Статья посвящена математическому моделированию областей повышенных деформаций земной коры, возникающих при подготовке камчатских землетрясений. Для этого произведено обобщение классической модели ...косейсмических деформаций земной коры, которое заключалось во введении повышающих коэффициентов, зависящих от эффективности снятия энергии упругих деформаций. На основании разработанной модели произвдено моделирование полей деформации, возникающих при подготовке двух камчатских землетрясений. Показано, что области повышенных деформаций распространяются на сотни километров от очагов готовящихся землетрясений как на поверхности земной коры, так и в ее толще.
In Črna Jama, which is part of Postojnska Jama, underground measurement of VLF (Very Low Frequency) radio signals was periodically carried out in 2012 and 2013 for detection of possible pre-seismic ...and/or other anomalies and to ascertain suitability of VLF monitoring in a natural cave environment. The modulation of the VLF signal was connected with a powerful atmospheric front and changes of the precipitation level. VLF data showed day and night changes and also significant changes between dry and rainy periods when water from the surface reached the cave chamber through about 30 m of limestone roof. During VLF monitoring we did not receive earthquake precursor signals. VLF monitoring in a karst cave could be an option for future research in understanding pre-seismic and other anomalies. On-line connection with other VLF surface or cave monitoring sites in Europe is necessary in future VLF registration. Results of preliminary VLF monitoring showed Črna Jama to be a suitable place for future studies. Key words: VLF radio signals, noise sounds, pre-seismic anomalies, Črna Jama, Slovenia.
Continuous He, 222Rn concentrations and gamma dose rate were simultaneously monitored for pre-seismic signatures at two thermal springs in India that are separated at a distance of approximately 1612 ...km. The recordings of six month monitoring period (September 15, 2007–March 15, 2008) are presented here. In this paper, we make a cross correlation study of the simultaneously recorded multi-component gas-geochemical data from the two thermal springs. In the monitoring period a number of prominent fluctuations beyond the regular diurnal variations in the gas composition were recorded. We attempt to find out the linkage between the recorded distinct variations with local and remote seismic activities. Anomalous fluctuations in the spring gases were observed during the period December 24–27, 2007 at both the thermal springs and these anomalies may be correlated to the distant (~1000 km) China earthquake of magnitude M = 6.3 that occurred on January 09, 2008. Based on the obtained sequence of data points a time series analysis to relate earthquake magnitude, epicentral distance and precursor time through statistical methods and empirical equations related to the zone of influence is made. Concurrent monitoring of multi-component gas-geochemical anomalies recorded at a number of distant sites appears to be a potential tool to deal with the commonly debated question of earthquake precursors.
Abstract
Pre-seismic anomaly detection plays a crucial role in reducing economic losses and casualties caused by earthquakes. This paper proposes a novel four-step approach for pre-seismic anomaly ...detection. In the first step, a series of pre-seismic features are extracted by analyzing the earthquake catalog and geomagnetic signals. In the second step, the multi-view learning strategy is employed to obtain fusion features. In the third step, multiple seismic stations in one seismic zone are treated as a seismic station network, and a pre-seismic anomaly detection model is constructed based on the station network. In the final step, four evaluation indicators are introduced to comprehensively evaluate the detection results. Verification results show that the proposed method is effective and achieves better performance than other existing methods.
AbstractWhen the fault in a focal area enters the critical state, nonlinear accelerated deformation and disturbance changes may occur during tide-induced loading and unloading. In this study, the ...anomalies in the Korla volumetric strain caused by earth tide were investigated using a theoretical model of tidal force. Results show that the step changes in the Korla volumetric strain may be triggered by tidal force within a short time frame, ranging from a few to tens of days, prior to a moderate earthquake. The azimuthal angles at the time of step changes are mainly distributed in the ranges of 124–158° and 185–228°, and the azimuth angle at the time of many nearby medium-to-strong earthquakes occurring in this step concentration area, suggesting that the step anomalies in the Korla volumetric strain are closely related to the horizontal tide-induced force in a specific direction. Using the Schuster method, it was found that the tide-induced azimuth angle of the step changes occurred mostly at the minimum value of the solid tide, providing evidences of the modulation of the solid tide. These results may present new ideas for using crustal deformation observations for short-term earthquake predictions.
Earthquake prediction by using total electron content is a commonly used seismic research method. The long short-term memory model is a kind of method to predict time series and has been used for the ...prediction of total electron content, and the relative power spectrum method is one of the pre-seismic infrared anomaly detection algorithms in the frequency domain. In this paper, a new method combining these two algorithms is used to extract abnormal signals; thus scientists can more easily detect anomalies of total electron content similar to those before the Qinghai and Yunnan earthquakes happened on 21 May 2021. There are pre-seismic anomalies with the high-value relative power spectrum near two epicenters. To validate the correlation between anomalies and earthquakes statistically, the spatiotemporal characteristics of TEC anomalies are analyzed based on connected region recognition. Then, the proportion of earthquake-related anomalies (the correlation rate), the proportion of earthquakes outside the predicted range (the miss rate), and the ratio of the proportion of earthquakes within the predicted range to the spatiotemporal occupancy of anomalies, which is called the probability gain, were used to assess the method. The appropriate parameters of the algorithm for the miss rate below 50% were searched. The highest probability gain is 1.91, which means anomalies of total electron content may decrease the uncertainty of earthquake prediction.
Research of seismic infrared remote sensing has been undertaken for several decades, but there is no stable and effective earthquake prediction method. A new algorithm combining the long short-term ...memory and the density-based spatial clustering of applications with noise models is proposed to extract the anomalies from the multichannel infrared remote sensing images of the Fengyun-4 satellites. A statistical analysis is used to validate the correlation between the anomalies and earthquakes. The results show that the correlation rate is 64.29%, the hit rate is 68.75%, and the probability gain is about 1.91. In the Madoi and YangBi earthquake cases, the infrared anomaly detected in this paper is correlated with the TEC anomaly found in the previous research. This indicates that it is feasible to combine multi-source data to improve the accuracy of earthquake prediction in future studies.
В работе рассматриваются предсейсмические аномалии сигналов электромагнитного излучения в диапазоне очень низких частот (ОНЧ) и геоакустической эмиссии, зарегистрированных на Камчатке в 2013 году. ...Выявлены признаки возникновения аномальных возмущений в исследуемых сигналах и особенности их проявления. Проведен совместный анализ предсейсмических аномалий в сигналах электромагнитного ОНЧ-излучения и геоакустической эмиссии методом наложения эпох. Представлены оценки вероятности возникновения таких аномалий в рассматриваемых геофизических сигналах.
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