Античные и средневековые городища на дне Иссык-Куля

В статье дается обзор результатов многолетних подводных археологических разведок на озере Иссык-Куль. Приводятся данные по местоположению некоторых затопленных городищ античности и средних веков (Тору-Айгыр, Кара-ой, Чигу). Описываются наиболее интересные артефакты, найденные на дне озера.В статті дається огляд результатів багаторічних підводних археологічних розвідок на озері Іссик-Куль. Наводяться дані про місцезнаходження деяких затоплених городищ античності і середньовіччя (Тору-Айгир, Кара-ой, Чігу). Описуються найцікавіші артефакти, знайдені на дні озера.The article is a review of the results of many years’ underwater archaeological researches at lake Issik Kul. Data about the place of location of some Ancient and Medieval towns (Toru-Aygir, Kara-oy, Chigu) are given. Most interesting artefacts found at the bottom of the lake are described

Search for an exosphere in sodium and calcium in the transmission spectrum of exoplanet 55 Cancri e

[Abridged] The aim of this work is to search for an absorption signal from exospheric sodium (Na) and singly ionized calcium (Ca$^+$) in the optical transmission spectrum of the hot rocky super-Earth 55 Cancri e. Although the current best-fitting models to the planet mass and radius require a possible atmospheric component, uncertainties in the radius exist, making it possible that 55 Cancri e could be a hot rocky planet without an atmosphere. High resolution (R$\sim$110000) time-series spectra of five transits of 55 Cancri e, obtained with three different telescopes (UVES/VLT, HARPS/ESO 3.6m & HARPS-N/TNG) were analysed. Targeting the sodium D lines and the calcium H and K lines, the potential planet exospheric signal was filtered out from the much stronger stellar and telluric signals, making use of the change of the radial component of the orbital velocity of the planet over the transit from -57 to +57 km/sec. Combining all five transit data sets, we detect a signal potentially associated with sodium in the planet exosphere at a statistical significance level of 3$\sigma$. Combining the four HARPS transits that cover the calcium H and K lines, we also find a potential signal from ionized calcium (4.1 $\sigma$). Interestingly, this latter signal originates from just one of the transit measurements - with a 4.9$\sigma$ detection at this epoch. Unfortunately, due to the low significance of the measured sodium signal and the potentially variable Ca$^+$ signal, we estimate the p-values of these signals to be too high (corresponding to <4$\sigma$) to claim unambiguous exospheric detections. By comparing the observed signals with artificial signals injected early in the analysis, the absorption by Na and Ca$^+$ are estimated to be at a level of approximately 2.3$\times 10^{-3}$ and 7.0$\times 10^{-2}$ respectively, relative to the stellar spectrum.Comment: 15 pages, 8 figures, submission updated after English language editing, submission updated to correct a mistaken cross-reference noticed in A&A proo

Relative sea-level rise around East Antarctica during Oligocene glaciation

During the middle and late Eocene (∼48-34 Myr ago), the Earth's climate cooled and an ice sheet built up on Antarctica. The stepwise expansion of ice on Antarcticainduced crustal deformation and gravitational perturbations around the continent. Close to the ice sheet, sea level rosedespite an overall reduction in the mass of the ocean caused by the transfer of water to the ice sheet. Here we identify the crustal response to ice-sheet growth by forcing a glacial-hydro isostatic adjustment model with an Antarctic ice-sheet model. We find that the shelf areas around East Antarctica first shoaled as upper mantle material upwelled and a peripheral forebulge developed. The inner shelf subsequently subsided as lithosphere flexure extended outwards from the ice-sheet margins. Consequently the coasts experienced a progressive relative sea-level rise. Our analysis of sediment cores from the vicinity of the Antarctic ice sheet are in agreement with the spatial patterns of relative sea-level change indicated by our simulations. Our results are consistent with the suggestion that near-field processes such as local sea-level change influence the equilibrium state obtained by an icesheet grounding line

Comparing gravity-based to seismic-derived lithosphere densities: a case study of the British Isles and surrounding areas

Lithospheric density structure can be constructed from seismic tomography, gravity modelling, or studies using both data sets. The different approaches have their own uncertainties and limitations. This study aims to characterise and quantify the uncertainties in gravity modelling of lithosphere densities. To evaluate the gravity modelling we compare between the gravity-based and lithosphere densities based on seismic velocities. This study proposes a new gravity modelling approach to estimate lithosphere densities,using a crustal model, lithospheric isostasy, and gravity field observations. To quantify the effect of uncertainty in the crustal model, three models are implemented in this study: CRUST1.0, EuCrust-07, and a high resolution P-wave velocity model of the British Isles and surrounding areas. Different P-wave velocity-to-density conversions are used to study the uncertainty in these conversion methods. The crustal density models are forward modelled into gravity field quantities using a method that is able to produce spherical har1monic coefficients. Deep mantle signal is assumed to be removed by removing spherical harmonic coefficients of degree 0-10 in the observed gravity field. The uncertainty in the resulting lithosphere densities due to the different crustal models is ±110 kg/m3, which is the largest uncertainty in gravity modelling. Other sources of uncertainty, such as the VP to density conversion (±10 kg/m3), long-wavelength truncation (±5 kg/m3), choice of reference model (< ±20 kg/m3), and Lithosphere Asthenosphere Boundary uncertainty (±30 kg/m3), proved to be of lesser importance. The resulting lithosphere density solutions are compared to density models based on a shear wave velocity model [Schaeffer and Lebedev(2013)]. The comparison shows that the gravity-based models have an increased lateral resolution compared to the tomographic solutions. However, the density anomalies of the gravity-based models are threetimes higher. This is mainly due to the high resolution in the gravity field. To account for this, the gravity-based density models are filtered with a spatial Gaussian filter with 200 km halfwidth, which results in similar density estimates (±35 kg/m3) with the tomographic approach. Lastly, the gravity-based density is used to estimate laterally varying conversion factors, which show to correlate with major tectonic regions. The independent gravity-based solutions could help in identifying different compositional domains in the lithosphere, when compared to the tomographic solutions

Postseismic deformation following the 1997 Umbria-Marche (Italy) moderate normal faulting earthquakes

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 , Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

A benchmark study for glacial-isostatic adjustment codes

The study of Glacial Isostatic Adjustment (GIA) is gaining an increasingly im-portant role within the geophysical community. Understanding the response of the Earth to loading is crucial in various contexts, ranging from the the interpretation of modern satellite geodetic measurements (e. g. GRACE and GOCE) to the projections of future sea level trends in response to climate change. Modern modeling approaches to GIA are based on various techniques that range from purely analytical formulations to fully numerical methods. Despite various teams independently investigating GIA, we do not have a suitably large set of explicitly validated numerical results through which they may be validated; a community benchmark data set would clearly be valuable. Following the example of the mantle convection community, here we present, for the first time, the results of a benchmark study of codes designed to model GIA. The approaches benchmarked are based on significantly different codes and different techniques. This effort is performed within the Working Group 4 (WG4) of the ESF COST Action ES0701 “Improved constraints on models of Glacial Isostatic Adjustment”. Our aims are: i) testing the codes currently in use by the various teams, ii) establish a sufficiently large set of agreed results, iii) correct possible systematic errors embedded in the various physical formulations or computer implementations, and iv) facilitate the dissemination of numerical tools for surface loading studies to the community and to young scientists. The test computations are mainly based on models with spherical symmetry and Maxwell rheology and include inputs from various different methods and solution techniques: viscoelastic normal modes, spectral finite–elements and finite–elements. The tests involve the loading and tidal Love numbers and their relaxation spectra, the deformation and gravity variations driven by surface loads characterized by simple geometry and time–history, and the rotational fluctuations in response to glacial unloading. In spite of the significant differences in the numerical methods employed, the test computations show a satisfactory agreement between the results provided by the participants. Most of the existing misfits have been addressed during the preparation of the manuscript, some others are currently the subject of analysis within the WG4 community