检索结果-南通市图书馆

The subduction of the Copiapó aseismic ridge,is the causing.of the formation of metallic minerals deposits in north of Chile and Argentina?

在线全文

学校读者我要写书评

暂无评论

Geodesy and Geodynamics 2019年第6期10卷 471-476页

作者： Mario Gimenez Gemma Acosta Orlando Alvarez Agustina Pesce Federico Lince King.r Andres Folguera instituto geofisico sismologico volponi FCEFNUniversidad Nacional de San JuanCONICETRuta 12 Marguesado(Jardin de Los Poetas)RiνadaviaSanJuanArgentina IDEAN-CONICET Universidad de Buenos Aires Argentina

The results obtained in this work evince that the metallic mineral deposits located in the northern region of the Chilean-Pampean flat slab(in northern Chile and north-western Argentina),at approximately 27°30’S,would be related to the subduction of the Copiapo aseismic *** analysis of the gravity anomalies and vertical gravity gradient allows inferring.a deflection and truncation of the main trend of the Andean structures at the extrapolated zone of the Copiapo ridge beneath South ***,the general NNE-trend of the Andean structures are rotated locally to an ENE-strike within the area of the Ojos del Salado-San Buena Ventura *** explain that this anomalous behavior of the gravity derived anomalies is related to the deformational effects imprinted by the ridge *** with a low subduction angle(y dehydration of the subducting.*** addition,a higher degree of mantle melting.could be produced by a thicker oceanic ***,we interpret that the processes associated to the subduction of the Copiapo aseismic ridge(emplaced on a thickened oceanic crust due to a local compensation of the seamounts)are the cause of formation and emplacement of big metallic mineral deposits in this region of Chile and Argentina.

关键词： Aseismic ridge Satellite gravity Ojos del Salado-San Buena Ventura lineament Metallic mineral deposits

Rupture area analysis of the Ecuador (Musine) Mw = 7.8 thrust earthquake on April 16, 2016, using.GOCE derived gradients

在线全文

学校读者我要写书评

暂无评论

Geodesy and Geodynamics 2017年第1期8卷 49-58页

作者： Orlando Alvarez Andres Folguera Mario Gimenez lnstituto geofisico y sismologico lng Volponi Universidad Nacional de San Juan Argentina Consejo Nacional de Investigaciones Cientificas y Tecnicas Argentina indean-instituto de Estudios Andinos "Don Pablo Groeber" Departamento de Cs. Geologicas FCEN Universidad de Buenos Aires Argentina

The Ecuador Mw - 7.8 earthquake on April 16, 2016, ruptured a nearly 200 km long zone along the plate interface between Nazca and South American plates which is coincident with a seismic gap since 1942, when a Mw - 7.8 earthquake happened. This earthquake occurred at a margin characterized by moderately big to giant earthquakes such as the 1906 （Mw 8.8）. A heavily sedimented trench explains the abnormal lengths of the rupture zones in this system as inhibits the role of natural barriers on the propagation of rupture zones. High amount of sediment thickness is associated with tropical climates, high erosion rates and eastward Pacific dominant winds that provoke orographic rainfalls over the Pacific slope of the Ecuatorian Andes. Offshore sediment dispersion off the oceanic trench is controlled by a close arrangement of two aseismic ridges that hit the Costa Rico and South Ecuador margin respectively and a mid ocean ridge that separates the Cocos and Nazca plate trapping.sediments. Gravity field and Ocean Circulation Explorer （GOCE） satellite data are used in this work to test the possible relationship between gravity signal and earthquake rupture structure as well as registered aftershock seismic activity. Reduced vertical gravity gradient shows a good correlation with rupture structure for certain degrees of the harmonic expansion and related depth of the causative mass; indicating. such as in other analyzed cases along the subduction margin, that fore-arc structure derived from density heterogeneities explains at a certain extent propagation of the rupture zones. In this analysis the rupture zone of the April 2016 Ecuador earthquake developed through a relatively low density zone of the fore-arc sliver. Finally, aftershock sequence nucleated around the area of maximum slips in the rupture zone, suggesting.that heterogeneous density structure of the fore-arc determined from gravity data could be used in forecasting.potential damaged zones associated with big rupture

关键词： Gravity field and Ocean Circulation Explorer(GOCE)Vertical gravity gradientEcuador earthquakeTrench sedimentsRupture zone

Goce derived geoid changes before the Pisagua 2014 earthquake

在线全文

学校读者我要写书评

暂无评论

Geodesy and Geodynamics 2018年第1期9卷 50-56页

作者： Orlando Alvarez Mario Gimenez Andrés Folguera Sofia Guillen Claudia Tocho instituto geofisico y Sismológico lng volponi FCEFyNUniversidad Nacional de San JuanArgentina Consejo Nacional de Investigaciones Cientificas y Técnicas Argentina INDEAN-instituto de Estudios Andinos"Don Pablo Groeber" Departamento de Cs.GeologicasFCENUniversidad de Buenos AiresArgentina Facultad de Ciencias Astronómicas y Geofisicas Universidad Nacional de La PlataArgentina

The analysis of space-time surface deformation during.earthquakes reveals the variable state of stress that occurs at deep crustal levels, and this information can be used to better understand the seismic cycle. Understanding.the possible mechanisms that produce earthquake precursors is a key issue for earthquake prediction. In the last years, modern geodesy can map the degree of seismic coupling.during.the interseismic period, as well as the coseismic and postseismic slip for great earthquakes along subduction zones. Earthquakes usually occur due to mass transfer and consequent gravity variations, where these changes have been monitored for intraplate earthquakes by means of terrestrial gravity measurements. When stresses and correspondent rupture areas are large, affecting.hundreds of thousands of square kilometres（as occurs in some segments along plate interface zones）, satellite gravimetry data become relevant. This is due to the higher spatial resolution of this type of data when compared to terrestrial data, and also due to their homogeneous precision and availability across the whole *** gravity missions as GOCE can map the Earth gravity field with unprecedented precision and resolution. We mapped geoid changes from two GOCE satellite models obtained by the direct approach,which combines data from other gravity missions as GRACE and LAGEOS regarding.their best characteristics. The results show that the geoid height diminished from a year to five months before the main seismic event in the region where maximum slip occurred after the Pisagua Mw = 8.2 great megathrust earthquake. This diminution is interpreted as accelerated inland-directed interseismic mass transfer before the earthquake, coinciding.with the intermediate degree of seismic coupling.reported in the region. We highlight the advantage of satellite data for modelling.surficial deformation related to preseismic displacements. This deformation, combined to geodetical and seismological dat

关键词： Satellite gravimetry Pre-seismic geoid changes Great megathrust earthquakes Subduction zones Forecasting.and monitoring

The westward lithospheric drift,its role on the subduction and transform zones surrounding.Americas:Andean to cordilleran orogenic types cyclicity

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2020年第4期11卷 1219-1229页

作者： Eugenio Aragon Fernando D'Eramo Marco Cuffaro Carlo Doglioni Eleonora Ficini Lucio Pinotti Silvina Nacif Manuel Demartis Irene Hernando Tomas Fuentes Centro de Investigaciones Geologicas Universidad Nacional de La PlataArgentina instituto de Ciencias de La Tierra Biodiversidad y Ambiente(ICBIA).Departamento de GeologíaUniversidad Nacional de Río Cuarto(UNRC-CONICET)Ruta 36 Km 601Río CuartoCordobaArgentina Istituto Geologia Ambientale e Geoing.gneria-CNR Italy Dipartimento de Scienzedella Terra Universita La SapienzaItaly instituto Geofísico sismologico F.volponi Universidad Nacional de San JuanArgentina

We investigate the effect of the westerly rotation of the lithosphere on the active margins that surround the Americas and find good correlations between the inferred easterly-directed mantle counterflow and the main structural grain and kinematics of the Andes and Sandwich arc *** the Andes,the subduction zone is shallow and with low dip,because the mantle flow sustains the slab;the subduction hing. converges relative to the upper plate and generates an uplifting.doubly verging.*** Sandwich Arc is generated by a westerly-directed SAM(South American) plate subduction where the eastward mantle flow is steepening.and retreating.the subduction *** this context,the slab hing. is retreating.relative to the upper plate,generating.the backarc basin and a low bathymetry sing.e-verging.accretionary *** Central America,the Caribbean plate presents a more complex scenario:(a) To the East,the Antilles Arc is generated by westerly directed subduction of the SAM plate,where the eastward mantle flow is steepening.and retreating.the subduction zone.(b) To the West,the Middle America Trench and Arc are generated by the easterly-directed subduction of the Cocos plate,where the shallow subduction caused by eastward mantle flow in its northern segment gradually steepens to the southern segment as it is infered by the preexisting.westerly-directed subduction of the Caribbean *** the frame of the westerly lithospheric flow,the subduction of a divergent active ridge plays the role of introducing.a change in the oceanic/continental plate’s convergence angle,such as in NAM(North American)plate with the collision with the Pacific/Farallon active ridge in the Neogene(Cordilleran orogenic type scenario).The easterly mantle drift sustains strong plate coupling.along NAM,showing.at Juan de Fuca easterly subducting.microplate that the subduction hing. advances relative to the upper *** lower/upper plate convergence coupling.also applies along strike to the neigh

关键词： Lithospheric drift Converging.hing. Diverging.hing. Slab rollbakc Terranes

Within plate seismicity analysis in the segment between the high Cordillera and the Precordillera of northern Mendoza(Southern Central Andes)

在线全文

学校读者我要写书评

暂无评论

Geodesy and Geodynamics 2018年第1期9卷 13-24页

作者： Julián Olivar Silvina Nacif Lucas Fennell Andrés Folguera CONICET-Universidad de Buenos Aires Instituto de Estudios Andinos"Don Pablo Groeber"(IDEAN)Facultad de Ciencias Exactas y NaturalesPabellón 11Ciudad UniversitariaBuenos AiresC1428EGAArgentina CONICET-instituto geofisico-Sismológico"lng.F.S.volponi"(IGSV) Ruta 12 km17 Jardfn de los Poetas MarquesadoRivadaviaProvincia de San JuanArgentina

Crustal seismicity in northwestern Mendoza Province in Argentina, corresponding.to the transition zone between the Chilean-Pampean flat subduction zone（26.5-33.5°S） and the Southern Central Andes normal subduction zone to the south, is studied in order to i） identify its relationship with the mapped structure, ii）determine deformational mechanisms and iii） constrain the geometry of the fold and thrust belt in the lower crust. Through this, we aim to determine which are the structures that contribute to Andean construction, east of the Frontal Cordillera in Argentina and at the western Principal Cordillera in Chile. Data from a temporary local seismic network are reprocessed in order to achieve a precise location of hypocenters and, whenever possible, to build focal mechanisms. Results are interpreted and compared with previous seismic studies and structural models. Analyzed seismicity is grouped around the eastern front of Frontal Cordillera, with hypocenters mainly at depths of 25-40 km. Contrasting.y, earthquakes in the Principal Cordillera to the west are located at the axial Andean sector and Chilean slope, with depths shallower than 15 km. Obtained focal mechanisms indicate mainly strike-slip displacements, left lateral at Frontal Cordillera and right lateral at Principal Cordillera. Based on these observations, new possible structural models are proposed, where seismogenic sources could be either associated with inherited basement structures from the Cuyania-Chilenia suture; or correspond to deep-blind thrusts linked with a deeper-than-previously-assumed decollement that could be shared between Frontal Cordillera and western Precordillera. This deeper decollement would coincide in turn with the one determined from receiver function analysis for the eastern Sierras Pampeanas in previous works, potentially implying.a common decollement all through the fold and thrust belt configuration. Apart from this, a new interpretation of seismogenic structures in Principal

关键词： Crustal seismicity Seismogenic structures Frontal cordillera Blind thrusts Decollement