Further Remarks on Extra Roots of Rayleigh Equation and Somigliana Waves

The extra roots of the Rayleigh equation for an elastichalfspace contribute to the solution only for large enough values of thePoisson coefficient (a > 0.309). One of them corresponds to leaking modeswith the phase velocity less than the velocity of the longitudinal wave.A similar wave with distinct dispersion may exists in the case where anelastic halfspace is covered by a thin layer with lower velocities of elasticwaves. The thickness of a layer should be not too small in comparisonwith the wave length

Унифицированная модель расчетов производительности технических средств при реализации транспортных и транспортно­технологических операций

Productivity is one of the important performance indicators of transport and transport-technological vehicles. The authors confirmed the necessity to unify this indicator calculations for an extensive range of agricultural goods and extensive works on their movement. (Research purpose) To develop universal interconnected stages of detecting the operational productivity of transport and transport-technological vehicles when performing mechanized work in crop production. (Materials and methods) The values of operational performance were determined based on the analysis of norm-forming factors and statistical processing. A systematic approach was used to identifying individual elements of the cargo transportation cycle. The authors studied each of the methodological approaches and the mathematical tools used to calculate the performance indicators of various technical devices. (Results and discussion) After a step-by-step modeling of transport and transport-technological processes, a unified formula of the target function (optimality criterion) was obtained. Having implemented a more convenient calculation algorithm and having transformed the mathematical apparatus, the authors obtained the vehicle production rates for the transportation of mineral fertilizers to the place of their application. (Conclusions) The authors implemented a detailed mathematical description of the transport and transport-technological process stages. They identified the functional relationships between operational parameters and production and agrolandscape conditions.  A universal algorithm was developed making it possible to determine the values of the operational performance for transport and transport-technological vehicles. The authors determined the values of the coefficient enabling the unification and comparison of the algorithm for identifying the production rates for transport and transport-technological work. It was found out that with an increase in the length of transportation from 3 to 54 kilometers, this coefficient increases 3.8 times. This variation was explained by an increase in the purely transport phase of the process.Производительность – один из важных эксплуатационных показателей транспортных и транспортно-технологических средств. Подтвердили необходимость унифицировать расчеты этого показателя на фоне обширной номенклатуры сельскохозяйственных грузов и большого количества работ по их перемещению. (Цель исследования) Разработать универсальные взаимосвязанные этапы определения эксплуатационной производительности транспортных и транспортно-технологических средств при реализации механизированных работ в растениеводстве. (Материалы и методы) Определили значения эксплуатационной производительности посредством анализа нормообразующих факторов и статистической обработки. Использовали системный подход к определению отдельных элементов цикла транспортировки грузов. Изучили каждый из методических подходов и применяемые математические аппараты для определения производительности технических средств различных типов. (Результаты и обсуждение) После поэтапного моделирования реализации транспортных и транспортно-технологических процессов получили унифицированную формулу целевой функции (критерия оптимальности). В результате реализации более удобного алгоритма расчета и преобразования математического аппарата вычислили значения норм выработки для транспортных средств при транспортировке минеральных удобрений к месту их внесения. (Выводы) Провели детальное математическое описание этапов реализации транспортного и транспортно-технологического процесса. Определили функциональные зависимости между эксплуатационными параметрами и производственными и агроландшафтными условиями. Разработали универсальный алгоритм, для расчета значения эксплуатационной производительности транспортных и транспортно-технологических средств. Определили значения коэффициента, позволяющего унифицировать и сопоставить алгоритм вычисления норм выработки на транспортные и транспортно-технологические работы. Выявили, что с увеличением длины транспортировки от 3 до 54 километров этот коэффициент повышается 3,8 раза. Данное варьирование объяснили ростом чисто транспортной фазы выполнения процесса.

Оптимальное соотношение основных механизированных работ при прямоточном внесений удобрений

Use of transport and technological means is carried out according to the direct-flow scheme and includes stage-by-stage performance as the main standard-setting operations (fertilizers transportation, movement and their distribution across a field), and auxiliary (return from a field and loading of fertilizers). The method of comparison of main types of operations at fertilizers application is given. An estimation criterion is a ratio of cargo movements on a road and across a field, proportionality coefficient between movement of freight and a fertilizers distribution area across the field. These indicators depend on transportation distances and doses of fertilizers application, and also on technology factor that is freight moving frequency across the field. The last characteristic is taken as the optimized parameter. An extremum of this indicator was searched due to a classical method. Optimum values of estimated indicators with the accounting of a variation of a ratio of load capacity and operating width of technical means are received. Concrete combinations of transportation distances and doses of fertilizers application are specified. The authors defined conditions of effective use of tractor and perspective automobile transport and technological means. They recommended to use the automeans allowing to change operating width. Realization of the stated methodological approach will make it possible to select an optimum ratio of the mechanized operations at direct-flow fertilizers application, to exclude additional cargo movements across the field, to cut fuel consumption, to increase productivity. Productivity of transport and technological means increases by 2.0; 1.3 and 1.15 times respectively to length of furrow 3; 9 and 27 km at fertilizers application by a dose of 0.06 kg per sq.m.Использование транспортно-технологических средств осуществляется по прямоточной схеме и включает поэтапное выполнение как основных нормообразующих работ (перевозку удобрений, перемещение и распределение их по полю), так и вспомогательных (возвращение средств с поля и погрузку удобрений). Приведен метод сопоставления основных видов работ при внесении удобрений. В качестве оценочных критериев приняты соотношение грузоперемещений по дороге и по полю, коэффициент пропорциональности между перемещением груза по полю и площадью распределения удобрений. Эти показатели зависят от расстояний транспортировки и доз внесения удобрений, а также от технологического фактора - плотности перемещений груза по полю. Последняя характеристика принята за оптимизируемый параметр. Поиск экстремума этого показателя проводили классическим методом. Получены оптимальные значения оценочных показателей с учeтом варьирования соотношения грузовместимости и ширины захвата технических средств. Указаны конкретные сочетания расстояний перевозки и доз внесения удобрений. Определены условия эффективного использования тракторных и перспективных автомобильных транспортно-технологических средств. Рекомендовано использовать автосредства, позволяющие изменять ширину захвата. Реализация изложенного методологического подхода к выбору оптимального соотношения механизированных работ при прямоточном внесении удобрений позволит исключить дополнительные грузоперемещения по полю, снизить расход топлива, повысить производительность. Показали, что производительность транспортно-технологических средств возрастает в 2,0; 1,3 и 1,15 раза соответственно для длины гона 3; 9 и 27 км при внесении удобрений дозой 0,06 кг/кв.м

The Slab Puzzle of the Alpine‐Mediterranean Region: Insights from a new, High‐Resolution, Shear‐Wave Velocity Model of the Upper Mantle

Mediterranean tectonics since the Lower Cretaceous has been characterized by a multi‐phase subduction and collision history with temporally and spatially‐variable, small‐scale plate configurations. A new shear‐wave velocity model of the Mediterranean upper mantle (MeRE2020), constrained by a very large set of over 200,000 broadband (8‐350 s), inter‐station, Rayleigh‐wave, phase‐velocity curves, illuminates the complex structure and fragmentation of the subducting slabs. Phase‐velocity maps computed using these measurements were inverted for depth‐dependent, shear‐wave velocities using a stochastic particle‐swarm‐optimization algorithm (PSO). The resulting three‐dimensional (3‐D) model makes possible an inventory of slab segments across the Mediterranean. Fourteen slab segments of 200‐800 km length along‐strike are identified. We distinguish three categories of subducted slabs: attached slabs reaching down to the bottom of the model; shallow slabs of shorter length in down‐dip direction, terminating shallower than 300 km depth; and detached slab segments. The location of slab segments are consistent with and validated by the intermediate‐depth seismicity, where it is present. The new high‐resolution tomography demonstrates the intricate relationships between slab fragmentation and the evolution of the relatively small and highly curved subduction zones and collisional orogens characteristic of the Mediterranean realm

Surface wave tomography across Afar, Ethiopia: crustal structure at a rift triple-junction zone

The Afar Depression in northeast Africa contains the rift triple-junction between the Nubia, Arabia and Somalia plates. We analyze Rayleigh wave group velocity from 250 regional earthquakes recorded by 40 broadband stations to study the crustal structure across Afar and adjacent plateau regions in northern Ethiopia. The dispersion velocities are inverted to obtain surface wave tomographic maps for periods between 5 and 25 seconds, sensitive to approximately the top 30 km of the lithosphere. The tomographic maps show a significant low dispersion velocity anomaly (>20%) within the upper crust, below the site of recent dyke intrusions (2005–present) in the Dabbahu and Manda-Hararo magmatic segments. Similar low velocity regions are imaged where magma intrusion in the Afar crust has been inferred over the last decade from seismicity or volcanic eruptions. We invert two group velocity curves to compare the S-wave velocity structure of the crust within an active magmatic segment with that of adjacent areas; the active region has a low velocity zone (Vs ∼ 3.2 km/s), between about 6–12 km, which we infer to be due to the presence of partial melt within the lower crust

Application of Surface wave methods for seismic site characterization

Surface-wave dispersion analysis is widely used in geophysics to infer a shear wave velocity model of the subsoil for a wide variety of applications. A shear-wave velocity model is obtained from the solution of an inverse problem based on the surface wave dispersive propagation in vertically heterogeneous media. The analysis can be based either on active source measurements or on seismic noise recordings. This paper discusses the most typical choices for collection and interpretation of experimental data, providing a state of the art on the different steps involved in surface wave surveys. In particular, the different strategies for processing experimental data and to solve the inverse problem are presented, along with their advantages and disadvantages. Also, some issues related to the characteristics of passive surface wave data and their use in H/V spectral ratio technique are discussed as additional information to be used independently or in conjunction with dispersion analysis. Finally, some recommendations for the use of surface wave methods are presented, while also outlining future trends in the research of this topic

Asymmetric ocean basins

While the superficial expression of oceanic ridges is generally symmetric, their deeper roots may be asymmetric. Based on a surface wave tomographic, we construct a global cross section parallel to the tectonic equator. VS indicate a difference between the western and eastern flanks of the three major oceanic rift basins. In general, the western limbs have a faster velocity and thicker lithosphere relative to the eastern or northeastern one, whereas the upper asthenosphere is faster in the eastern limb than in the western limb. We interpret the difference between the two flanks as the combination of mantle depletion along the oceanic rifts and of the westward migration of the ridges and the lithosphere relative to the mantle. The low-velocity layer in the upper asthenosphere is assumed to represent the decoupling between the lithosphere and the underlying mantle. These results could be explained in the frame of the westward drift of the lithosphere relative to the underlying mantle

Asymmetric ocean basins

While the superficial expression of oceanic ridges is generally symmetric, their deeper roots may be asymmetric. Based on a surface wave tomographic three-dimensional model of the Earth's upper 300 km, we construct a global cross section parallel to the equator of the net rotation of the lithosphere, the so-called tectonic equator. Shear wave velocities indicate a difference between the western and eastern Hanks of the three major oceanic rift basins (Pacific, Atlantic, and Indian ridges). In general, the western limbs have a faster velocity and thicker lithosphere relative to the eastern or northeastern one, whereas the tipper asthenosphere is faster in the eastern limb than in the western limb. We interpret the difference between the two flanks as the combination of mantle depletion along the oceanic rifts and of the westward migration of the ridges and the lithosphere relative to the mantle. The low-velocity layer in the upper asthenosphere at the depth of 120-200 km is assumed to represent the decoupling between the lithosphere and the underlying mantle. It is also well defined by the distribution of radial anisotropy that reaches minimum values close to the rifts, but with an eastward offset. These results could be explained in the frame of the westward drift of the lithosphere relative to the underlying mantle