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STATE OF ART AND PERSPECTIVE ON DATABASE CONSTRUCTION FOR LOW-TEMPERATURE THERMOCHRONOLOGY
DAI Meng-yao, WANG Ping, LI An-bo, DING Lu, LIU Pin-qin, DAI Jin-gen, ZHANG Hui-ping, LIU Shao-feng
SEISMOLOGY AND GEOLOGY    2023, 45 (6): 1432-1451.   DOI: 10.3969/j.issn.0253-4967.2023.06.011
Abstract230)   HTML24)    PDF(pc) (5500KB)(157)       Save

Low-temperature thermochronology is a key technology for studying neotectonics and landscape evolution. However, it is intrinsically different from the other geochronological methods in the data expression, analysis and interpretation. In recent years, with the widespread adoption of low-temperature thermochronology techniques, the size volume of data has continuously increased, giving rise to many studies on tectonic geomorphic evolution based on big data. However, these data are mostly scattered across literature from different sources, with inconsistent formats and contents, and varying data quality, which to a certain extent hampers innovative research based on big data. There is a need to construct specialized databases to cope with the growing low-temperature thermochronology data and meet the demands of innovative research using big data.

In this paper, four conventional geochronological databases, including National Geochronological Data Base, Geochron, Petlab, DataView, and recent databases, AusGeochem and Sparrow are reviewed for comparison of their capability in data sources, data volume, data storage structure, completeness of data content, data entry methods, data retrieval methods, coverage areas, database update patterns, and data analysis tools. The conventional geochronological databases, of which the thermochronological data comprise only a small part, are generally stored in databases similar to or outside this subject, such as radioisotope chronology database, geochronology database, petrological mineral and geological analysis databases. They amplify the commonalities between different disciplines, and thus focus only on the presentation of sample units. It is not suitable for “big data” research, because all the data are managed by relational database with strictly structured tables and limited data sources. It was found that conventional geochronological databases design approaches are often suitable for absolute age data. However, low-temperature thermochronology differs from conventional geological dating methods, as its age values only record cooling time. The more geologically significant cooling history comes from numerical simulations based on elevation profiles, track lengths, and the diffusion dynamics models of the(U-Th)/He system. Additionally, the innovation in experimental techniques also imposes new requirements on the construction of thermochronology databases.

Comparing with the conventional geochronology databases, recent databases focus more on low-temperature thermochronological data and support both the structured and unstructured data with variable data sources, which makes it more comprehensive and professional. These databases own the characteristics of flexibility and expandability, especially for the addition of new dating methods and experimental methods, the storage of big data and the linkage between laboratories and database. Using different types of database platform and associated APIs, both relational and non-relational data can be involved and managed for data query, analysis and visualization. However, the construction of these recent databases is still in the preliminary exploration stage, and ensuring the continuous growth of data remains a challenge. Moreover, establishing a flexible numbering system for sustainable and expandable unique identification of samples and data is also an important task for recent databases. Finally, in addition to raw data, numerous thermal history information is included in published paper related to fission track. These interpretations or inverted results constitute interpretive data, which are crucial for reconstructing cooling history or tectonic uplift. Therefore, how to incorporate such data into the database is also a question that must be considered during database design.

The key to supporting the database lies in the users who it oriented. Considering the needs of users in professional field for scientific research management, experimental analysis and “big data” innovative research, as well as in view of the problems existing in the current databases, we put forward following suggestions for the future construction of low-temperature thermochronology database.

Firstly, in order to ensure the activity of specific low-temperature thermochronology database. from a technical perspective, artificial intelligence technologies such as natural language processing or other forms of machine learning algorithms should be utilized to semi-automatically or automatically extract information from paper, assisting users in quickly extracting relevant information and understanding the content of the literature. Platforms like Semantic Scholar, GeoDeepDive, and DeepShovel have implemented interactive features in data mining, wherein data is normalized and automated into the database based on user-specified rules, significantly reducing manpower and time costs in data acquisition, providing great convenience. In terms of ideology, the open-sharing academic ecosystem has given rise to open-sharing platforms such as arXiv for preprints, data repositories like Pangaea, and the Deep-Time Digital Earth integrated online research platforms, drastically shortening the cycle from research and experimentation to publication. This facilitates the incorporation of the latest research data into databases, greatly expanding the data sources. Regarding user volume, academic social networks possess advantages in academic tracking and dissemination, breaking down academic-related hierarchies, promoting academic exchange and cooperation, and attracting more users.

Secondly, more detailed data storage capabilities and simpler data operation behaviors help improve the expansibility of the database. Most existing geochronological databases use relational databases, which are a strictly structured way of storing data. The most typical data structure presentation form is two-dimensional table, which is very suitable for logical geological data. However, non-relational databases are not tables but databases oriented towards structured and unstructured data storage requirements, which have filled the gaps in relational databases. In practical applications, the advantages of both types of databases can be combined to comprehensively include basic geological information and interpretive information, achieving the effect of New SQL.

Thirdly, highlight its highlight. Chronological data of sample and the single data that make up the sample chronology are significant, it will be effective in distinguishing low-temperature thermochronology from other similar disciplines if the coding style of sample and single data that are not registered on IGSN can be standardized to highlight the characteristics of subject data.

Finally, by combining the strengths of both conventional and recent databases, incorporating the concept of open academia, leveraging advanced information mining and transmission technologies, and utilizing a storage approach that combines structured and unstructured data, it can greatly meet the comprehensive needs of users, ranging from laboratories to scientists, and further to data consumers.

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GRAIN SIZE AND MICROSTRUCTURE CHARACTERISTICS OF HOLOCENE MEGAFLOOD SLACK WATER DEPOSITS IN THE MIDDLE REACHES OF THE YARLUNG TSANGPO RIVER
XU Bo, WANG Ping, WANG Hui-ying, GUO Qiao-qiao, SHI Ling-fan, SHI Yu-xiang
SEISMOLOGY AND GEOLOGY    2023, 45 (2): 305-320.   DOI: 10.3969/j.issn.0253-4967.2023.02.001
Abstract375)   HTML27)    PDF(pc) (6489KB)(237)       Save

The terrain in southeastern Tibet is steep and the valleys are crisscrossed. Since the Quaternary, glacial ice and debris have blocked the course of the Yarlung Tsangpo River and its tributary river valleys to form giant dammed lakes, and the huge flood deposits formed by the dammed lake outburst floods are often associated with moraines, ice water deposits, lacustrine deposits, aeolian sand or other running water sediments to form complex river valley accumulation landforms. Different types of sediments in alpine and canyon areas are similar in morphology, structure and fabric, and are difficult to distinguish. Grain size and morphological characteristics are the most important structural characteristics of sediment, and the distribution rules are controlled by many factors such as sedimentary environment, physical properties of detrital material, transporting medium and transporting mode, etc., which is an important proxy index for restoring paleoclimate and inverting paleoenvironment. However, the relevant research on identifying sediment types in alpine valley area of southeast Tibet by grain size and morphology index is still in the exploratory stage. In order to understand the particle size characteristics and spatial differentiation laws of outburst flood sediments and the micromorphological characteristics of particle surfaces, we collected 33 samples of Holocene flood retention sediments preserved along the river within about 350km from the outlet of the Jiacha Gorge in the middle reaches of the Yarlung Tsangpo River to Pai Town, and measured them with Malvern 3000 laser diffraction particle size meter and Zeiss Signma scanning electron microscope, combined with digital geomorphology(DEM)data extracted river channel width and steepness coefficient. The features of spatial distribution law of particle size are analyzed, and the following understanding is obtained. The particle size of outburst flood retention deposits is characterized on the whole by fine-silty sand(2.57~5.18Φ)with poor sorting, positive skew and narrow peak state. Two end element models are obtained: The main peak of EM1 terminal element is 3.16Φ, with an average percentage content of 42.7%, which may represent the alluvial characteristics of higher energy of outburst floods in alpine valley areas, and the main peak of EM2 terminal elements is 2.06Φ with an average percentage content of 55.6%, which can be used to indicate the accumulation process of the outburst flood lag deposits. Affected by the width of the river, the EM1 content has a tendency to increase downstream, while EM2 has the opposite trend. The surface microstructure of quartz particles in the outburst flood lag deposits is mainly characterized by mechanical scratches, shell-like fractures, upturn cleavage and cleavage steps, with low structural maturity, mostly angular shape, and rare denudation pores of chemical origin. As a typical representative of climbing sand dunes in the valley area of the semi-humid monsoon area, the genesis of the dunes is of great guiding significance for revealing the source of sand dunes in the valley area of the alpine valley area, identifying paleoflood deposit and aeolian deposit, distinguishing aeolian deposit and paleoflood slackwater deposits on both sides of the riverbank, and windbreak and sand fixation engineering in the Yarlung Tsangpo River. By comparing the particle size and surface micromorphology characteristics of the known outburst flood deposits of the Yarlung Tsangpo River, we believe that the sand source of the Fozhang dunes is mainly from the outburst flood deposits and was transformed later by wind forces.

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LATEST PROGRESS ON ACTIVITY OF HESHAN-MODAOMEN SEGMENT, XIJIANG FAULT
LU Bang-hua, WANG Ping, WANG Hui-ying, LAI Zhong-ping, DENG Zhi-hui, BI Li-si, WAN Wan-he
SEISMOLOGY AND GEOLOGY    2020, 42 (6): 1370-1384.   DOI: 10.3969/j.issn.0253-4967.2020.06.007
Abstract758)   HTML    PDF(pc) (11462KB)(131)       Save
The Xijiang Fault is an important NW-trending fault with a length of~200km, located in the western part of the Pearl River Delta. A M4 3/4 earthquake occurred at the northern end of the fault(Sihui)in 1445 and a magnitude 5 earthquake occurred at the southern end of the fault(Modaomen Waters)in 1905. Heshan is the boundary between the southern and the northern segments of this fault. The southern segment which is called Heshan-Modaomen segment is mainly hidden faults. The activity of Heshan-Modaomen segment remains controversial due to the lack of systematic studies for the deep and shallow exploration, which affects the assessment and prevention of earthquake disaster risk. In this paper, we concentrate particularly on the distribution and activity of Heshan-Modaomen segment using seismic geological surveys, shallow seismic exploration, joint borehole profile detection, and Quaternary geochronology.
Field geological surveys show that the fault zone is prominently normal sinistral strike-slip faults, striking about N310°~330°W, with a width of 10~20m. Most of them dip northeast at angles of 60°~80°. Observations on typical outcrop show that cataclasite, breccias and siliceous rocks are developed on the faults. Fault planes often have smooth and polished surfaces and no fault geomorphology has been developed along the fault zone. The overlying eluvial weathered soil materials have not been disturbed or cut. We carried out shallow cross-fault sounding of 7 profiles in the hidden section of the fault zone using longitudinal wave reflection method of multifold coverage observation system. As a result, we obtained the reflection time sections of the target stratum and the main structure. A total of 13 breaking points to be investigated were explained. We also performed cross-fault drilling at the location of the seismic data interpretation profile and catalogued drilling cores. 14C and OSL samples were collected systematically. The 14C dating was performed by the BETA Laboratory in the United States and 16 valid age data were obtained. OSL dating was performed by the OSL Laboratory of China University of Geosciences(Wuhan)and 6 age data were obtained.
This paper presents the study results of two representative cross-fault profiles. The shallow exploration survey line XJ1 and the row drill profile P1 are located in the southern section of the fault where six boreholes are arranged. We find the existence of bedrock faults on the joint borehole profile. The grooves developed thereupon are filled with the late Pleistocene paleochannel deposits with no obvious faults observed. The overlying Holocene strata are horizontal and continuous, without cutting and disturbance. Combined with the stratigraphic age, we infer that the fault has been inactive for at least about 11 000 years. The shallow exploration survey line XJ2 and row drill profile P3 are located in the northern section of the fault, where a total of seven boreholes are arranged. The borehole sections reveal the existence of fault crushed zone in the underlying bedrock(Cambrian hornstone). The tectonites are mainly fault breccias and cataclastic rocks with chlorite alteration. Groove landforms are formed along the fault zone with strong erosion at the later stage, and filling and accumulation occurred since the Holocene transgression with no fracture cutting or stratum disturbance. According to the landform, the occurrence of faults and the development of transverse active faults, the Heshan-Modaomen segment of Xijiang Fault can be further divided into two segments with the boundary of Zhupai Island. Both of them have been inactive since the Holocene.
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APPLICATION OF TOPOGRAPHIC SLOPE AND ELEVATION VARIATION COEFFICIENT IN IDENTIFYING THE MOTUO ACTIVE FAULT ZONE
YANG Xiao-ping, WANG Ping, LI Xiao-feng, XIE Chao, ZHOU Ben-gang, HUANG Xiong-nan
SEISMOLOGY AND GEOLOGY    2019, 41 (2): 419-435.   DOI: 10.3969/j.issn.0253-4967.2019.02.010
Abstract1125)   HTML    PDF(pc) (17652KB)(661)       Save
The eastern Himalaya syntaxis is located at the southeastern end of the Qinghai-Tibet Plateau and is the area where the Eurasian plate collides and converges with the Indian plate. The Namjabawa is the highest peak in the eastern section of the Himalayas, and the Yarlung Zangbo River gorge is around the Namjabawa Peak. The NE-striking Aniqiao Fault with right-lateral strike-slip is the eastern boundary fault of the Namjabawa syntaxis. Motuo Fault is in the east of and parallel to the Aniqiao Fault, distributing along the valley of the Yarlung Zangbo River. The section of Yarlung Zangbo River valley at the eastern side of the Namjabawa area is located in the southern foothills of the Himalayas and belongs to the subtropical humid climate zone with dense tropical rainforest vegetation. Dense vegetation, large terrain elevation difference, strong endogenetic and exogenic forces, and abundant valley deposition bring enormous difficulty to the research on active faults in this area.
Since 1990s, surface morphology can be quantitatively expressed by digital elevation models as the rapid development of remote sensing technology. Geomorphic types and their characteristics can be quantified by geomorphological parameters which are extracted from DEM data, describing geomorphologic evolution and tectonic activity. But to date, researches based on quantitative geomorphic parameters are mainly focus on the differential uplift of regional blocks. In the study and mapping of active faults, surface traces of active faults are acquired by visual interpretation of remote sensing images. It has not been reported to identify the location of active faults via the change of quantitative geomorphic parameters. The distribution map of topographic elevation variation coefficient is suitable to reflect the regional erosion cutting and topographic relief, and the places with higher topographic elevation variation coefficient are more strongly eroded. In this paper, we attempt to identify the active faults and explore their distribution in the Yarlung Zangbo Gorge in the east of the Namjabawa Peak based on the application of two quantitative geomorphic parameters, namely, the topographic slope and the elevation variation coefficient.
Using the DEM data of 30m resolution, two quantitative geomorphic parameters of topographic slope and elevation variation coefficient in Namjabawa and its surrounding areas were obtained on the ArcGIS software platform. On the topographic slope distribution map, the slope of the eastern and western banks of the Yarlung Zangbo River near Motuo is steep with a slope angle of more than 30°. Under the background of steep terrain, there are gentle slope belts of 5°~25° distributing intermittently and NE-striking. On the distribution map of topographic elevation variation coefficient, the elevation variation coefficient of the Yarlung Zangbo River near Motuo is greater than 0.9. On the background of the high topographic fluctuation area, it develops gently topographic undulating belts with elevation variation coefficient of 0.2~0.9. The belts are intermittently distributed and northeastern trending. Through the field geological and geomorphological investigation and trench excavation, it is found that the abnormal strips of the above-mentioned geomorphological parameters are the locations where the active faults pass. The above results show that the quantitative analysis of the topographic slope and the coefficient of variation of elevation can help us find active faults in areas with large terrain slope, serious vegetation coverage and high denudation intensity.
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GEOLOGICAL EVIDENCES OF LATE QUATERNARY ACTIVITY OF MOTUO FAULT IN EASTERN HIMALAYAN SYNTAXIS
XIE Chao, YANG Xiao-ping, HUANG Xiong-nan, WANG Ping, LI Zheng-fang, ZHOU Ben-gang
SEISMOLOGY AND GEOLOGY    2016, 38 (4): 1095-1106.   DOI: 10.3969/j.issn.0253-4967.2016.04.023
Abstract844)      PDF(pc) (7113KB)(886)       Save

Motuo Fault locates at the east of Namjagbarwa Peak in eastern Himalayan syntaxis.Based on the remote sensing interpretation,the previous work,and with the field investigation,this paper obtains the spatial distribution and movement characteristics of Motuo Fault in China,and geological evidences of late Quaternary activity.Two trenches in Motuo village and Dongdi village located in Yalung Zangbo Grand Canyon reveal that the Motuo Fault dislocates the late Quternary stratum and behaves as a reverse fault in Motuo village and normal fault in Dongdi village.Motuo Fault is dominated by left-lateral strike-slip associated with the faulted landforms,with different characteristics of the tilting movement in different segments.The trench at Didong village reveals the latest stratum dislocated is~2780±30 a BP according to radiocarbon dating,implying that Motuo Fault has ruptured the ground surface since late Holocene.The movement of left-lateral strike-slip of Motuo Fault is related to the northward movement process of Indian pate.

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ages of the recent two episodes of glacially dammed lakes along the upstream of the yarlung zangbo gorge
LI Cui-ping, WANG Ping, QIAN Da, TANG Mao-yun
SEISMOLOGY AND GEOLOGY    2015, 37 (4): 1136-1146.   DOI: 10.3969/j.issn.0253-4967.2015.04.016
Abstract962)      PDF(pc) (5227KB)(840)       Save

There are many episodes of multiple-level lacustrine terraces along the entrance of the Yarlung Zangbo Great Canyon. Besides, very thick fluvio-lacustrine sediments are buried beneath the cover of the riverbed. Optically stimulated luminescence and radiocarbon dating provide an approximate timeline of upper valley deposits and reveal at least two glacially dammed lake events (Ⅰ and Ⅱ) which have deposition ages of 7~9ka (Ⅰ) and 20~30ka(Ⅱ), respectively. The recent two episodes of glacially dammed lakes produced two steps of lacustrine terraces (T1, T2) correspondingly, which are of elevations 2906~2 956m and 3100~3 060m. The formation of paleo-dammed lakes reflects that the Zelunglung Glacier in the west slope of Mt. Namche Barwa had progressively advanced to block the Yarlung Tsangpo River during the early Holocene and the Last Glacial Maximum. The glacially dammed lake I has a relatively smaller extent. Its lacustrine sediments are distributed mainly from Datuoka to Mirui with maximum thickness about 5~8m. Its end is roughly at the south of Milin County. The glacially dammed lake Ⅱ occupies a large area with the end roughly nearby Lang County. Its sediments are exposed from Datuoka to Wolong with maximum thickness about 100m. After the later fluvial erosion, the lacustrine sediments of this lake formed 1~3 levels of secondary terraces.

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FEATURE AND FORMATION MECHANISM OF THE QUATERNARY FAULT PLANE AT XILINGANG,FOSHAN CITY
DONG Hao-gang, HUANG Chang-sheng, ZENG Min, ZHAO Xin-wen, GUO Liang-tian, WANG Ping
SEISMOLOGY AND GEOLOGY    2012, (2): 313-324.   DOI: 10.3969/j.issn.0253-4967.2012.02.010
Abstract1213)      PDF(pc) (9601KB)(748)       Save
A Quaternary fault plane was found located at Chencun Town of Foshan City,which is thought as a late Quaternary active fault by many researchers. To explain the formation mechanism of this fault plane,a series of work was carried out,such as geomorphologic survey,validation by exploratory trench,shallow seismic reflection and dating of Quaternary system,etc. According to the analysis of the geomorphologic features,the contrast between bedrock fault and Quaternary fault,and the characteristics of shallow seismic reflection,there are few geomorphologic signs of recent tectonic activities. The displacement of Quaternary bottom and the rupture in the rocks were not formed in the same tectonic stress field,and the bedrock fault didnt offset the Quaternary formation according to the shallow seismic reflection characteristics. Thus,a conclusion is drawn that the Xilingang Fault plane wasnt generated by tectonic movement but the gravity inequilibrium.
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OPTICAL STIMULATED LUMINESCENCE SAMPLING AND DATING OF BORING CORE IN URBAN ACTIVE FAULT EXPLORATION
WANG Ping, CHEN Jie, LU Yan-chou, LIU Jin-feng
SEISMOLOGY AND GEOLOGY    2005, 27 (4): 689-697.  
Abstract1313)      PDF(pc) (567KB)(955)       Save
The reliability of ages from optically stimulated luminescence (OSL) dating of boring core has a stringent dependence on characteristic of samples,and on motheds of boring and sampling. When using a full core collected at boring,the uncertainty of estimation to equivalent dose at OSL dating is affected by some factors,such as mixture occurring in soft soil and sand,contamination due to mud penetrating into sample,the possible influence of heat from pressure and attrition on luminescence signals. In addition,a potential effect on dose rate of samples from boring cores should be emphasized,that is,the effect of change of water content and equilibrium of radioactivity. The basic conditions for sampling,protocols and methods of luminescence dating are important to for sampling correctly in the field. As general requirements for drilling in urban active fault exploration,this paper gives suggestions on sampling from boring core for OSL dating,and factors affecting results of measurement are also discussed.
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NEW EVIDENCE OF QUATERNARY LEFT-LATERAL STRIKE-SLIP MOVEMENT ALONG THE EASTERNMOST SEGMENT OF THE ALTUN FAULT
WANG Ping, LU Yan-chou, CHEN Jie
SEISMOLOGY AND GEOLOGY    2005, 27 (1): 55-62.  
Abstract1266)      PDF(pc) (5290KB)(1013)       Save
Previous results about the magnitude and rate of strike-slip movement along the eastern segment of the Altun Fault are quite inconsistent with each other. This is mostly because that the Quaternary strike-slip rate was inferred mainly from the offset of drainage system or from interglacial sediments,while these data focused mainly on late Quaternary. Tracing the early Pleistocene alluvial gravel bed outcropped along the easternmost segment of the Altun Fault,we discovered that the western boundary of the ancient alluvial fan deposits of the Shulehe River is now about 10km away from the outlet of the river. We believe that this is an important evidence indicating that the Quaternary left-lateral strike-slip displacement along the easternmost segment of the Altun Fault is about 10km. Basing on the analysis of terraces at the outlet of the Shulehe River,we conclude that the 2.8km elbow-like winding of the Shulehe River channel along the Altun Fault indicates not only the left-lateral strike-slip of the Altun Fault,but also the effect of lateral erosion at the meander reach of the river. The magnitude of the Quaternary dislocation and slip rate along the easternmost segment of the Altun Fault are discussed in this paper as well.
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OPTICAL STIMULATED LUMINESCENCE (OSL) DATING OF LATE PLEISTOCENE TERRACE DEPOSITS IN THE EASTERN SEGMENT OF THE ALTYN TAGH FAULT AND ITS TECTONIC IMPLICATION
WANG Ping, LU Yan-chou, CHEN Jie
SEISMOLOGY AND GEOLOGY    2004, 26 (4): 716-726.  
Abstract1543)      PDF(pc) (3961KB)(856)       Save
The ages of terrace deposits along the Shulehe River system are determined by the use of Optical Stimulated Luminescence (OSL) dating technique. The possible tectonic implications of the obtained age data are discussed as follows: (1) The Duanjiagou,Shulehe,and Tashihe Rivers are three rivers of different characters from the Shulehe River system. Several levels of terraces of different altitudes and corrosion rates were developed in the intermont basin and mountain front on the eastern segment of the Altyn Tagh fault. These terraces are the result of differential uplift of the fault blocks. (2) On the southern margin of the Changma basin,7 levels of terraces were developed along the Shulehe River. OSL dating results show that those over 100m high terraces were formed mainly about 40000 years ago,and this may indicate the intensive uplift of the Daxueshan-Xiangmaoshan Mountains and the new activity of the Changma seismic belt. The rate of tilted uplift of the southern part of the Changma basin is inferred to be 2.5mm/a. (3) At Zhaobishan gorge,five levels of terraces of the Shulehe River are still well preserved. Among them,the T3 terrace of 40~60m elevation above the stream level might be related to the new tectonic activity of the region. The T5 terrace of over 150m elevation above the stream level observed at the boca has an ESR age of approximately 200ka and an uplift rate of 0.7mm/a. (4) On the Hongliuxia fault block uplift,4 levels of terraces were developed along the Duanjiasha River. Dating results of the T1,T2 and T3 terraces show that a linear relation exists between the heights and the ages of the terraces,from which an uplift rate of 0.6mm/a can be deduced. The Hongliuxia and the Zhaobishan fault block uplifts are the fault blocks controlled by the strike-slip movement of the Altyn Tagh Fault. They have approximately the same rate of uplift that is quite different from that of the range-front uplift of the Daxueshan-Xiangmaoshan Mountains,indicating that the uplift deformation of the Tibetan Plateau in the late stage of late Pleistocene occurred mainly along the Changma active fault zone. (5) Four levels of terraces were developed at the fan apex of the Tashihe River,and the age of the T3 terrace is dated to be 78.8±5.5ka. It is postulated,therefore,that the terraces at the apex of the Tashihe River alluvial fan were formed in the middle to late stages of late Pleistocene. On the basis of OSL dating results of terrace deposits and the investigation of tectonic landforms,it is concluded that periodic uplift has occurred in the Nanjieshan fault block at 300 ka BP or during the middle to late stage of late Pleistocene.
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THE HEADWARD MIGRATION RATE AND AGE OF KNICKPOINTS OF THE GULLIES AT EASTERN PIEDMONT OF HELANSHAN MT.
Cui Li-ming, Wang Ping, Pan Zu-shou, Liao Yuhua, Wang Yi-peng, Song Fang-min
SEISMOLOGY AND GEOLOGY    1990, 12 (1): 87-95.  
Abstract1199)      PDF(pc) (2962KB)(1111)       Save
Based on the measurements of the positions of knickpoints in the gullies passing throngh pluvial fans,this paper deals with the factors that influence the headward migra tion rate of knickpoints in the gullies dissecting the east piedmont fans of Helanshan Mt. The relation between the position and age of knickpoint hasbeen established. The result shows that at least 3 prehistoric events of magnitude,as large as that of 1739 Pingluo earthquake have occured along the eastern Piedmont fault of Helan Mountain since Holocene. The recurrence interval of great earthquakes in this area is determined to be 2500-3500 years.
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THE PLASTIC DEFORMATION CHARACTERISTICS AND REGIONAL STRAIN FIELD ON THE SOUTHERN SEGMENT OF THE TANCHENG-LUJIANG FAULT ZONE
Xu Jiawei, Wang Ping, Ching Rengao, Ye Zhoujie
SEISMOLOGY AND GEOLOGY    1984, 6 (4): 1-16.  
Abstract1249)      PDF(pc) (7620KB)(599)       Save
The studied segment shows its major,transcurrent ductile shear zone with a considerable sinistral displacement.The rock formation (Pt-T1+2) at a depth of 5—15km may have cropped out in this area during its and subsequent erosion,many plastic-deformed strctures in it.The deformed zone was involved in the Indo-China orogeny.On the basis of measurements and analyses on a lot of pebbles within the shear zone,it is known that K1 (the Flinn') is 1.178 and 1.053,which suggests a variation of simple shear and a plain strain with a constant volume of the studied zone.The intensely deformed belts are generally 40—50km in width,with an average a/c ratio of 27.68 and the maximum more than 87.37.The intensity of strain decreases rapidly with increasing distance from the shear fault zone,as well as with decreasing".depth to which the fault goes.For the Pt formation at the greatest depth,a/c value ranges from 30.58,Z1-12.71-12.98,Z2-2.54,and G-1.50.It follows that the differential horizontal slip may occur between various structures.On the condition that the elongation strain e1 and e3 are 4.95 and -0.817 within the intensely deformed belt,respectively,the belt in question has been elongated 164.23km in length and shortened 272.5km in width,to a corresponding 200km and 50km for the time being.The deformed belt was associated with syntectonic dynamothermal metamorphism,represented by greenschist facies and retrogressive metamorphism of early amphibolite ones.The internal belt was formed by high shear strain,with an angle ranging from 0—20°and a shear strain culculated to be more than 11.34.Developed here are four sorts of models involving viscous shear,ductile shear,ductile-brittle shear and brittle shear within the earth's crust.
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