Ground Penetrating Radar: Analysis of point diffractors for modeling and inversion

International audienceThe three electromagnetic properties appearing in Maxwell's equations are dielectric permittivity, electrical conductivity and magnetic permeability. The study of point diffractors in a homogeneous, isotropic, linear medium suggests the use of logarithms to describe the variations of electromagnetic properties in the earth. A small anomaly in electrical properties (permittivity and conductivity) responds to an incident electromagnetic field as an electric dipole, whereas a small anomaly in the magnetic property responds as a magnetic dipole. Neither property variation can be neglected without justification. Considering radiation patterns of the different diffracting points, diagnostic interpretation of electric and magnetic variations is theoretically feasible but is not an easy task using Ground Penetrating Radar. However, using an effective electromagnetic impedance and an effective electromagnetic velocity to describe a medium, the radiation patterns of a small anomaly behave completely differently with source-receiver offset. Zero-offset reflection data give a direct image of impedance variations while large-offset reflection data contain information on velocity variations

Physical impacts of the CE 1600 Huaynaputina eruption on the local habitat: Geophysical insights

[ESP] El impacto climático global de la erupción del volcán Huaynaputina (IEV6) en 1600 está bien documentado pero las consecuencias regionales sobre las construcciones y los habitantes están poco conocidas. La localización de varios pueblos sepultados bajo los depósitos espesos del Huaynaputina no es claramente mencionada en las crónicas españolas. Investigaciones geofísicas realizadas durante el periodo 2015-2016 sobre diferentes sitios de ruinas a menos de 16 km del cráter constituyen la parte inicial de un proyecto denominado “Huayruro”, cuyo objetivo es entender mejor los impactos físicos y socio-económicos de esta erupción. Varios métodos e instrumentos geofísicos fueron utilizados: un drone y modelos numéricos de terreno de alta resolución, un geo-radar con imágenes 3D del subsuelo, el magnetismo, las imágenes infra-rojas y el electro-magnetismo. Esta investigación geofísica preliminar ha permitido identificar la futura estratégia y la mejor instrumentación para cartografiar el área del antiguo pueblo enterrado de Calicanto, localizando con precisión su extensión y los muros de las habitaciones. Este mapeo servirá para los futuros estudios tefro-estratigráficos y arqueológicos. El objetivo final del proyecto es diseminar los resultados del estudio multidisciplinar al público incluyendo la creación de un museo de sitio

The Huayruro Project: mapping the Calicanto Inca area buried by the A.D. 1600 Huaynaputina eruption, with geophysical imaging and remote sensing

We present geophysical and remote sensing observations near the Quinistaquillas town (southern Peru), in the framework of the HUAYRURO Project. This Inca zone was buried during the A.D. 1600 Huaynaputina eruption, the most important volcanic phenomenon of the last 400 years. The eruption had a global impact, due to the volume of emitted ash (2-3 times the one emitted by Vesuvius in A.D. 79). This lead to a 1.13°C cooling of the planet and caused a worlwide agricultural crisis. During the eruption, the Calicanto-Chimpapampa zone was covered by ashes and pyroclastic flows, with a thickness in the range [1 - 20] m. From 2015 to 2017, remote sensing and geophysical methods were deployed to map a ~ 1 km*2 km area, up to 3-m depth

The ice-free topography of Svalbard

We present a first version of the Svalbard ice-free topography (SVIFT1.0) using a mass-conserving approach for mapping glacier ice thickness. SVIFT1.0 is informed by more than 900’000 point-measurements of glacier thickness, totalling almost 8’300 km of thickness profiles. It is publicly available for download. Our estimate for the total ice volume is 6’253km3, equivalent to 1.6cm sea-level rise. The thickness map suggests that 13% of the glacierised area is grounded below sea-level. Thickness values are provided together with a map of error estimates that comprise uncertainties in the thickness surveys as well as in other input variables. Aggregated error estimates are used to define a likely ice-volume range of 5’200-7’400km3. The ice-front thickness of marine-terminating glaciers is a key quantity for ice-loss attribution because it controls the potential ice discharge by iceberg calving into the ocean. We find a mean ice-front thickness of 133m for the archipelago

Development of an Agile beam georadar prototype for the investigation of pLanetary environment (AGILE)

International audienceWe present the project of developing a radar system presenting agility resulting from a great versatility in the emission of the wavefront. The idea is to build a system using an array of antennas that can automatically reconfigure itself to focus its radiance on a desired target. This new microwave sensor is intended to detect and characterize a target burried in a medium that can be inhomogeneous in various fields like geophysics, medical, planetology, .... The aim is illustrated by analytical simulations using the DORT method. The instrumental developments are described, with numerical validations of the principle of misalignment of the antenna beam. The project emerged after a CNES R&T study for modify the prototype of WISDOM radar

The Making of an Imperial Agricultural Landscape in the valley of Belén

Resumen del trabajo presentado en el 25th EAA Annual Meeting: Beyond paradigms, celebrado en Bern (Suiza), del 4 al 7 de septiembre de 2019Agricultural planning is not limited to works of terracing, land allotment and hydraulic engineering. As a collective social practice, agriculture also requires the formalization of a corporate coordination system, based on devices such as calendars and ceremonies, which relate the collective of farmers with the space-time of agricultural practice in a given socio-economic and political context. We present an unusual architectural structure located in the Altos de Arica (south-central Andes), whose circular shape and combination of windows and niches echo the characteristics of a special Inca building of Cuzco¿s main square: the sunturhuasi. By means of a 3D multiscale modelling-based simulation, we demonstrate the landscape and astronomical potential of this architecture. The results are consistent with ethno-historical information about the Inca agricultural calendar and related astronomical observation practices. Taking into account the local archaeological context, we suggest that this special architecture constituted a central stage of an imperial built environment related to the political economy of maize production.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 800617

Perspectives in ground-penetrating radar at high latitudes: From occasional imaging to automated continuous monitoring

International audienceAmong different geophysical methods employed for glacier and permafrost characterization, Ground-Penetrating Radar has been employed many times since its first developments.However these GPR characterization were and are still mostly performed during field campaigns which can be sparse in time, expensive and human resource demanding, and can be limited by the difficulty to access areas.The purpose of this short paper is to present two approaches for northern latitudes features imaging during field mission and discuss the benefits brought by hardware and software improvements to develop the field of long-term monitoring. The main objective of this paper is to highlight the new paradigm that the internet of things brought to the field of surface GPR characterization of high latitude environment

Modelo 3D del edificio "sunturhuasi"

Topografía: Marta Crespo y Thibault Saintenoy; Modelización 3D: Marta Crespo; Modelización del horizonte: Thibault Saintenoy ; Simulación arqueoastronomica: Thibault Saintenoy y César González3D model of an Inca building generated from a multi-scale photogrammetric survey, anchored to a digital elevation model (DEM) “Advanced Elevation Serie 4m” of the study area, georeferenced after the Chilean geodetic network; horizon from the centre of the building generated from the same DEM ; archaeo-astronomical simulation to be run with the Scenery 3D plug-in of Stellarium software.Programa Altos Arica (CIHDE-CONICYT, Archam-CNRS), RoadNet_Andes MSCA 800617 UE H2020 (Incipit-CSiC). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 800617.Peer reviewe

The making of an imperial agricultural landscape in the Valley of Belén

As the Inca Empire was predominantly agrarian, the integration of local farming communities into a corporate agricultural system constituted a great challenge for the imperial political economy. The authors thus analyse an unusual circular structure in the Altos de Arica region of northern Chile, which resembles an important building - called 'sunturhuasi' - in the capital, Cusco. They explore this structure using three-dimensional modelling, identifying its probable use in astronomical observations and hence its clear connection with the Inca agricultural calendar, ultimately suggesting that it was central to an imperial built environment related to the political economy of maize production.Archaeological research at Incahullo and in the Valley of Belén was funded by the Mission archéologique Arica-Belén of the French Ministry of Europe and Foreign Affairs, and by the Fondecyt 11121665 project. Archaeoastronomical analysis and simulation were funded by MSCA 800617 RoadNet_Ande