Abstract:The Global Positioning System (GPS) based on satellites and the networks of dual frequency receivers are actively used for geodetic and geophysical applications, as well as for studying the ionosphere and troposphere. The atmospheric water content is in the focus of research as a key parameter for determining of the accuracy of weather forecasting and hydrological monitoring. The precision of atmospheric water content calculations depends on the accuracy of determination of the delays of signals propagating from GPS satellites to ground-based GPS receivers when geodynamic measurements are conducted. This paper describes a technique that allows us to estimate the integrated water vapor (IWV) in the atmosphere from measurements of GPS satellite signal delays.We consider remote sensing of the lower atmosphere by GPS measurements to detect the water vapor content in the conventional vertical column to the top level of the troposphere (up to 12 km above the Earth's surface). In studies of the propagation of signals from GPS satellites to ground receivers, the atmospheric water vapor is taken into account as a 'wet' component (ZWD) of the zenith tropospheric delay (ZTD). ZTD is the sum of ZHD (hydrostatic or 'dry' delay) and ZWD ('wet' delay). ZWD values can be converted with a very high confidence in integrated water vapor (IWV) values for each installed GPS receiver. Аннотация: Система спутникового позиционирования GPS с использованием сетей двухчастотных приемни-ков активно применяется не только для решения задач геодинамики, но и для исследования ионосферы и тропосферы. Особый интерес представляет оценка атмосферного влагосодержания, так как это один из ведущих параметров определения точности прогнозов погоды и гидрологического мониторинга. Точность оценки влагосодержания определяет точность оценки задержки GPS-сигнала при геодинамических измере- GEODYNAMICS & TECTONOPHYSICS P U B L I S H E D B Y T H E I N S T I T U T E O F T H E E A R T H ' S C R U S T S I B E R I A N B R A N C H O F R U S S I A N A C A D E M Y O F S C I E N C E S R e c e n t G e o d y n a m i c s O.F. Lukhneva et al.: The determination of atmospheric water content… 546ниях. В работе описывается методика, позволяющая оценивать значение интегрального влагосодержания атмосферы по измеряемым фазовым задержкам сигнала спутников GPS. Рассматривается дистанционное зондирование нижней части атмосферы посредством GPS-измерений с целью определения содержания водяного пара в условном вертикальном столбе до уровня верхней части тропосферы (до 12 км над поверхностью Земли). Атмосферный водяной пар учитывается в процессе распро-странения сигналов от GPS-спутников до наземных приемников в виде «влажной» компоненты полной тро-посферной задержки (ZWD). Полная тропосферная зенитная задержка (ZTD) является суммой «сухой», или гидростатической (ZHD), и «влажной» (ZWD) компонент. Данные по ZWD могут быть преобразованы с очень высокой достоверностью в данные по суммарному водяному пару (IWV) над каждым установленным GPS-приемником.Ключевые слова: GPS; дистан...
The orientation of deformation process development during rifting controls the strike of the regional active faults, which determine the epicentral field structure features in the northeast part of the Baikal rift system (BRS), characterized by current high seismic activity. Rose charts were plotted for the number of faults of each strike range. For zones of epicenter concentrations, the polygons of seismic data projection were determined in accordance with the general strike of most of the active faults and their average length. Taking into account the anisotropy of the fracture network, the spatiotemporal analysis of the earthquake epicentral field was carried out using GIS technology. The seismic activity migration episodes as a result of crustal deformation are inherent to a non-stationary seismic process for the investigated area. Migrations, characterized by constant rate, are recurred in places of intense lithosphere fracturing and change the direction in potential M ≥5 earthquake and swarms occurrence sites. Ordered sequences of energy clusters most likely propagate at a depth of the fluid-saturated layer beneath the thickened granite batholith where the heat accumulated warms up the fluid and apparently reduces the viscosity of seismoactive layer. The existence of thickened plastic lithospheric layer and viscosity reduction of brittle crustal layer are conditions probably conducive to migration of seismic activity.
The article describes the possibility of using the passive satellite measurements of the atmosphere to investigate the vertical patterns of pressure, temperature and relative humidity and simulate the altitude dependence of the refractive index of air. The seasonal parameters were determined for the exponential model showing the tropospheric refraction over observation points IRKM (Irkutsk), ULAZ (Ulan-Ude) and BADG (Badary). Post-processing of the input GPS data was conducted to ensure the highest positioning accuracy. In addition to high-precision geodesy, the global positioning method was used for determining the total tropospheric zenith delays (ZTD), which values are used to solve the problems of radio physics and meteorology. The angles of refraction and the true distances were estimated and compared in different seasons of the year. This study shows that the angles of refraction at the observation points located in the Baikal zone do not differ significantly in order of magnitude from the values estimated for other climatic zones.
The article discusses the macroseismic data on the December 9, 2020, M w 5.5 Kudara earthquake which occurred in the Selenga River delta (Middle Baikal, Eastern Siberia, Russia). This is the strongest seismic event in the study area over a 50-year period. The bulk of macroseismic data was obtained with internet questionnaire posted on the website of the Baikal Branch of the Geophysical Survey of the Russian Academy of Sciences. In total, 1433 responses were received from 120 places (villages, towns and cities) in Eastern Siberia, with most of them was obtained from large cities. In addition, a field survey was carried out in the near-field, which revealed slight non-structural damage to buildings in several settlements. The maximum intensity assessed VI–VII MSK-64 or VI EMS-98 was observed in the Kudara village. Taking into account the macroseismic data obtained, we have prepared a map of intensity data points. The largely observed shakings (intensity IV MSK-64/EMS-98) were noted at epicentral distances of over 500 km; intensity II MSK-64/EMS-98 was noted at a distance of up to 980 km. The Kudara earthquake allowed us to test the internet questionnaire in real conditions of strong seismic impact. The results obtained confirm the rather high efficiency of the internet questionnaire in the conditions of the Baikal region, however, some limitations associated with the responses spatial distribution are exist. A detailed study of the Kudara earthquake allowed us to gain new experience useful for the further development of macroseismology in Eastern Siberia.
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