Obtaining the most accurate and reliable gravimetric data has always been and remains the main task of gravimetry. The purpose of the authors’ long-term research and this work in particular is to determine interference in gravimetric data caused by various external influences and to find ways to take them into account or eliminate them. The proposed method of iteratively taking pressure and tidal correction into account made it possible to increase the accuracy of single gravimetric readings to ±2 µGal. The main instruments for many years of research were relative automated gravimeters of the CG Autograv series from Scintrex; the main results obtained in this work are shown based on their example. In CG-5 and CG-6 gravimeters, the instrumental accuracy is 1.0 and 0.1 µGal, respectively. However, it cannot be said that a single reading will give the gravity increment with the specified accuracy. Relative gravimeters, in addition to the desired value, also record the device response to inertial influence, changes in meteorological factors, and its own hardware errors, which cannot be eliminated without additional information. Under the conditions of the Zapolskoye geophysical observatory in the Vladimir region, continuous gravimetric, seismic, and meteorological measurements were carried out for 8.5 months. The obtained data made it possible to analyze the possibility of partially taking the influence of the atmospheric pressure and determining the correct delta factors for 20 groups of waves with periods of 48 days or less into account. The minimum duration of the gravimetric series to obtain delta factors of waves with periods from 0.02 to 3.38 cycles per day was also estimated at 6 months.

This study estimates the impact level of storm microseisms on long-term gravimetric measurements. Gravimetric measurements were conducted at the Zapolskoe, Obninsk, and Murmansk sites using CG-5 Autograv relative gravity meters. Seismic measurements were carried out concurrently with gravimetric measurements at Zapolskoe. The analysis of these measurements demonstrates the feasibility of utilizing seismic data as control information to estimate the high-frequency noise component of gravimetric data. Based on the additional seismic information from the services of the Incorporated Research Institutions for Seismology, the correspondence between the attenuation of the noise component in gravimetric measurements and the data from the modeled sensitive element of the gravimeter, which utilizes seismic series as an input, is identified. The first characterization of the storm-induced background noise of gravimetric measurements at the Murmansk site is obtained. Furthermore, the possibility of predicting measurement errors based on meteorological forecasts is refined, which can aid in the planning of gravimetric work.

Marine gravimetry aims to obtain accurate and reliable data on gravity field anomalies in water areas. Modern gravimetric systems such as Chekan-AM feature high accuracy due to the novel circuit and design solutions in the conditions specified in the technical description. The article discusses the influence of ambient temperature and humidity on the accuracy of the Chekan-AM gravimeter. These meteorological factors matter both during short measurement periods, within individual survey lines, and long periods, during expeditions far away from the reference points. For 18 months, the authors of the article have been carrying out laboratory tests of the gravimeter with simultaneous registration of meteorological parameters. Based on the observation results, the correlation dependences of the zero-point drift of the gravimeter sensitive element on seasonal temperature and humidity variations were calculated. Marine expeditions data were also studied, with analysis of the temperature impact over a short time period during the marine gravimetric survey. Based on the results of the experiments it was shown that meteorological monitoring should be performed in the course of gravimetric surveys, including those onboard research vessels. An additional thermal noise becomes noticeable in the survey conducted in an area with low variations in the gravity field, and it should be considered when analyzing and evaluating the results.

Transient processes in gravimetric data spanning more than 12 years are considered. During this time, more than 15 trips were made from the fundamental gravimetric point Ledovo to the first class point Zapolskoe and back using two CG 5 Autograv automated relative gravimeters. The most significant parameters that affect the readings of the instruments were identified: ambient temperature, the values of the zero drift of the sensing element of the gravimeter, and the direct increment of gravity. The zero drift was taken into account using a second-order polynomial prediction, and the remaining two parameters were described by a logarithmic dependence. The natural logarithm equation allows describing the functions by measuring the coefficient before the logarithm (logarithmic) and additional (linear). The value of the logarithmic coefficients characterizing the duration of transient processes has a linear dependence on temperature, which means that it can characterize the measurement time at the point in the case of a significant temperature change. The magnitude of the linear coefficients characterizing the increase in gravity depends linearly on temperature when the instruments are moved to a colder environment. When the instruments are moved to a warmer environment (10°), the dependence becomes more complex, possibly random, which also requires an increase in the measurement time at the point. The usual duration of measurements at gravimetric stations is 10 min. The relevance of taking temperature into account at measurement points depends on the required accuracy, for example, for a temperature difference of 10°C, the RMS of gravimetric measurements was ±0.025 mGal.

The phenomenon of synchronous episodic increase in gravimetric noise at the stations distant by thousands of kilometers from each other is described. The comparison with microseismic noise suggests inertial rather than gravimetric origin of the recorded anomalies. The duration of anomalous enhancement in microvibrations ranges from a few hours to a few days. The nature of synchronous microvibrations involving significant segments of the Earth’s lithosphere is unclear; the probable causes are discussed. The conducted analysis has shown that among the key factors responsible for the increase in the microseismic noise in the European part of Russia is the influence of marginal seas, in particular, the storm-generated microseisms. The allowance for this phenomenon is necessary in planning and conducting high-precision gravity surveys and long-term gravity observations.

Aerogravimetric survey is a rapidly developing and promising method for studying the gravity field in remote regions of the Earth. However, its practical use involves difficulties. Thus, during flights, inertial interference occurs due to engine-induced vibration of the fuselage. Earlier, various options for antivibration designs were tested. During its annual aerogravimetric works, the Schmidt Institute of Physics of the Earth, Russian Academy of Sciences (IPE RAS), employs a quite efficient option, which, however, cannot be regarded as complete. For the first time, a high-frequency seismometer was used to evaluate the efficiency of a gravimeter antivibration system used in aerogravimetric operations. Vibration suppression was assessed in a wide frequency range. During experimental flights, a decrease in vibration noise was detected at a frequency of 2 Hz, which is relevant for gravimetric equipment. The experimental results confirm the adequacy of the applied antivibration equipment. The antivibration platform developed at IPE RAS significantly reduces vibrations affecting the GT-2M aerogravimetric system. The possibility of using the Baikal-ACN high-frequency seismometer in an unconventional field of application is demonstrated.

Abstract—The empirical results on estimating the resolution and high-frequency noise in the Earth’s gravity models are presented. The Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences participated in a marine gravity survey in the Indian Ocean. Based on the survey data, gravity maps were constructed for ten regions with a total of 611 986 gravimetric points. The root mean square measurement error is at most 0.27 mGal. The differences between measured gravity and predictions by the EGM2008 gravity model are calculated. The statistical processing of the differences shows that they vary from –25 to 44 mGal on the shelf and from –7.4 to 6.2 mGal on the abyssal plain with a root mean square value of 1.33 mGal. The results of the survey indicate that the anomalies in the ultra-high-degree model can only be used for constructing gravity maps on the scale of 1 : 500 000 or smaller.

Исследованы непериодические повышения интенсивности микросейсмического шума. На протяжении четырех месяцев осуществлялись синхронные геофизические наблюдения гравиметрами ScintrexCG5 Autograv в Обнинске, Мурманске, Екатеринбурге и Красноярске. При проведении измерений были зарегистрированы множественные случаи синхронного повышения интенсивности микросейсмических шумов, как в пунктах гравиметрических наблюдений, так ив ряде сейсмометрических пунктов северовосточной части Евразии. Продолжительность зарегистрированного аномального повышения микровибраций составляет от нескольких часов до нескольких суток. Высокочувствительные гравиметры регистрируют не только гравитационное поле и его вариации, связанные с приливными изменения силы тяжести и другими неприливными и метеорологическими явлениями, но и высокочастотные вариации, связанные в первую очередь с воздействием процессов инерциального характера. Гравиметры и сейсмографы обладают различными характеристиками, однако, высокочастотное воздействие, от общего источника регистрируется обоими приборами, с той лишь разницей, что в гравиметре оно считается помехой и характеризуется среднеквадратичным отклонением (СКО). СКО гравиметрических данных, и СКО, посчитанное по рядам измерений сейсмометров, обнаруживают высокое сходство. Сопоставление с микросейсмическими шумами позволяет говорить об инерциальной, а не о гравиметрической природе зарегистрированных гравиметрами аномалий. Результаты исследования корреляционных связей сигналов объясняются крупными локальными вариациями микросейсм и метеорологических характеристик, их влиянием на тонкую структуру геофизических сигналов, регистрируемых гравиметрами. Кратковременные полугодовые наблюдения обнаружили особенности геофизических процессов на обширной территории Евразии. Дальнейшие исследования позволят выявить тонкую структуру взаимных влияний геофизических процессов по данным наблюдений чувствительными гравиметрами и сейсмометрами. Учет этого явления необходим при планировании и выполнении высокоточных гравиметрических съемок и долговременных гравиметрических наблюдений. Nonperiodic intensity increase of microseismic noise was researched. During four months, synchronous geophysical observations were carried out using Scintrex CG5 Autograv gravimeters in Obninsk, Murmansk, Yekaterinburg and Krasnoyarsk. During the measurements, multiple cases of synchronous intensity increase of microseismic noise were recorded, both at the gravimetric observation points and at a number of seismometric points in northeastern Eurasia. The duration of the registered anomalous increase in microvibrations ranges from several hours to several days. Highly sensitive gravimeters register not only the gravitational field and its variations associated with tidal changes of gravity and other nontidal and meteorological phenomena, but also highfrequency variations associated primarily with the effects of inertial processes. Gravimeters and seismographs have different characteristics, however, both instruments record highfrequency effects from a common source, with the only difference that in the gravimeter it is considered interference and is characterized by standard deviation (RMS). RMS of gravimetric data, and RMS, calculated by series of seismometers measurements, show high similarity. Comparison with microseismic noise suggests an inertial rather than a gravimetric nature of anomalies recorded by gravimeters. The results of the signals correlation study are explained by large local variations of microseisms and meteorological characteristics, their influence on the fine structure of geophysical signals recorded by gravimeters. Shortterm semiannual observations revealed features of geophysical processes in the vast territory of Eurasia. Further studies will reveal the fine structure of the mutual influences of geophysical processes according to observation data by sensitive gravimeters and seismometers. Consideration of this phenomenon is necessary when planning, performing highprecision gravimetric surveys, and longterm gravimetric observations

To determine the degree of influence of meteorological factors on long-term gravimetric measurements, crustal reaction to the variable atmospheric pressure is estimated in the frequency range corresponding to the period of accumulation of one and series of single counts of the gravimeter. The experiment revealed a change in the level of microseismic oscillations caused by variable atmospheric pressure. The experimental results of long-term observations at a gravimetric measurement point indicate that the level of microseismic oscillations is significantly lower at higher atmospheric pressure. With a decrease in atmospheric pressure, the highest amplitudes in the microseismic noise spectrum are observed in the frequency range of 0.05–0.5 Hz. The necessity of removing daily variations in the microseism levels caused by variable ambient temperature is shown.

Long-term fixed-tilt observations are carried out at a geophysical observatory. The dependence of gravimetric tilt on ambient air temperature is determined.

The joint study of the long-term stationary gravity observations using the Autograv CG-5 gravimeter in the conditions of a geophysical observatory and the data from the UGRA seismic station is carried out. The mathematical model of the sensing element of the gravimeter is constructed. The analysis of the gravimetric and seismic data is carried out. The corrections reducing the random component of the error in the gravimeter's measurements are obtained.

Continuous high-precision long-term gravity measurements are carried out at the geophysical observatory located in the experimental base of Vladimir State University. The long time series of gravity acceleration and its standard deviation are obtained. The factors responsible for the increases in the studied deviations are analyzed. The recommendations for improving the accuracy of relative gravity measurements are formulated.

Continuous long-term highly precise gravity measurements at the Dolgoe Ledovo gravity station operated by the Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, are carried out. The long-term time series of tidal corrections are obtained, and the values of the delta factor are specified for this station, which enables the correct intercomparison of the absolute gravity instruments.

Проведены непрерывные высокоточные долговременные гравиметрические наблюдения в геофизической обсерватории, расположенной на экспериментальной базе Владимирского государственного университета. Получены длинные ряды наблюденных значений ускорения силы тяжести и ее стандартного отклонения. Выполнен анализ причин повышения приведенных погрешностей. Даны рекомендации для повышения точности измерения относительными гравиметрами.

Проведены непрерывные высокоточные долговременные гравиметрические наблюдения на гравиметрическом пункте “Долгое Ледово”, расположенном на экспериментальной базе ИФЗ РАН. Получены длинные ряды значений приливной поправки и уточнены величины дельта-фактора, позволяющего корректно проводить сличение абсолютных гравиметров.