Orogenic mass changes detectable in satellite gravity missions

3Long term GNSS time series detect vertical crustal movement rates, which typically at orogens demonstrate uplift. The orogenic uplift can be ascribed to tectonic and post-glacial adjustments and crustal thickening. We investigate the sensitivity of satellite gravity change rate observations to detect the associated mass changes. Gravity change rate joint with uplift monitoring allows to distinguish the mechanism of uplift (Braitenberg and Shum, 2016). We use known vertical uplift rates over specific orogens to predict the gravity change for different geodynamic hypotheses of pure uplift and mantle inflow, or crustal thickening and isostatic Moho lowering. The sensitivity of gravity as a tool to distinguish the two mechanisms is investigated. The estimate of this tectonic signal is important, when the observed gravity change rates of GRACE and future missions are interpreted exclusively in terms of hydrologic changes tied to climatic variation. We find that in some areas, as the Tibetan plateau and the Himalayan- Alpine range, the tectonic signal is measurable by satellite gravity and contributes to a better understanding of the geodynamic processes leading to orogenesisEGU2017-16481openopenBraitenberg, C.; Pivetta, T.; Morsut, FBraitenberg, Carla; Pivetta, TOMMASO FERRUCCIO MARIA; Morsut, Federic

Geophysical Challenges for Future Satellite Gravity Missions: Assessing the Impact of MOCASS Mission

The GRACE/GRACE-FO satellites have observed large scale mass changes, contributing to the mass budget calculation of the hydro-and cryosphere. The scale of the observable mass changes must be in the order of 300 km or bigger to be resolved. Smaller scale glaciers and hydrologic basins significantly contribute to the closure of the water mass balance, but are not detected with the present spatial resolution of the satellite. The challenge of future satellite gravity missions is to fill this gap, providing higher temporal and spatial resolution. We assess the impact of a geodetic satellite mission carrying on board a cold atom interferometric gradiometer (MOCASS: Mass Observation with Cold Atom Sensors in Space) on the resolution of simulated geophysical phenomena, considering mass changes in the hydrosphere and cryosphere. Moreover, we consider mass redistributions due to seamounts and tectonic movements, belonging to the solid earth processes. The MOCASS type satellite is able to recover 50% smaller deglaciation rates over a mountain range as the High Mountains of Asia compared to GRACE, and to detect the mass of 60% of the cumulative number of glaciers, an improvement respect to GRACE which detects less than 20% in the same area. For seamounts a significantly smaller mass eruption could be detected with respect to GRACE, reaching a level of mass detection of a submarine basalt eruption of 1.6 109 m3. This mass corresponds to the eruption of Mount Saint Helens. The simulations demonstrate that a MOCASS type mission would significantly improve the resolution of mass changes respect to existing geodetic satellite missions

Seamount growth to be observed in future satellite gravity missions

Growing seamounts bear a hazard to navigation, especially if their summit reaches shallow depths and they reach the ocean surface. A seamount that expands up to the surface and creates an island, is detectable by remote sensing images, but not if the island retracts below the surface. Real time gravity observations detect the mass change independently of the optical detection, the limiting factor being only the noise level of the data acquisition in relation to the signal generated by the mass change. Starting from realistic size-frequency distributions of seamounts, we estimate the expected signals of seamount growth. We develop a method to compare the signal to the spectral noise characteristics of a GRACE-type mission, expandable to a possible mission with improved noise curve. We evaluate the expected gravity changes of seamounts and find that a noise curve of GRACE improved by a factor 10 would be sufficient to detect a realistic sea mount growth with a latency of 1 year. The detection threshold though has a tradeoff with the time resolution, since resolution improves for increased time periods over which the satellite observation can be averaged

Geophysical Challenges for Future Satellite Gravity Missions: Assessing the Impact of MOCASS Mission

AbstractThe GRACE/GRACE-FO satellites have observed large scale mass changes, contributing to the mass budget calculation of the hydro-and cryosphere. The scale of the observable mass changes must be in the order of 300 km or bigger to be resolved. Smaller scale glaciers and hydrologic basins significantly contribute to the closure of the water mass balance, but are not detected with the present spatial resolution of the satellite. The challenge of future satellite gravity missions is to fill this gap, providing higher temporal and spatial resolution. We assess the impact of a geodetic satellite mission carrying on board a cold atom interferometric gradiometer (MOCASS: Mass Observation with Cold Atom Sensors in Space) on the resolution of simulated geophysical phenomena, considering mass changes in the hydrosphere and cryosphere. Moreover, we consider mass redistributions due to seamounts and tectonic movements, belonging to the solid earth processes. The MOCASS type satellite is able to recover 50% smaller deglaciation rates over a mountain range as the High Mountains of Asia compared to GRACE, and to detect the mass of 60% of the cumulative number of glaciers, an improvement respect to GRACE which detects less than 20% in the same area. For seamounts a significantly smaller mass eruption could be detected with respect to GRACE, reaching a level of mass detection of a submarine basalt eruption of 1.6 109 m3. This mass corresponds to the eruption of Mount Saint Helens. The simulations demonstrate that a MOCASS type mission would significantly improve the resolution of mass changes respect to existing geodetic satellite missions

Geodetic monitoring in Nepal: preliminary results from Gorkha earthquake (25 April 2015)

The Himalaya arc is one of the most complex and tectonically active areas in the world, a very long (2500km) plate boundary capable of catastrophic earthquakes up to 8 Mw (Rajendran and Rajendran, 2011). Segments of the complex fault system, that accomodate the deformation between Asia and India, lie in correspondence of densely populated cities (i.e. 7.8 Mw on 25 April 2015). A good monitoring system, composed of seismographs and a geodetic network, is the indispensable scientific base to assess and mitigate the risk in this area and to get a better understanding of the dynamics of those geodynamic processes. In this contribution we present the preliminary data and analysis from two GNSS stations located in Nepal, one near to the Everest Pyramid (EvK2CNR), the other one near to the Nagarkot city. Both the antennas seem to have sensed and measured the deformation due to the last catastrophic quake occurred on 25 April 2015. The GNSS time series in the Nagarkot station showed an abrupt change in the displacement, that could be the effect of the near field deformation associated to the quake. A forward model approach, using the Okada model (1985), has been used to verify the compatibility of the observed field to the modeled deformation. The other station that is farther from the fault seems to have recorded a transient deformation. We further analyze the noise level of the station and possible atmospheric induced signals. Using the Okada model to simulate different displacement scenarios due to different earthquake parameters, we are able to assess the sensitivity of the network and efficiently program the installation of further stations

Zinc(II)-methimazole complexes: synthesis and reactivity

The tetrahedral S-coordinated complex [Zn(MeImHS)(4)](ClO4)(2), synthesised from the reaction of [Zn(ClO4)(2)] with methimazole (1-methyl-3H-imidazole-2-thione, MeImHS), reacts with triethylamine to yield the homoleptic complex [Zn(MeImS)(2)] (MeImS = anion methimazole). ESI-MS and MAS C-13-NMR experiments supported MeImS acting as a (N, S)-chelating ligand. The DFT-optimised structure of [Zn(MeImS)(2)] is also reported and the main bond lengths compared to those of related Zn-methimazole complexes. The complex [Zn(MeImS)(2)] reacts under mild conditions with methyl iodide and separates the novel complex [Zn(MeImSMe)(2)I-2] (MeImSMe = S-methylmethimazole). X-ray diffraction analysis of the complex shows a ZnI2N2 core, with the methyl thioethers uncoordinated to zinc. Conversely, the reaction of [Zn( MeImS)(2)] with hydroiodic acid led to the formation of the complex [Zn(MeImHS)(2)I-2] having a ZnI2S2 core with the neutral methimazole units S-coordinating the metal centre. The Zn-coordinated methimazole can markedly modify the coordination environment when changing from its thione to thionate form and vice versa. The study of the interaction of the drug methimazole with the complex [Zn(MeIm)(4)](2+) (MeIm = 1-methylimidazole) - as a model for Zn-enzymes containing a N-4 donor set from histidine residues shows that methimazole displaces only one of the coordinated MeIm molecules; the formation constant of the mixed complex [Zn(MeIm)(3)(MeImHS)](2+) was determined

Social norms and problematic gaming among adolescents: The role of Internet use coping motives.

Problematic gaming (PG) is a public health issue among adolescents worldwide. Although several studies have documented that peer influences constitute a relevant risk factor for adolescent problematic behaviors, little research is currently available on PG. The aim of this study was to examine the contribution of social norms and perceived friends' gaming frequency on participants' own gaming frequency and PG, by testing potential differences among groups with low vs. high motive to use the Internet (e.g., online gaming) as a coping strategy. A survey was administered to 470 adolescent gamers (mean age = 15.49 years; SD = 1.05 years; 77.9 % males). A theoretical model was tested through path analysis and multi-group comparisons were performed. Path analysis revealed that social norms and perceived friends' gaming frequency were positively associated to participants' gaming behaviors and PG. Additionally, different patterns between groups emerged. Our findings confirmed the relative importance of peer influences on adolescents' gaming behaviors and PG and showed that adolescents who rely more on online gaming to cope with negative affect may be more vulnerable to social influence processes than other peers. These findings may provide useful indications for prevention programs targeting adolescent PG. [Abstract copyright: Copyright © 2023 Elsevier Ltd. All rights reserved.

Gravity as a tool to improve the hydrologic mass budget in karstic areas

Monitoring the water movements in karstic areas is a fundamental but challenging task due to the complexity of the drainage system and the difficulty in deploying a network of observations. Gravimetry offers a valid complement to classical hydrologic measurements in order to characterize such systems in which the recharge process causes temporarily accumulation of large water volumes in the voids of the epi-phreatic system. We show an innovative integration of gravimetric and hydrologic observations that constrains a hydrodynamic model of the Škocjan cave system (Slovenia). We demonstrate how the inclusion of gravity observations improves water mass budget estimates for the Škocjan area based on hydrological observations only. Finally, the detectability of water storage variations in other karstic contexts is discussed with respect to the noise performances of spring and super-conducting gravimeters

Gravimetry and petrophysics in the Chad basin area: determination of the basement depth and the implication for defining a scientific drilling site (ICDP-CHADRILL project)

The Chad basin is a huge intracratonic sag-basin (2.5 million km2) in the North Central Africa. In this work, we investigated the basement depth under the Chad Lake using the inversion of gravity residual data obtained by the regression analysis between gravity and topography data. It has been carried on with a collaboration between the University of Trieste and the Institut de Physique du Globe, Strasbourg (IPGS) in order to contribute to the decision of the location of a ICDP drilling site (Bol, SE Chad Lake). This project consists in a compared analysis between gravity data with other geological/geophysical data and their interpretation in terms of tectonic features. The main objectives of this work are: (1) estimation of the basement depth under the Chad basin through a joint analysis and interpretation of satellite and terrestrial gravity data (GOCE, BGI) [1] with borehole data and density values of Cameroon-Chadian rock samples. (2) Estimation and interpretation of the Bouguer and residual gravity anomalies. The results obtained gave us information about the basement depth and the thickness of sediment infill of the basin. Observing the residual values of gravity anomaly field we found a large negative anomaly (-30 mGal) under the Chad basin connected to the presence of low-density sediments. Furthermore, there are several positive anomalies around the edges of the basin [3] and a pattern of linear negative anomalies outside of it. Both types of trends are linked to the presence of rifts and extensional structures. Using the inversion modelling, we could observe a deepening variation of the depth of the basement moving from the southern part (2-3 km) to the northern (4-6 km) one of the Chad Lake. The deepening of the basement is connected to the Termit rift basin and the values are consistent with previous seismic surveys [2]. The depth of the basement under the city of Bol is between 3 and 4 km, but unfortunately, there are no other geological/geophysical constraints to confirm these values. For the drilling purpose, since in the inversion we used a minimum value of the density contrast (200 kg/m3) among the range defined (200-400 kg/m3), it is possible to assume that the maximum expected depth of the basement is about 4 km. We suggest an integrative geophysical survey, such as a seismic reflection campaign to get more detailed information about the structure of the basement (faults, highs and lows) as well as on the variability of its depth and the thickness of the sediment cover