Geological Tectonics Research Articles

Environmental Isotope Hydrogeochemical Characteristics and Instructions of Geothermal Water in Xianyang Urban Area

In order to find out the origin of geothermal water in Xianyang urban area and provide scientific basis for sustainable use, taking the geothermal water as study object, we systematically studied supply circulation mechanism of geothermal water in Xianyang urban area through environmental isotope hydrogeochemical methods, and come to the conclusion: geothermal water in Xianyang urban area is bounded by shore fracture of Wei River, which shows totally different hydrogeochemical features. The differences suggests that the geothermal water belongs to different tectonic geology units and sedimentary environment. The distribution characteristics of environmental isotope such as δD、δ18O and 14C confirmed that geothermal water exists contact between the study area and northwest of Wei River. The supply water source of geothermal water comes from the atmospheric precipitation of Holocene in northwest direction, its updating ability is poor except partial deep fault slightly being recharged from modern atmospheric water.

Quasi-synchronous multi-parameter anomalies associated with the 2010–2011 New Zealand earthquake sequence

Abstract. Positive thermal anomalies about one month before the 3 September 2010 Mw = 7.1 New Zealand earthquake and "coincidental" quasi-synchronous fluctuations of GPS displacement were reported. Whether there were similar phenomena associated with the aftershocks? To answer it, the following was investigated: multiple parameters including surface and near-surface air temperature, surface latent heat flux, GPS displacement and soil moisture, using a long-term statistical analysis method. We found that local thermal and deformation anomalies appeared quasi-synchronously in three particular tectonic zones, not only about one month before the mainshock, but also tens of days before the 21 February 2011 Mw = 6.3 aftershock, and that the time series of soil moisture on the epicenter pixel had obvious peaks on most of the anomalous days. Based on local tectonic geology, hydrology and meteorology, the particular lithosphere-coversphere-atmosphere coupling mode is interpreted and four mechanisms (magmatic-hydrothermal fluids upwelling, soil moisture increasing, underground pore gases leaking, and positive holes activating and recombining) are discussed.

Relation between the in-situ stress field and geological tectonics of a gold mine area in Jiaodong Peninsula, China

Relation between the in-situ stress field and geological tectonics of a gold mine area in Jiaodong Peninsula, China

Tectonically Active Landscapes

OK, I admit that I am a hard-rock geologist by training, and that I do not have formal education in geomorphology. However, my career has led me into seismic hazards assessment, where I have gained appreciation and respect for geomorphic methods used in assessing the age of fault movements (this from a person who once considered everything younger than Precambrian to be uninteresting “cover”). Because of my second career in geologic hazards, the subject matter of this book is intensely interesting to me, and I approached the book review as a learning experience. I was not disappointed. I was surprised and pleased at the depth to which the tectonic background is incorporated into the geomorphic discussions. In fact, the discussions of tectonic settings of the study areas in Chapter 1 are worthy of a tectonics textbook, and I found them to be a valuable review. For me, it was a comforting point of departure for delving into the geomorphic consequences of those upper-mantle and crustal processes. That tie back to basic tectonic processes is maintained throughout the book, making it valuable reading for anyone involved in the study of tectonic processes, structural geology, or geologic hazards. This is especially true for those who are focused on the crustal and mantle processes themselves, and who have not given much consideration of the effects of those …

Hydrogen, oxygen, helium and strontium isotopic constraints on the formation of oilfield waters in the western Qaidam Basin, China

Surveys and exploration for oil and gas have revealed many oil-field brines in the Tertiary strata of the western Qaidam Basin, China. The source and formation of these brines are unclear. Brine samples collected from petroleum wells in the oilfield area were analyzed for their general chemical composition and for hydrogen, oxygen, strontium and helium isotopes in order to trace their origin, formation, and resource distribution. Results show that the concentrations of resources such as K, B, Sr, Br and Li are unusually enriched in oil-field brines and have excellent potential for development and utilization in future. The geology, H, O, Sr and He isotopic composition, the chemical composition, and the geophysical measurements all show that the tertiary oil-field brines predominantly originated from the deep mixture of formation water and magmatic residual fluids in the western Qaidam Basin. The tectonic geology, intense and frequent magmatic-hydrothermal activity as well as high 3He/ 4He ratio indicate that the magmatic fluids possibly originate from the upper mantle-derived magmatic fluids. Thus, according to our interpretation of the formation and evolution of the oilfield brine, this source is adequate for the volume and composition to be explored and utilized latterly.

EARTHQUAKE AND TSUNAMI HAZARD IN MYANMAR

Myanmar, lying in a major seismic belt, is indeed earthquake-prone and is vulnerable to hazards from moderate and large magnitude earthquakes, including tsunami hazards along its long coastal areas. The seismotectonics of the region indicates that earthquakes in Myanmar mostly have originated along an active subduction zone (Andaman Megathrust Zone) in the west and along a large transform fault zone (Sagaing Fault Zone) in the middle part of the country. In the past, at least two large magnitude earthquakes along that subduction zones were tsunamigenic. Of course, the tsunami generated by the giant 2004 Sumatra Earthquake also caused moderate damage in some parts of the Myanmar Coast. Thus, it is evident that Myanmar is vulnerable to hazards from moderate and large magnitude earthquakes, including tsunami hazards along its long coastline.The active fault studies (from paleoseismological survey through tectonic geodesy), upgrade and newly installation of seismic station networks, public awareness and curriculum development, building code development and technical training program are priority requirements in the country. Recently, researchers on tectonic geology recognize some active segments of the Sagaing, Kyaukkyan and Kabaw faults, as well as marine and fluvial terraces which seemed to be associated with subduction of India and Burma (Myanmar) plates along the Bengal tectonic boundary. Their study should be extended by providing some instrumentation schemes like global positioning system (GPS) network. Myanmar Earthquake Committee (MEC) has developed a seismic zone map of Myanmar in deterministic approach in 2006, for the sake of providing general information to the user for various purposes, and for public information. Technical development is needed for the completeness of the next generation of seismic zone map of Myanmar which is to be incorporated in Building Code, which in turn requires researches and findings on tectonics of Myanmar.

A Study of Seismic Anisotropy of Wenchuan Earthquake Sequence

AbstractUsing aftershock data of the 2008 Wenchuan earthquake, recorded by seismic stations in the seismic source area and around, with the systematic analysis method (SAM) of shear‐waves splitting, this paper analyzes the anisotropic characteristics in the crust along the Longmenshan fault belt where the Wenchuan earthquake occurred and obtains the directions of the principal compressive stress field in the crust and its spatial distributions. The results show spatial differences: plotting a boundary approximately in Anxian area in the middle of Longmenshan fault belt, the polarization directions of fast shear‐waves at stations located at the northeast segment of Longmenshan fault belt are at NE direction, consistent with the strike of the faults. However, the polarization directions of fast shear‐waves at stations located at the southwest segment are at NW direction, perpendicular to the strike of the faults. This pattern also indicates that the southwest segment of the Longmenshan faults are mainly in thrust fault and the northeast segment are of obviously strike‐slip component. In this study, the polarization directions of fast shear‐waves are scattered at stations near the intersection area of the Longmenshan faults, the Xianshuihe faults and the Anninghe–Xiaojiang faults. It is possibly attributed to the local complex geological tectonics around the seismic source area, consistent with the characteristics of the complex direction of the principal compressive stress in this zone.

Three-dimensional P-wave velocity structure of the crust beneath Hainan Island and its adjacent regions, China

Using over 3 500 first P arrival times recorded by nine digital seismic stations from Hainan Digital Seismic Network during 1999∼2005, a 3-D P-wave velocity model of the crust under Hainan Island and adjacent regions has been determined. The results show that the pattern of velocity anomalies in the shallower upper crust is somewhat associated with the surface geological tectonics in the region. A relative low-velocity anomaly appears north of the Wangwu-Wenjiao fault zone and a relative high-velocity anomaly appears south of the Wangwu-Wenjiao fault zone, corresponding to the depressed areas in north Hainan Island, where many volcanoes are frequently active and geothermal values are relatively higher, and the uplifted and stable regions in central and south of the Hainan Island. In the middle and lower crust velocities are relatively lower in east Hainan than those in west Hainan, possibly suggesting the existence of the upwelling of hot materials from the mantle in east Hainan. The pattern of velocity anomalies also indicates that NW faults, i.e., the Puqian-Qinglan fault, may be shallower, while the E-W Wangwu-Wenjiao fault may be deeper, which perhaps extends down to Moho depth or deeper.

Plate tectonic structural geology to detailed field and prospect stress prediction

Arguably the first successful application of the theory of continental drift to petroleum exploration was in 1959 by the pioneers S. W. Carey and L. G. Weeks whose collaboration led to the discovery of the world class Gippsland Basin. Plate tectonics, as the theory is now known, was still nascent and not prominent during peak global oil exploration success in the 1960s. As discovery rates continue to decline, large scale description of separating and colliding continents has become increasingly impotent in the ever more complex hunt for the next barrel. Emphasis is turning from new basins and plays to smaller intra-basin discoveries related to a more detailed understanding of basin forming faults and their local stress effects on traps and trap geometries. Improved oil recovery is not only about finding new fields, but also demands detailed stress information for horizontal wellbore stability to economically and effectively increase reserves and recovery rates by extracting new oil from old fields. As a result, expensive wellbore based measurements have been deployed in the past 15 years. These precision measurements have then been averaged between wells for stress prediction but stress directions are known to vary abruptly by up to 90° over distances of less than 3 km. A solution lies in the seismic recognition of globally synchronous compressional pulses which, like a heartbeat, have added predictability of stress fields hence to stress analysis. This repetition of stress provides a workflow for stress consistent seismic interpretation that can predict horizontal and vertical changes in the direction of the maximum horizontal compressional component of a stress SH (SHD) and also in the magnitude of the stress, SHM. It is now possible to derive pre-drill at any desired point, important exploration and production variables such as stress related fault seal and open fracture orientation. Similarly, important reservoir development parameters such as fracture gradients and wellbore stability prediction will maximise recovery efficiencies and reduce development costs. This technique will also aid in effective carbon dioxide sequestration, a challenging new field of endeavour.

The effects of karst collapse on the environments in north China

In this paper, a systematic study was completed on the distribution features and origins of karst collapses in north China. There are 65 modern karst collapse areas with 1,416 karst collapse pits and 38 paleo–karst collapse areas with 3,654 paleo-collapse pillars. Modern karst collapses are mainly distributed in the plain region of the east Taihang and Yanshan Mountains and are concentrated in three zones from the west to the east in this region. The regional distribution features of karst collapses in north China are controlled by the boundary of the geological tectonics, condition of soluble rock and the extent of human activities. From the results, three-grade indices have been adopted to establish a classification scheme for karst collapse in north China. The effects of karst collapses on the environments in north China are summarized using a karst collapse classification scheme.

Characteristics of mantle degassing and deep-seated geological structures in different typical fault zones of China

n this paper a comprehensive tracing study is conducted on mantle degassing and deep-seated geological structures in different types of fault zones in the continent of China based on the helium isotope data, coupled with some indices such as CO 2 / 3 He, CH 4 / 3 He and 40 Ar/ 36 Ar, and geological tectonics data. There are four representative types of fault zones: (1) Lithospheric fault zones in the extensional tectonic environment are characterized by a small Earth’s crust thickness, a lower CH 4 / 3 He-high R and lower CO 2 / 3 He-high R system, the strongest mantle de-gassing, and the dominance of mantle fluid, as is represented by the Tancheng-Lujiang fault zone. (2) The lithospheric fault zones or the subduction zone in the strongly compresso-tectonic envi-ronment, for instance, the Bangonghu-Nujiang fault zone, are characterized by a huge thick Earth’s crust, with the R/Ra values within the range of 0.43―1.13, and weak mantle degassing with mantle-source helium accounting for 5%―14% of the total. (3) The deep-seated fault zones at the basinal margins of an orogenic belt are characterized by R values being on order of magnitude of 10 -7 , and the CH4/3He values, 10 9 ―10 10 , CO 2 / 3 He values, 10 6 ―10 8 ; as well as much weak mantle degassing. (4) The crustal fault zones in the orogenic belt, such as the Yaojie fault zone (F 19 ), possess a high CH 4 / 3 He-low R (10 -8 ) and high CO 2 / 3 He-low R system, with no obvi-ous sign of mantle degassing. Studies have shown that the deep-seated huge fault zones are the major channel ways for mantle degassing, the main factors controlling the intensity of mantle degassing are fault depth, tectonic environment and crust thickness; the intensity of mantle de-gassing can reflect the depth and the status of deep-seated tectonic environment of fault, while the geochemical tracing studies of gases can open up a new research approach; upwelling ac-tivity of hydrothermal fluids from the deep interior of the Earth may be one of the driving forces for the formation and evolution of the huge deep fault zones. Piedmont fault zones are the locations where deep-seated tectonic activity and crust/mantle structure are transformed, which are of great significance in understanding the mechanisms of formation of orogenic belts and basins.

Seismotectonic environment of occurring the February 3, 1996 Lijiang M=7.0 earthquake, Yunnan province

Lijiang-Daju fault, the seismogenic fault of the 1996 Lijiang M=7.0 earthquake, can be divided into Lijiang-Yuhu segment in the south and Yuhu-Daju segment in the north. The two segments show clear difference in geological tectonics, but have the similar dynamic features. Both normal dip-slip and sinistral strike-slip coexist on the fault plane. This kind of movement started at the beginning of the Quaternary (2.4–2.5 Ma B.P.). As to the tectonic types, the detachment fault with low angle was developed in the Early Pleistocene and the normal fault with high angle only after the Mid-Pleistocene (0.8 Ma B.P.). Based on the horizontal displacements of gullies and the vertical variance of planation surfaces cross the Lijiang-Daju fault at east piedmont of Yulong-Haba range, the average horizontal and vertical slip rates are calculated. They are 0.84 mm/a and 0.70 mm/a since the Quaternary and 1.56 mm/a and 1.69 mm/a since the Mid-Pleistocene. The movements of the nearly N-S-trending Lijiang-Daju fault are controlled not only by the regional stress field, but also by the variant movement between the Yulong-Haba range and Lijiang basin. The two kinds of dynamic processes form the characteristics of seismotectonic environment of occurring the 1996 Lijiang earthquake.

Study on distribution characteristics of strong earthquakes in Sichuan-Yunnan area and their geological tectonic background

In the paper, the distribution characteristics of strong earthquakes in Sichuan-Yunnan area and their geological tectonic background, especially the relation to Sichuan-Yunnan and Sichuan-Qinghai crustal blocks have been studied. The main results are: a) Strong earthquakes in Sichuan-Yunnan area distribute mainly in Sichuan-Yunnan and Sichuan-Qinghai crustal blocks; b) Most of strong earthquakes of the two blocks distribute mainly along their boundary faults; c) A few strong earthquakes are not obviously related to active faults. It shows that the relation between strong earthquakes and geological tectonics can be very complex; d) There is a certain correlativity for seismic activities among boundary faults of the two blocks, but they have different features; e) There are some anomalous changes of velocity structures in the deep crust of boundary faults of the two blocks. Many boundary faults, especially Longmenshan fault, cut obviously the Moho discontinuity. The Xianshuihe fault, a typical strike-slip fault, has no obvious indication of cutting the Moho discontinuity, but has distinct low-velocity zone in different depths.

Structural characteristics and petroliferous features of Tarim Basin

Using the modern tectonic geology theories and methods such as the plate tectonic analysis, the paleo-structure analysis, the structural-lithofacies analysis, and the fault related fold and petroleum system, and combining with the seismic data, well drilling data and the circumferential field geology, study on the structural characteristics and petroleum prospect in the Tarim Basin has been carried out. Results show that the Tarim Basin is a large superimposition and combination basin with continental crustal basement, composed of a Paleozoic craton and Meso-Cenozoic foreland basins. The characteristics of the basin are: the kernel part of the basin is the marine facies Paleozoic craton, superimposed 4 continental facies foreland basins. Though the scale of the paleozoic craton of the Tarim Basin is relatively small, the structure is steady. The petroleum prospect of the Paleozoic craton is: multiphase pool-generation and accumulation controlled by ancient uplift. The Meso-Cenozoic foreland basins in the Tarim Basin, which are distributed on the cratonic circumference and are a long-term subsidence, turned into rejuvenated foreland basins after the Meso-Cenozoic period. The petroleum prospects are: coal-bed generating hydrocarbon, abundant natural gas, pool-generation in later and recent periods, the oil and gas distribution controlled by the foreland thrust belt. The structural characteristics of Tarim provide it with a superimposition and combination petroleum system of multiple resources, multiple reservoirs and multiphase pool-generation. The oil and gas exploration prospect covers two large fields: the Paleozoic craton and the Meso-Cenozoic foreland thrust belt.

インドネシア，フローレス島中部，パジャワ地熱地域のテク卜ニクス， 火山および層序に関する地質学的研究

遠隔離島小規模地熱の探査に関する研究協力（ESSEIプロジェク卜）の一環として，インドネシア，フローレス島中部のパジャワ地熱地域とその周辺地域において，1998年以来，広域地質の研究が実施されてきた．この地域では4Ma以降，中央部と南海岸部において火山活動が起こった．この両地域はフローレス島からアロール島にかけて特徴的なエシェロン状火山島構造の要素を構成している．これら両地域では，過去250万年の聞に，約800mの隆起が起こった．中央部においては約2.5Maにウェラスカルデラが形成され，その後カルデラ火山活動の後は，ほとんど，火山活動が終息している．南海岸部では，4Ma 以降，現在に至るまで，火山活動が続いている．とくに顕著な出来事はパジャワリフトゾーンの出現であり，これは東側の北進するオーストラリア付加体ブロックと西側の相対的に静止したスンダランドブロックとの聞に生じた南北方向の左横ずれせん断応力に関係づけられる．パジャワリフトゾーンはおそらく0.8-0.2 Ma頃の，NNW-SSE方向に伸びた火山体の形成によって始まった．次いで，この稜線付近より，東側の火山体の崩落が起こった．その後，この崩落域はパジャワシンダーコーン群を生成し，これはNNW SSE方向のリフトゾーンに沿って20kmにわたって配列する60個以上のシンダーコーンから成る．調査地域の大部分の火山岩類は玄武岩質，ソレイアイ卜岩系であるが，このパジャワリフトゾーンの噴出岩は南北に伸びた火山体とパジャワシンダーコーン群とを合めて，安山岩質，カルクアルカリ岩系であり，かつ組成的に非常に均質な特徴をもつ．このことは，パジャワシンダーコー ン群の多数のコーン配列の地下で岩脈群マクマが相互に連結していることを示唆する．調査地域の3つ の蒸気湧出域といくつかの高温温泉湧出域は，熱源としてのパジャワリフトゾーンマグマ系に密接に伴って分布している．

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This Memoir presents a detailed account of one of the most critical and interesting parts of the Lewisian complex of NW Scotland; a detached fragment of a supercontinent made up of Laurentia, Siberia and Baltica, which existed at the end of the early Proterozoic period. The Gairloch area, together with neighbouring Loch Maree, is the only part of the mainland Lewisian outcrop where Palaeoproterozoic supracrustal rocks (the Loch Maree Group] and their relationships to the Archaean basement can be studied, and has been the subject of a considerable amount of research, spanning a period of more than forty years. The Loch Maree Group represents an amalgamation of oceanic, trench, and arc assemblages with continental basement, and forms part of a Palaeoproterozoic collisional orogen stretching from Labrador through South Greenland to Scandinavia. The author is Emeritus Professor of Tectonic Geology at Keele University, England, and has studied the structural geology of Precambrian terrains in many parts of the world. He has mapped the area covered by the Memoir in detail, at a scale of 1:10 000, and has an intimate knowledge of the geology, acquired over many years.

NZ society for earthquake engineering reconnaissance team to Seattle, USA

Our report describes the observations and assessments of the members of the reconnaissance team which visited Seattle, Tacoma, Olympia and surrounding areas a few days after the magnitude 6.8 Nisqually earthquake struck on 28 February, 2001. The report covers the tectonic setting and geology of the region, the source of the earthquake, its strong ground motions, ground damage - liquefaction and landslides, damage to buildings, bridges, lifelines, emergency management, community response, and lessons for New Zealand.

U-Pb, Rb-Sr isotopic chronology of Jinning granites in the Songpan-Ganze Orogenic Belt and its tectonic significances

A series of Jinning granites are located in the eastern margin of the main part of the Songpan-Ganze Orogenic Belt. The research is focused on Gezong and Donggu granites in the Danba area. From the viewpoint of isotopic chronology, geochemistry and tectonic geology, their formation ages, origins and geneses of source materials, and the influences of Himalayan tectonic thermal events are discussed- It is suggested that they were the products of Jinning tectono-magmatism. The source materials were the poorly matured volcano-sedimentary rocks formed in the middle-late period of the middld-Proterozoic. They represent in fact the basement of the old Yangtze Block. The late Proterozoic erogenic belt of the entire western margin of the Yangtze Block, including the Danba area, should be the key part of the old Yangtze Block.

Research on the seismotectonics of the January 17, 1995 HanshinM7.2 earthquake

Based on the geological tectonics, aftershock activity, earthquake surface rupture and peak ground motion, the geometric and dynamic characteristics of seismogenic tectonics about the 1995 Hanshin earthquake are analysed. Nojima fault and Rokko fault have the same trending direction, but opposite dips. Their rising and falling plates are in symmetrically diagonal distribution. The two faults can be defined as thrust-strike slip faults and constitute a pivotal strike-slip fault. The earthquake just occurred at the pivot, which is the seismotectonics for the earthquake to develop and occur. The pivotal movement along a strike-slip fault often leads to the occurrence of large earthquakes, whose dynamic process can be demonstrated by the stress analysis on the torsion of a beam with rectangle section. The displacement of earthquake surface rupture, aftershock density and peak acceleration change in a certain range of epicentral distance just similar as the shear stress changes from the center to the sides in the rectangle section. The distribution characteristics of the heaviest damage areas are also discussed in the article from the aspects of special geological tectonics and seismotectonic condition. The result obtained from the article can be applied not only to realizing the potencial earthquake sources in middle-long time, but also to build reasonably the prediction model about earthquake hazard.

Statistical testing of the relation between burst of aftershocks and strong earthquakes

According to geological tectonics and seismic activites this paper devided North China (30°–45°N, 105°–130°E) into four areas. We analyzed the North China earthquake catalogue from 1970 to 1986 (from 1965 to 1986 for Huabei, the North China, plain region) and identified forty-two bursts of aftershock. Seven of them occurred in aftershock regions of strong earthquakes and seventeen of them in the seismic swarm regions. The relation between strong earthquakes with the remaining eighteen bursts of aftershocks has been studied and tested statistically in this paper. The result of statistical testing show that the random probabilityp of coincidence of bursts of aftershock with subsequent strong earthquakes is less than six percent. By Xu’sR scoring method the efficacy of predicting strong earthquake from bursts of aftershock is estimated greater than 39 percent.