ALBERT

Description: 〈span〉〈div〉Summary〈/div〉The strength of the lithosphere plays a key role in the formation and evolution of tectonic plate boundaries. Localized lithospheric deformation associated with plate tectonics requires a mechanism for weakening across the entire width of the lithosphere, including the strongest cold ductile region. We explore the microphysics of weakening of lithospheric materials, and in particular the coupled evolution of mineral grain size and intragranular defects and their control on lithospheric strength. We propose a model for the interaction between grain-boundaries and dislocation density to reduce the net free energy of grains during dynamic recrystallization (DRX). The driving forces for DRX arise from heterogeneity in dislocation density and grain boundary curvature. Our model shows that grain growth driven by variation in grain boundary curvature can be impeded by variation in dislocation density; this occurs because as the grains grow, to minimize their surface energy, their dislocation density and associated internal energy may increase and offset the driving forces for grain growth. The correlation between grain size and dislocation density can for example arise because the dislocation accumulation in smaller grains is suppressed due to the large stress that is needed to bend and elongate a short dislocation (as dictated by the small grain size), while the larger grains can have long dislocations and reach a steady state dislocation density dictated by the applied stress. In a lithospheric setting, slower grain growth means that it would require less mechanical work to establish weak localized shear zones through grain damage, and retard the healing of previously damaged zones. Furthermore, the competition of two different time-scales - that of grain growth and the dislocation kinetics - can lead to oscillating behavior over 1 to 10 years as the grain size and dislocation density advance towards their steady states. These oscillations are likely to have an effect on the rheology of lithospheric rocks, e.g. their strengthening and weakening through time, and have a potential application to geological processes such as postseismic creep in ductile shear zones.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉Locating and monitoring passive seismic sources provides us important information for studying subsurface rock deformation, injected fluid migration, regional stress conditions as well as fault rupture mechanism. In this paper, we present a novel passive-source monitoring approach using vector-based elastic time-reversal imaging. By solving the elastic wave equation using observed multicomponent records as boundary conditions, we first compute back-propagated elastic wavefields in the subsurface. Then, we separate the extrapolated wavefields into compressional (P-wave) and shear (S-wave) modes using the vector Helmholtz decomposition. A zero-lag cross-correlation imaging condition is applied to the separated pure-mode vector wavefields to produce passive-source images. We compare imaging results using three implementations, i.e., dot-product, energy and power. Numerical experiments demonstrate that the power imaging condition gives us the highest resolution and is less sensitive to the presence of random noises. To capture the propagation of microseismic fracture and earthquake rupture, we modify the traditional zero-lag cross-correlation imaging condition by summing the multiplication of the separated P- and S-wavefields within local time windows, which enables us to capture the temporal and spatial evolution of earthquake rupture. 2D and 3D numerical examples demonstrate that the proposed method is capable of accurately locating point sources, as well as delineating dynamic propagation of hydraulic fracture and earthquake rupture.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉Magnitudes of differential stress in the lithosphere, especially in the crust, are still disputed. Earthquake-based stress drop estimates indicate median values 〈 10 MPa whereas the lateral variation of gravitational potential energy per unit area (〈span〉GPE〈/span〉) across significant relief indicates stress magnitudes of ca. 100 MPa in average across a 100 km thick lithosphere between the Indian lowland and the Tibetan plateau. These standard 〈span〉GPE〈/span〉-based stress estimates correspond to membrane stresses, because they are associated with a deformation that is uniform with depth. We show here with new analytical results that lateral variations in 〈span〉GPE〈/span〉 can also cause bending moments and related bending stresses of several hundreds of MPa. Furthermore, we perform two-dimensional thermo-mechanical numerical simulations (1) to evaluate estimates for membrane and bending stresses based on 〈span〉GPE〈/span〉 variations, (2) to quantify minimum crustal stress magnitudes that are required to maintain the topographic relief between Indian lowland and Tibetan plateau for ca. 10 Ma and (3) to quantify the corresponding relative contribution of crustal strength to the total lithospheric strength. The numerical model includes viscoelastoplastic deformation, gravity and heat transfer. The model configuration is based on density fields from the CRUST1.0 data set and from a geophysically and petrologically constrained density model based on 〈span〉in situ〈/span〉 field campaigns. The numerical results indicate that values of differential stress in the upper crust must be 〉 ca. 180 MPa, corresponding to a friction angle of ca. 10°, to maintain the topographic relief between lowland and plateau for 〉 10 Ma. The relative contribution of crustal strength to total lithospheric strength varies considerably laterally. In the region between lowland and plateau and inside the plateau the depth-integrated crustal strength is approximately equal to the depth-integrated strength of the mantle lithosphere. Simple analytical formulae predicting the lateral variation of depth-integrated stresses agree with numerically calculated stress fields, which show both the accuracy of the numerical results and the applicability of simple, rheology-independent, analytical predictions to highly variable, rheology-dependent, stress fields. Our results indicate that (1) crustal strength can be locally equal to mantle lithosphere strength and that (2) crustal stresses must be at least one order of magnitude larger than median stress drops in order to support the plateau relief over a duration of ca. 10 Ma.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉Scanning magnetometers are increasingly used to characterize the magnetization of mineral grains in rock samples. Up-scaling this measurement technique to large numbers of individual particles is hampered by the intrinsic non-uniqueness of potential-field inversion. Here it is shown that this problem can be circumvented by adding tomographic information that determines the location of the possible field sources. Standard potential theory is used to prove a uniqueness theorem which completely characterizes the mathematical background of the corresponding source-localized inversion. It exactly resolves under which conditions a potential field measurement on a surface can be uniquely decomposed into signals from the different source regions. The intrinsic non-uniqueness of potential field inversion prevents that the source distribution inside the tomographically outlined regions can be recovered, but the potential field of each region is uniquely defined. For scanning magnetometers in rock magnetism, this result implies that magnetic dipole vectors of large numbers of individual magnetic particles can be reliably reconstructed from surface scans of the magnetic field, if the particle positions are independently determined. This provides an incentive to improve scanning methods for future paleomagnetic applications.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉The most common earthquake forecasting models assume that the magnitude of the next earthquake is independent from the past. This feature severely limits the capability to forecast large earthquakes with high probabilities. Here we investigate empirically on the magnitude-independence assumption, exploring if: i) background and triggered earthquakes have the same frequency-magnitude distribution, ii) variations of seismicity in the space-time-magnitude domain encode some information on the future earthquakes size. For this purpose, and to verify the stability of the findings, we consider seismic catalogues covering different space-time-magnitude windows, such as the Alto Tiberina Near Fault Observatory (TABOO), the California and Japanese seismic catalogues. Our approach is inspired by the nearest-neighbour method proposed by Baiesi & Paczuski (2004) and elaborated by Zaliapin et al. (2008) to distinguish between triggered and background earthquakes. Here we implement the same metric-based correlation to identify the precursory seismicity of any triggered earthquake; this allows us to analyse, for each triggered earthquake, the space-time-magnitude distribution of the seismicity that likely contributed to its occurrence. Our results show that the magnitude-independence assumption holds reasonably well in all catalogues, with a remarkable exception that is consistent with a previous independent study; this departure from the magnitude-independence assumption shows that larger events tend to nucleate at a higher distance from the ongoing sequence. We also notice that the reliability of this assumption may depend on the spatial scale considered; it holds for seismic catalogues of large areas, but we identify possible departures in small areas, reflecting different ways to release locally seismic energy. Finally, we come across an important issue that may lead to misleading results in similar studies, i.e., if a seismic catalogue appears overall complete above a fixed magnitude threshold, it may still yield spurious signals into the analysis. Specifically, we show that some significant departures from the magnitude-independence assumption do not survive when considering spatiotemporal variations of the magnitude of completeness.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉Vp/Vs models provide important complementary information to Vp and Vs models, relevant to lithology, rock damage, partial melting, water saturation, etc. However, seismic tomography using body-wave traveltime data from local or regional earthquakes does not constrain Vp/Vs well due to the different resolution of Vp and Vs models, with the Vp models usually better constrained than Vs. Since surface-wave data are most sensitive to Vs, which leads to complementary strengths with respect to body-wave data, we jointly invert body- and surface-wave data to better resolve the Vp/Vs models. In order to show the robustness of our joint inversion method, we compare the results to other approaches, including dividing Vp by Vs models and Vp/Vs parameterization with body-wave or both body- and surface-wave data, using synthetic data and real data from the southern California plate boundary region. We confirm that Vp/Vs models from body-wave inversion obtained by division tend to include artifacts, even when both Vp and Vs models seem reasonable. The joint inversion with Vp/Vs parameterization is found to improve the Vp/Vs ratio model significantly and the resultant Vp/Vs model shows more geologically consistent features, such as high Vp/Vs along fault traces at shallow depths likely indicating fault-related damage. The Vp/Vs model also exhibits contrasts at intermediate depths along the Peninsular Range compositional boundary, and high Vp/Vs in the lower crust near the Salton Sea region correlated with high heat flow and may indicate partial melting. The improved Vp/Vs as well as individual Vp and Vs models are useful for earthquake relocation, high-resolution Moho depth imaging, and interpretation of other data and tectonic evolution in the region.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉Interpretation of surface fault scarps and palaeoseismic trenches is a key component of estimating fault slip rates, earthquake recurrence rates and maximum magnitudes for hazard assessments. Often these analyses rely on the assumption that successive earthquakes all breached the surface and that the ruptures are recorded topographically, or by the deposits exposed in a trench. The M〈sub〉〈span〉w〈/span〉〈/sub〉7.2 1992 Suusamyr earthquake, Kyrgyzstan, is an apparently problematic case for such analyses because its ruptures show significant displacement but are only mapped as having broken the surface along small, disparate portions of the fault. Here we present the results of surveys conducted along the Suusamyr Fault to establish whether that is the case. Two sets of ruptures were identified following the earthquake. They are unusually short for their displacement and are separated by a 25 km gap. Using satellite imagery, high-resolution digital elevation models and palaeoseismic trenching we first reassess the distribution of the 1992 ruptures and then reconstruct the Holocene earthquake record to establish the extent to which the 1992 earthquake is representative of the rupture behaviour of this fault. We find evidence for at least two prehistoric surface rupturing earthquakes in the Holocene: one ∼3 ka and one 〉8 ka that, along with the modern event, gives recurrence intervals of ∼3 kyr and ∼5 kyr. Within spatial gaps between segments of the 1992 ruptures there are clear prehistoric surface ruptures and the ruptures in each prehistoric earthquake were discontinuous. We conclude that there is significant variability in the surface rupture pattern of successive earthquakes on the Suusamyr Fault, with implications for the completeness of palaeoseismic records obtained from thrust scarps.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉We provide a six-component (6-C) polarization model for 〈span〉P〈/span〉-, 〈span〉SV〈/span〉-, 〈span〉SH〈/span〉-, Rayleigh-, and Love-waves both inside an elastic medium as well as at the free surface. It is shown that single-station 6-C data comprised of three components of rotational motion and three components of translational motion provide the opportunity to unambiguously identify the wave type, propagation direction, and local 〈span〉P〈/span〉- and 〈span〉S〈/span〉-wave velocities at the receiver location by use of polarization analysis. To extract such information by conventional processing of three-component (3-C) translational data would require large and dense receiver arrays. The additional rotational components allow the extension of the rank of the coherency matrix used for polarization analysis. This enables us to accurately determine the wave type and wave parameters (propagation direction and velocity) of seismic phases, even if more than one wave is present in the analysis time window. This is not possible with standard, pure-translational 3-C recordings. In order to identify modes of vibration and to extract the accompanying wave parameters, we adapt the multiple signal classification algorithm (MUSIC). Due to the strong nonlinearity of the MUSIC estimator function, it can be used to detect the presence of specific wave types within the analysis time window at very high resolution. We show how the extracted wavefield properties can be used, in a fully automated way, to separate the wavefield into its different wave modes using only a single 6-C recording station. As an example, we apply the method to remove surface wave energy while preserving the underlying reflection signal and to suppress energy originating from undesired directions, such as side-scattered waves.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉The Sentinel-1 mission comprises two synthetic aperture radar satellites, each with a 12 day orbital repeat, orbiting 6 days apart within a narrow tube. The mission design promises the ability to respond quickly to earthquakes with InSAR, and to facilitate production of interferograms with good interferometric correlation globally. We report on our efforts to study global seismicity using Sentinel-1 Interferometric Wide-Swath data between April 2015 and December 2016. We select 35 potentially detectable terrestrial earthquakes in the range 5.5 ≤ 〈span〉Mw〈/span〉 ≤ 7.8 on the basis of their locations, depths and magnitudes, and process the first post-event interferogram with the shortest possible time-span for each using the ISCE software. We evaluate each interferogram for earthquake deformation signals by visual inspection. We can identify deformation signals attributable to earthquakes in 18 of these interferograms (51%); a further six interferograms (17%) have ambiguous interferometric phase affected by tropospheric noise. 11 events (31%) could not be identified from their interferograms. The majority of these failed detections were due to interferogram decorrelation, particularly apparent for earthquakes that occurred between 15°N and 15°S, where climate conditions promote dense vegetation. The majority of the ambiguous interferograms are affected by tropospheric noise, suggesting that techniques to mitigate such noise could improve detection performance. The largest event we do not detect with Sentinel-1 data is a 〈span〉Mw〈/span〉7.0 earthquake that occurred in Vanuatu in April 2016; we also fail to detect the 2016 〈span〉Mw〈/span〉6.2 Kurayoshi earthquake in one out of two possible 24-day interferograms. We propose these as upper and lower estimates on the magnitude of completeness for earthquakes studied with Sentinel-1 data; to raise the magnitude of completeness we suggest that more frequent (e.g. six day) recurrence may be necessary in low latitude areas.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉The correct estimation of site-specific attenuation is crucial for the assessment of seismic hazard. Downhole instruments provide in this context valuable information to constrain attenuation directly from data. In this study, we apply an interferometric approach to this problem by deconvolving seismic motions recorded at depth with those recorded at the surface. In doing so, incident and surface-reflected waves can be separated. We apply this technique not only to earthquake data but also to recordings of ambient vibrations. We compute the transfer function between incident and surface-reflected waves in order to infer frequency dependent quality factors for S-waves. The method is applied to a 87 m deep borehole sensor and a co-located surface instrument situated at a hard-rock site in West Bohemia/Vogtland, Germany. We show that the described method provides comparable attenuation estimates using either earthquake data or ambient noise for frequencies between 5-15 Hz. Moreover, a single hour of noise recordings seems to be sufficient to yield stable deconvolution traces and quality factors, thus, offering a fast and easy way to derive attenuation estimates from borehole recordings even in low to mid seismicity regions.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉Injection of CO〈sub〉2〈/sub〉 into tight reservoirs produces both gravity change and ground deformation, which provide great opportunities for more accurate coupled inverse modelling. In this study, we incorporate signals generated from several synthetic models to estimate the CO〈sub〉2〈/sub〉 distribution in the reservoir. A relationship is found that connects density variations to volumetric changes associated with injected CO〈sub〉2〈/sub〉, taking advantage of a common set of model parameters for both gravitational and geo-mechanical inverse modelling. This is achieved by assuming that the injected CO〈sub〉2〈/sub〉 increases pressure in the reservoir, which in turn generates extra porosity that is then filled in by the CO〈sub〉2〈/sub〉 mass in the generated space. Tikhonov regularization, supported by the Generalized Cross Validation (GCV) technique for finding the optimized model, is used to solve the ill-posed inverse problems. The results indicate that with a combination of gravity and ground deformation monitoring, the uncertainty and ambiguity in gravimetric modelling due to high levels of noise is mitigated by implementing highly accurate ground deformation measurements, which normally have a higher signal to noise ratio.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉As the number of seismic sensors grows, it is becoming increasingly difficult for analysts to pick seismic phases manually and comprehensively, yet such efforts are fundamental to earthquake monitoring. Despite years of improvements in automatic phase picking, it is difficult to match the performance of experienced analysts. A more subtle issue is that different seismic analysts may pick phases differently, which can introduce bias into earthquake locations. We present a deep-neural-network-based arrival-time picking method called ”PhaseNet” that picks the arrival times of both P and S waves. Deep neural networks have recently made rapid progress in feature learning, and with sufficient training, have achieved super-human performance in many applications. PhaseNet uses three-component seismic waveforms as input and generates probability distributions of P arrivals, S arrivals, and noise as output. We engineer PhaseNet such that peaks in the probability distributions provide accurate arrival times for both P and S waves. PhaseNet is trained on the prodigious available data set provided by analyst-labeled P and S arrival times from the Northern California Earthquake Data Center. The dataset we use contains more than seven hundred thousand waveform samples extracted from over thirty years of earthquake recordings. We demonstrate that PhaseNet achieves much higher picking accuracy and recall rate than existing methods when applied to the waveforms of known earthquakes, which has the potential to increase the number of S-wave observations dramatically over what is currently available. This will enable both improved locations and improved shear wave velocity models.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉The low frequency earthquakes (LFEs) that constitute tectonic tremor are often inferred to be slow: to have durations of 0.2 to 0.5 s, a factor of 10 to 100 longer than those of typical 〈span〉MW〈/span〉 1-2 earthquakes. Here we examine LFEs near Parkfield, CA in order to assess several proposed explanations for LFEs’ long durations. We determine LFE rupture areas and location distributions using a new approach, similar to directivity analysis, where we examine how signals coming from various locations within LFEs’ finite rupture extents create differences in the apparent source time functions recorded at various stations. We use synthetic ruptures to determine how much the LFE signals recorded at each station would be modified by spatial variations of the source-station travel time within the rupture area given various possible rupture diameters, and then compare those synthetics with the data. Our synthetics show that the methodology can identify inter-station variations created by heterogeneous slip distributions or complex rupture edges, and thus lets us estimate LFE rupture extents for unilateral or bilateral ruptures. To obtain robust estimates of the sources’ similarity across stations, we stack signals from thousands of LFEs, using an empirical Green’s function approach to isolate the LFEs’ apparent source time functions from the path effects. Our analysis of LFEs in Parkfield implies that LFEs’ apparent source time functions are similar across stations at frequencies up to 8 to 16 Hz, depending on the family. The inter-station coherence observed at these relatively high frequencies, or short wavelengths (down to 0.2 to 0.5 km), suggest that LFEs in each of the 7 families examined occur on asperities. They are clustered in patches with sub-1-km diameters. The individual LFEs’ rupture diameters are estimated to be smaller than 1.1 km for all families, and smaller than 0.5 km and 1 km for the two shallowest families, which were previously found to have 0.2-s durations. Coupling the diameters with the durations suggests that it is possible to model these 〈span〉MW〈/span〉 1-2 LFEs with earthquake-like rupture speeds: around 70% of the shear wave speed. However, that rupture speed matches the data only at the edge of our uncertainty estimates for the family with highest coherence. The data for that family are better matched if LFEs have rupture velocities smaller than 40% of the shear wave speed, or if LFEs have different rupture dynamics. They could have long rise times, contain composite sub-ruptures, or have slip distributions that persist from event to event.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉On June 24, 2015, a 230,000 cubic metre landslide slid into the triangle bayou at the intersection of the Yangtze and Daning Rivers and generated a river tsunami that ran up 6.2 metres on the opposite shoreline at Wushan town. The slope failure and resulting waves killed two people and damaged many shipping facilities. Based on field surveys and eyewitness observations, we apply the ‘Tsunami Squares’ method to model the Hongyanzi landslide and its generated waves. Landslide simulations indicate a maximum impact velocity of ∼16 m/s that matches well with an eyewitness video. The computed post-slide mass stopped on the near riverbed with a shape fitting the observed geological profile. Tsunami simulations reveal a large region of wave impacts that coincide with the observed runup heights. The successful reproduction of the dynamics of this landslide-generated river tsunami emphasizes the capacity and efficiency of Tsunami Squares modeling in emergency reaction and risk assessment.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉Improvement of global 3D Earth density and velocity models is based in part on measurements of Earth’s normal mode eigenfrequencies and splitting function coefficients. Despite many methods developed inconsistency in measurements still exists and it is difficult to understand which results are more precise, that is which methods introduce less systematic biases in the measurements. Therefore, the main goal of this study is to test the performances of typically used techniques in low-frequency normal mode studies: the optimal sequence estimation stacking method and the autoregressive method in the frequency domain, where validation of the estimates is performed with the phasor walkout method. Motivations for their utilization are their easy and fast implementation and their accurate performances when it comes to eigenfrequency estimates. For this purpose, we first perform the analysis with synthetic seismograms in order to evaluate how the station distributions and noise levels impact the estimates of eigenfrequencies and structure coefficients. Synthetic seismograms are calculated for a 3D realistic Earth model, which includes Earth’s rotation as well as ellipticity and other lateral heterogeneities. They were computed by means of normal mode summation and a perturbation theory for modes up to 1 mHz. The three methods above are also applied to long-period seismometer and superconducting gravimeter data recorded after six earthquakes of magnitude greater than 8.3. Finally, our study shows that the optimal sequence estimation is sensitive to the station distribution under the noise influence, while the autoregressive method for frequency estimation gives us reasonable estimates within the estimated error bars. Moreover, we present new estimates of eigenfrequencies and Q-factors for 〈sub〉0〈/sub〉S〈sub〉2, 0〈/sub〉S〈sub〉3, 2〈/sub〉S〈sub〉1〈/sub〉 and 〈sub〉3〈/sub〉S〈sub〉1〈/sub〉 multiplets. A new value for the 〈span〉c〈/span〉〈sub〉20〈/sub〉 structure coefficient of 〈sub〉0〈/sub〉S〈sub〉2〈/sub〉 multiplet −0.7233 ± 0.0623 μHz is obtained.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉We propose a novel approach to compute the gravity field due to density anomaly in both outside and inside of the solid Earth with high accuracy and efficiency. The high accuracy comes from the direct employment of the analytic gravitation solution between any point on a two-dimensional (2D) plane in the horizontal direction and individual mass cubes. The high computational efficiency comes from two aspects: 1, the application of the highly efficient 2D discrete convolution algorithm; and 2, a newly developed algorithm for the optimized computation of the weight coefficient matrix. Numerical examples for applying to compare with analytical solutions demonstrated its excellent accuracy. Comparison with other state-of-the-art gravity modeling algorithm has proved that this algorithm has superior performance in both accuracy and efficiency. Application to analyze real topography demonstrated the practicality. This algorithm will be an attractive candidate for carrying out the forward modeling step in geophysical inversion problems with the claimed and proved advantages.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉We assess the stress field that drives lithospheric deformation, focusing on the active New Zealand plate boundary zone between the Australian and Pacific plates. Here there is a rich database for the horizontal velocity field and crustal structure, used to derive gravitational potential energy (GPE). We solve the stress balance equations, in the context of a thin sheet model of a viscously deforming lithosphere, for characteristic deviatoric stresses and viscosities, defined as the integral of these with depth (divided by the layer thickness), using the stress method of Flesch 〈span〉et al.〈/span〉 (2001), where the input parameters are the fields of strain rate and GPE that apply to the sheet. Synthetic tests show that the stress method is able to resolve the stress field to high (20 per cent) levels of noise in the input strain rates, and the mean stress is a very robust feature of the inversions, regardless of noise levels. We invert for the stress and viscosity fields in New Zealand, calculating the field of GPE from topography/bathymetry and crustal data, and the field of strain rates from either a long term (multi millennial) velocity field inferred from the rate and pattern of Quaternary faulting, or a short term (decadal) velocity field directly observed with decadal Global Positioning System (GPS) measurements. In addition, we consider the effect of shear stresses on the subducted plate interface along the Hikurangi Margin (5–15 MPa), or regionally. We explore the effect of GPE on the inversion results by calculating these for a range of deforming layers (ie thin sheet with 35–150 km thickness), in effect sampling the lithospheric strength in the crust and mantle. The results show that the derived stress magnitudes (square root second invariant of the stress deviator) are in the range 0–35 MPa, with mean values of 13 ± 1 MPa for all models, comparable to typical earthquake stress drops. Gravitationally induced stresses account for approximately half of the full deviatoric stress. Effective characteristic viscosities are 0.5 - 5 × 10〈sup〉21〈/sup〉 Pas in the deforming zone, with an approximate inverse relation between strain rate and viscosity, most likely controlled by thermal structure and/or lithology.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉I present a source-independent fracture imaging method to use passive seismic data for mapping subwavelength natural fractures. Unlike conventional source-dependent imaging that often adopts reflection-type seismic imaging with known source that is not available in passive seismic surveys, the proposed fracture imaging approach relies on the transmission and diffraction data without the need for source information. I assume that passive seismic data can be decomposed into two types of data: primary transmission wave data and diffraction (coda) wave data. The imaging formula states that primary waves should coincide with coda waves at scatterer points at the time of scattering. Instead of generating source wavefields in the conventional imaging method, the proposed method only need to propagate transmission wave data and diffraction wave data from the receiver arrays and apply an imaging condition to produce an image of fractures. This imaging procedure can be used for processing P-wave or S-wave. In synthetic examples, I evaluate the proposed method in several aspects: inaccurate source location, inaccurate velocity model, sparse receivers and irregular receiver spacing, elastic data, and joint surface and borehole acquisitions. I found that the proposed approach performed well (or even better) comparable to source-dependent fracture imaging when assuming exact source information is known. With perturbed source locations with random shifts (e.g., estimated source location with errors), however, fractures were missing in the source-dependent fracture imaging results but the proposed approach was not influenced. In the presence of velocity errors and sparse and irregular receiver spacing, the proposed method produces better fracture images than the source-dependent imaging results.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉We introduce a formalism for estimating local spatial averages of the core-mantle boundary (CMB) radial magnetic field and its time derivatives, based on magnetic field observations collected by low-Earth-orbit satellites. This provides a useful alternative to conventional core field modelling based on global spherical harmonic basis functions, where noise in the polar regions maps into all harmonics, and model regularization and spectral truncation are required. A powerful perspective offered by the proposed technique is formal appraisal of the spatial resolution and variance of the resulting field averages. We use the Green’s functions for the Neumann boundary value problem to link the satellite observations to the radial magnetic field on the CMB and estimate field averages using a modified Backus-Gilbert inversion approach. Our approach builds on the Subtractive Optimally Localized Averages (SOLA) method developed in helioseismology, that seeks averaging kernels as close as possible to a chosen target kernel. We are able to account for both internal and external field sources and can easily incorporate data error covariance information, for example describing along-track serial error correlation. As a proof of concept we present a global map collecting local estimates of the radial main field (MF) constructed on a grid at the CMB with one degree spacing in latitude and longitude, derived from one month of three component vector magnetic field data collected by the 〈span〉Swarm〈/span〉 satellite trio, using data from dark and geomagnetically quiet times. Using sums and differences of the field components taken along track and in the east-west direction we obtain estimates with spatial resolution kernel widths varying between 18 and 54 degrees depending on the latitude, and a standard deviation of approximately 10μT (i.e. 5% of the mean CMB field amplitude). The morphology of our CMB radial field map agrees well with results from conventional spherical harmonic field models. In a second application, we determine local estimates of the average rate of change, or secular variation (SV), of the radial field at the CMB, initially considering two year time windows, and performing the analysis on data collected by either the 〈span〉Swarm〈/span〉 or CHAMP satellites. We obtain stable local estimates of the SV at the CMB, and present maps of estimates with averaging kernel widths of approximately 42, 33 and 30 degrees on the equator, with corresponding standard derivations of 0.25, 2.5 and 5 μT/yr. By subtracting SV estimates constructed at different epochs we are able to calculate the local aggregated secular acceleration (SA) and to study its time changes. Differencing SV estimates 2 years apart, and considering an averaging kernel width of 42 degrees on the equator, we obtain SA maps very similar to those found in the CHAOS-6-x7 field model truncated at SH degree 10. Using our approach we are able to directly control the width of the spatial averaging kernel and the length of the time window, enabling us to directly study the robustness of the inferred SA. Pushing to higher resolution in time, considering one year differences of SV estimates constructed using one year windows, we are able to track the evolution of coherent SA structures in time-longitude plots at the equator. At 25° W in mid 2007 we find a distinctive SA ’cross-over’ event, with strong, oppositely signed and adjacent, SA features rapidly changing sign within a year. Our method is well suited for studying such spatio-temporally localized SA events at high resolution; there will be further opportunities for such investigations as the time series of data provided by the 〈span〉Swarm〈/span〉 mission lengthens.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉The evolution of the ratio between P- and S-wave velocity (〈span〉V〈/span〉〈sub〉P〈/sub〉/〈span〉V〈/span〉〈sub〉S〈/sub〉) with increasing fluid-saturated porosity is computed for isotropic rocks containing spheroidal pores. The ratio 〈span〉V〈/span〉〈sub〉P〈/sub〉/〈span〉V〈/span〉〈sub〉S〈/sub〉 is shown to either decrease or increase with increasing porosity, depending on the aspect ratio α of the pores, fluid to solid bulk modulus ratio ζ, and Poisson’s ratio ν〈sub〉0〈/sub〉 of the solid constituents of the rock. A critical initial Poisson’s ratio ν〈sub〉0, crit〈/sub〉 is computed, separating cases where 〈span〉V〈/span〉〈sub〉P〈/sub〉/〈span〉V〈/span〉〈sub〉S〈/sub〉 increases (if ν〈sub〉0〈/sub〉 〈 ν〈sub〉0, crit〈/sub〉) or 〈span〉decreases〈/span〉 (if ν〈sub〉0〈/sub〉 〉 ν〈sub〉0, crit〈/sub〉) with increasing porosity. For thin cracks and highly compressible fluids, ν〈sub〉0, crit〈/sub〉 is approximated by 0.157 ζ/α, whereas for spherical pores ν〈sub〉0, crit〈/sub〉 is given by 0.2 + 0.8ζ. When ν〈sub〉0〈/sub〉 is close to ν〈sub〉0, crit〈/sub〉, the evolution of 〈span〉V〈/span〉〈sub〉P〈/sub〉/〈span〉V〈/span〉〈sub〉S〈/sub〉 with increasing fluid-saturated porosity is near neutral and depends on subtle changes in pore shape and fluid properties. This regime is found to be relevant to partially dehydrated serpentinites in subduction zones (porosity of aspect ratio near 0.1 and ζ in the range 0.01–0.1), and makes detection of these rocks and possibly elevated fluid pressures difficult from 〈span〉V〈/span〉〈sub〉P〈/sub〉/〈span〉V〈/span〉〈sub〉S〈/sub〉 only.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉Secondary microseismic sources emit seismic waves over long time spans. Reoccurring signals with similar slowness and frequency therefore arrive at seismic arrays. Blind source separation techniques can be used to identify and isolate such reoccurring signals from other signals and from diffuse seismic noise. Along these lines, we use non-negative matrix factorization as blind source separation technique to decompose continuous seismic array records. We model the recorded energy as a mixture of a few components with static slowness-frequency and time dependent amplitudes. Components and amplitudes are fitted to optimally explain the recorded seismic energy over time. These components represent secondary microseismic signals with quasi-static slowness-frequency vector and fluctuating amplitude. Each fitted component reveals the geographical origin (through the slowness-frequency vector) and time evolution of an active secondary microseism with high precision because it is separated from other signals and diffuse seismic noise. Furthermore, relative travel times can be automatically extracted for the signals that correspond to a specific component that can potentially be used in tomographic studies. We show two examples of seismic signals that were extracted with this technique, one focusing on P-waves from the typhoons Goni and Atsani, and another showing secondary microseism PKP signals from typhoon Glenda.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉Locating microseismic events is essential for many areas of seismology including volcano and earthquake monitoring and reservoir engineering. Due to the large number of microseismic events in these settings, an automated seismic location method is required to perform real time seismic monitoring. The measurement environment requires a precise and noise-resistant event location method for seismic monitoring. In this paper, we apply Multichannel Coherency Migration (MCM) to automatically locate microseismic events of induced and volcano-tectonic seismicity using sparse and irregular monitoring arrays. Compared to other migration-based methods, in spite of the often sparse and irregular distribution of the monitoring arrays, the MCM can show better location performance and obtain more consistent location results with the catalogue obtained by manual picking. Our MCM method successfully locates many triggered volcano-tectonic events with local magnitude smaller that 0, which demonstrates its applicability on locating very small earthquakes. Our synthetic event location example at a carbon capture and storage site shows that continuous and coherent drilling noise in industrial settings will pose great challenges for source imaging. However, automatic quality control techniques including filtering in the frequency domain and weighting are used to automatically select high quality data, and can thus effectively reduce the effects of continuous drilling noise and improve source imaging quality. The location performance of the MCM method for synthetic and real microseismic datasets demonstrates that the MCM method can perform as a reliable and automatic seismic waveform analysis tool to locate microseismic events.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉The unification of local height systems has been a classical geodetic problem for a long time, the main challenges of which are the estimation of offsets between different height systems and the correction of tilts along the levelling lines. It has been proposed to address these challenges with clock networks. The latest generation of optical clocks as well as the dedicated frequency links, e.g., optical fibres, are now approaching to deliver the comparison of frequencies at the level of 1.0 × 10〈sup〉−18〈/sup〉. It corresponds to an accuracy of about 1.0 cm in height difference. Clock networks can thus serve as a powerful tool to connect local height systems. To verify the idea, we carried out simulations using the EUVN/2000 (European Unified Vertical Network) as a priori input. Four local height systems were simulated from the EUVN/2000 by introducing individual offsets and tilts, and were re-unified by using measurements in clock networks. The results demonstrate the great potential of clock networks for height system unification. In case that the offsets between different height systems and tilts along national levelling lines in both longitudinal and latitudinal directions are considered, three or four clocks measurements for each local region are sufficient for the unification. These clocks are to be interconnected and should be properly arranged so that they can sense the levelling tilts where necessary. Our results also indicate that even clocks with one magnitude poorer accuracy than the desired ones can still unify the height systems to some extent, but it may cause a shift for the re-unified system.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉We investigate slip-distribution models of the 2011 Tohoku earthquake, with a particular focus on diffracted tsunamis and uplift-induced waves along the back-arc region of the Japanese Island Arc.The 2011 Tohoku earthquake produced a large amplitude tsunami that diffracted around Kyushu Island before reaching Korea. At the same time, this earthquake co-seismically induced short-period small-amplitude sea waves in the East Sea. We performed tsunami simulations using seven fault models of the Tohoku earthquake to examine whether the models can accurately reproduce the observed waveforms in the open sea of the western Pacific Ocean, the South Sea of Korea, and the coast of the East Sea. For each fault model, we investigate tsunami features due to geomorphological characteristics of the Korean Peninsula in the Korea offshore. To determine which slip distribution model shows a good performance in the tsunami simulations, we set three criteria; the delay time between observations and synthetic waveforms, the normalized mean residual, and the normalized RMS misfit. Depending on the study region, all models show varying degrees of accuracy. The fault dimensions and the amount of slip have a larger effect on the RMS misfit then the slip distribution patterns of the fault models for observations along the Korean coast and the western coast of Japan.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉The study of radiation patterns in poroelastic media allows us to visually explore the possibility of reconstructing crucial model properties describing reservoir rocks, and to examine the coupling effects between different parameters during full-waveform inversion (FWI). In this paper, we derive analytical formulae for the radiation patterns of single parameter perturbations in fluid-saturated porous media by deriving scattered wavefields based on plane-wave theory and the far-field approximation. We illustrate these scattered wavefields via their radiation patterns expressed as a function of the angle between the incident and scattered waves. To simplify the algebra, we consider poroelastic waves at seismic (low) frequencies, where the fast compressional wave and shear wave are propagating modes but the slow compressional wave is severely dispersive. To verify our derivation of the analytical radiation patterns, we also compute them numerically by perturbing one parameter at a single point, keeping the other parameters fixed at their background values. We find that all the analytical radiation patterns match the wavefronts of the numerically computed scattered wavefields, well indicating that our derivations are correct. Parameters such as the solid density, fluid density, viscosity of the fluid, and intrinsic permeability, have similar radiation patterns and thus show strong coupling effects. Therefore, we anticipate difficulties in recovering these parameters in a multi-parameter FWI procedure. In an attempt to mitigate these trade-offs, we analyze different parameterizations which result in different radiation patterns. As the patterns that we observe are similar to those of the elastic case, we anticipate that parameter separation might be easier when inverting for velocities than for moduli.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉In the Sea of Marmara, areas of gas seepage or cold seeps are tightly related to the faults system and understanding the spatial and temporal dynamics in gas-related processes is crucial for geohazard mitigation. Although acoustic surveys proved to be efficient in detecting and locating cold seeps, temporal variability or trends in the gas-related processes are still poorly understood. Two arrays of 10 ocean bottom seismometers were deployed in the western part of the Sea of Marmara in 2011 and 2014, respectively. In addition to the local seismic events, the instruments recorded a large number of short duration events and long-lasting tremors. Short duration events are impulsive signals with duration 〈 1 s, amplitude well above the noise level and a frequency spectrum with one or two narrow peaks. They are not correlated from one site to another, suggesting a very local source. Tremors consist of sequences of clustered impulsive signals lasting for minutes to more than an hour with a multi-peak frequency spectrum. Based on evidence of known seepage and by analogy with volcanic and hydrothermal models, we suggest that short duration events and tremors are associated with gas migration and seepage. There is a relationship between tremors associated with gas emission and the local seismicity, although not systematic. Rather than triggering gas migration out of the seabed, locally strong earthquakes act as catalysts when gas is already present or gas emission is already initiated.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉Long-period Rayleigh wave Horizontal to Vertical amplitude (H/V) ratios at a station provide information about local earth structure that is complementary to phase velocity. However, a number of studies (Ferreira and Woodhouse, 2007; Lin 〈span〉et al.〈/span〉, 2012) have observed that significant scatter appears in these measurements making it difficult to use H/V ratio measurements to resolve earth structure. Some of the scatter in these measurements has been attributed to local geological structure while some has remained unaccounted for. Most Global Seismographic Network (GSN) stations contain two nearby high-quality broadband seismometers (e.g. in the same vault, but on different piers or in different boreholes). For each broadband sensor in the IRIS/USGS component of the GSN, we estimate H/V ratios of fundamental mode Rayleigh waves using M 〉 6.5 earthquakes from 2001 to 2018 (around 19,000 measurements). We compute these ratios at a number of discrete periods (25, 50, 75, 100, and 150 s) and find that for well-isolated Rayleigh waves (windows where the correlation coefficients between radial and the phase-shifted vertical components are greater than 0.9) significant scatter in H/V ratios occurs between co-located sensors (greater than 25 per cent at 100 s period). This suggests the scatter in H/V ratio measurements can be at least partially attributed to extremely local phenomena such as sensor emplacement in the vault. We also find that H/V ratios can vary as a function of event back-azimuth, indicating that care must be taken when computing average ratios for a station, as a large number of events from a given region could bias H/V ratio measurements at a station.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉We analyse noise characteristics of spatial and temporal correlation of 260 continuous GPS sites from Crustal Movement Observation Network of China (CMONOC). These data sets were mainly collected between 2010 and 2016, with an average of 6 yr of position time-series. In the functional analysis, a clear regional dependence of seasonal movements has been observed and other significant periodic signals are detected nearby the GPS draconitic period and its harmonics. The distribution of these periodic signals shows a spatial correlation, along with non-negligible local inconsistencies. In the stochastic analysis, impacts of the periodicities on the noise assessment have been investigated and Maximum likelihood estimation is used to study noise properties for deseasonalized residual time-series having the seasonal signals removed and filtered residual time-series having other periodic signals removed further. We demonstrate that for both solutions, the flicker noise is thought to be the dominant time-correlated noise and velocity uncertainties may be underestimated 8–10 times if assuming a pure white noise. Ignoring the periodicities could bias the estimation of noise amplitude, spectral index and velocity uncertainty. After removing the periodic signals, the median flicker noise magnitude shows an average of ∼10 per cent reductions and the noise process shifts closer towards white noise. A correlation between the index variations and RMS variations has been observed, indicating that the index varies more significantly for sites with more periodic signals removed. Besides, the spectral index in the vertical component has a better spatial correlation than that in the horizontal and the spatial distribution of the index of deseasonalized solutions seems to correlate well with the amplitudes of seasonal signals, probably implying common sources of spatial variations of these characteristics. Furthermore, analyses of intersite correlations indicate that the correlation induced from the periodic signals displays a similar pattern to the deseasonalized solutions, confirming that the period pattern is spatially correlated and can induce time-series correlations. Finally, the stochastic processes of the common mode noise are predominantly featured by spatially correlated flicker and white noise over a wide range, consistent with previous results.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉As temperature increases with depth and the creep resistance of rock decreases exponentially, a high-viscosity sub-lithospheric layer, just beneath the ‘elastic’ lithosphere is expected to exist. Depending on the temperature profile, a low-viscosity asthenosphere may also exist if the temperature deeper down gets high enough. Since the temperature profile is expected to change laterally – especially from below the oceans to cratonic areas underneath continents, rock properties of the lithosphere, high-viscosity sub-lithosphere and low-viscosity asthenosphere are expected to change laterally. Our aim is to constrain sub-lithospheric properties (depth, thickness and viscosity), lateral lithospheric thickness variations and asthenospheric properties using observed GIA data. A Coupled Laplace-Finite Element Method is used to compute gravitationally self-consistent sea level with time-dependent coastline and rotational feedback in addition to changes in deformation, gravity and the state of stress. We start with the VM5a-ICE-6G_C model combination and then modify the lithospheric, sub-lithospheric and asthenospheric properties (including lateral thickness variation) while keeping the mantle viscosities the same as VM5a. Through this study, we confirm that the sub-lithospheric and asthenospheric properties can significantly affect the predicted global relative sea level (RSL), present-day gravity rate-of-change (g-dot) and uplift rate (u-dot) in Laurentia and Fennoscandia. In addition, incorporating the elastic lithosphere with lateral thickness variation, sub-lithosphere and asthenosphere can improve the fit to global RSL, but the predicted peak values of g-dot and u-dot in Laurentia may decrease slightly but not significant enough to affect the fit to the observed data. Our results prefer an elastic lithosphere that has maximum thickness of 140 km under continental cratons but reduces to 60 km underneath the oceans. The results preferred depth of the asthenospheric bottom is around 190–200 km with asthenospheric viscosity around 10〈sup〉20〈/sup〉Pa s. Finally, we show that the best laterally heterogeneous mantle model we found in previous publication when combined with the lithosphere with lateral thickness variaion gives the best fit to global RSL and peak g-dot and u-dot in Laurentia simultaneously.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉We implement an analytical model based on flexural deflection of a thin elastic disc to investigate the magnitude of lithospheric decompression caused by deglaciation at upper crustal magmatic reservoirs. Considering a published numerical climate model describing the space–time evolution of deglaciation after the Last Glacial Maximum (LGM) along the Southern Volcanic Zone (SVZ) of the Andes, we demonstrate that changes in pressure at upper crustal levels (〈10 km depth) at the scale of several hundred years are of the order of 10–100 MPa. Total decompression and decompression rate (300–150 kPa yr〈sup〉−1〈/sup〉) are 1–2 orders of magnitude larger than values previously estimated by other authors who assume that glacial loads are supported by an elastic half-space, that is, of infinite elastic thickness. The large decompression caused by flexural unbending of an elastic plate of finite thickness as assumed here can easily surpass the tensile strength of rocks (5–20 MPa), creating adequate conditions for failure of the reservoir walls, dike propagation inside and outside the reservoir and the eventual collapse of the reservoir accompanying an explosive eruption. We apply our results to the analysis of post-glacial eruptions of SVZ volcanoes, which erupted large volumes (〉10 km〈sup〉3〈/sup〉) of mafic ignimbrites hundreds to thousands of years after deglaciation onset. We show that this time lag is necessary to achieve a decompression of several tens of megapascals at depths of several kilometres that are consistent with the location of magmatic reservoirs as estimated by independent petrologic, seismic and/or geodetic studies. Moreover the northward increase of this time lag is in agreement with a smaller size of the Andean ice cap in the north than in the south during the LGM. For wet, volatile-rich magmas typical of subduction zones, the effect of large decompression at upper crustal reservoirs caused by flexural unbending of the lithosphere after deglaciation could play a major role in promoting large explosive eruptions through devolatization of the magma, during past deglaciation events as demonstrated here for the LGM along the SVZ and current accelerated ice retreat caused by climate change over large segments of subduction-related arcs at higher latitudes.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉The unification of local height systems has been a classical geodetic problem for a long time, the main challenges of which are the estimation of offsets between different height systems and the correction of tilts along the levelling lines. It has been proposed to address these challenges with clock networks. The latest generation of optical clocks as well as the dedicated frequency links, for example optical fibres, are now approaching to deliver the comparison of frequencies at the level of 1.0 × 10〈sup〉−18〈/sup〉. It corresponds to an accuracy of about 1.0 cm in height difference. Clock networks can thus serve as a powerful tool to connect local height systems. To verify the idea, we carried out simulations using the EUVN/2000 (European Unified Vertical Network) as 〈span〉apriori〈/span〉 input. Four local height systems were simulated from the EUVN/2000 by introducing individual offsets and tilts, and were reunified by using measurements in clock networks. The results demonstrate the great potential of clock networks for height system unification. In case that the offsets between different height systems and tilts along national levelling lines in both longitudinal and latitudinal directions are considered, three or four clocks measurements for each local region are sufficient for the unification. These clocks are to be interconnected and should be properly arranged so that they can sense the levelling tilts where necessary. Our results also indicate that even clocks with one magnitude poorer accuracy than the desired ones can still unify the height systems to some extent, but it may cause a shift for the reunified system.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉Waveform backprojection (BP) is a key technique of earthquake-source imaging, which has been widely used for extracting information of earthquake source evolution that cannot be obtained by kinematic source inversion. The technique enjoys considerable popularity, owing to the simplicity of its implementation and the robustness of its processing, but the physical meaning of BP images has remained elusive. In this study, we reviewed the mathematical representation of BP and hybrid BP (HBP) methods, following the pioneering work of Fukahata 〈span〉et al〈/span〉. (〈a href="http://academic.oup.com/gji#bib15"〉2014〈/a〉), to clarify the physical implications of BP images. We found that signal intensity in BP and HBP images is scaled with the amplitude of the Green’s function that corresponds to a unit-step slip, which results in the signal intensity being depth dependent. We propose variants of BP and HBP, which we call kinematic BP and HBP, respectively, to relate the BP signal intensity to slip motion of an earthquake by modifying the normalizing factors used in the original BP and HBP methods. The original BP and HBP images remain useful for assessing the spatiotemporal strength of the wave radiation, which scales with the amplitude of the Green’s function, whereas the kinematic BP and HBP methods are suitable for imaging the slip motion that is responsible for the high-frequency radiation produced during the source-rupture process.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉 〈strong〉Moment Tensors of hydraulically induced AEs:〈/strong〉 Hydraulic fracturing is an important technique in the development of enhanced geothermal systems and unconventional resources. Although the fracture modes induced by hydraulic fracturing influence the recovery efficiency of the resources, the current understanding of this relationship is insufficient. In this study, we considered the acoustic emissions (AEs) induced during hydraulic fracturing under uniaxial loading conditions in the laboratory, and applied a moment tensor analysis by carefully correcting the coupling condition and directivity of AE transducers. Experiments were conducted for two types of Kurokami–jima granite samples: those with a rift plane perpendicular (Type H) or parallel (Type V) to the expected direction of fracture propagation (i.e. along the loading axis). In the experiments, both sample types experienced a significant number of shear, tensile and compressive events. The dominant fracture mode for Type H samples is found to be tensile events in which the fracture plane is parallel to the loading axis, whereas for Type V samples, shear events are dominant. This difference suggests that the dominant fracture modes induced by hydraulic fracturing are highly dependent on the relationship between the direction of fracture propagation and orientation of pre-existing weak planes.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉We present a sensitivity analysis aimed at testing whether observables related to glacial isostatic adjustment can support or refute the occurrence of a low viscosity melt-rich layer (MRL) above the mantle transition zone, as required by the ‘transition-zone water-filter’ model (Bercovici & Karato 2003). In total, 1600 model runs were performed sampling a range of MRL thicknesses (1, 10 and 20 km) and viscosities (10〈sup〉15〈/sup〉–10〈sup〉19〈/sup〉 Pa·s), plausible viscosity values in the upper and lower mantle regions and four distinct ice histories. To determine decay time constraints, we consider relative sea level (RSL) data from two sites [Ångerman River (ÅR), Sweden and Richmond Gulf (RG), Canada] and use a new method of observational sea level data correction. Comparing model output of postglacial decay times and ${\skew{6}\dot{J}_2}$ to observational constraints, we find numerous possible solutions, largely as a result of parameter trade-off. The investigated observables are sensitive to the existence of an MRL and reasonable variations in its thickness and viscosity. The magnitude and nature of this sensitivity varies between the two data types as well as the adopted background viscosity structure. Decay time results from either considered location do not strictly support or exclude MRL existence. However, both locations offer MRL viscosity requirements for given thicknesses, with ÅR being more restrictive. RG constraints allow MRL viscosities as low as 10〈sup〉16〈/sup〉 Pa·s (10 km) and 10〈sup〉17〈/sup〉 Pa·s (20 km). ÅR results narrow these permitted viscosity ranges to 10〈sup〉18〈/sup〉 Pa·s or greater for both 10 and 20 km MRL thicknesses. In the case of a 1 km thick MRL, ÅR constraints permit the viscosity to be as low as 10〈sup〉17〈/sup〉 Pa·s, whereas those of RG permit any MRL viscosity. The decay time observations are satisfied by only a small subset of ‘background’ mantle viscosities (regardless of the MRL properties), none of which support a spherically symmetric solution of Earth viscosity. Finally, comparing model output to the observed ${\skew{6}\dot{J}_2}$ value did not provide any constraints on MRL properties. However, our results show that this observable has a strong preference for viscosity values in the lower mantle that are equal to or greater than 10〈sup〉22〈/sup〉 Pa·s.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉We investigated an 〈span〉M〈/span〉〈sub〉w〈/sub〉 ∼ 6.2 earthquake doublet on the border of the USA and Canada using ALOS2 Light-of-Sight displacements and GPS measurements. We selected three L-band ALOS-2 interfergorams with temporal baselines of one yr to extract coseismic deformation maps, in which master and slave images were both acquired in July. A subpixel-based alignment and another range spectral splitting techniques under the GAMMA InSAR software framework were applied to improve the interferometric coherence and reduce the effects of phase anomalies in two of the three interferometric pairs due to either ionospheric delay or a potential focusing issues in the generation of the ALOS2 SLC data. The updated interferograms convincingly reveal deformation fringe patterns produced by the two earthquakes. We conducted a nonlinear geophysical inversion to estimate the geometric parameters of the earthquakes with the InSAR and GPS measurements. The best-fitting model shows that a thrust faulting on a reverse fault and left-lateral strike-slip faulting on a nearly vertical fault with the centroid depths of 9.3±0.6 and 8.4±0.7 km, respectively, are most likely responsible for the earthquake doublet. The eastern Denali fault (EDF) and Duke River fault are major active faults in the region and the earthquake doublet could be due to reactivation of the part of the two faults system.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉In this paper, we present a series of mathematical abstractions for seismologically relevant wave equations discretized using finite-element methods, and demonstrate how these abstractions can be implemented efficiently in computer code. Our motivation is to mitigate the combinatorial complexity present when considering geophysical waveform modelling and inversion, where a variety of spatial discretizations, material models, and boundary conditions must be considered simultaneously. We accomplish this goal by first considering three distinct classes of abstract mathematical models: (1) those representing the physics of an underlying wave equation, (2) those describing the discretization of the chosen equation onto a finite-dimensional basis and (3) those describing any spatial transforms. A full representation of the discrete wave equation can then be constructed using a hierarchical nesting of models from each class. Additionally, each class is functionally orthogonal to the others, and with certain restrictions models within one class can be interchanged independently from changes in another. We then show how this recasting of the relevant equations can be implemented concisely in computer software using an abstract object-oriented design, and discuss how recent developments in the numerical and computational sciences can be naturally incorporated. This builds to a set of results where we demonstrate how the developments presented can lead to an implementation capable of multiphysics waveform simulations in completely unstructured domains, on both hypercubical and simplical spectral-element meshes, in both two and three dimensions, while remaining concise, efficient and maintainable.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉Traveltime approximation plays an important role in seismic data processing, for example, anisotropic parameter estimation and seismic imaging. By exploiting seismic traveltimes, it is possible to improve the accuracy of anisotropic parameter estimation and the resolution of seismic imaging. Conventionally, the traveltime approximations in anisotropic media are obtained by expanding the anisotropic eikonal equation in terms of the anisotropic parameters and the elliptically anisotropic eikonal equation based on perturbation theory. Such an expansion assumes a small perturbation and weak anisotropy. In a realistic medium, however, the assumption of small perturbation likely breaks down. We present a retrieved zero-order deformation equation that creates a map from the anisotropic eikonal equation to a linearized partial differential equation system based on the homotopy analysis method. By choosing the linear and nonlinear operators in the retrieved zero-order deformation equation, we develop new traveltime approximations that allow us to compute the traveltimes for a medium of arbitrarily strength anisotropy. A comparison of the traveltimes and their errors from the homotopy analysis method and from the perturbation method suggests that the traveltime approximations provide a more reliable result in strongly anisotropic media.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉Guided waves in a water layer overlaying an elastic half-space are known as normal modes. They are often present in seismic recordings at long offsets in shallow-water environment and generally considered coherent noise. The normal modes, however, carry important information about the near-surface and, as demonstrated by a number of authors, can be used to obtain the shallow velocity model. There is a growing evidence that the latter needs not to be isotropic due to various geological reasons. Motivated by that, we consider the normal-mode propagation in case the elastic half-space exhibits orthorhombic anisotropy. We derive the period equation that describes the normal-mode phase velocity dispersion. To simplify the complicated expression, we present acoustic and ellipsoidal orthorhombic approximations. We also outline the approach towards the group velocity and group azimuth calculation and apply it to the ellipsoidal case to obtain concise and intuitive expressions. Using numerical test, we study the relation between phase and group domains in elastic orthorhombic case. The deviation between velocities and azimuths in these domains is the strongest for low frequencies and it rapidly decreases with increasing frequency. For higher frequencies, the anisotropy effects of the underlaying half-space are barely detectable since the observed signal is composed mainly of the direct acoustic wave, resulting in the two domains being nearly indistinguishable.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉Understanding why Earth’s lithosphere is divided into several plates while other terrestrial bodies have unbroken lids is a long-standing challenge, often addressed with the help of numerical modelling. A key mechanism defining the transition between these two convective regimes is the formation of shear zones that cut through the entire lithosphere in regions with high stresses. Here we present a modelling study in which lithospheric stresses resulting from small-scale convection in the upper mantle are analysed. We perform model simulations that include elasticity and a free surface and evaluate how these physical complexities affect stress distribution inside the lithosphere, which in turn controls the depths of yielding and the possible initiation of subduction. We show that the spatial distribution of stress is significantly altered by the presence of elastic deformation only when the model lithosphere acts as a thick plate capable of bending. Whether or not this is the case depends on the viscosity model. For an Arrhenius viscosity limited by a cut-off value that produces an essentially rigid lid, flexure dominates the observed lithospheric stress pattern in simulations with a free surface. The amplitudes of the stress are, when a free surface is assumed but elasticity is neglected, largely overestimated. Including both a free surface and elasticity results in stresses with maximum amplitudes close to those observed in the traditional models with a viscous rheology and a free-slip upper boundary, suggesting that having no additional complexity is, in a way, better than employing just a free surface. We also demonstrate how the use of impermeable free-slip side boundaries can result in the formation of unnatural, laterally locked convection cells, and bias the results of a parametric study. For each point in the parameter space, we perform several simulations with slightly different initial temperature fields in order to statistically eliminate the occurrence of locked states.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉The design of an array configuration is an important task in array seismology during experiment planning. Often the array response function (ARF), which depends on the relative position of array stations and frequency content of the incoming signals, is used as the array design criterion. In practice, additional constraints and parameters have to be taken into account, for example, land ownership, site-specific noise levels or characteristics of the seismic sources under investigation. In this study, a flexible array design framework is introduced that implements a customizable scenario modelling and optimization scheme by making use of synthetic seismograms. Using synthetic seismograms to evaluate array performance makes it possible to consider additional constraints. We suggest to use synthetic array beamforming as an array design criterion instead of the ARF. The objective function of the optimization scheme is defined according to the monitoring goals, and may consist of a number of subfunctions. The array design framework is exemplified by designing a seven-station small-scale array to monitor earthquake swarm activity in Northwest Bohemia/Vogtland in central Europe. Two subfunctions are introduced to verify the accuracy of horizontal slowness estimation; one to suppress aliasing effects due to possible secondary lobes of synthetic array beamforming calculated in horizontal slowness space and the other to reduce the event’s mislocation caused by miscalculation of the horizontal slowness vector. Subsequently, a weighting technique is applied to combine the subfunctions into one single scalar objective function to use in the optimization process.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉We develop a new method for measuring ellipticity of Rayleigh waves from ambient noise records by degree-of-polarization (DOP) analysis. The new method, named DOP-E, shows a good capability to retrieve accurate ellipticity curves separated from incoherent noise. In order to validate the method we perform synthetic tests simulating noise in a 1-D earth model. We also perform measurements on real data from Antarctica and Northern Italy. Observed curves show a good fit with measurements from earthquake records and with theoretical ellipticity curves. The inversion of real data measurements for 〈span〉vS〈/span〉 structure shows a good agreement with previous models. In particular, the shear-wave structure beneath Concordia station shows no evidence of a significant layer of liquid water at the base of the ice. The new method can be used to measure ellipticity at high frequency and therefore it will allow the imaging of near-surface structure, and possibly of temporal changes in subsurface properties. It promises to be useful to study near-surface processes in a wide range of geological settings, such as volcanoes, fault zones and glaciers.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉The interaction of subducted oceanic lithosphere with the discontinuities of the mantle transition zone (MTZ) provides insight into the composition and temperature of the subducted slab as well as potential melting of the slab or the surrounding mantle and loss of volatiles from the slab. Detailed mapping of the structure of the MTZ will help to better understand how slabs transport material and volatiles into the mantle and how phase transitions affect the slab dynamics. Here we use a dense network of seismic stations in northern Anatolia to image the structure of the MTZ discontinuities in detail using 〈span〉P〈/span〉-wave receiver functions. With a station spacing of about 7 km and a surface footprint of ∼35 km × ∼70 km, analysing receiver functions calculated from teleseismic earthquakes that occurred during an ∼18-month deployment produced clear images of where the MTZ interacts with the Tethys/Cyprus slabs that either lie flat on the 660-km discontinuity or pass into the lower mantle. We observe an undulating 660-km discontinuity depressed by up to 30 km and a slightly depressed (1–2 km) 410-km discontinuity, apparently undisturbed by the slab. The MTZ is thickened to ∼270 km as result of the cool slab in the MTZ influencing the 660-km discontinuity and includes an arrival at ∼520-km depth likely from the top of a flat lying slab or a discontinuity related to a solid–solid phase transition in the olivine component of the mantle. We find evidence for low-velocity zones both above and below the 410-km discontinuity and above the 660-km discontinuity. The low-velocity zones around the 410-km discontinuity might be the result of hydration of the MTZ from the slab and upward convection of MTZ material into the upper mantle. The origin of the low-velocity zone around the 660-km discontinuity is less clear and could be related to sedimentation of subducted mid-ocean ridge basalts. The small footprint of the seismic array provides accurate information on the structure of the MTZ in an area influenced by subduction and shows small-scale changes in MTZ structure that might be lost in studies covering larger areas with sparser sampling.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉We perform non-linear time-series analysis on a harmonic tremor seismogram recorded at 830 m away from the centre of the crater during the 2011 eruption at Shinmoedake, Japan. We found features suggesting the existence of period doubling bifurcation in the harmonic tremor signal, implying that the harmonic tremor might be generated by a non-linear process. In order to quantify the non-linearity in the harmonic tremor signal, we measure the correlation dimension 〈span〉D〈/span〉 and the maximal Lyapunov exponent λ. For one short but stable segment of the harmonic tremor seismogram, we obtained 〈span〉D〈/span〉 = 1.12 and λ = 0.03 s〈sup〉−1〈/sup〉. This result implies that the stable oscillation of the harmonic tremor is predominantly a limit cycle with small amounts of chaos present. We then use surrogate data analysis to check that our measurements of 〈span〉D〈/span〉 and λ do not include any false positive detection of non-linearity. Limit cycles imply that the harmonic tremor is generated by self-sustained oscillations. We show that the autonomous Julian tremor model is able to exhibit period doubling bifurcation. We also show that the non-autonomous Julian tremor model with a step like increase and decrease in input pressure is able to exhibit oscillations of varying amplitude while keeping a constant frequency spectrum. Both phenomena were observed at Shinmoedake. We also demonstrate that the non-autonomous Julian tremor model with a transient input pressure is able to exhibit long period-like events in addition to harmonic tremor-like events, implying that the same non-linear mechanism could be responsible for the generation of both type of events.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉Reservoir models are numerical representations of the subsurface petrophysical properties such as porosity, volume of minerals and fluid saturations. These are often derived from elastic models inferred from seismic inversion in a two-step approach: first, seismic reflection data are inverted for the elastic properties of interest (such as density, 〈span〉P〈/span〉-wave and 〈span〉S〈/span〉-wave velocities); these are then used as constraining properties to model the subsurface petrophysical variables. The sequential approach does not ensure a proper propagation of uncertainty throughout the entire geo-modelling workflow as it does not describe a direct link between the observed seismic data and the resulting petrophysical models. Rock physics models link the two domains. We propose to integrate seismic and rock physics modelling into an iterative geostatistical seismic inversion methodology. The proposed method allows the direct inference of the porosity, volume of shale and fluid saturations by simultaneously integrating well-logs, seismic reflection data and rock physics model predictions. Stochastic sequential simulation is used as the perturbation technique of the model parameter space, a calibrated facies-dependent rock physics model links the elastic and the petrophysical domains and a global optimizer based on cross-over genetic algorithms ensures the convergence of the methodology from iteration to iteration. The method is applied to a 3-D volume extracted from a real reservoir data set of a North Sea reservoir and compared to a geostatistical seismic AVA.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉We investigate slip-distribution models of the 2011 Tohoku earthquake, with a particular focus on diffracted tsunamis and uplift-induced waves along the backarc region of the Japanese Island Arc. The 2011 Tohoku earthquake produced a large amplitude tsunami that diffracted around Kyushu Island before reaching Korea. At the same time, this earthquake coseismically induced short-period small-amplitude sea waves in the East Sea. We performed tsunami simulations using seven fault models of the Tohoku earthquake to examine whether the models can accurately reproduce the observed waveforms in the open sea of the western Pacific Ocean, the South Sea of Korea, and the coast of the East Sea. For each fault model, we investigate tsunami features due to geomorphological characteristics of the Korean Peninsula in the Korea offshore. To determine which slip distribution model shows a good performance in the tsunami simulations, we set three criteria; the delay time between observations and synthetic waveforms, the normalized mean residual, and the normalized RMS misfit. Depending on the study region, all models show varying degrees of accuracy. The fault dimensions and the amount of slip have a larger effect on the RMS misfit then the slip distribution patterns of the fault models for observations along the Korean coast and the western coast of Japan.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉Economically important deposits of nickel-copper and platinum group elements tend to be associated with small mafic-ultramafic intrusions characterized by compositional layering. Our rock magnetic study of an exploration drill core recovered from a typical small intrusion from the recently discovered Kun-Man'e ore field have found that concentration-independent hysteresis parameters of the studied rocks generally co-vary with petrological characteristics, such as major element abundances and compositions of olivine and clinopyroxene. Although monoclinic pyrrhotite and defect-poor magnetite both contribute to magnetic properties of the samples, we argue that hysteresis parameters are not affected significantly by pyrrhotite content. Rather, the variations in the hysteresis parameters reflect variations in median grain-size of magnetite crystals. The correlation between the rock-magnetic grain-size indicators and geochemical crystallization temperature indicators suggests that the size of magnetite crystals is controlled by cooling regime. Compared to conventional laborious crystal size distribution (CSD) studies, rock magnetic measurements can provide a quick and sensitive way to evaluate CSD of magmatic magnetite in mafic and ultramafic rocks.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉The Reykjanes geothermal system is a high-temperature seawater system situated in SW-Iceland. Interferometric analysis of the Sentinel-1 satellite synthetic aperture radar (InSAR) data has been used to determine a time series of ground deformation induced by geothermal utilization between April 2015 and October 2017. Surface displacements have been estimated at coherent pixels, indicating a steady and linear subsidence within a sub-circular bowl centered on the well field at a maximum near-vertical rate of about 25 mm/yr, together with horizontal contraction. The average line-of-sight (LOS) displacement rates from ascending and descending tracks are inverted to determine the characteristics of the deformation source at depth, modeling the geothermal reservoir as a body of simple geometry within an elastic half space. The results indicate a deformation source at about 1 km depth contracting at a rate of (0.7–0.9) × 10〈sup〉5〈/sup〉 m〈sup〉3〈/sup〉/yr during the 2015–2017 period. Using pressure and temperature monitoring data at 900 m depth as well as an analysis of the reservoir structure and rock properties, we infer that the recent estimated volume change can be attributed to processes in the steam cap situated in the topmost part of the geothermal reservoir, in the 800–1200 m depth range. Processes involve a combination of compaction under pressure decrease and/or thermal contraction due to cooling of the rocks within or near the steam cap. The steam cap expanded in response to a sudden pressure drop resulting from the increase in extraction of geothermal fluids for a new power plant in 2006.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉The seismic speed and anisotropy are two methods frequently used to image the assembly inside the Earth. We study the crust assembly beneath the Biga Peninsula and the surrounding area in Northwest Turkey using the accelerometer and broadband recordings where short-to-medium period (5-20 s) Love-Rayleigh surface waves are utilized to extract the group-phase speed data (fundamental mode). Single-station and two-station techniques are engaged to understand the detected surface waves for the speed and anisotropy assemblies. The single-station group speeds are inverted in a tomographic approach to attain the two-dimensional group speed diagrams. The least-squares inversion procedure is utilized to find the speed-depth profiles (one-dimensional) under each grid location. The one-dimensional results are cooperatively inferred to attain the three-dimensional appearance of the S-wave speeds below the measured region. This process is reiterated for Love and Rayleigh waves. Isotropic configuration is not sufficient to concurrently describe the present detected Love-Rayleigh surface waves. Vertical transverse isotropic crust assembly is found to better elucidate the detected data showing the Rayleigh-Love discrepancy. Complex arrangement of sills and dykes due to the widespread plutonic and volcanic activity in the region linked to the interaction between the Turkish plate and the African plate (northward subducting) is thought to depict the crust assembly deformations causing the detected long-wavelength vertical transverse isotropy. The mineral orientation within horizontal sills and vertical dykes following the magma flow, which is independent of seismic wavelength, adds to the detected anisotropy. The upper crust vertical transverse isotropy is mostly negative; i.e. SV-wave is faster than SH-wave, which is assumed to be due to the existence of dykes. The middle-to-lower crust vertical transverse isotropy is commonly positive; i.e. SH-wave is faster than SV-wave, which is assumed to be due to the existence of sills. The two-station analyses operating on cross-correlograms give analogous vertical transverse isotropic results to those of the single-station estimates.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉The representative elementary volume (REV) is a critically important concept in fractured rock investigations as it tells us at what scale the fractured domain can be represented by an anisotropic tensor as opposed to requiring the details of each individual fracture for modeling purposes. Whereas the REV size and corresponding tensor characteristics for the hydraulic conductivity (〈span〉K〈/span〉) in fractured rock have been the subject of numerous previous investigations, no studies to date have focused on the electrical conductivity (σ). This is despite the fact that geoelectrical measurements are arguably the most popular means of geophysically investigating fractured rock, typically via azimuthal resistivity surveying where the observed electrical anisotropy is commonly used to infer hydraulic characteristics. In this paper, we attempt to fill this void and present a systematic numerical study of the impacts of changes in fracture-network properties on the REV size and equivalent tensor characteristics for both the electrical and hydraulic conductivities. We employ a combined statistical and numerical approach where the size of the REV is estimated from the conductivity variability observed across multiple stochastic fracture-network realizations for various domain sizes. Two important differences between fluid and electric current flow in fractured media are found to lead to significant differences in the REV size and tensor characteristics for σ and 〈span〉K〈/span〉; these are the greater importance of the matrix in the electrical case and the single-power instead of cubic dependence of electric current flow upon aperture. Specifically, the REV for the electrical conductivity will always be smaller than that for the hydraulic conductivity, and the corresponding equivalent tensor will exhibit less anisotropy, often with notably different principal orientations. These findings are of key importance for the eventual interpretation of geoelectrical measurements in fractured rock, where we conclude that extreme caution must be taken when attempting to make the link to hydraulic properties.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉Stress is a crucial factor that affects the permeability, and the influence of stress on permeability has been studied extensively by many investigators. In this article the relationship between confining pressure and permeability is investigated. For this purpose, a void ratio- pressure model based on the theory of incompressible elastic porous media is first proposed, then, based on the model and Kozeny-Carman equation, a new pressure–permeability relationship is proposed. Finally the relationship is utilized to predict the permeability of coal and mudstone under different confining pressure, and these predictions are compared with other models and found to be in better agreement with experimental data reported recently.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉We perform nonlinear time series analysis on a harmonic tremor seismogram recorded at 830 m away from the centre of the crater during the 2011 eruption at Shinmoedake, Japan. We found features suggesting the existence of period doubling bifurcation in the harmonic tremor signal, implying that the harmonic tremor might be generated by a nonlinear process. In order to quantify the nonlinearity in the harmonic tremor signal, we measure the correlation dimension 〈span〉D〈/span〉 and the maximal Lyapunov exponent λ. For one short but stable segment of the harmonic tremor seismogram, we obtained 〈span〉D〈/span〉 = 1.12 and λ = 0.03 s〈sup〉−1〈/sup〉. This result implies that the stable oscillation of the harmonic tremor is predominantly a limit cycle with small amounts of chaos present. We then use surrogate data analysis to check that our measurements of 〈span〉D〈/span〉 and λ do not include any false positive detection of nonlinearity. Limit cycles imply that the harmonic tremor is generated by self-sustained oscillations. We show that the autonomous Julian tremor model [〈span〉Julian〈/span〉, 1994] is able to exhibit period doubling bifurcation. We also show that the non-autonomous Julian tremor model with a step like increase and decrease in input pressure is able to exhibit oscillations of varying amplitude while keeping a constant frequency spectrum. Both phenomena were observed at Shinmoedake. We also demonstrate that the non-autonomous Julian tremor model with a transient input pressure is able to exhibit long period-like events in addition to harmonic tremor-like events, implying that the same nonlinear mechanism could be responsible for the generation of both type of events.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉We present a joint analysis of newly acquired gravity and teleseismic data in the North Tanzanian Divergence, where the lithospheric break-up is at its earliest stage. The impact of a mantle upwelling in more mature branches of the East African Rift has been extensively studied at a lithospheric scale. However, few studies have been completed that relate the deep-seated mantle anomaly detected in broad regional seismic tomography with the surface deformation observed in the thick Archaean Pan-African suture zone located in North Tanzania. Our joint inversion closes the gap between local and regional geophysical studies, providing velocity and density structures from the surface down to ca. 250 km depth with new details. Our results support the idea of a broad mantle upwelling rising up to the lithosphere and creating a thermal modification along its path. However, our study clearly presents an increasing amplitude of the associated anomaly both in velocity and density above 200 km depth, which cannot be solely explained by a temperature rise. We infer from our images the combined impact of melt (2-3%), composition and hydration that accompany the modification of a thick heterogenous cratonic lithosphere are a response to the hot mantle rising. The detailed images we obtained in density and velocity assert that Archaean and Proterozoic units interact with the mantle upwelling to restrict the lithosphere modifications within the Magadi-Natron-Manyara rift arm. The composition and hydration variations associated with those units equilibrate the thermal erosion of the craton root and allow for its stability between 100 and 200 km depth. Above 80 km depth, the crustal part is strongly affected by intruding bodies (melt and gas) which produces large negative anomalies in both velocity and density beneath the main magmatic centers. In addition to the global impact of a superplume, the velocity and density anomaly pattern suggests a 3D distribution of the crust and mantle lithospheric stretching, which is likely to be controlled by inherited fabrics and enhanced by lateral compositional and hydration variations at the Tanzanian craton-orogenic belt boundary.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉We report palaeomagnetic and K–Ar geochronologic results of two volcanic sequences from Ethiopia. The Belessa section, dated around 29–30 Ma and spanning ∼1 km in thickness, is related to the Oligocene Afro-Arabian traps, whereas the ∼700-m-thick Debre Sina section was emplaced during the Miocene in two periods around 10–11 and 14–15 Ma. We sampled 67 flows of predominantly basaltic rocks near Belessa and 59 rhyolitic to trachybasaltic flows near Debre Sina. From a geodynamic viewpoint, the magnetostratigraphy of the Belessa sequence confirms that the Ethiopian traps were emplaced at a minimum rate of ∼1 m/kyr, with a possible acceleration of the volume of volcanism over time. To provide insight into the evolution of the geomagnetic field in the Afro-Arabian region over the past 30 Myr, we combined our results with previous studies in the same area. Recentred directional distributions were elongated in the meridian plane, in coherence with field models for a dipole-dominated field. The dispersion 〈span〉S〈/span〉 of the virtual geomagnetic poles, representative of the vigour of palaeosecular variation, was approximately 50% higher during the 10–30 Ma interval than during the past 5 Myr. As the reversal frequency 〈span〉f〈/span〉 was more than two times lower during the Early Oligocene than during the Plio-Pleistocene, it appears that 〈span〉S〈/span〉 and 〈span〉f〈/span〉 are uncorrelated in this near-equatorial region. It remains an open question whether this apparent decoupling is ascribable to a local anomaly, is only sporadic in time, or represents a general feature of the geodynamo.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉The non-linear interaction of ocean surface waves produces coherent infrasound noise—microbaroms—between 0.1 and 0.5 Hz. Microbaroms propagate through the atmosphere over thousands of kilometres due to low absorption and efficient ducting between the ground and the stratopause. These signals are globally and permanently detected by the International Monitoring System (IMS) infrasound network, which has been established to monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty. At the International Data Centre (IDC) in Vienna, where IMS data are routinely processed, microbarom detections appear in overlapping frequency bands, and are treated as false alarms. Therefore, understanding the variability in microbarom detections is essential to support the IDC in the reduction of the false alarm rate. In this study, microbarom amplitudes and the direction of arrivals at the German infrasound station IS26 were modelled. For the simulations, the source was described by an operational ocean wave interaction model, and the signal amplitude was modelled using a semi-empirical attenuation relation. This relation strongly depends on middle atmosphere (MA; i.e. 15–90 km altitude) dynamics; however, vertical temperature and wind profiles, provided by numerical weather prediction (NWP) models, exhibit significant biases and differences when compared with high-resolution lidar soundings in altitudes where infrasound signals propagate. To estimate uncertainties in the modelled amplitude, a fully autonomous lidar for MA temperature measurements was installed at IS26. Temperature and wind perturbations, considering observed biases and deviations, were added to the operational high-resolution atmospheric model analysis produced by the European Centre for Medium-Range Weather Forecasts. Such uncertainties in horizontal winds and temperature strongly impact propagation conditions, explaining almost 97 per cent of the actual detections, compared to 77 per cent when using the direct output of the NWP model only. Incorporating realistic wind and temperature uncertainties in NWP models can thus significantly improve the understanding of microbarom detections as well as the detection capability of a single station throughout the year.〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉The interaction of subducted oceanic lithosphere with the discontinuities of the mantle transition zone (MTZ) provides insight into the composition and temperature of the subducted slab as well as potential melting of the slab or the surrounding mantle and loss of volatiles from the slab. Detailed mapping of the structure of the MTZ will help to better understand how slabs transport material and volatiles into the mantle and how phase transitions affect the slab dynamics. Here we use a dense network of seismic stations in northern Anatolia to image the structure of the MTZ discontinuities in detail using P-wave receiver functions. With a station spacing of about 7 km and a surface footprint of ∼35 km by ∼70 km, analysing receiver functions calculated from teleseismic earthquakes that occurred during an ∼18 month deployment produced clear images of where the mantle transition zone interacts with the Tethys/Cyprus slabs that either lie flat on the 660-km discontinuity or pass into the lower mantle. We observe an undulating 660-km discontinuity depressed by up to 30 km and a slightly depressed (1–2 km) 410-km discontinuity, apparently undisturbed by the slab. The MTZ is thickened to ∼270 km as result of the cool slab in the MTZ influencing the 660-km discontinuity and includes an arrival at ∼520-km depth likely from the top of a flat lying slab or a discontinuity related to a solid-solid phase transition in the olivine component of the mantle. We find evidence for low-velocity zones both above and below the 410-km discontinuity and above the 660-km discontinuity. The low velocity zones around the 410-km discontinuity might be the result of hydration of the MTZ from the slab and upward convection of MTZ material into the upper mantle. The origin of the low velocity zone around the 660-km discontinuity is less clear and could be related to sedimentation of subducted mid-ocean ridge basalts. The small footprint of the seismic array provides accurate information on the structure of the MTZ in an area influenced by subduction and shows small-scale changes in MTZ structure that might be lost in studies covering larger areas with sparser sampling.〈/span〉

Description: 〈span〉〈div〉SUMMARY〈/div〉Long-period Rayleigh wave horizontal to vertical amplitude (H/V) ratios at a station provide information about local earth structure that is complementary to phase velocity. However, a number of studies have observed that significant scatter appears in these measurements making it difficult to use H/V ratio measurements to resolve earth structure. Some of the scatter in these measurements has been attributed to local geological structure while some has remained unaccounted for. Most Global Seismographic Network (GSN) stations contain two nearby high-quality broad-band seismometers (e.g. in the same vault, but on different piers or in different boreholes). For each broad-band sensor in the IRIS/USGS component of the GSN, we estimate H/V ratios of fundamental mode Rayleigh waves using 〈span〉M〈/span〉 〉 6.5 earthquakes from 2001 to 2018 (around 19 000 measurements). We compute these ratios at a number of discrete periods (25, 50, 75, 100 and 150 s) and find that for well-isolated Rayleigh waves (windows where the correlation coefficients between radial and the phase-shifted vertical components are greater than 0.9) significant scatter in H/V ratios occurs between colocated sensors (greater than 25 per cent at 100 s period). This suggests the scatter in H/V ratio measurements can be at least partially attributed to extremely local phenomena such as sensor emplacement in the vault. We also find that H/V ratios can vary as a function of event backazimuth, indicating that care must be taken when computing average ratios for a station, as a large number of events from a given region could bias H/V ratio measurements at a station.〈/span〉

Description: The precision of the universal time UT1 forecast for the short time intervals (up to two months) is researched in this paper based on the celestial mechanical model of the Earth axial rotation irregularity. It is shown that use of the approximate low-parametric model for the problem of the Earth axial rotation velocity variation forecast on the short time intervals is justified. The approximate model is obtained by the averaging of the variable parameters that is exposed to small variations in consequence of perturbation factors nonstationarity. The method of weight coefficients distribution in approximation algorithm that takes into account the irregular oscillations of the Earth axial rotation velocity is suggested. The precision of the forecast that is identical to published by IERS one is achieved with the help of weighted least squares method.

Description: A solution of the problem of modeling the compensatory system’s sustainability on the basis of the algebraic formalization of the general concept of the system is proposed. By a compensatory sustainability is meant the internal structure of the system’s links, which ensures the interchangeability of its structural resources.

Description: List of Photo available in this pdf.

Description: The article illustrates the analysis of oscillations of a flat multi-storey framework as discrete dissipative systems (DDS) at pulse influence by the time analysis method (TAM). Brief theoretical prepositions of TAM, such as description of the equation of motion of the DDS and expressions of response parameters, are given. The design dynamic model of the structure represents the flat three-storey shear frame having three degrees of freedom. The calculation results are oscillograms of internal response characteristics and reaction parameters of the system on the time slice t ϵ [0;8] sec. The multi-cycle nature of deformation of racks and also the change of parameters of plastic zones of framework supporters in the process of non-linear oscillations are considered.

Description: When carrying out water treatment processes, a significant amount of hydroxide sediments is formed, which have a low water-yielding capacity. In the paper, the sediment of sewage treatment facilities of water pipes, which is formed in the conditions of low turbidity and medium color of water in a water source, was investigated. The effect of seasonal variations in turbidity, color and temperature of the treated water on the specific resistance of sediment filtration is shown. The features of sediment formation in sedimentation tanks of various types are considered. It is shown that the conditions for the formation of sediment affect its properties. It is established that the return of washing water, realized on one of the blocks of main water treatment facilities, increases the turbidity of the water to be purified and leads to the formation of sediments that are easier to be conditioned. At the same time, the sediment, formed in two-tier sedimentation tanks, when they are condi...

Description: The wealth of our country is not only people and a multinational culture, but also a vast territory on which the areas of a unique animal and plant world, depending on their geographical location, have spread. In order to preserve the natural environment on the territory of our country, since the Soviet era, protected natural areas, hunting facilities have been created, and a hunting resources fund has been established. In Russia, there are about 5,000 hunting users, who carry out hunting activities in 7,000 hunting farms, employing about 80,000 people. The territory of the hunting area may include lands of various categories of the Land Fund of the Russian Federation and lands for various special purposes, as well as limitedly defensible lands. According to the current legislation, a differentiated approach is used to regulate the use of these lands, which makes it difficult to use and manage this type of land, and accordingly the industry. The article deals with the problems, ...

Description: The acceleration of hardening of compositions, based on cement and low cement binding materials, is possible in special conditions of concrete mixtures consolidation when a disperse system “binding aggregate” is being consolidated by a small amount of water. These are so-called methods of vibration pressing and pressing. Vibration pressing presupposes a binary mechanical influence on the consolidated mixture – vibration and pressure, generated by a power installation of a press or a set-on weight the strength of which is widely variable. No need for mixture plastic state sustention in the conditions of such influences imposes special requirements both for the mixture composition design and modes of its consolidation and strengthening. At present, a recovery of industrial powder wastes which do not possess the binding properties, while being produced by the traditional methods of building materials manufacture with the use of easy-to-place mixtures (vibration pressing, tamping, a...

Description: This article deals with the particular objects of the reconstructed historical architectural sights in Tsaritsin and considers the architecture of the Soviet Neoclassicism of Stalingrad’s post-war restoration of the 1940s and the 1950s. It shows what the architects’ efforts were directed to and considers the style and compositional arrangement of buildings of the time. The study is conducted by means of the analysis of the materials found in central and regional archives, the literature review, and field observations (measuring and photographic registration). The article provides the description and analysis of the architecture of the city’s most significant buildings of the time. It analyses and classifies main specificities of architectural details and principles of their use in various types of buildings of the Soviet Neoclassicism. It also highlights the role of the architectural detail in creation of an image of the Hero City. The article also provides a new record of photo...

Description: The increase of energy efficiency and energy saving are the main indicators of the improvement and growth of the competitiveness of the Russian economy. One of the system approaches is saving of energy resources through heat recovery. The use of heat recovery units and assessment of the boundaries of their effective use are rather relevant for regions with a long heating period and low negative temperatures. The study proves that special climatic conditions of the Southern Urals provide certain benefits when using heat recovery units in the cold season, relative to other regions, which allows us to use them effectively in ventilation and air conditioning systems throughout the year.

Description: All papers published in this volume of IOP Conference Series: Materials Science and Engineering have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

Description: The current article describes green pigments’ manufacturing and application problems. Verditer green, or green pigment, is a group or chemical compounds used in various branches of industry, especially in manufacturing paints used for decoration and restoration of engineering constructions and other buildings. The properties and methods of obtaining verditer green from industrial waste are presented with the properties of viridian and cobalt green taken as the examples of green pigments. The technology of obtaining chromium oxide III, chromium hydroxide III, cobalt green including the required equipment, is given with the focus on the calcination process, the chemical reactions are performed both in description and chemical formulae, the different methods of obtaining the pigments, depending on the demanded pigment’s colour, are offered, and the technical and chemical requirements for the raw material and the pigments’ compound are listed.

Description: The industry that forms sulphide-bearing wastewater imposes a big man-made burden on the ambient environment. Existing treatment methods of sulphide-bearing wastewater intend for insignificant decrease of sulphide concentration, water purification without further use, and storing of sediments at polygons. Transportation of sulphide-bearing wastewater causes heavy corrosion of pipe system. The developed modern technology allows carrying out quality purification of wastewater, obtaining circulating water for process purposes as well as commodity products used in the main technology. The relevant is development of optimal techniques for sanitation of sulphide-bearing wastewater from the position of using the pollutant as a finished reagent solution. Research on the processes of forming sulphide-bearing wastewater was carried out, selection of purification method by treatment using ferrous sulphate was conducted, conditions for efficient use of this method with the purpose to develo...

Description: A significant increase in the construction of high-rise buildings in Russia is observed in the last decades. Ekaterinburg takes the second place in Russia after Moscow as regards the annual construction volumes. The first high-rise buildings in the Urals region were built as early as in 19th century and the height of these buildings reached approximately 75 meters. Nowadays, two northernmost skyscrapers in the world are located in Ekaterinburg, one of which is a part of a business district "Ekaterinburg-City". The height of these skyscrapers is above 150 meters. The incompleteness of the Russian regulatory basis for designing high-rise buildings makes it necessary to carry out a large amount of additional design and construction processes. Therefore, despite the experience of previous projects, designers have to create individual innovative design solutions for every new high-rise building. This article describes the features of design of the high-rise building is the Iset Tower...

Description: Here mechanical systems with the Nambu bracket is discussed. We consider some examples of the Nambu mechanics. The main idea that the superintegrability of mechanical system leads to the Nambu bracket. Some applications for the field theory are given.

Description: The system of automated computation of the insolation duration is considered as applied to the tasks of architectural design. The model and algorithm of computation and plotting are given. The system allows to perform computation in a point, inside a contour, plotted on a territory or a building’s wall. By way of illustration, shadow movement animation is performed, as well as building of the sectors of light indicating at the reasons of limited insolation. The influence of the computation date on the insolation duration is considered. It is demonstrated that changing the date of the normative computation from March 22 to April 22 reduces the region of unacceptable insolation by 50...70%. The examples of computation are given. The system interface is considered. A brief description of the system’s software implementation is provided. The models are designed in the AutoCAD package. The programs are written in the AutoLisp programming language.

Description: The urbanization of territories, changes in the lifestyle of the population, significant deterioration of the environment require a change in the traditional approach of the formation of urban and architectural space. In view of the limited time budget of the modern city dweller, it is necessary to revise the existing system of active green recreation, bringing it as close as possible to the space for life and work. Because of the limitations of territorial resources and aggressiveness of the external environment, the trend of green space "green building". This concept involves the active formation of several types of landscaping at the same time. That requires a special approach to the design of the "green" object. The article deals with the levels of the complex of factors that are necessary in the design of ecological space at various stages.

Description: The article offers an approach to building collapse risk evaluation with damage localization. As a rule, the risk includes the probability and value of loss. The probability of failure for separate construction is determined by known methods, but for risk-management decisions these methods are too complicated. The solutions of the problem, using the specified theoretical base, are considered: for structural damages of the constructions the simple rules of criticality degree determination are used; they are based on fuzzy logic, which ensures the efficiency of structural state assessment. The represented risk assessment method is also based on technological and social loss cost evaluation for various areas under failed constructions and different accident scenarios. The risk oriented approach can be applied in few related areas of construction, from design to insurance.

Description: The territorial technosphere is a dynamic system described by a system of differential equations. The initial data of these equations take into account the conditions of normal functioning of the territorial technosphere and emergency situations. Changing the parameters of the impact of the technosphere allows you to influence the quality of the environment and to maintain it in a stable state. An effective mechanism for controlling the territorial technosphere as a dynamic system should be the elimination of inoperable States using: the formation of a set of informative parameters; control and registration of values of informative parameters; creation of a database of normative and actual values of informative parameters, formation of control actions.

Description: The chemical control department of the Kuibyshev refinery (known as KNPZ) registers a systematic increase in river water hardness and alkalinity. The increase of these values changes the reagent softening mode of clearing agents with weighted sediments. It is required to carry out a constant analysis of water alkalinity before reagent softening. The researchers collected data of average monthly values of the Volga-river water samples from Samara Hydroelectric Station, the Samara-river water samples from the Bezymyanka heat power-station, the Volga-river water samples from Kuibyshev refinery as well as hourly water samples from the same stations and compared it with the data on average daily Volga-river water discharge from Zhiguly hydroelectric power station, obtained in 2016, from July till October. The analysis of the data showed that changes of the Volga-river water discharge had no effect on the increase of water alkalinity and hardness of the KNPZ river intake.

Description: A new concept smart robots for massage with plane and spatial parallel mechanisms is shown. Plane and spatial parallel robots (PPR and SPR) are based on triangular and octahedral structures. Every one of sides of triangle and ribs of octahedron is linear drive. Ends of the adjacent linear drive are connected with by cylindrical (for triangle) and spherical (for octahedron) joints. As result PPR and SPR have three and twelve degrees of freedom, and they can adapt to body of patient and. Possibility of full automation some kinds massage by autonomous portable smart PPR and SPR is shown. The use of these robots will allow the masseur remotely via the Internet to serve several patients at the same time in real time. PPR and SPR are portable multifunctional smart robots for various rehabilitation applications. Both kinds parallel robots will be discussed in detail.

Description: The issues of protection and improvement of the environment surrounding residents of the cities are one of key in modern town planning. Their decision has to be a component of design and planning work. Throughout all evolution of the architectural and landscape environment of the city as anthropogenic ecosystem the quality of his territories in many respects defined gardening, which minimizes negative impact of factors of the urbanized environment on the person But in the modern cities its area decreases, the condition of vegetation worsens that, finally, leads to violation of spatial interrelations of an anthropogenic and natural component of the urban environment. The territorial growth of the cities has aggravated a problem of preservation of a natural landscape. The total area of public green areas in the majority of city districts does not meet the operating town-planning standards Owing to this fact in the Russian town planning to the forefront there were questions of form...

Description: The paper presents the results of experimental studies on the effect of silica-containing components on the structure and properties of cellular concrete. It is shown that the creation of the optimal pore structure of concrete and the structure of the interporous frame, the intensification of hydration and crystallization processes in hydrothermal treatment can improve the physical and mechanical characteristics of cellular concrete. At the level of modern knowledge about the structure and properties of cellular concrete, the potential for increasing its strength characteristics has been studied. Through the effective use of the energy potentials of the multicomponent binder, including Portland cement, calcium lime and activated silica components, the nanopore structure of the matrix stone is formed.

Description: Contemporary models of solids of thermoelasticity requires to include multiphysics coupling and employ non classical e.g. elastic behavior. The permanent generalization of elastic model is the Cosseratt micropolar model. Now this model is to be applied to growing solids, biomaterials, granular media, concrete. The basic concepts of the continuum mechanics is considered in connection with the difference in the dimensions of the continuum and external space. New field variables are introduced representing complex continuum properties. A generalization of the model of the micropolar continuum has been proposed. The action and the action density for the complex continuum model are discussed. A new field-theoretic model of a nonlinearly elastic continuum is developed assuming existence of an isometric immersing into an external plane space.

Description: In the modern society a constant search is performed for the options to improve the energy efficiency of constructed residential and public buildings to reduce the cost of their operation and the human impact on the environment. One of the possible ways of the problem solution is using new construction and thermal insulation materials and products that meet modern requirements, for example, fencing and supporting construction made of polystyrene concrete. The authors carried out some research works, concerning the aforementioned improvement of deformation and strength characteristics of building material, by modeling its structure in the Institute of New Materials and Technologies of Ural Federal University. The research and mathematical modeling of the dependence of the composite material characteristics on the properties of raw materials and structure will allow predicting the strength of manufactured structures and determining the ratio and quality of raw materials of polysty...

Description: To purify aquatic environments from various toxicants, we obtained a carbon-mineral sorbent from the reed stems of the South (Phragmitesaustralis) by carbonization. At the stage of carbonization of the crushed reed, a carcass, containing carbon and silicate constituents, is formed. Depending on the type of feedstock and the carbonization temperature of the organic component, the content of the silicate component varies in the range of 20-30%. The process is carried out until a sorbent containing 70-80% of the carbon component, 29-19% of the silicate component and 1% of water is obtained. The adsorption capacity of the obtained carbon-mineral sorbent towards to medium and macromolecular organic compounds, and heavy metals was studied. As a result, it was established that the carbon-mineral sorbent obtained from the reed stems of the South (Phragmitesaustralis) has moderately distributed sizes of macro- and micropores. The presence of two constituents, carbon and silicate, in the ...

Description: One of the new and promising directions in the wastewater treatment technologies and treatment of precipitation is the use of the probiotic agents. A lot of brands of probiotics, which differ in their composition, concentration and cost are offered by the producers on the market. The research results of the “Pip Plus Water” probiotic influence on the concentration of organic contaminants in the model wastewater solution are presented in this article. An additional point is that the changes in the quality indices of the wastewater, which is taken from municipal sewage treatment facilities, because of the contact with a probiotic have been investigated. The characteristics, describing the active sludge compaction process before and after the addition of the probiotic agent, have been obtained. The preliminary study stage has showed that the probiotic agent being considered has a positive impact on the certain sewage quality indicators and the precipitation properties. The ability ...

Description: The article presents the results of the study of the landscape-botanical complexes in the zone of influence of the Orenburg gas condensate field. The studies have found that the area objects in most cases are located on the territory of arable land, which occupy 60-90% of the terrain of the study area. Previously, natural vegetation was cut down and new trees and shrubs were planted. The studies have shown that during the reconstruction and construction works at industrial sites the soil was removed. During the work with the water wash the existing vegetation was subjected to species transformations, which led to the death of communities that can not withstand constant excessive moisture. Thus, the role of the floodplain as a natural filter under the condition of surface water pollution was violated. Water-washing works led to a change of the Ural river bed: the right bank became more steep, the river bed expanded, which affected the decrease in the flow rate, the process of sil...

Description: The article presents the results of the study of the vegetation cover, in particular, the floristic and phytocenotic features of the territory of oil and gas extraction of the North-Eastern coast of the Caspian Sea, the southeast of the Caspian lowland are determined. Also, modern ecological and technological methods and a monitoring program are reflected, which will allow us to identify and assess the level of man-made impact, to develop a system of compensation processes that balances the ecological system as a whole. It is shown that the production activity of the oil and gas industry remains one of the main reasons for the negative impact on the stability of the vegetation cover of the studied areas.

Description: The article discusses features of dynamic characteristics in a parallel-staging launch vehicle’s elastic design. In contrast to traditional forms of body transverse vibrations in rockets with tandem staging, the parallel-staging scheme features vibrational forms of spatial character which are associated with longitudinal and torsional vibrations of side blocks of the rocket. The attention in the paper is drawn to the simplicity and clarity of drawing up general equations of dynamics in the form of d’Alambert-Kane, as well as to the features of projections of overload forces and the main engines thrust onto the related and inertial axes.

Description: The article gives a short review of modern trends in the development of architectural space and essential factors that influence this process: material and technical; and socio-cultural. The introduction touches upon modern requirements for organizing the living environment. The body of the article defines and analyses the factors determining the development of the modern architectural space. They represent two different trends of influence: material and technical; and socio-cultural. The body starts with the description of material and technical factors that include development and improvement of material and technical resources, technological progress, changes in the engineering and technical requirements. The author pays particular attention to their impact on modern construction concept and space planning. The article further on investigates socio-cultural factors that are regarded as the underlying for the process of shaping a modern architectural space. Among socio-cultura...

Description: An analogue of confidence intervals with a given level of possibility for output variable in a fuzzy linear regression model has been developed in the paper. The methods of fuzzy regression analysis extend the methods of classical regression analysis and allow to solve different problems in conditions of fuzzy and incomplete initial information without the limits of the probabilities methods. The developed approach opens up new opportunities for predicting of output fuzzy variable.

Description: The article deals with the problem of architectural and city planning attractiveness of large cities due to the growing population and increased traffic. The author focuses on the negative impact of constructing multi-level highway intersections in the city structure in the light of socio-ecological, emotional-psychological, artistic-aesthetic and cultural-religious aspects. The article solves the problems of urban areas by integrating multi-level traffic intersections. The construction of low-rise settlements in the zones with much gardening, forest areas near lakes and rivers compensates city unattractiveness. Apparently, the solution of the problem is the harmonious combination of public administrative zones of "point" construction with buildings of different types in combination with low-rise buildings of a country type. The effective combination is based on developing a good transport system, based on multi-level traffic intersections. We suggest combining these zones with ...

Description: The paper presents a historical perspective on the emergence and development of Russian monotowns. It also studies the lack of a case-by-case approach to the modern Russian monotowns architectural appearance formation of as well as contemporary creative approaches to the design process of architectural works and design. This paper makes the case for creative approaches to the creation modern objects in the monotown's architectural space. It provides an example of a creative approach to the architectural object design, at the initial designing stage enabling to individualize a future project, reflecting a part of the author's creative self-identity. A “self-concept" is given as an example of a design approach. That approach ensured the use of a graph unit - a prototype-based visual component formation of the organization corporate identity, reflected both in the building architecture, small architectural objects, and in design items. The visualization, accompanying the paper, is ...

Description: The International Conference on Construction, Architecture and Technosphere Safety (ICCATS-2018) was organized by South Ural State University (national research university), Chelyabinsk, Irkutsk National Research Technical University, Irkutsk and Ural Federal University named after the first President of Russia B.N. Yeltsin, Ekaterinburg on 26-28 of September, 2018. The conference program encompassed a wide range of topics and was divided into 9 sections: building materials and products; construction, buildings and structures; construction technology and organization; engineering networks and equipment. foundations, bases and underground structures; engineering and computer graphics in construction design; architecture, urban studies and design; analysis, assessment and technologies of natural and man-made disasters reduction; industrial ecology and waste-water treatment. More than 236 participants from 28 cities of the Russia and other countries attended the confe...

Description: The concept of safety and life support of the population in the context of urbanization is one of the most systemically important concepts of human ecology. Legislative and regulatory documents, concerning the radiation safety of the population and personnel, have been considered. Conceptual issues have been critically analyzed. The article deals with the problems of ensuring the radiation and environmental safety in the construction industry. The problem of radiation hygiene support of technological processes and construction is of particular importance. The radiation control of working conditions needs to be carried out in accordance with the legislative and regulatory acts accepted in Russia. The issues of the relevance of radiation risks have been considered in the context of working conditions in the construction industry that were specially assessed. The activities to reduce workers’ exposure from natural radionuclides should be carried out in all cases, when this dose exc...

Description: The article reveals the study of spatial distribution of the density of public and business objects with the use of geoinformation technologies. The source of the data was data from the open geoinformation project OpenStreetMap. Earlier, we showed that for the radial component of the density of public and business facilities. This paper is a continuation of the previous one. The angular distribution of density of public and business objects is studied by example of the largest city - Ekaterinburg. Spatial density has "tails" that characterize the predominant directions of the city development. At the same time, the average spatial configuration for the average density distribution shows the radial-ring structure for urban planning. The obtained results are interpreted within the framework of the "frame-fabric".

Description: It is important to check the projects created on the basis of BIM. In this case, an automated process of checking and evaluating the quality of the BIM-model is necessary, for example, for express checking in the state expertise. At the same time, it is necessary to take into account the technological and organizational features of construction and installation works. This issue is especially important and relevant for facilities that are dangerous and technologically complex (for instance, stadiums, high-rise buildings, hydroelectric power stations, bridges). In the article the authors propose to approach the examination of the state expertise of the projects of these objects from the position of the model of object technological dependencies. The key factor of this model is a description of the technology of the facility construction, which displays the technological interrelation of the works, their quantification and the definition of the time domain of these works. The mode...

Description: The article provides an overview of the dependencies connecting structure of concrete with young’s modulus. The developed method experimental evaluation of the known dependencies. In the studies used samples with different number and different size of crushed stone. Shows the compositions of the used concretes. According to the results of the tests were obtained the theoretical diagrams of the concrete. The paper presents the results of experimental studies of various compositions of concrete. Part of the dependency of the young’s modulus was checked for consistency with experimental data. Proposed practical methodology for the evaluation of the concrete structure. According to the results of the comparison proposed a theoretical model for the estimation of the young’s modulus for concrete structures.

Description: The current state, development and transformation of transport infrastructure in urban areas are due to factors such as increased safety, environmental requirements, as well as the provision of new opportunities through the connection of vehicles to the Internet. Connected, Autonomous and electric vehicles have become key areas of development in the automotive industry. By the end of 2020, there will be more than 14 million connected vehicles on the roads of Russia, 3.5 million of which are trucks and more than 10 million personal cars. In this paper, the object of the study is the transport interchange of regional importance as a structural component of a single urban space of the city district of Tyumen, Tyumen region. The authors present the results of theoretical research and practical work on the implementation of geospatial systems and technologies in the design of roads. The features of the design of this object using GIS technologies are considered. The analysis of the d...

Description: Relative statistical indicators of injuries in construction are higher than the general rate for all types of economic activity. In this paper, the assessment has been made of the occupational risks during buildings construction with consideration to the peculiarities of technological stages. The occupational risks were assessed with regard to the probability of danger and seriousness of consequences. The highest risks were revealed for the following works: land plot fencing, demolition of the existing buildings, foundation excavation, trenching for communications, erecting outer walls of buildings, and wiring. The most frequently occurring accidents are falling from height and electric injuries. Namely these risks require putting more focus on them and using individual approach when trying to minimize them.

Description: The article deals with the problem of protecting the population and the environment from the negative impact of an agricultural enterprise built on the territory of a settlement prior to the enactment of land and urban codes. The enterprise under consideration refers to hazardous production facilities of the third hazard class. In accordance with the urban development plan for the city of Zavodoukovsk, the enterprise was in the residential development zone. Taking into account that, since the establishment of the company, not only the production capacities but also the area allocated for the land plot have increased, there is an urgent need to resolve the issues of its future activities on the territory of the settlement in accordance with the current legislation.

Description: The application of the theory of fractal geometry in construction materials production allows revealing a new possibility to model the properties of materials and processes. The fractal theory can be used in the research of the processes of cement paste hardening as the formation of a cluster structure; the structure and properties of dispersed media; structural characteristics of the porous material; cracking caused by various factors, using data received at predicting the collapse of critical structures. The investigation of surface properties of aggregate, using a fractal approach, allowed one to reveal the direct dependence between the physical and mechanical characteristics of the concrete and the value of the fractal dimension of such aggregate. Thus, application of the method based on the determination of the fractal dimension of the aggregate, allows predicting the properties of concrete as well as to regulate its physical and mechanical properties by selecting or modify...

Description: The identification of modern approaches and the specifics of the improvement of architectural solutions for residential buildings of an affordable price category in non-capital cities of the Russian Federation has become the main task of the research. From the generalization and analysis of the overall results of the development of the housing sector in the Russian Federation, the authors proceed to the consideration of the situation in one of the megacities of the country - Samara. With the example of seven residential compounds being built or newly built in this city, the approaches to the formation of architectural solutions that are characteristic of local conditions at the present stage of housing construction have been shown. A particular attention was paid to the social infrastructure and the functional and spatial organization of residential complexes, environmental and social aspects. The conclusion about the gradual increase of consumer properties of affordable housing...