in San'gedun-Songshan area of Changma active fault zone, Yuemen area in west part of the Northern Qilianshan fault zone, the Ciyaokou-Kushuigou area in the middle part of Northern Qilianshan fault zone and Jiayuguan area of the Jiayuguan active fault, and likely in Shibaocheng-Changmadaba area in eastern part of Altyu tagh active fault and Gaotai area of Gaotaichezhan active fault. The authors suggest that more attention should be paid to active fault and major earthquake cycle in the study related to earthquake movement.
A REVIEW ON STUDY OF ACTIVITY OF XIANSHUIHE FAULT ZONE SINCE THE HOLOCENE
XIONG Tan-yu, YAO Xin, ZHANG Yong-shuang
2010, 16(2): 176-188.
Abstract (368) HTML (124) PDF (1261KB)(54)
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The Xianshuihe fault zone is a large active seismic-genetic zone in mountainous regions of southwest China. Based on previous studies, in combination with field investigation, the authors systemically summarized the research status about Holocene activity of Xianshuihe fault zone. The fault zone is divided by the Huiyuan Temple into two segments, the northwestern and southeastern segments, which are sub-divided into eight parts. Since the Holocene, the fault has occurred as a strike slip fault with thrust characteristic. The whole strike-slip generally displays an activity rate of about 10mm/a and a vertical deformation of 2mm/a or less. The activity rate is changeable in the fault, e.g., 10~20mm/a in the northwestern segment but smaller than 10mm/a in the southeastern segment. Accordingly the seismic activity is significantly stronger in the northwestern segment than in the southeastern segment. The earthquakes occurred with skip metastasis and have recurrent nature in situ. The surface rupture characteristics recorded in the historical earthquakes are consistent with those reported in the earthquake surface rupture. The research on seismic risk assessment along the Xianshuihe fault zone needs to be greatly improved.
GEOLOGICAL CHARACTERISTICS OF AND METALLOGENIC MODEL FOR LARGE-SCALE SAYAK COPPER ORE FIELD IN BALKHASH METALLOGENIC BELT, CENTRAL ASIA
CHEN Xuan-hua, WANG Zhi-hong, YANG Nong, CHEN Zheng-le, HAN Shu-qin
2010, 16(2): 189-202.
Abstract (138) HTML (83) PDF (1709KB)(6)
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The Sayak ore field is the only area with the occurrence of large-scale skarn-type copper deposit in Balkhash metallogenic belt, Kazakhstan, Central Asia. In this paper the geological characteristics, ore-field structures and metallogenic model of Sayak ore field are described in detail. Sayak ore field is located in the Sayak graben-synclinorium, including several spatially isolated skarn copper deposits, porphyry Cu (Mo) deposits, Cu-Mo veins and a series quartz vein deposits, which consist of a metallogenic series with skarn-type and porphyry deposits as the two end deposits. The deposits in the ore-field are mainly located in the contact zone between the Middle Carboniferous limestones and the Late Carboniferous granitoids, with a special assemblage of skarn-type Cu-Au-Mo mineralizations. The metallogenic time of main copper deposits in Sayak ore-field is in the Middle to Late Hercynian, with the main and secondary metallogenic ages of 335±2 Ma and 308±10Ma, respectively. The ore bodies are mainly located in the saddle-top segments of locally developed anticlines in the graben-synclinorium, strongly controlled by the tectono-magmatism activities. The most relative granitoids with the copper metallogenesis in Sayak ore field are diorite with Cu content up to >1% and granodiorite up to >0.2%. The copper reserve in the Sayak ore field is estimated to be ~575 kt Cu.
GEOLOGICAL CHARACTERISTICS AND METALLOGENIC MODEL OF SUPER-LARGE KOUNRAD PORPHYRY COPPER DEPOSIT, KAZAKHSTAN
HAN Shuqin, CHEN Xuanhua, YANG Nong, CHEN Zhengle, SHI Wei, Ye Baoying
2010, 16(2): 203-212.
Abstract (293) HTML (193) PDF (978KB)(20)
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The Kounrad porphyry copper deposit was discovered 70 years ago in the Balkhash Metallogenic Belt of the Central Asian Metallogenic Domain, . It is a typical super-large porphyry copper deposit developed under the tectonic environment of continental margin arc, with a metallogenic model of granodiorite. The vertical and lateral zonings of the wall rock alteration and ore mineral assemblages are obviously observed in the deposit. High content ore in the leaching zone and the ore deposition at a very shallow depth made it easy to be mined. It is suggested that the metallogenesis of the deposit was controlled by the circular structure, and had a very close relation with the secondary quartzite and argillic alteration.
THE GEOLOGICAL CHARACTERISTICS AND DEVELOPMENT PROSPECTS OF KUIGAN-MAIBULAK COPPER ORE DEPOSITS IN BALKHASH METALLOGENIC BELT
Wang Zhihong, Chen Xuanhua, Yang Nong, Chen Zhengle, Han Shuqin
2010, 16(2): 213-222.
Abstract (134) HTML (101) PDF (1177KB)(28)
Abstract:
The Kuigan-Maibulak copper ore region on south bank of the Balkhash Lake is geologically located at the northwestern part of to the Chuyili-North Tianshan metallogenic sub-province, which is belonging to the circum-Balkhash-Junggar metallogenic province of the Balkhash metallogenic belt. It is composed of a series of small or medium porphyry copper deposits. This paper gives a brief introduction of geological features, wall-rock alterations, mineralizations, and mineral assemblages of the ore region and the main characteristics of the deposits, including Kaskirmis, Vostok Ⅱ and Ⅲ porphyry and vein-type copper deposits, and the Vostok Ⅰ Mo-chalcopyrite deposit, the evaluation of the reserves, the development and prospects of the deposits. According to the granodiorite porphyry magmatism and Cu-Au-Mo mineralization series of the Kuigan-Maibulak copper ore region, it is suggested that the Kuigan-Maibulak copper ore region and the North Balkhash copper deposit belt (with super-large Kounrad and Aktogai porphyry copper deposits and so on) on south and north banks of the Balkhash Lake have similar geological characteristics for porphyry copper deposit. The Kuigan-Maibulak copper ore region is considered to be an ore-forming and prospective zone for super-large porphyry copper deposits.