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Ionospheric precursors of strong earthquakes observed using six GNSS stations data during continuous five years(2011-2015)

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Geodesy and Geodynamics 2023年第1期14卷 65-79页

作者： H.E.Eshkuvatov B.J.Ahmedov Y.A.Tillayev M.Arslan Tariq M.Ali Shah Libo Liu Ulugh Beg Astronomical institute Astronomy St.33Tashkent 100052Uzbekistan national University of Uzbekistan University St.4Tashkent 100174Uzbekistan institute of Fundamental and Applied research National Research University TIIAMEKori Niyoziy 39Tashkent 100000Uzbekistan Centre for Earthquake Studies National Centre for PhysicsIslamabadPakistan Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijingChina College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China Heilongjiang Mohe Observatory of geophysics Institute of Geology and GeophysicsChinese Academy of SciencesBeijingChina

This study reports the morphological characteristics of anomalous variations in Global Navigation Satellite System Total Electron Content(GNSS-TEC) prior to the strong local earthquakes(EQ) that occurred during the period of *** have analyzed 20 earthquakes of magnitude M> 5.6.A statistical technique is implemented on the data of six GNSS stations located in Tashkent,Kitab,and Maidanak in Uzbekistan,and Islamabad,Multan,Quetta in *** results show continuous anomalous variations in TEC during 24 h befo re the occupancy of local *** is shown that the precursors before the occurrence of strong earthquakes,in particular of magnitude 5.7,7.7,7.5,7.8 and 7.3 are detected near Eastern Uzbekistan(26 May 2013),Southwestern Pakistan(24 September 2013),Hindukush region of Afghanistan(26 October 2015),and Central Nepal(25 April 2015) and(12 May 2015),*** ionospheric anomalies appearing before the strong earthquakes at six GNSS stations are registered in 14cases(70%) out of 20 selected *** is depicted that anomalies referred to as ionospheric precursors appeared about 1-7 days prior to the occurrence of strong earthquakes.

关键词： GNSS TEC Earthquakes Ionospheric precursors

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Lithospheric stress in Mongolia,from earthquake source data

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Geoscience Frontiers 2017年第6期8卷 1323-1337页

作者： Demberel Sodnomsambuu Anatoly V.Klyuchevskii institute of astronomy and geophysics of Mongolian Academy of Sciences UlaanbaatarMongolia institute of the Earth Crust Russian Academy of SciencesSiberian BranchIrkutskRussia

Lithospheric stress in Mongolia has been studied using mechanisms of 84 M_(LH)≥ 4 earthquakes that occurred in the 20 th century and instrumental seismic moments of 17,375 M_(LH)≥2.5 events recorded between 1970 and *** M_(LH)≥ 3.5 earthquakes mostly have strike-slip mechanisms in southern and central Mongolia,with frequent reverse-slip motions in the west and normal slip in the north,especially,in the area of Lake *** principal stresses are,respectively,S_H>S_v>S_h in the center and in the south;high horizontal compression with S_H>S_h>S_v in the west;and a heterogeneous stress pattern with S_v>S_H>S_h in the *** to seismic moments of M_(LH)=2.5 events,oblique slip generally predominates over the territory,at S_v≈S_H>>S_h,while frequent strike slip motions in the west record high horizontal compression(S_H>S_v>S_h).Earthquake mechanisms show the principal horizontal compression S_H to be directed W-E in the east,NE-SW in the central and Gobi-Altay regions,and approximately N-S in the west of *** patterns of principal lithospheric stresses in the territory of Mongolia have undergone three events of dramatic change for a few recent decades,and these events were synchronous with three similar events in the Baikal rift system(BRS):in the latest 1960 s,latest 1970 s to earliest 1980 s,and in the latest 1980 s to earliest 1990 *** seismicity of Mongolia has been controlled by superposition of variable stresses associated with rifting activity pulses in the neighbor BRS on the background of quasi-stationary super-regional compression.

关键词： Lithospheric stress Mongolia Geodynamics Earthquake source data

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Interferometry observations of low-latitude E-region irregularity patches using the Sanya VHF radar

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Science China(Technological Sciences) 2014年第8期57卷 1552-1561页

作者： LI GuoZhu NING BaiQi HU LianHuan Key Laboratory of Ionospheric Environment Institute of Geology and GeophysicsChinese Academy of Sciences Beijing national Observatory of Space Environment Institute of Geology and GeophysicsChinese Academy of Sciences

Interferometry plays an important role in revealing fine-scale structures of ionospheric *** placing an additional receiving array of four 5-element Yagi antennas in the north of the main East-West array of the Sanya VHF radar,multiple interferometry baselines with components parallel and perpendicular to the magnetic meridian are *** baselines allow us to study the three-dimensional(3D)behavior of low-latitude ionospheric field-aligned irregularity(FAI)over *** multiple non-collinear receiving baselines,an experiment for which the Sanya VHF radar operated as an interferometer was performed on 10 July *** E-region FAI echoes with periods of several minutes were observed during 0745-0915 UT;mean Doppler velocity was around -30 m/s with spectral widths of about 50 m/*** interferometry results show fine-scale structures of E-region FAI with a zonal scale size of 15 km or *** addition,we found that the periodic variations of echo intensity shown in radar range-time-intensity(RTI)maps were produced by spatially separated E-region irregularity *** patches drifted westward with a velocity of about 40-60 m/s and could be associated with propagating gravity *** results provide a clearer picture of the characteristics of FAI and thus help to investigate the generation and dynamics of low-latitude ionospheric irregularities in the Chinese sector.

关键词： ionospheric E-region field-aligned irregularity patch radar interferometry

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Pitfalls in interpretation of shallow seismic data

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Applied geophysics 2012年第1期9卷 87-94,117页

作者： Ahmed Ismail Edward Smith Andrew Phillips Andrew Stumpf Illinois State Geological Survey Division University of Illinois Urbana-Champaign national research institute of astronomy and geophysics

High-resolution shallow seismic methods are the most widely used geophysical methods in near surface characterization. However, in many cases interpreting the seismic images can be misleading. In this article, we present three case studies where results from P-wave seismic reflection, SH-wave seismic reflection, and multi-channel analysis of surface wave （MASW） surveys were incorrectly interpreted because of inadequate constraints on either the surveyed sites surface or subsurface conditions. A P-wave reflection survey feature was first interpreted as a shallow fault zone but it was later determined to result from a high level of background noise as the acquisition passed through a road intersection. A SH-wave seismic reflection survey feature was interpreted to be a reverse dip-slip fault but targeted drilling showed it was deep local erosion into the bedrock surface. Finally, in an MASW survey, a steeply dipping feature was first interpreted as a bedrock valley. However, later exploratory drilling showed the feature to be a shallow layer of very soft lake sediment that severely damped most of the applied surface wave frequency band. Although initial interpretations were incorrect, they stimulated discussions among geophysicists and geologists and underscored the need for meaningful cooperation and discourse between the scientists before, during, and after geophysical data acquisition.

关键词： Seismic reflection multi-channel analysis of surface wave interpretation pitfalls

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Three-dimensional seismic attenuation tomography of egypt

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Natural Science 2012年第8期4卷 608-623页

作者： Elsayed Fergany Mamdouh Abass Carlos Vargas Department of Geosciences Universidad Nacional de Colombia Bogota Colombia national research institute of astronomy & geophysics Helwan Cairo Egypt

The main purpose of the paper is assessing the three-dimensional (3-D) seismic tomography beneath egyptto reveal the laws of the tectonic activity, dynamic features of the crust and the upper mantle as well as the thermal structure. Thecoda wave attenuation (Q-1c ) was obtained using the single scattering theory for the central frequencies of interest laid between 1 and 24 Hz. A regionalization of the estimated Q-1c values was performed by means of a generalized inversion *** obtained spatial distribution of 3-D attenuation results revealshigh contrasts between East and West egypt. A remarkable contrast in the attenuation levels was compared with the tectonic structures, geothermal gradient and heat flow features. The highest attenuations are concentrated in the east and north western offshore regionsat central frequency 1.5 Hzthat draw a good matching with the seismic andthermal features of egypt. Smaller attenuation levels were detected with young sediments of the Nile Valley from South to the northern triangle of Nile Delta basin except seismic active areas. Low or normal attenuation was detected at western desert where there is a stable and simple shelf. We can conclude that the extended highest attenuation joins to the strong seismic sources and geothermal structures at lower frequency and the centralized high attenuation takes place at moderate seismic sources at a higher frequency. The 3D attenuation maps can draw not only tectonic and geothermal structures but also the general geologic structure map.

关键词： Seismic Coda Waves Attenuation Tomography Seismicity Tectonic Geothermal Geologic Epoch

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Relevance of AEM and TEM to Detect the Groundwater Aquifer at Faiyum Oasis Area, Faiyum, egypt

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International Journal of Geosciences 2014年第6期5卷 611-621页

作者： A. A. Basheer A. I. Taha A. El-Kotb F. A. Abdalla S. O. Elkhateeb Geology Department Faculty of Science South Valley University Qena Egypt Geomagnetic and Geoelectric Department National Research Institute of Astronomy and Geophysics Cairo Egypt

This study investigates the groundwater aquifer located in Fayuim oasis. In this study, two of the electromagnetic measurement methods have been used in determining the hydrological situation in the Fayoum oasis. The first is airborne electromagnetic (AEM) which, sometimes is referred to as Helicopter electromagnetic (HEM) and the second is ground Time-domain Electromagnetic method (TEM). The subsurface consists of four geoelectrical layers with a rough slope towards the center. The third and the fourth layers in the succession are suggested to be the two-groundwater aquifers. The third layer saturates with fresh water overlying saline water which exists in the bottom of the second one. It is worth mentioning that the depth of the fresh water surface undulates between the surface level in two lakes in the study area and 57 meters below the ground, whereas the thickness of the fresh water aquifer varies from 13 to 36 meters. The depth of the saline water surface undulates between 59 and 81 meters below the ground. In general, airborne electromagnetic surveying has the advantage of fast resistivity mapping with high lateral resolution. Groundbased geophysical surveys are often more accurate, but they are definitely slower than airborne surveys. It depends on targets of interest, time, budget, and manpower available by the method or the combination of methods that will be chosen. A combination of different methods is useful to obtain a detailed understanding of the subsurface resistivity distribution.

关键词： Airborne Electromagnetic [Frequency-Domain] Ground Electromagnetic [Time-Domain] AEM TEM Hydrogeophysics Al Faiyum Oasis/Lake egypt

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Multiscale Stategies in Automatic Image-Domain Waveform Tomography

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Journal of Earth Science 2015年第4期26卷 577-585页

作者： Yujin Liu Zhenchun Li Department of geophysics China University of Petroleum Exploration & Production research institute SINOPEC

Multiscale strategies are very important in the successful application of waveform-based velocity inversion. The strategy that sequentially preceeds from long to short scale of velocity model, has been well developed in full waveform inversion （FWI） to solve the local mininum problem. In contrast, it＇s not well understood in the image-domain waveform tomography （IWT）, which back-projects incoherent waveform components of the common image gather into velocity updates. IWT is less prone to local minimum problem but tends to build long-scale model with low resolution. In order to build both long- and short-scale model by IWT, we discuss several multiscale strategies restricted in the image domain. The strategies include model reparameterization, objective function switching and gradient rescaling. Numerical tests on Marmsousi model and real data demonstrate that our proposed multiscale IWT is effective in buidling velocity model with wide wavenumber spectrum.

关键词： velocity estimation waveform inversion tomography multiscale inversion common image gather.

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The Holocene Activity Evidence of the Yema River-Daxue Mountain Fault in Western Qilian Mountain

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Acta Geologica Sinica(English Edition) 2013年第6期87卷 1569-1584页

作者： LUO Hao HE Wengui YUAN Daoyang SHAOYanxiu Key Laboratory of Engineering Geomechanics Institute of Geology and Geophysics Chinese Academy of Sciences Earthquake research institute of Lanzhou China Earthquake Administration Lanzhou national Geophysical Observatory

Altyn Tagh fault controls the deformation characteristics of the northern margin of the Qinghai-Tibet *** 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 *** them,the Yema River-Daxue Mountain fault is one of the important structural transform faults in the study *** 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 *** excavated trenches imply a total of 6 paleoearthquake 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,*** 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 *** 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.

关键词： paleoearthquake earthquake recurrence interval reference magnitude Yema River-Daxue Mountain fault Altyn Tagh fault

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An Asthenospheric Upwelling Beneath Central Mongolia——Implications for Intraplate Surface Uplift and Volcanism

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Acta Geologica Sinica(English Edition) 2021年第S01期95卷 70-72页

作者： Matthew J.COMEAU Michael BECKEN Alexey V.KUVSHINOV Alexander GRAYVER Johannes KAUFL Erdenechimeg BATMAGNAI Shoovdor TSERENDUG Sodnomsambuu DEMBEREL Institut für Geophysik Universitat MünsterGermany institute of geophysics ETHZürichSwitzerland institute of astronomy and geophysics Mongolian Academy of SciencesUlaanbaatarMongolia

Intraplate processes,such as continental surface uplift and intraplate volcanism,are enigmatic and the underlying mechanisms responsible are not fully *** Mongolia is an ideal natural laboratory for studying such proc... 详细信息

关键词： magnetotellurics electrical resistivity lithosphere structure intraplate volcanism surface uplift mantle upwelling lithosphere removal thermo-mechanical modeling

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Detecting seismic electromagnetic ELF anomalies associated with the 2010 Yushu earthquake in China by DEMETER observations and ELF Lithosphere-Atmosphere-Ionosphere coupling propagating model

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Science China(Technological Sciences) 2023年第4期66卷 1192-1202页

作者： LIAO Li ZHAO ShuFan SHEN XuHui ZEREN ZhiMa PENG HuaiYun LU HengXin institute of geophysics China Earthquake AdministrationBeijing 100081China national institute of Natural Hazards Ministry of Emergency Management of ChinaBeijing 100085China China research institute of Radiowave Propagation Qingdao 266107China

Over the last century,abnormal electromagnetic(EM)emissions associated with earthquake(EQ)activities have been widely reported and recorded by ground-based and satellite ***,the frequency at which abnormal EM emissions have been detected *** addition,whether low Earth orbit(LEO)satellites can detect EM anomalies from EQs remains *** this paper,we take the Yushu earthquake as an example to address these concerns by DEMETER satellite observations and a newly constructed lithosphere-atmosphere-ionosphere model of extremely low frequency(ELF)wave *** results illustrate that the frequency of ELF EM anomalies of the Yushu earthquake is mainly at 200–400 *** observations and simulations illustrate that the power-frequency curve of the ELF EM wave from an underground source has a peak power frequency at 200–400 Hz,which is significantly different from the ELF EM wave radiated from the ground source.

关键词： seismic electromagnetic anomalies extremely low frequency(ELF)wave low Earth orbit(LEO)satellites lithosphereatmosphere-ionospheremodel

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