ARTICLE | doi:10.20944/preprints201705.0150.v1
Subject: Physical Sciences, Fluids & Plasmas Keywords: Geophysical Fluid Dynamics; Geostrophic flows; Thermal forcing; Analytical model
Online: 19 May 2017 (16:33:10 CEST)
Starting with a hypothetical geostrophic zonal current in an unbounded ocean, the investigation points out the response of this simple system to a thermal forcing, applied to the free surface and consistent with the maintenance of the geostrophic balance. The main result is the formation of a meridional component of the current, according to the Sverdrup relation, such that the full velocity vector rotates clockwise for heating and anticlockwise for cooling to adjust eventually in the initial zonal direction for large depths.
ARTICLE | doi:10.20944/preprints201811.0595.v1
Subject: Physical Sciences, Nuclear & High Energy Physics Keywords: muon radiography; cosmic rays; tracking detectors; imaging; geophysical prospection; mining
Online: 26 November 2018 (14:09:10 CET)
Muon radiography is an imaging technique based on the measurement of the absorption of cosmic ray muons. This technique has recently been used successfully to investigate the presence of unknown cavities in the Bourbon Gallery in Naples and in the Cheops Pyramid at Cairo. The MIMA detector (Muon Imaging for Mining and Archaeology) is a muon tracker prototype for the application of muon radiography in the Archaeological and Mining fields. It is made of three couples of X-Y planes each consisting of 21 scintillator bars with silicon photomultiplier read-out. The detector is compact, robust, easily transportable and has a low power consumption: all of that makes the detector ideal for measurements in narrow and isolated environments. With this detector we have performed a measurement from inside the Temperino mine in the San Silvestro archaeo-mining park in Tuscany. The park includes about 25 km of mining tunnels arranged on several levels that have been excavated since the Etruscan time. The measured muon absorption was compared to the simulated one, obtained from the information provided by 3D laser scanner measurements and the cartographic maps of the mountain above the mine, in order to obtain information on the average density of the rock. This allowed to confirm the presence of a partially accessible exploitation opening and gave some hints on the presence of a high density body within the rock.
ARTICLE | doi:10.20944/preprints201805.0384.v1
Subject: Engineering, Civil Engineering Keywords: fracture grouting; cement-silicate grout; geophysical prospecting; seepage; Yellow River Embankment
Online: 28 May 2018 (05:45:00 CEST)
Fracture grouting has been a widely used mitigation measure against seepage in the Yellow River Embankment. However, there is currently a lack of systematic investigation for evaluating the anti-seepage effectiveness of fracture grouting employed in this longest river embankment in China. Therefore, in this work, laboratory and in-situ experiments are carried out for investigating the reinforcement effect of fracture grouting in the Jinan Section of the Yellow River Embankment. In particular, firstly, the laboratory tests concentrate on studying the optimum strength improvement for cement-silicate grout by varying the content of backfilled fly ash and bentonite as admixtures. Flexural strength and Scanning Electron Microscope photographs are investigated for assessing the strength and compactness improvement. Subsequently, based on the obtained optimum admixtures content, in-situ grouting tests are carried out in the Jinan Section of the Yellow River Embankment to evaluate the anti-seepage effectiveness of fracture grouting, where geophysical prospecting and pit prospecting methods are employed. Laboratory results show that, compared with pure cement-silicate grouts, the gelation time of the improved slurry is longer and gelation time increases as fly ash content increases. The optimum mixing proportion of the compound cement-silicate grout is 70% cement, 25% fly ash and 5% bentonite, and the best volume ratio is 2 for the investigated cases. Geophysical prospecting using the Ground Penetrating Radar and High Density Resistivity methods can reflect the anti-seepage effectiveness of fracture grouting on site. It shows that the grouting material mainly flows along the axial direction of the embankment. The treatment that is used to generate directional fracture is proved to be effective. The injection hole interval distance is suggested to be 1.2 m, where the lapping effect of the grouting veins is relatively significant. For the investigated cases, the average thickness of the grouting veins is approximately 6.0 cm and the corresponding permeability coefficient is averagely 1.6 × 10−6 cm/s, which meets the anti-seepage criterion in practice.
ARTICLE | doi:10.20944/preprints202011.0605.v1
Subject: Earth Sciences, Atmospheric Science Keywords: parameter-free spectral clustering; Lagrangian Coherent Structures; clusters; geophysical flows; unsupervised machine learning
Online: 24 November 2020 (09:25:02 CET)
In Lagrangian dynamics, the detection of coherent clusters can help understand the organization of transport by identifying regions with coherent trajectory patterns. Many clustering algorithms, however, rely on user-input parameters, requiring a priori knowledge about the flow and making the outcome subjective. Building on the conventional spectral clustering method of Hadjighasem et al (2016), a new parameter-free spectral clustering approach is developed that automatically identifies parameters and does not require any user-input choices. A noise-based metric for quantifying the coherence of the resulting coherent clusters is also introduced. The parameter-free spectral clustering is applied to two benchmark analytical flows, the Bickley Jet and the asymmetric Duffing oscillator, and to a realistic, numerically-generated oceanic coastal flow. In the latter case, the identified model-based clusters are tested using observed trajectories of real drifters. In all examples, our approach succeeded in performing the partition of the domain into coherent clusters with minimal inter-cluster similarity and maximum intra-cluster similarity. For the coastal flow, the resulting coherent clusters are qualitatively similar over the same phase of the tide on different days and even different years, whereas coherent clusters for the opposite tidal phase are qualitatively different.
ARTICLE | doi:10.20944/preprints201811.0612.v1
Subject: Earth Sciences, Geophysics Keywords: geophysical signal processing; pattern recognition; temporal convolutional neural networks; seismology; deep learning; nuclear treaty monitoring
Online: 29 November 2018 (03:37:48 CET)
The detection of seismic events at regional and teleseismic distances is critical to Nuclear Treaty Monitoring. Traditionally, detecting regional and teleseismic events has required the use of an expensive multi-instrument seismic array; however in this work, we present DeepPick, a novel seismic detection algorithm capable of array-like performance from a single trace. We achieve this directly, by training our single-trace detector against labeled events from an array catalog, and by utilizing a deep temporal convolutional neural network. The training data consists of all arrivals in the International Seismological Centre Catalog for seven seismic arrays over a five year window from 1 Jan 2010 to 1 Jan 2015, yielding a total training set of 608,362 detections. The test set consists of the same seven arrays over a one year window from 1 Jan 2015 to 1 Jan 2016. We report our results by training the algorithm on six of the arrays and testing it on the seventh, so as to demonstrate the transportability and generalization of the technique to new stations. Detection performance against this test set is outstanding. Fixing a type-I error rate of 1%, the algorithm achieves an overall recall rate of 73% on the 141,095 array beam picks in the test set, yielding 102,394 correct detections. This is more than 4 times the 23,259 detections found in the analyst-reviewed single-trace catalogs over the same period, and represents an 8dB improvement in detector sensitivity over current methods. These results demonstrate the potential of our algorithm to significantly enhance the effectiveness of the global treaty monitoring network.
ARTICLE | doi:10.20944/preprints202012.0248.v1
Subject: Earth Sciences, Geophysics Keywords: cryolithozone; geophysical monitoring; pulsed electromagnetic sounding; cross-well exploration; vector finite-element method; numerical simulation; high-performance computing
Online: 10 December 2020 (10:39:26 CET)
The paper is dedicated to the topical problem of examining permafrost state and the processes of its geocryological changes by means of geophysical methods. To monitor the cryolithozone, we propose and scientifically substantiate a new technique of pulsed electromagnetic cross-well sounding. Based on the vector finite-element method, we created a mathematical model of the cross-well sounding process with a pulsed source in a three-dimensional spatially heterogeneous medium. A high-performance parallel computing algorithm was developed and verified. Through realistic geoelectric models of permafrost with a talik under a highway, constructed following the results of electrotomography field data interpretation, we numerically simulated the pulsed sounding on the computing resources of the Siberian Supercomputer Center of SB RAS. The simulation results suggest the proposed system of pulsed electromagnetic cross-well monitoring to be characterized by a high sensitivity to the presence and dimensions of the talik. The devised approach can be oriented to addressing a wide range of issues related to monitoring permafrost rocks under civil and industrial facilities, buildings and constructions.
CASE REPORT | doi:10.20944/preprints202107.0469.v1
Subject: Earth Sciences, Atmospheric Science Keywords: Research Infrastructures (RIs); Engineering Geological conditions; Integrated geophysical methods; Daya Bay Neutrino Laboratory (DBNL); China Spallation Neutron Source (CSNS)
Online: 21 July 2021 (08:17:01 CEST)
Research Infrastructures (RIs) are essential to achieve excellence in innovative scientific research. However, because of limited land availability and specific geological requirements, evaluating the viability of a site for a new RI can be a challenging task. Stringent safety construction requirements include developing site-specific architectural and geoengineering solutions, minimizing construction disturbances, and reinforcing rock and soil in a timely fashion. For successful development of the RIs in China, such as the Daya Bay Neutrino Laboratory (DBNL), and the China Spallation Neutron Source (CSNS), an integrated approach of joint geophysical methods including the electrical resistivity tomography (ERT), controlled-source audio-frequency magneto telluric (CSAMT)), gravity and seismic refraction methods, and geological mapping and surveys were carried out. Geophysical parameters, such as electrical resistivity, density, and seismic velocity show inverse proportion to the degree of rock fracturing or weathering. The results show that the low values of geophysical parameters suggest the weathered/fractured rock, while high values reveal the fresh bedrock. The Engineering Geological Suitability Index (EGSI) value can represent the individual EGSI values at a constant and summed over varying depths. EGSI methodology is an improvement on the existing siting process, and has been applied this to CSNS. Our integrated approach provides clearer insight of the subsurface for site suitability of RIs in challenging engineering geological conditions, and removes any ambiguity caused by a single geophysical parameter. The obtained geological knowledge of the area not only provides engineers with much-needed information about the construction conditions of a potential site, but also gives scientists the opportunity to explore the local geology. In this study, we demonstrate our innovative approach for siting RIs, as demonstrated by the synthetic evaluation of the site location and utilization for two established RIs (DBNL and CSNS).
Subject: Earth Sciences, Geophysics Keywords: mineral physics; ultrasonic interferometry; resonant ultrasound spectroscopy; law of corresponding states; equations-of-state; Columbia University; American Geophysical Union
Online: 29 March 2019 (07:54:57 CET)
From 1964 to the early 1970s, Orson Anderson led a research program at the Lamont Geological Observatory in the newly-emerging field of “mineral physics”. In collaboration with colleagues Edward Schreiber and Naohiro Soga, Orson exploited the techniques of physical acoustics to study the behavior of the sound velocities of minerals at elevated pressures and temperatures. This research program also included semi-empirical studies of relationships between the bulk modulus and the molar volume of solids and the use of lattice dynamics to calculate the elastic moduli of cubic structures as a function of pressure to predict instabilities, as well as theoretical investigations of the Lagrangian vs. Eulerian formulations of finite strain equations of state.