Abstract— Long-term (1962‒2020) observations of air temperature and atmospheric pressure at two weather stations in the region of Petropavlovsk-Kamchatsky, Kamchatka Krai, are analyzed to examine the hypotheses about a connection between increased and decreased meteorological parameter values and their contrasting changes with a final stage of preparation of local Kamchatka earthquakes with magnitudes 5.2‒8.3, which occurred at epicentral distances of 22–440 km and caused perceptible shaking with intensity IMSK-64 ≥ 4–5. To identify meteorological anomalies, we used an empirical method comparing daily mean air temperatures and atmospheric pressures with daily averages of their annual seasonal-mean functions and a formalized method estimating the minimum normalized entropy En, the logarithm of the curtosis coefficient logκ, and the autoregressive measure of nonstationarity Q2 of the time series of air temperature and atmospheric pressure in a moving time window with a length of 112 days shifted by one day. Various types of meteoanomalies before earthquakes were studied on time intervals of seven and 30 days. The correlation between the detected anomalies and subsequent earthquakes was evaluated from the ratio of reliability and validity of the conditional meteorological precursor. It is found that the manifestation of various types of meteorological anomalies before earthquakes is mainly of a random nature. The lack of a pronounced correlation between air temperature increases and subsequent earthquakes casts doubt on the reality of the mechanism of generation of thermal surface anomalies before earthquakes in the lithosphere‒atmosphere‒ionosphere‒magnetosphere coupling (LAIMC) model for the study region. The methods used for meteorological data analysis can be applied in seismic forecasting in the region of the Petropavlovsk-Yelizovo agglomeration, Kamchatka Krai, for diagnosing weather-dependent anomalies in the changes of the ground-based observation data.

The article presents data on the types of observations and information resources of the Kamchatka Branch of the Geophysical Survey of the Russian Academy of Sciences (as of 2022), which can be used by scientific and educational organizations of the Russian Federation for studying precursors and developing methods for predicting earthquakes and volcanic eruptions, solving a wide range of research tasks in the field of geophysical monitoring of seismically active areas and others. Information resources and observation data are illustrated on the example of the Unified Information System of Seismological Data of the KB GS RAS and time series data of meteorological, hydrogeological observations and observations of volumetric radon activity in the soil gas at the Moroznaya station.

В основу изучения свойств сейсмического шума на Камчатке положена идея, что шум является важным источником информации о процессах, предшествующих сильным землетрясениям. Рассматривается гипотеза, что увеличение сейсмической опасности сопровождается упрощением статистической структуры сейсмического шума и увеличением пространственных корреляций его свойств. В качестве статистик, характеризующих шум, использованы энтропия распределения квадратов вейвлет-коэффициентов, ширина носителя мультифрактального спектра сингулярности и индекс Донохо–Джонстона. Значения этих параметров отражают сложность: если случайный сигнал близок по своим свойствам к белому шуму, то энтропия максимальна, а остальные два параметра минимальны. Используемые статистики вычисляются для шести кластеров станций. Для каждого кластера станций вычисляются ежесуточные медианы свойств шума в последовательных временных окнах длиной 1 сутки, в результате чего образуется 18-мерный (3 свойства и 6 кластеров станций) временной ряд свойств. Для выделения общих свойств изменения параметров шума используется метод главных компонент, который применяется для каждого кластера станций, в результате чего информация сжимается до 6-мерного ежесуточного временного ряда главных компонент. Пространственные когерентности шума оцениваются как совокупность максимальных попарных квадратичных спектров когерентности между главным компонентами кластеров станций в скользящем временном окне длиной 365 суток. С помощью вычисления гистограмм распределения номеров кластеров, в которых достигаются минимальные и максимальные значения статистик шума в скользящем временном окне длиной 365 суток, оценивалась миграция областей сейсмической опасности в сопоставлении с сильными землетрясениями с магнитудой не менее 7.

Based on the long-term observations of the wells on the Petropavlovsk-Kamchatsky Test Site, the Kamchatka Peninsula, the paper analyzes manifestations of three main types of seismohydrogeological effects – hydrogeological precursors, coseismic pressure jumps and postseismic effects of the vibrational impact of seismic waves in measurements of the pressure and chemical composition of groundwater, depending on the earthquake parameters (magnitude, epicentre distance, intensity of seismic impact in the observation areas). The paper presents data on the earthquakes that were preceded by hydrogeological precursors in several (n = 2–4) wells. It is discussed whether it is possible to use hydrogeological precursors to predict strong earthquakes in Kamchatka. The authors also discuss the results of their experimental use in a real-time environment with weekly reports on the current observational data for the Kamchatka Branch of the Russian Expert Council. By the example of water level observations in YUZ-5 Well, the authors analyzed coseismic jumps in the groundwater pressure due to rupture formation in the sources of local Mw 6.0 earthquakes and four types of effects of the vibrational impact of seismic waves during local and distant Mw = 6.8–9.3 earthquakes at epicentral distances from 80 to 14 600 km; the study demonstrates that such effects depend on the earthquake parameters and the intensity of seismic impact in the well area.

— Anomalies in the ionic and gas composition of groundwater before earthquakes (hydrogeochemical precursors, hereinafter HGCP) are considered according to data of systematic observations in ten self-flowing wells and springs in seismically active regions of Russia (Kamchatka Peninsula), Uzbekistan, Japan, and Iceland. Using an extended set of earthquake parameters, it was shown that HGCP were manifested for 1–9 months in the near and intermediate zones of the future earthquake sources with M w = 5.3–7.8. Such properties of hydrogeochemical precursors allow their use for predicting the magnitude and time of expected seismic events, as well as their impact in the observation area. A model is presented for a registered precursor in the form of the ionic composition of groundwater in self-flowing well based on observational data on concentrations of anions and cations and on a mathematical model for the mixing of two waters of contrastingly different composition in a zone of increased conductivity. Calculations for one of the wells are presented as an illustrative example of the chemical composition of two mixing waters in the aquifer and in the wellbore. This model and observational data are used to estimate parameters of the disturbed state of the well–aquifer system during the preparation of an earthquake: the relaxation time of the water pressure pulses ( t 0 ) and the movement time of mixed water (τ 0 ). The morphology and duration of HGCP are controlled by relations between t 0 and τ 0 . The further development of HGCP studies and their application in predicting earthquakes require a technical modernization of the system of hydrogeochemical observations and the development of HGCP models for individual wells.

The relevance of the work is determined by the necessity to develop the hardware part of the seismic subsystem of the Large-Scale Research Facilities functioning at the Federal Research Center of the Geophysical Survey of the Russian Academy of Sciences to study seismic signals in groundwater pressure changes. For this purpose, the well monitoring on the territory of the Petropavlovsk-Kamchatsky test site, Kamchatka Peninsula, was updated using Keller equipment, Switzerland (sensors of PAA36 XiW CTD Si, PAA36 XiW modifications, data logger GSM-2), Campbell Scientific Inc, USA (CR6 and CR1000 data loggers) and a budgetary hydrogeodynamic data recorder (HDDR) based on the STK-1 minicomputers, created at the Kamchatka Branch of the GS RAS. A description has been provided concerning the sets of digital equipment installed in four wells for precise recording of groundwater pressure variations with a frequency of 20.00–0.08 Hz. Consideration is being given to the characteristics of the equipment installed in individual wells and to the problems solved in the process of updating the well observation system in order to study vibration effects and hydrogeodynamic precursors of earthquakes. The paper presents the newly obtained results of recording the high-frequency variations in groundwater pressure in wells during the 2020–2021 local and remote earthquakes. A discussion is provided of new possibilities for studying vibration effects on changes in ground water pressure with a frequency comparable to the frequency of recording seismic events by seismometric equipment. Using a new equipment for recording water pressure in the unique well E-1 made it possible to record, a hydrogeodynamic precursor in real time before the March 16, 2021, Mw=6.6 earthquake which occurred at the epicentral distance of 350 km from the well.

Аномальные изменения физико-химических параметров подземных вод перед землетрясениями, называются гидрогеологическими предвестниками (далее ГП). ГП обусловлены процессами подготовки землетрясений и могут использоваться для решения задач сейсмического прогнозирования, в первую очередь, для оценки времени сильных землетрясений [1, 21]. Для изучения ГП проводятся наблюдения на скважинах и источниках за вариациями давления, разгрузки, температуры и химического состава подземной воды и газов. На полуострове Камчатка такие наблюдения были начаты в 1977 г. с периодичностью наблюдений на сети скважин и источников один раз в 3−6 сут. С 1996 г. используются автоматизированные средства регистрации уровня/давления, температуры и электропроводности воды в пьезометрических скважинах Е-1, ЮЗ-5 и в самоизливающейся скважине М-1 [4].

Многообразие откликов давления подземных вод при похождении сейсмических волн является широко обсуждаемым вопросом при проведении наблюдений в скважинах [1, 6, 8, 10, 11, 12]. Даже при одном и том же землетрясении в близко расположенных скважинах могут проявляться различные эффекты вибрационного воздействия в изменениях давления подземных вод – колебания (осцилляции), понижения и повышения различной продолжительности. Познавательный интерес представляет объяснение такого многообразия на основе соответствующих моделей гидрогеодинамических процессов в системе скважина-водовмещающая порода. В работе [6] на примере данных многолетней регистрации уровня воды в скважине ЮЗ-5 с периодичностью 5 мин. были выделены четыре типа откликов давления подземной воды при землетрясениях в диапазоне магнитуд Мw = 6.8 – 9.1 и эпицентральных расстояний de=80 – 14600 км и рассмотрены модели их формирования. С использованием широкополосных записей землетрясений на ближайшей сейсмостанции, продемонстрирована зависимость проявления четырех выделенных типов откликов давления воды от амплитудно-частотного состава сейсмических волн и параметров интенсивности вибрационного воздействия, таких как удельная плотность сейсмической энергии и максимальная скорость сейсмических волн в районе скважины. Таким образом, на примере одной скважины с известными строением, упругими и фильтрационными свойствами водовмещающих пород было продемонстрировано, что разнообразие откликов давления подземной воды на динамическую деформацию водовмещающих пород определяется инициацией различных гидродинамических процессов в системе скважина-водовмещающая порода, сопровождающихся колебаниями, а также ростом или понижением давления различной продолжительности, в зависимости от амплитудно-частотного состава максимальных фаз сейсмических волн. При этом ведущими факторами, вызывающими разнообразие эффектов вибрационного изменения давления (напора) подземных вод, являются вертикальные смещения ствола скважины, усиление вариаций давления в системе скважина-водовмещающая порода на определенных резонансных частотах сейсмического воздействия [9], а также локальные понижения и повышения давления в водовмещающей породе вследствие неоднородности ее строения и, соответственно, неоднородного изменения поля давления подземных вод вблизи скважины [6, 8, 11]. Индивидуальные особенности отдельных скважин в проявлениях вибрационных эффектов и в целом разнообразие откликов уровня/давления воды в наблюдательных скважинах является отражением совокупности гидродинамических процессов, инициированных воздействием сейсмических волн различного амплитудно-частотного состава, и локализованным распределением импульсов повышения или понижения давления в пространстве неоднородных водовмещающих пород вблизи ствола скважины на расстояниях от первых метров до сотен метров. Определенный вклад в многообразии откликов давления при воздействии сейсмических волн также вносят упругие свойства подземной воды [11]. В частности, при наличии в воде свободного газа ее сжимаемость резко повышается, и величина коэффициента Скемптона, равного отношению изменений давления воды к общему напряжению в скелете породы, резко уменьшается [4, 6]. В этом случае в изменениях давления подземных вод, например, в скважинах Е-1, полуостров Камчатка и BV, Калифорния, США, вибрационные эффекты проявляются в монотонных повышениях уровня воды в течение суток-десятков суток после наиболее сильных землетрясений с интенсивностью сотрясений не менее 5-6 баллов по шкале MSK-64. Таким образом, многообразие откликов давления подземных вод в скважинах на прохождение сейсмических волн в общем виде объясняется особенностями локальных условий наблюдательных скважин – различиями их конструкции, упругими и фильтрационными свойствами водовмещающих пород и неоднородностью их строения. Это обстоятельство предполагает создание моделей вибрационного воздействия на основе прецизионных данных наблюдений за вариациями давления подземных вод для каждой наблюдательной скважины, используемой в системе геофизического мониторинга. Для решения этой задачи в отношении наблюдательных скважин на территории Петропавловск-Камчатского полигона, в 2017–2021 гг. была выполнена модернизация системы наблюдений с использованием цифровых средств прецизионной регистрации давления подземных вод с частотой от 20 до 0.008 Гц. В работе представлены данные о выполненной модернизации и первые результаты наблюдений вибрационных эффектов в изменениях давления подземных вод, полученных с использованием нового оборудования.

Abstract—In my comment on the paper by A.A. Lyubushin, G.N. Kopylova, and Yu.K. Serafimova, I focus on the problem of legitimacy of seismological data pertaining to the unconventionally low frequency range from the standpoint of metrology and question the validity of the obtained results. The latter aspect is associated with the fact that in the discussed paper of Lyubushin et al. (2021), the estimates of confidence intervals in the calculated statistics are completely absent, which is at odds with the generally accepted approaches to the presentation of the results of measurement data processing. Without conducting such estimates, the authors made an unjustified conclusion about the correlation of the studied processes and, as a consequence, about a triggering effect of the irregularity of the Earth’s rotation on the seismic process.

The purpose of the study is generalization of data on the manifestations of hydrogeological earthquake precursors and volcanic activations based on long-term observations in the wells of the eastern part of the Kamchatka Peninsula. The main problem under consideration is the connection between the manifestations of hydrogeological precursors in several wells with the values of the magnitude Mw and epicentral distance of earthquakes to the wells de as well as with the parameters of seismic action in the observation area including specific density of seismic wave energy e and macroseismic intensity of shaking IMSK-64. The study results revealed that hydrogeological precursors in two-four wells had been manifesting for the period from 1 to 9 months before the strongest earthquakes with Mw = 6.6–7.8 at the epicentral distances de = 90–300 km. Such earthquakes were accompanied by the shakings of the intensity of IMSK-64 = 4–6 points. The specific density of seismic energy under such earthquakes was minimum 0.1 J/m3. The hydrogeological precursors were confined to the area for which the ratios of the earthquake epicentral distance de to the maximum linear size of the earthquake source L, km ranged from 1 to 3.7. Using the established relationships between the manifestations of hydrogeological precursors and earthquake parameters, weekly prognostic conclusions were made for expert earthquake prediction councils based on the data of current observations in wells. The well located at the distance of 15 and 20 km from the Koryaksky and Avacha active volcanoes featured the anomalous rise of groundwater pressure before the eruptions in 1991 and 2008– 2009. Therefore, a conclusion can be drawn that observation equipment operating in wells, the study results of hydrogeological precursors of earthquakes and volcanic eruptions as well as their application experience in the work of expert councils can form the scientific and technical basis for the development of geoinformation prediction technology for natural disasters in the Kamchatka Krai.

The high-precision water level measurements with a time interval of 5–10 min were carried out in 1996–2017 in the YuZ-5 well, Kamchatka. In the obtained time series, water level variations caused by the passage of seismic waves (hydrogeoseismic variations—HGSV) during 19 earthquakes with M w = 6.8–9.1 that occurred at the epicentral distances of 80–14.6 thousand km are identified. Based on the HGSV morphological features, four main types of these variations are distinguished: oscillations (I); short (up to tens of hours) rises (II) in the water level superimposed on the fluctuations; short rises (III); and long (1.5–3 months) falls in the water level ( IV). The dependence of the occurrence of the revealed GHSV types on the earthquakes’ parameters (magnitude and distance), on the specific energy density and maximum velocities of seismic waves, and on the amplitude-frequency content of ground motion according to the records at the nearest seismic station is con-sidered. Hydrogeodynamic processes of HGSV formation are analyzed by several examples using numerical mod-eling. It is shown that the forced and free fluctuations amplitude in the water level amplitude (types I and II) can arise due to the intensification of the groundwater pressure variations in the well-water-bearing rock system during the passage of surface seismic waves with the periods corresponding to the resonant frequency of the well ( τ = 44.6 s). The rise in the water level in well lasting for tens of minutes to hours (HGSV variation types II and III) is due to the short increase in pressure when the steady state of water flow in the direct vicinity of the well is violated; the strong local earthquakes accompanied by ground shaking with intensity I msk-64 ≥ 5 cause long falls in the water level (type IV) due to pressure drop with amplitudes up to 0.1 bar within a radius up to several hundred meters from the well.

The high-precision water level measurements with a sampling interval of 5–10 min were carried out in 1996–2017 in the YuZ-5 well, Kamchatka. In the obtained time series, water level variations caused by the passage of seismic waves (hydrogeoseismic variations—HGSV) during 19 earthquakes with Мw = 6.8–9.1 which occurred at epicentral distances of 80–14.6 thousand km are revealed. Based on the HGSV morphological features, four main types of these variations are distinguished: oscillations (I); short (up to tens of hours) water level rises superimposed on oscillations (II); short rises (III); and long (1.5–3 months) drawdowns (IV). The dependence of the occurrence of the revealed GHSV types on earthquake parameters (magnitude and distance), specific energy density and maximum seismic wave velocity, and the amplitude-frequency content of ground motion is analyzed based on the records at a nearest seismic station. Based on several case studies, hydrogeodynamic processes of HGSV formation are investigated using numerical modeling. It is shown that the forced and free amplitude fluctuations in the water level (types I and II) can arise due to the enhancement of groundwater pressure variations in the well–water-bearing rock system during the passage of surface seismic waves with periods corresponding to the resonant frequency of the well (τ = 44.6 s). The rise in the water level in well lasting for tens minutes to hours (types II and III of HGSV variation) is caused by the short increase in pressure under violation of the steady water flow in the direct vicinity of the well; strong local earthquakes accompanied by ground shaking with intensity Imsk-64 ≥ 5 cause sustained drawdowns (type IV) due to pressure drop with the amplitudes up to 0.1 bar within a radius of up to a few hundred meters from the well.

Hydrogeochemical precursors of the earthquakes (HGCP) in changes of ion-salt and gas composition of underground waters from self-discharging wells and springs on the territory of Petropavlovsk-Kamchatsky test site, Kamchatka Peninsula, Russia and Tashkent test site, Republic of Uzbekistan are considered. There has been analyzed the connection of HGCP with parameters of earthquakes — with correlation between magnitudes and epicentral distances, as well as with values of specific density of seismic energy in the wave, intensity of ground shaking and other parameters of earthquake impact in the regions of observation. In Kamchatka wells HGCP were revealed before the earthquakes with Mw = 6.5 to 7.8 at epicentral distances de = 100 to 310 km at relatively narrow ranges of values of seismic energy density in the wave (0.1 to 0.3 J/m3), volumetric coseismic deformation of water-containing rocks (one to tens 10-9) and maximal velocities of seismic waves (3.5–7.7 cm/sec). HGCP took place in the zones with intensity of the earthquakes not less than 4 to 6 by MSK-64 scale and were confined to the intermediate zones of sources of future earthquakes. Duration of HGCP development and their appearance before the following earthquakes amount to 1 to 9 months, which allows using such precursors for prediction of time of strong earthquakes.

Рассматриваются основные этапы организации и технического развития системы специализированных наблюдений за физико-химическими параметрами подземных вод на сети скважин и источников на территории Петропавловского геодинамического полигона, Камчатка. Основное внимание уделяется описанию гидрогеохимических и гидрогеодинамических предвестников камчатских землетрясений ( М w = 6.6 - 7.8), проявляющихся в течение недель-месяцев до сейсмических событий в аномальных изменениях химического состава и уровней подземных вод, и их использованию в практике работы специализированных советов по прогнозу землетрясений. Показано, что созданная в КФ ФИЦ ЕГС РАН система автоматизированных наблюдений за параметрами подземных вод в скважинах позволяет диагностировать гидрогеодинамические предвестники в изменениях уровня воды в режиме близком к реальному времени и давать, в отдельных случаях, количественные оценки величин пред- и косейсмической деформации водовмещающих пород, что может найти применение при проведении геофизического мониторинга и среднесрочном прогнозировании времени сильных землетрясений в Камчатском регионе.

A new method is presented for statistical analysis of long-term time series of water level observations aimed at distinguishing short-term disturbances; observation data from the YuZ-5 well, located in the Petropavlovsk Geodynamic Test Area, eastern Kamchatka, are considered. These data (from July 27, 2012, to February 1, 2018) are remarkable for their degree of detail: the sampling rate of the water level and atmospheric pressure measurements was 5 min and the sensitivity (accuracy) was ±0.1 cm for water level recording and ±0.1 hPa for atmospheric pressure. Also, five strong earthquakes with M w = 6.5–8.3 occurred at epicentral distances of d e = 80–700 km during the observation period. A thorough analysis of the hydrodynamic regime of the observation well over a long period and the high quality of observation data, together with the data on strong seismic events, allow us to consider the possibility of using formalized statistical methods of water level data processing for diagnostics of anomalous conditions. As a result of factor and cluster analysis applied to the sequence of multidimensional vectors of the statistical properties of water level time series in successive one-day-long time windows, after adaptive compensation for atmospheric pressure, four different statistically significant states of time series, replacing each other in time, are distinguished. Geophysical interpretation of the anomalous conditions of the water level time series (with a probability of 0.013) is carried out in comparison to strong earthquakes, technical conditions of observations, and seasonal features of the hydrodynamic regime in the observation well. It is shown that this method of water level data processing can detect short-term anomalies in the hydrogeodynamic regime of a well, significantly supplementing traditional processing of water level data aimed mostly at finding low-frequency trends in water level changes. This method can be applied in geophysical monitoring and prediction of earthquakes from online processing of water level data in wells.

В данной работе представлены оригинальные данные, полученные в КФ ФИЦ ЕГС РАН по результатам комплексной обработки записей землетрясения, произошедшего 13.10.2018 г.

This paper is concerned with the main stages in the setting-up and technical development of a system specializing in physical and chemical parameters of groundwater at a network of wells and springs in the Petropavlovsk Geodynamic Test Area, Kamchatka. The focus is on a description of hydrogeochemical and hydrogeodynamic precursors to Kamchatka earthquakes (Мw = 6.6‒7.8) that occur a few weeks to a few months before a seismic event, manifesting themselves in anomalous changes in chemical composition and groundwater level. The precursors are discussed in application to their use at specialized councils on earthquake prediction. It is shown that the system of automated observation of groundwater parameters at wells as developed at the Kamchatka Branch of the Geophysical Survey of the Russian Academy of Sciences (KB GS RAS) is capable of identifying hydrogeodynamic precursors of water-level in near real time and of providing, in some particular cases, quantitative estimates of pre-seismic and coseismic deformation of water-saturated rocks. This can be useful in geophysical monitoring and intermediate-term prediction of strong earthquakes for the Kamchatka region.

The results of the long (2011–2016) investigation of background seismic noise (BSN) in Kamchatka by the method suggested by Doct. Sci. (Phys.-Math.) A.A. Lyubushin with the use of the data from the network of broadband seismic stations of the Geophysical Survey of the Russian Academy of Sciences are presented. For characterizing the BSN field and its variability, continuous time series of the statistical parameters of the multifractal singularity spectra and wavelet expansion calculated from the records at each station are used. These parameters include the generalized Hurst exponent α*, singularity spectrum support width Δα, wavelet spectral exponent β, minimal normalized entropy of wavelet coefficients En, and spectral measure of their coherent behavior. The peculiarities in the spatiotemporal distribution of the BSN parameters as a probable response to the earthquakes with М w = 6.8–8.3 that occurred in Kamchatka in 2013 and 2016 are considered. It is established that these seismic events were preceded by regular variations in the BSN parameters, which lasted for a few months and consisted in the reduction of the median and mean α*, Δα, and β values estimated over all the stations and in the increase of the En values. Based on the increase in the spectral measure of the coherent behavior of the four-variate time series of the median and mean values of the considered statistics, the effect of the enhancement of the synchronism in the joint (collective) behavior of these parameters during a certain period prior to the mantle earthquake in the Sea of Okhotsk (May 24, 2013, M w = 8.3) is diagnosed. The procedures for revealing the precursory effects in the variations of the BSN parameters are described and the examples of these effects are presented.