Lithospheric structure across the Himalayan-Tibetan orogen: a petrological and geophysical study

Abstract HKT-ISTP 2013 A

LZER0: A Cost-Effective Multi-Purpose GNSS Platform

Recent advances in Global Navigation Satellite System (GNSS) technology have made low-cost sensors available to the mass market, opening up new opportunities for real-time ground deformation and structure monitoring. In this paper, we present a new product developed in this framework by the National Institute of Oceanography and Applied Geophysics–OGS in collaboration with a private company (SoluTOP SAS): a cost-effective, multi-purpose GNSS platform called LZER0, suitable not only for surveying measurements, but also for monitoring tasks. The LZER0 platform is a complete system that includes the GNSS equipment (M8T single-frequency model produced by u-blox) and the web portal where the results are displayed. The GNSS data are processed using the RTKLIB software package, and the processed results are made available to the end user. The relative positioning mode was adopted both with real-time and post-processing RTKLIB engines. We present three applications of LZER0—cadastral, monitoring, and automotive—which demonstrate that it is a flexible, multi-purpose platform that is easy to use in terms of both hardware and software, and can be easily deployed to perform various tasks in the research, educational, or professional sectors

A New Southern North Atlantic Isochron Map: Insights Into the Drift of the Iberian Plate Since the Late Cretaceous

This paper presents a new southern North Atlantic plate model from Late Cretaceous to present, with the aim of constraining the kinematics of the Iberian plate during the last 83.5 Myr. This model is presented along with a detailed isochron map generated through the analysis of 3 aeromagnetic tracks and ~400 ship tracks from the National Centers for Environmental Information database. We present a new technique to obtain well‐constrained estimates of the Iberia‐North America plate motions from magnetic anomalies, overcoming the scarcity of large‐offset fracture zones and transform faults. We build an integrated kinematic model for NW Africa, Morocco, Iberia, Europe, and North America, which shows that the deformation is partitioned between Pyrenees and Betic‐Rif orogenic domain during the Late Cretaceous‐Oligocene time interval. In the Eastern Betics domain, the calculated amount of NW Africa‐Iberia convergence is ~80 km between 83.5 and 34 Ma, followed by ~150 km since the Oligocene. The motion of Iberia relative to Europe in the Central Pyrenees is characterized by overall NE directed transpressional motion during the Campanian and the Paleocene, followed by NW directed transpressional movement until the Lutetian and overall NNW directed convergence from Bartonian to Chattian. This motion occurs along the axis of the Bay of Biscay from the Santonian–Campanian boundary to the middle Priabonian, subsequently jumping to King's Trough at Anomaly 17 (36.62 Ma)

The Central Asia collision zone: numerical modelling of the lithospheric structure and the present-day kinematics

[eng] The Central Asia region is dominated by the Zagros orogen in the western sector and the Himalaya-Tibetan orogen in the eastern sector, which resulted from the subduction of the Tethys oceanic lithosphere towards the NNE and the subsequent collision of the Arabia and India plates with the Eurasia plate during the Cenozoic. The collisions produced tectonic escapes toward lateral regions (in Anatolia and south-eastern Tibet), oblique convergence in the Zagros fold-and-thrust belt, the formation of the Makran subduction zone and shortening in Himalaya, Karakorum and Tibetan Plateau. Different mountain belts also developed far into the continent interiors, e.g. Caucasus, Alborz, Kopet Dagh, Pamir and Tian Shan. The lithosphere structure plays an important role in controlling the surface deformation and its propagation inside the continent. The compositional and strength heterogeneities within the lithosphere directly affect the tectonic behaviour of the region and, hence, the evolution of the orogenic systems. This Thesis focalizes on the characterization of the lithospheric structure of the Zagros and the Himalayan-Tibetan orogens and on the role of the lithospheric structure and rheology in the accommodation of the deformation related to the Arabia and India convergence against Eurasia. The lithospheric structure of the Zagros and the Himalaya-Tibetan orogens has been characterized from the thermal, compositional and seismological viewpoint using an integrated geophysical-petrological modelling approach. The models make compatible seismic, density and thermal modelling findings, and allow quantifying the effect of mineral physics on previous results from integrated thermal models. The results obtained in the Zagros orogen reveal that the transition from the Arabian to the Eurasian lithosphere is characterized by a thinning of the lithospheric mantle extending from the suture zone beneath the Zagros range to the Alborz in the North and the Central Iran. The lithospheric mantle composition is compatible with a Proterozoic peridotitic mantle-type beneath the Arabian Platform, the Mesopotamian Foreland Basin and the accreted terrains of the Eurasia plate, and with a more depleted Phanerozoic harzburgitic mantle-type below the frontal parts of the Zagros range. In the Himalaya-Tibetan orogen, the results suggest that the present-day lithospheric mantle structure is laterally-varying within the Tibetan Plateau in the east-west direction. The lithospheric mantle is thicker and more buoyant in the western sector than in the north-eastern sector. The lherzolitic mantle-type is the dominant mantle composition, but it changes to a more fertile composition beneath the Tarim Basin, to a Fe-Mg-rich mantle beneath Tian Shan, Junggar and Altai regions, and to highly MgO-depleted mantle in the north-eastern Tibetan Plateau. The results on the present-day lithospheric structure of the Zagros and the Himalaya-Tibetan orogens have been combined with the present-day kinematics, geodetic observations and stress data to characterize the current deformation patterns in the Central Asia region related to the tectonic convergence of the Arabia and India plates with Eurasia. The thin-sheet approach allowed investigating the effect of the lithospheric structure, rheology, boundary conditions, and friction coefficient on the predicted velocity and stress fields. The models reproduce the main directions of the velocities in Central Asia by only imposing the convergence of Arabia and India plates respect to the fix Eurasia, and varying the rheology parameters. The models simulate the observed kinematics including the counter-clockwise rotation of Arabia and Iran triggering the westward escape of Anatolia, and the eastward extrusion of the northern Tibetan Plateau structural domains. Besides the large scale, the models offer a coherent result in regions with little or no data coverage, as in the case of the Arabia-India inter-collision zone, over large areas of Pakistan and entire Afghanistan. The study has been supported by the project ATIZA (CGL2009-09662-BTE), and the FPI grant associated to.[spa] Asia Central está dominada por dos importantes orógenos, el orógeno del Zagros y el sistema Himalaya-Tibet, resultantes de de la colisión de las placas Arábiga e India con el margen meridional de la placa Eurasiática. Esta Tesis se focaliza en: 1) la caracterización del manto litosférico a través de un metódo de modelización geofísico-petrológico integrado y 2) el estudio del efecto de la estructura litosférica y de la reología en la deformación neotectónica relacionada con la convergencia de Arabia y de India respecto a Eurasia utilizando una metodología basada en la aproximación de lámina delgada (thin-sheet). En el caso del orógeno del Zagros, los resultados revelan que el manto litosférico se adelgaza debajo de Irán Central, del Alborz y parcialmente debajo de la cordillera del Zagros. En el caso del sistema Himalaya-Tibet, los resultados indican una litosfera engrosada en el sector occidental, debajo de la cordillera Himalaya, Meseta del Tibet, Kunlun Shan y Tian Shan, y un adelgazamiento debajo de las cuencas de Tarim y de Junggar. En el sector oriental los resultados confirman que la Meseta del Tibet está suportada por una litosfera más adelgazada y caliente en el norte que en el sur. Ha sido necesario introducir variaciones laterales de composición mantélica, relacionadas con procesos del manto litosférico superior, en todos los perfiles modelados evidenciando la presencia de diferentes dominios litosféricos. El estudio de la deformación neotectónica ha revelado el rol clave de la reología en la reproducción del campo de esfuerzos y de velocidades en Asia Central, sugiriendo una litosfera menos rígida en la Meseta del Tibet que en la meseta de Irán. En conjunto, la deformación es más rápida en la zona de colisión India-Eurasia que en la zona de colisión Arabia-Eurasia. Finalmente, la presencia de un manto adelgazado en el noreste del Tibet y la consecuente disminución de viscosidad debida al aumento de temperatura explicarían la presencia de fallas extensionales en la Meseta del Tibet y reconciliarían el modelo con los datos de flujo de calor elevado y bajas velocidades sísmicas registrados en la región. Esta tesis ha sido financiada por el proyecto ATIZA (CGL2009-09662-BTE) y la beca FPI asociad

Applicability of Cost-Effective GNSS Sensors for Crustal Deformation Studies

The geodetic monitoring of the continuous crustal deformation in a particular region has traditionally been the prerogative of the scientific communities capable of affording high-price geodetic-class instruments to track the tiny movements of tectonic plates without losing precision. However, GNSS technology has been continuously and rapidly growing, and in the last years, new cost-efficient instruments have entered the mass market, gaining the attention of the scientific community for potentially being high-performing alternative solutions. In this study, we match in parallel a dual-frequency low-cost receiver with two high-price geodetic instruments, all connected to the same geodetic antenna. We select North-East Italy as testing area, and we process the data together with the observations coming from a network of GNSS permanent stations operating in this region. We show that mm-order precision can be achieved by cost-effective GNSS receivers, while the results in terms of time series are largely comparable to those obtained using high-price geodetic receivers

Vertical crustal movements in Italy from tidal gauge and satellite altimetry data

Geophysical Research Abstracts Vol. 12, EGU2010-12894-3,2010 EGU General Assembly 2010 Vienna, 2-7 /05/201

Sea level variability and trends in the Adriatic Sea \uedn 1993-2008 from tide gauges and satellite altimetry. Physics and Chemistry of the Earth

The scope of this paper is to give a consistent view of the low frequency sea level variability in the Adriatic Sea from both satellite altimetry and tide gauge records. We analyze 16 years of sea level observations from multi-satellite altimetry and tide gauge records in the time interval 1993\u20132008. First, the impact of the corrections applied to the altimetry-derived sea level variations and the consistency of the altimetric and the tide gauge sea level observations are evaluated. Both observations are then used to characterize sea level trends, interannual variability and land vertical motion in the Adriatic region. Eight tide gauges along the coast show very coherent interannual sea level variations, with an increase in sea level before 2001 and decrease afterwards. The average of the eight de-seasoned time-series agrees with the basin average of the altimeter data, with correlation coefficient 0.84 and root mean square difference 12 mm. The linear change is higher for altimetry than for tide gauges and strongly depends on the length of the time-interval, being 3.2 \ub1 0.3 mm/yr and 1.9 \ub1 0.3 mm/yr in the interval 1993\u20132008. The steric contribution to sea level change correlates well with the sea level suggesting that the low frequency variability is likely related to oceanic and climatic processes and mainly due to temperature and salinity variations. The decadal sea level variability is correlated in Adriatic and Eastern Mediterranean, anti-correlated in Adriatic and Ionian Sea. At a given location, the trend of the differences of sea level observations by tide gauges and co-located satellite altimetry gives the vertical land motion, if we assume that the sea level signals are truly common. We find trends statistically significant at the 90% confidence level at two locations, that indicate land uplift along the eastern coast in Rovinj (3.0 \ub1 1.2 mm/yr) and land subsidence in Marina di Ravenna (1.5 \ub1 1.1 mm/yr), while at other locations, e.g. in Trieste (1.3 \ub1 1.1 mm/yr) the significance is lower. The results agree in general in sign with GPS derived rates, but not in magnitude, like in Marina di Ravenna, where the strong subsidence measured by GPS is related to the local anthropogenic subsidence. The differences are partly explained by the spatial distance between the tide gauge and the co-located altimeter locations

Continental Deformation in Central Eurasia: Insights From a Neotectonic Study

The Central Eurasia region hosts wide deforming areas, with diffused or localized deformation occurring even hundreds of kilometres behind the Arabia-Eurasia and India-Eurasia plate boundaries. A key-parameter controlling the propagation of deformation to the continent interiors is the lithosphere strength. By using a numerical technique based on the thin-sheet approximation, we explore the present-day deformation in Central Eurasia and the relative contributions of the lithospheric structure, rheology, boundary conditions, and friction coefficient on faults on the predicted velocity and stress fields. The lithosphere strength is calculated from the lithosphere structure and thermal regime. A crustal and lithospheric map derived from the combination of elevation and geoid anomaly with thermal analysis, showing thin lithosphere beneath the Iranian Plateau and thick lithosphere beneath the Tibetan Plateau, is used to build a reference model. Changes in the rheological parameters, friction coefficient on faults and velocity boundary conditions have been applied. A model with thin lithosphere in NE-Tibet following previous geophysical studies has been also considered. Models have been evaluated by comparing the predictions with available data on seismic deformation, stress directions and GPS velocities. A first order approximation of the velocity and stress directions is obtained, reproducing the counter-clockwise rotation of Arabia and Iran, the westward escape of Anatolia, and the eastward extrusion of the northern Tibetan Plateau. To simulate the observed extensional faults within Tibet a weaker lithosphere is required, provided by i) a change in the rheological parameters or ii) reduction of the lithosphere thickness in NE-Tibet. The temperature increase generated by the lithospheric thinning would allow also reconciling the model with the high heat flow and low mantle seismic velocities observed in the area.Peer Reviewe

Combining the present-day lithospheric structure of Central Eurasia with plate kinematics: study of the current deformation along the southern margin of the Eurasia plate

Annual TOPO-EUROPE workshop, Antibes (France), Oct 4-7, 2015We model the neotectonic deformation in Central Eurasia to nvestigate the relative contributions of the lithospheric structure, rheology, boundary conditions, and friction coefficient on faults on the predicted velocity and stress fields related to the tectonic convergence of the Arabia and India plates against a fix Eurasia plate. The applied geodynamic modelling technique (SHELLS, Bird et al., 2008) allows inferring the surface velocity field, stress directions, tectonic regime and strain distribution by applying velocity conditions to the model boundaryThe present work is supported by ATIZA (CGL2009-09662-BTE), TECLA (CGL2011-26670), Topo-Iberia (CSD2006-0004) projects. A big thank you to Peter Bird for the helpful be reproduced with the thin-sheet approach.and constructive discussions on thin-sheet model