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A Preliminarily Statistic and Synoptic Study about the Basic Currents over Southeastern Asia and the Initiation of Typhoons

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Journal of Meteorological Research 2018年第4期32卷 661-669页

作者： Yi-Bing XIE Shou-Jun CHEN I-Liang CHANG Yin-Liang HUANG department of geophysics Peking University Beijing 100871

The relation between the basic currents of the low latitudes and the initiation of typhoons is investigated statistic-ally and synoptically by means of recent aerological data. It is shown that about 80% of typhoons developed in the eastern part of the equatorial convergence zone between the equatorial westerlies and trade wind of West Pacific Ocean. The equatorial westerly is a large scale and quasi-steady phenomenon; therefore, it is probably reasonable to be called ＂basic current＂ and typhoons are considered as vortices of smaller scale. There is a quite definite relation- ship between the time, position, frequency of the initiation of typhoons and the position, strength of the basic cur-rents in the low latitudes. There is a quasi-periodical variation of the strength and position of the basic currents with a period longer than one month. This fact may be helpful for the extended forecast the initiation and development of ty-phoons.

关键词： In A Preliminarily Statistic and Synoptic Study about the Basic Currents over Southeastern Asia and the Initiation of Typhoons

An exceptionally strengthened East Asian summer monsoon event between 19.9 and 17.1 ka BP recorded in a Hulu stalagmite

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Science China Earth Sciences 2009年第3期52卷 360-368页

作者： L. R. EDWARDS department of Geology and geophysics University of Minnesota Minneapolis

A stalagmite-based isotope record (No. H82) from Nanjing Hulu Cave, spanning from 16.5 to 10.3 ka BP, provided strong evidence for a coherence relation between the East Asian summer monsoon (EASM) and the North Atlant... 详细信息

关键词： Nanjing Hulu Cave stalagmite East Asian summer monsoon event

Geothermal structure of the eastern Black Sea basin and the eastern Pontides orogenic belt:Implications for subduction polarity of Tethys oceanic lithosphere

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Geoscience Frontiers 2013年第4期4卷 389-398页

作者： Nafiz Maden department of geophysics Gmshane University

The numerical results of thermal modeling studies indicate that the lithosphere is cold and strong beneath the Black Sea basin. The thermal litbospheric thickness increases southward fiom the eastern Pontides orogenic belt （49.4 kin） to Black Sea basin （152.2 kin）. The Moho temperature increases from 367 C in the trench to 978 C in the arc region. The heat flow values for the Moho surface change between 16.4 mW m 2 in the Black Sea basin and 56.9 mW m 2 in the eastern Pontides orogenic belt. Along the southern Black Sea coast, the trench region has a relatively low geothermal potential with respect to the arc and back-arc region. The numerical studies support the existence of southward sub- duction beneath the Pontides during the late Mesozoic-Cenozoic.

关键词： Eastern Black Sea basinEastern PontidesHeat flowLithospheric thicknessGeodynamic evolutionSubduction polarity

Slope stability analysis of Balia Nala landslide, Kumaun Lesser Himalaya, Nainital, Uttarakhand, India

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第1期9卷 150-158页

作者： Mohit Kumar Shruti Rana Pitamber Dutt Pant Ramesh Chandra Patel department of Geology Kumaun University department of geophysics Kurukshetra University

Balia Nala is the outlet of the Nainital lake, flowing towards southeast direction. Presence of Nainital habitation at its right bank has high socio-economic importance. This study presents the stability analysis of a ravine/valley along Balia Nala. Variegated slates(lower Krol and upper Blaini formations) are the main rock types, wherever the outcrop does exist and rest of the area is covered by slope wash and river borne materials. Three sets of joints are presented in the area, but 4 sets of joints also exist at some locations. Nainital lake fault intersected by Manora fault from southwest direction passes through eastern side of the study area, and some small faults, which are sub-branches of Nainital lake fault, are observed(with 10 m offset) and promote the landslide in the area. This study shows that different kinds of discontinuities(joints, faults and shear zones) and rapid down cutting by the stream due to neotectonic activity affect the stability of the slope. The fragile lithology and deep V-shaped valley further accelerate the mass movement in the study area. In addition, rock mass rating(RMR), factor of safety(FOS) and graphical analysis of the joints indicate the study area as landslide-prone zone. This study will be helpful in not only reducing the risk on life of people, but also in assisting the ongoing civil work in the study area.

关键词： Rock mass rating(RMR) Factor of safety(FOS) Balia Nala landslide Slope stability analysis

Provenance studies on the heavy mineral placers along the coastal deposits of Odisha,eastern India

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Journal of Palaeogeography 2022年第2期11卷 275-285页

作者： Shayantani Ghosal Sudha Agrahari Debashish Sengupta department of Geology and geophysics Indian Institute of Technology KharagpurWest BengalIndia department of applied Geology Indian Institute of Technology(Indian School of Mines)DhanbadJharkhandIndia

The coastal deposits along the eastern part of the Indian Peninsula are known for the high abundance of heavy minerals. The present study, as discussed here, has been undertaken along the southwestern coastal part of Odisha, India, adjoining the charnockite-migmatite zone of the Eastern Ghat Mobile Belt(EGMB). The composition of the placers along the study area is primarily controlled by the detritus from the proximal hinterland rock type(s). The weathering index has been established based on the grain morphology, major element concentration and radioelement ratios. Petrological characteristics and grain morphology of monazite, zircon, ilmenite and rutile have been presented respectively, and their implications are discussed. The provenance study of these coastal placers is based on the abundance of rare earth elements(REE) and radioactive elements in the placer sands and the rock types in the study area. The tectonic implications are based on the major element abundance of the beach sands.

关键词： Monazite placers High background radiation area(HBRA) Eastern Ghat Mobile Belt(EGMB) Weathering Zircon Rare earth elements(REE) East coast of India

Response of Atmospheric Low-frequency Wave to Oceanic Forcing in the Tropics

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Advances in Atmospheric Sciences 2000年第4期17卷 569-575页

作者：付遵涛赵强乔方利刘式适 department of geophysics Peking University 100871 Beijing

The effects of oceanic forcing on the atmospheric low-frequency wave (LFW for short) in the tropics are analyzed, where ocean and atmosphere are taken as an independent system, respectively. Here oceanic effects are parameterized as evaporation-wind feedback (EWF for short) and forcing of SST. Under the modulation of EWF, forcing of SST plays a different role from that without EWF, So LFWs are diabatic waves, forced by the interactions of multiple factors, in the tropics. Key words Atmospheric LFW - Oceanic forcing - EWF - Radiative cooling - SST This paper was supported by “ First Institute of Oceanic Sciences, State Oceanic Administration, State Key Laboratory of Geophysical Fluid Dynamics and Numerical Modeling”.

关键词： Atmospheric LFW Oceanic forcing EWF Radiative cooling SST

Seismic Tomography and Surface Wave Analysis Based Methodologies on Evaluation of Geotechnical Properties of Volcanic Rocks: A Case Study

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Journal of Earth Science 2014年第2期25卷 348-356页

作者： Ali Erden Babacan Kenan Gelisli Hakan Ersoy Karadeniz Technical University Department of Geophysics Engineering

Economic development, industrialization and dense population in Trabzon City have caused residential construction to increase by 300% in the last decade. The settlement area is moun- tainous and covered with heavy vegetation. Thus, the steep-sided topography and heavy precipita- tion means floods and landslides are common and in areas with little flat land. Since the mass movements in some parts of city create an enormous danger for buildings, site selection for residen- tial areas becomes increasingly important. This paper describes geotechnical and seismic properties of Tertiary volcanic rock and establishes the link between these units and construction. In this study, refraction tomography and multichannel analysis surface wave methods were applied in order to seek the best construction site in the residential area. The results of the geophysical study were com- pared with the borehole applications. A series of geomechnical tests were carried out on the core samples. Following that, statistical correlations were conducted by regression analysis to evaluate re- lationships between measured parameters. Rock Quality Designation and weathering degree were also determined. The methodology defined in this investigation proves to be an appropriate ap- proach to determine geotechnical properties of the foundation rocks and soils and a proper guide on future geotechnical studies for other cities.

关键词： Trabzon City Turkey refraction tomography MASW ultrasonic geotechnical.

Testing the intraplate origin of mega-earthquakes at subduction margins

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Geoscience Frontiers 2012年第4期3卷 473-481页

作者： Prosanta K.Khan Partha Pratim Chakraborty G.Tarafder S.Mohanty department of applied geophysics Indian School of MinesDhanbadIndia department of Geology University of DelhiDelhiIndia National Geophysical Research Institute HyderabudIndia department of applied Geology Indian School of MinesDhanbadIndia

The disastrous Mw 9.3 （seismic moment 1.0 × 10^30 dyn/cm） earthquake that struck northwest Sumatra on 26 December 2004 and triggered -30 m high tsunami has rejuvenated the quest for identi- fying the forcing behind subduction related earthquakes around the world. Studies reveal that the stron- gest part （elastic core） of the oceanic lithosphere lie between 20 and 60 km depth beneath the upper （- 7 km thick） crustal layer, and compressive stress of GPa order is required to fail the rock-layers within the core zone. Here we present evidences in favor of an intraplate origin of mega-earthquakes right within the strong core part （at the interface of semi-brittle and brittle zone）, and propose an alternate model exploring the flexing zone of the descending lithosphere as the nodal area for major stress accumulation. We believe that at high confining pressure and elevated temperature, unidirectional cyclic compressive stress loading in the flexing zone results in an increase of material yield strength through strain hardening, which transforms the rheology of the layer from semi-brittle to near-brittle state. The increased compres- sive stress field coupled with upward migration of the neutral surface （of zero stress fields） under non- coaxial deformation triggers shear crack. The growth of the shear crack is initially confined in the near-brittle domain, and propagates later through the more brittle crustal part of the descending oceanic lithosphere in the form of cataclastic failure,

关键词： Flexing zone Non-coaxial deformation Shear crack Neutral surface Rheology Compressive stress

2-D viscoelastic FEM simulation on stress state in the deep part of a subducted slab

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Acta Seismologica Sinica(English Edition) 2002年第3期15卷 301-308页

作者：刘亚静叶国扬毛兴华宁杰远 department of geophysics Peking University Beijing 100871 China

The characteristics of the stress fields in deep subducting slabs are studied using viscoelastic plain strain finite element method. When introducing the new rheology structure given by Karato, et al into our computation, there emerge two regions with great shear stress just below the olivine-spinel phase transition zone, which encompass the low viscosity zone below the lower tip of the metastable wedge. Further, the directions of the main compressional stress of these two regions are all along the dip direction of the slab. These are in accordance with the seismic observations that there are two deep seismic zones in a slab and the directions of the main compressional stress in these two seismic zones are along the dip direction of the slab. Smaller effective viscosity probably caused by smaller grain size in the phase transformation zone does not have great influence on the stress state in the deep part of the slab. There is the maximum of shear stress at the transition region from olivine to spinel and the direction of the main compressional stress in this region is roughly perpendicular to the trend of the phase boundary no matter whether there exists metastable wedge, which nevertheless do not correspond to some well-known seismic observations.

关键词： subduction zone stress state numerical simulation viscoelasticity deep seismicity