检索结果-南通市图书馆

Chinese Science Bulletin 2012年第16期57卷 1990-1997页

作者： DIAO FaQi XIONG Xiong ZHENG Yong state key laboratory of geodesy and earth's Dyanmics Institute of Geodesy and GeophysicsChinese Academy of SciencesWuhan 430077China

Based on co-seismic displacements recorded by terrestrial GPS stations and seafloor GPS/acoustic stations, the static slip model of the 2011 Mw 9.0 Tohoku earthquake was determined by inverting the data using a layered earth model. According to a priori information, the rupture surface was modeled with a geometry that is close to the actual rupture, in which the fault dip angle increases with depth and the fault strike varies with the trend of the trench. As shown by the results inferred from the joint inversion, the "geodetic" moment is 3.68 × 10 22 Nm, corresponding to Mw 9.01, and the maximum slip is positioned at a depth of 13.5 km with a slip magnitude of 45.8 m. Rupture asperities with slip exceeding 10 m are mainly distributed from 39.6 to 36.97°N, over a length of almost 240 km along the trench. The slip was mostly concentrated at depths shallower than 40 km, up-dip of the hypocenter. "Checkerboard" tests reveal that a joint inversion of multiple datasets can resolve the slip distribution better than an inversion with terrestrial GPS data only-especially when aiming to resolve slip at shallow depths. Thus, the joint inversion results obtained by this work may provide a more reliable slip model than the results of other studies that are only derived from terrestrial GPS data or seismic waveform data.

关键词： GPS数据联合反演滑移模型地震位移地面海底静态东北

Rayleigh wave phase velocities of South China block and its adjacent areas

在线全文

学校读者我要写书评

暂无评论

Science China earth Sciences 2016年第11期59卷 2165-2178页

作者： L Jian XIE ZuJun ZHENG Yong ZHA XiaoHui HU Rui ZENG XinFu earthquake Administration of Jiangxi Province Nanchang 330039 China state key laboratory of geodesy and earth's Dynamics Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China

Using records of continuous seismic waveforms from 609 broadband seismic stations in the South China Block and its adjacent areas in 2010–2012, empirical Green's functions of surface waves were obtained from cross-correlation functions of ambient noise data between these stations. High quality phase velocity dispersion curves of Rayleigh waves were obtained using time-frequency analysis. These interstation dispersion curves were then inverted to build Rayleigh wave phase velocity maps at periods of 6–50 s. The results of phase velocity maps indicate that phase velocities at 6–10 s periods are correlated with the geological features in the upper crust. Major basins and small-scale grabens and basins display slow velocity anomalies; while most of the orogenic belts and the fold belts display high velocity anomalies. With the gravity gradient zone along Taihang Mountain to Wuling Mountain as the boundary for the phase velocity maps at period of 20–30 s, the western area mainly displays low velocity anomalies, while the eastern side shows high velocity anomalies. Phase velocities in the eastern South China Block south to the Qinling-Dabie orogenic belt is higher than that in the eastern North China Block to the north, which is possibly due to the differences of tectonic mechanisms between the North China Craton and the South China Block. The phase velocities at periods of40–50 s are possibly related to the lateral variations of the velocity structure in the lower crust and upper mantle: The low-velocity anomalies in the eastern part of the Tibetan Plateau are caused by the thick crust; while the Sichuan Basin and the southern part of the Ordos Basin display distinct high-velocity anomalies, reflecting the stable features of the lithosphere in these blocks. The lateral variation pattern of phase velocities in the southern part of the South China Block is not consistent with the surface trace of the block boundary in the eastern Yunnan Province and its vicinities. The pha

关键词： South China block Ambient noise Phase velocity tomography Crust and upper mantle

Magnitude and rupture duration from high frequency teleseismic P wave with projected landweber deconvolution

在线全文

学校读者我要写书评

暂无评论

Science China earth Sciences 2013年第1期56卷 13-21页

作者： ZHENG Yong NI SiDao CHEN Yong TAN Ying Don HELMBERGER state key laboratory of geodesy and earth's Dynamics Institute of Geodesy and Geophysics Chinese Academy of Sciences Institute of Geophysics Chinese Earthquake Administration Seismological laboratory California Institute of Technology

earthquake magnitude and rupture duration are among the most important parameters characterizing an earthquake for the purpose of early tsunami warning. While they can be routinely determined from broadband P waveforms with iterative inver- sion procedures, the inversion procedures may fail when the rupture either lasts longer than the interval between P and later ar- rivals or requires too much time or human intervention. Little contaminated by later arrivals, high frequency P waves are useful for modeling earthquake source processes, though the envelope waveform is affected by strong scattering in lithosphere. With high frequency envelopes from aftershocks as Empirical Green＇s Function （EGF）, the coda effects can be removed and more accurate relative source time function （RSTF） of the main shock can be obtained. Assuming that RSTFs cannot be negative, we use the projected Landweber deconvolution method （PLD） to obtain high frequency RSTFs because PLD method has the ad- vantage of non-negativity, causality, and compactness （finite duration）. We are able to determine rupture durations of four large earthquakes： the 2004 Sumatra-Andaman earthquake, the 2005 Nias event, the 2006 Java event, and the 2011 Tokuko earthquake. The rupture durations of the Sumatra-Andaman, Nias, and Tohuko events are found to be around 550, 1 i0, and 120 s respectively, consistent with previous studies. The rupture duration of the Java event is about 130 s, supporting that the Java event is a tsunami earthquake. The magnitudes of these earthquakes are found to depend on both the amplitude and the duration of the deconvolved waveforms, and can be approximated by integrating these waveforms.

关键词： high frequency deconvolution rupture duration magnitude

The electrical conductivity of eclogite in Tibet and its geophysical implications

在线全文

学校读者我要写书评

暂无评论

Science China earth Sciences 2014年第9期57卷 2071-2078页

作者： GUO YingXing WANG DuoJun SHI YaoLin ZHOU YongSheng DONG YongSheng LI Cai key laboratory of Computational geodynamics University of Chinese Academy of Sciences The state key laboratory of earthquake Dynamics Institute of Geology China Earthquake Administration College of earth Sciences Jilin University

The electrical conductivity of Tibetan eclogite was investigated at pressures of 1.5-3.5 GPa and temperatures of 500-803 K using impedance spectroscopy within a frequency range of 10-1 -10^6 Hz. The electrical conductivity of eclogite increases with increasing temperature （which can be approximated by the Arrhenius equation）, and is weakly affected by pressure. At each tested pressure, the electrical conductivity is weakly temperature dependent below -650 K and more strongly temperature de- pendent above -650 K. The calculated activation energies and volumes are 44±1 kJ/mol and -0.6±0.1 cm3/mol for low tem- peratures and 97±3 kJ/mol and -1.2±0.2 cm3/mol for high temperatures, respectively. When applied to the depth range of 45-100 km in Tibet, the laboratory data give conductivities on the order of 10^-15 -10^-4.5 S/m, within the range of geophysical conductivity profiles.

关键词： electrical conductivity high temperature and pressure eclogite

Near-surface Geothermal Gradient Observation and Geothermal Analyses in the Xianshuihe Fault Zone,Eastern Tibetan Plateau

在线全文

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 2017年第2期91卷 414-428页

作者： LIU Qianqian SHI Yanan WEI Dongping HAN Peng CHEN Shunyun LIU Peixun LIU Liqiang key laboratory of Computational geodynamics Chinese Academy of Sciences College of earth Science University of Chinese Academy of Sciences state key laboratory of earthquake Dynamics Institute of GeologyChina Earthquake Administration

The Xianshuihe fault（XSHF） zone, characterized by intense tectonic activity, is located at the southwest boundary of the Bayan Har block, where several major earthquakes have occurred, including the 2008 Wenchuan and the 2013 Lushan earthquakes. This study analysed underground temperature sequence data for four years at seven measuring points at different depths（maximum depth： 18.9 m） in the southeastern section of the XSHF zone. High-frequency atmospheric noise was removed from the temperature sequences to obtain relatively stable temperature fields and heat fluxes near the measurement points. Our measurements show that the surrounding bedrock at（the seven stations distributed in the fault zone） had heat flux values range from-41.0 to 206 m W/m^2, with a median value of 54.3 m W/m^2. The results indicate a low heat flux in the northern section of DaofuKangting and a relatively high heat flux in the southern section of Kangting, which is consistent with the temperature distributions of the hot springs near the fault. Furthermore, our results suggest that the heat transfer in this field results primarily from stable underground heat conduction. In addition, the underground hydrothermal activity is also an obvious factor controlling the geothermal gradient.

关键词： temperature sequence records geothermal gradient heat flow heat flux Xianshuihe fault zone Tibet Plateau Proto-Tethys

Global sea level variations from altimetry,GRACE and Argo data over 2005-2014

在线全文

学校读者我要写书评

暂无评论

geodesy and geodynamics 2015年第4期6卷 274-279页

作者： Feng Wei Zhong Min state key laboratory of geodesy and earth's Dynamics Institute of Geodesy and GeophysicsChinese Academy of Sciences

Total sea level variations（SLVs） are caused by two major components：steric variations due to thermal expansion of seawater,and mass-induced variations due to mass exchange between ocean and *** this study,the global SLV and its steric and mass components were estimated by satellite altimetry,Argo float data and the Gravity Recovery and Climate Experiment（GRACE） data over *** gravimetry observations from GRACE suggested that two-thirds of the global mean sea level rise rate observed by altimetry（i.e.,3.1 ± 0.3 mm/a from 2005 to 2014） could be explained by an increase in ocean ***,the global mean sea level was observed to drop significantly during the2010/2011 La Nina event,which may be attributed to the decline of ocean mass and steric *** early 2011,the global mean sea level began to rise rapidly,which was attributed to an increase in ocean *** findings in this study suggested that the global mean sea-level budget was closed from 2005 to 2014 based on altimetry,GRACE,and Argo data.

关键词： Sea level variations Gravity Recovery and Climate Experiment (GRACE)Altimetry ArgoOcean mass change La Nina event Steric sea level Sea level budget

Progress in satellite gravity recovery from implemented CHAMP,GRACE and GOCE and future GRACE Follow-On missions

在线全文

学校读者我要写书评

暂无评论

geodesy and geodynamics 2015年第4期6卷 241-247页

作者： Zheng Wei Xu Houze state key laboratory of geodesy and earth's Dynamics Institute of Geodesy and GeophysicsChinese Academy of Sciences

Firstly, the earth＇s gravitational field from the past Challenging Minisatellite Payload （CHAMP） mission is determined using the energy conservation principle, the combined error model of the cumulative geoid height influenced by three instrument errors from the current Gravity Recovery and Climate Experiment （GRACE） and future GRACE Follow-On missions is established based on the semi-analytical method, and the earth＇s gravitational field from the executed Gravity Field and Steady-state Ocean Circulation Explorer （GOCE） mission is recovered by the space-time-wise approach. Secondly, the cumulative geoid height errors are 1.727 × 10^-1 m, 1.839 × 10^-1 m and 9.025 × 10^ -2 m at degrees 70,120 and 250 from the implemented three-stage satellite gravity missions consisting of CHAMP, GRACE and GOCE, which preferably accord with those from the existing earth gravity field models involving EIGEN-CHAMP03S, EICEN-GRACE02S and GO_CONS GCF 2 DIR R1. The cumulative geoid height error is 6.847 × 10 ^-2 m at degree 250 from the future GRACE Follow-On mission. Finally, the complementarity among the four-stage satellite gravity missions including CHAMP, GRACE, GOCE and GRACE Follow-On is demonstrated contrastively.

关键词： CHAMP (Challenging Minisatellite Payload)GRACE (Gravity Recovery and Climate Experiment)GOCE (Gravity Field and Steady-state Ocean Circulation Explorer)GRACE Follow-OnEnergy conservation principle Semi-analytical method Space-time-wise approach

Precise geoid computation using Stokes-Helmert’s scheme and strict integrals of topographic effects

在线全文

学校读者我要写书评

暂无评论

geodesy and geodynamics 2019年第4期10卷 290-296页

作者： Dongmei Guo Huiyou He Peng Sang state key laboratory of geodesy and earth’s Dynamics Institute of Geodesy and Geophysics The Chinese Academy of Science

The high-precision local geoid model was computed based on the improved Stokes-Helmert0 s boundary value problem and strict integrals of topographic effects. This proposed method involves three ***, the mathematical form of Stokes-Helmert0 s boundary value problem was derived, and strict computational formulas regarding topographic effects were provided to overcome the disadvantage of planar approximations. Second, a gravimetric geoid model was constructed using the proposed StokesHelmert0 s scheme with a heterogeneous data set. Third, a least squares adjustment method combined with a multi-surface function model was employed to remove the bias between the gravimetric geoid model and the GNSS/leveling data and to refine the final local geoid model. The accuracy of the final geoid model was evaluated using independent GNSS/leveling data. Numerical results show that an external precision of 1.45 cm is achievable.

关键词： Geoid computation Stokes-Helmert’s method Surface integration Heterogeneous heights

Crustal S-velocity structure and radial anisotropy beneath the southern part of central and western North China Craton and the adjacent Qilian Orogenic Belt from ambient noise tomography

在线全文

学校读者我要写书评

暂无评论

Science China earth Sciences 2017年第10期60卷 1752-1768页

作者： LING Yuan CHEN Ling WEI ZiGen JIANG MingMing WANG Xu state key laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China College of earth Sciences University of Chinese Academy of Sciences Beijing 100049 CAS Center for Excellence in Tibetan Plateau earth Sciences Beijing 100101 China state key laboratory of geodesy and earth's Dynamics Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China key laboratory of the earth and Planetary Physics Chinese Academy of Sciences Beijing 100029 China

The crustal S-velocity structure and radial anisotropy along a dense linear portable seismic array with 64 broadband seismic stations were investigated from ambient noise tomography with about one-year-long ambient noise recordings. The array transverses the southern part of the central North China Craton(CNCC) and western NCC(WNCC) from east to west and reaches the adjacent Qilian Orogenic Belt(QOB). The phase velocity structures of Rayleigh waves at 5–35 s and Love waves at 5–30 s were measured. The crustal S-velocity structures(Vsv and Vsh) were constructed from the dispersion data(Rayleigh and Love waves,respectively) from point-wise linear inversion with prior information of the Moho depth and average crustal Vp/Vs ratio. The radial anisotropy along the profile was calculated based on the discrepancies between Vsv and Vsh as 2×(***)/(Vsh+Vsv). The results show distinct structural variations in the three major tectonic units. The crustal architecture in the southern CNCC is complicated and featured with wide-distributed low-velocity zones(LVZs), which may be a reflection of crustal modification resulting from Mesozoic-Cenozoic tectonics and magmatic activities. The pronounced positive radial anisotropy in the lower-lowermost crust beneath the Shanxi-Shaanxi Rift and the neighboring areas could be attributed to the underplating of mantle mafic-ultramafic materials during the Mesozoic-Cenozoic tectonic activation. In southern Ordos, the overall weak lateral velocity variations, relative high velocity and large-scale positive radial anisotropy in mid-lower crust probably suggest that the current crustal structure has preserved its Precambrian tectonic characteristics. The low-velocity westward-dipping sedimentary strata in the Ordos Block could be attributed to the Phanerozoic whole-basin tilting and the uneven erosion since late Cretaceous. Integrated with previous studies, the systematic comparison of crustal architecture was made between the southern and nor

关键词： North China Craton Qilian Orogenic Belt Ambient noise tomography Crustal S-velocity structure Radial anisotropy

Special Topic： Cretaceous greenhouse palaeoclimate and sea-level changes

在线全文

学校读者我要写书评

暂无评论

Science China earth Sciences 2017年第1期60卷 1-4页

作者： XiuMian HU Michael WAGREICH Benjamin SAMES state key laboratory of Mineral Deposits Research School of Earth Sciences and Engineering Nanjing University China Department of geodynamics and Sedimentology Center for Earth Sciences University of Vienna Austria

earth＇s climate has oscillated between greenhouse （warm） and icehouse （cold） modes throughout earth history. At present, earth is in the midst of an icehouse climate interval, despite the anthropogenic contribution to global warming and sea-level rise due to industrialization during the past two centuries. This led to a dramatic increase in atmospheric CO2, mainly caused by the extensive burning of fossils fuels. The Cretaceous （145 to 66 million years ago） is the youngest prolonged greenhouse climate interval in the Phanerozoic, marked by very high global mean temperatures with some extreme warming peaks （＇hothouse＇ or ＇supergreenhouse＇）, largely absence of permanent continental ice sheets, a mean global sea-level having been some 250 m higher than that of today, and levels of carbon dioxide 4 to 10 times higher than those of the pre-industrial era. If temperature will continue to rise as quickly as in the last three decades, we are close to being at the cusp to a new greenhouse climate interval facing quickly rising global sea-level and reaching atmospheric CO2 levels of the ＇Cretaceous supergreenhouse＇ in about the years 2190-2260 （Hay, 2011）. Evidence from earth＇s history indicates that glacial-interglacial climate mode changes as well as past sea-level changes such as in the Cretaceous greenhouse occurred at rates orders of magnitude slower than observed at present. The recent rise in global sea-level in response to rising levels of atmospheric greenhouse gases, the associated global warm- ing, and the waning of continental ice shields is a primary concern for human society. To predict future sea-levels we need a better understanding of the record of past sea-level changes, especially in the greenhouse palaeoclimate modes. Therefore, understanding the Cretaceous palaeoclimate is essential for a more accurate prediction of future global climate, sea-level rise and environmental changes in a prospective ＇Cretaceous-like＇ greenhouse earth.

关键词： greenhouse Cretaceous warming anthropogenic despite throughout