Epicenter Research Articles

Cross-Correlation among Seismic Events, Rainfalls, and Carbon Dioxide Anomalies in Spring Water: Insights from Geochemical Monitoring in Northern Tuscany, Italy

Variations in the CO2 dissolved in water springs have long been observed near the epicenters of moderate and strong earthquakes. In a recent work focused on data collected during the 2017–2021 period from a monitoring site in the Northern Apennines, Italy, we noticed a significant correlation between CO2 anomalies and moderate-to-weak seismic activity. Here, we extended this analysis by focusing on data collected from the same site during a different period (2010–2013) and by integrating the CENSUS method with an artificial neural network (ANN) in the already-tested protocol. As in our previous work, a fit of the computed residual CO2 distributions allowed us to evidence statistically relevant CO2 anomalies. Thus, we extended a test of the linear dependence of these anomalies to seismic events over a longer period by means of binary correlations. This new analysis also included strong seismic events. Depending on the method applied, we observed different time lags. Specifically, using the CENSUS methodology, we detected a CO2 anomaly one day ahead of the earthquake and another anomaly eleven days ahead. However, no anomaly was observed with the ANN methodology. We also investigated possible correlations between CO2 concentrations and rain events and between rain events and earthquakes, highlighting the occurrence of a CO2 anomaly one day after a rain event of at least 10 mm and no linear dependence of seismic and rain events. Similar to our previous work, we achieved a probability gain of around 4, which is the probably of earthquake increases after CO2 anomaly observations.

Detection of the pre-seismic anomalies in stratospheric temperature and radio emission using space-based observations

The present paper implements new approaches introduced in regard to pre-earthquake geo-chemical activity that results in lithosphere-atmosphere–ionosphere coupling (LAIC). Specifically, stratospheric temperature anomaly as a result of precursory atmospheric gravity wave (AGW) activity in the stratosphere is studied. A new technique is developed based on the parameters a) daily average temperature (Tmean), b) daily maximum temperature (Tmax), c) Tmean averaged over altitude, d) Tmax averaged over altitude. The new approach is applied to six earthquakes of Iran as well as Tohoku earthquake. Detected Anomalies are analyzed and discussed. Possible new variations such as stratospheric cooling as a result of active geomagnetic conditions are determined. Geographical maps and spatial distribution of temperature anomalies are presented to comprehend the possible source of variation. Moreover, space-based ULF emission observed by an in situ electric field detector (EFD) on board of China Seismic-Electromagnetic Satellite (CSES) is presented as associated with 3 earthquakes that occurred in 2019. Detailed analysis of satellite overpass proximity to the earthquake epicenter, earthquake magnitude, and dates are examined and ULF anomalies associated with 3 magnetic field components are discussed. Finally, a systematic approach to be implemented using the new techniques in real time is proposed.

Spatial Heterogeneity of b Values in Northeastern Tibetan Plateau and Its Interpretation.

The northeastern margin of the Tibetan Plateau (NE Tibetan Plateau) exhibits active geological structures and has experienced multiple strong earthquakes, with M ≥ 7, throughout history. Particularly noteworthy is the 1920 M81/2 earthquake in the Haiyuan region that occurred a century ago and is documented as one of the deadliest earthquakes. Consequently, analyzing seismic risks in the northeastern margin of the Tibetan Plateau holds significant importance. The b value, a crucial parameter for seismic activity, plays a pivotal role in seismic hazard analyses. This study calculates the spatial b values in this region based on earthquake catalogs since 1970. The study area encompasses several major active faults, and due to variations in b values across different fault types, traditional grid-search methods may introduce significant errors in calculating the spatial b value within complex fault systems. To address this, we employed the hierarchical space-time point-process (HIST-PPM) method proposed by Ogata. This method avoids partitioning earthquake samples, optimizes parameters using Akaike's Bayesian Information Criterion (ABIC) with entropy maximization, and theoretically allows for a higher spatial resolution and more accurate b value calculations. The results indicate a high spatial heterogeneity in b values within the study area. The northwestern and southeastern regions exhibit higher b values. Along the Haiyuan fault zone, the central rupture zone of the Haiyuan earthquake has relatively higher b values than other regions of this fault zone, which is possibly related to the sufficient release of stress during the main rupture of the Haiyuan earthquake. The b values vary from high in the west to low in the east along the Zhongwei fault. On the West Qinling fault zone, the epicenter of the recent Minxian-Zhangxian earthquake is associated with a low b value. In general, regions with low b values correspond well to areas with moderate-strong seismic events in the past 50 years. The spatial differences in b values may reflect variances in seismic hazards among fault zones and regions within the same fault zone.

Spatio-Temporal Variation Seismicity Pattern in East Java Between 2002 and 2022 Based on the b-value and Seismic Quiescence z-value

East Java is one of the seismically active regions in part of the Sunda Arc whose seismicity pattern must be studied. Therefore, a spatio-temporal analysis of seismicity between 2002 - 2022 in East Java has been conducted. This analysis aims to investigate the seismotectonic conditions in the East Java region over the last twenty years, especially the seismicity patterns associated with significant earthquakes in East Java. The analysis was carried out by quantifying the spatial and temporal variations of seismicity parameters using b-value and z-value. The used data used are earthquake data from the USGS earthquake catalog during 2002 - 2022 in the East Java region. The analysis was performed using the ZMAP 6.0 program code using the maximum likelihood method. The results of the temporal analysis of b-values show that almost all significant earthquakes in East Java were characterized by a decrease in b-values of up to 0.2. Spatially, the significant earthquake on 10 April 2021 was associated with a low b-value (0.9). Temporal z-value analysis shows that the significant East Java earthquake was preceded by a quiet period (positive z-value) between 4 - 5 years (2003 - 2008 and 2012 - 2016). Spatial analysis of the z-value in the last 7 shows an increase in the z-value before the significant earthquakes occurred on 16 July 2019, 18 March 2020, and 10 April 2021. Therefore, the results of this study indicate that the b-value and z-value potentially can be used as precursors of the significant East Java earthquake. HIGHLIGHTS This is the first time a correlation of b-value and z-value as seismicity parameters has been carried out in East Java, Indonesia, as an attempt to determine the significant earthquake precursors The significant earthquakes in East Java during 2002 - 2022 were marked by a decrease in b-value of up to 0.2 The quiet period in East Java lasted between 4 - 7 years, i.e. 2002 - 2009 and 2012 - 2016, characterized by a positive z-value peaked until +3.5 The z-value at the location of a significant earthquake epicenters show a positive value 2 - 3 years prior to the main quake GRAPHICAL ABSTRACT

CORRELATION OF RADON AND SEISMIC ACTIVITY IN THE BAIKAL RIFT ZONE ACCORDING TO EMANATION MONITORING DATA

Long series of the emanation monitoring organized at Tyrgan (2018–2023), Buguldeika (2020–2023) and Maksimikha (2022–2023) stations in the central part of the Baikal Region (the Eastern Siberia) are studied to reveal the relationship of the subsurface radon volumetric activity (RVA) with the seismicity of the Baikal rift zone (BRZ). The comparison of the weekly averaged RVA values at different stations and the degree of dependence of this parameter on the logarithm of the total earthquakes energy (LgΣE) showed that during the periods of seismic activity the impact of tectonic forces makes significant corrections in the character of emanations, which in general is determined by non-tectonic factors. It has been established that seismic activity represented by the enough strong for the Baikal Region earthquakes with K≥13.3 correspond to synchronicity intervals of RVA at different monitoring stations, as well as coincidence of maximum values of the logarithm of the total earthquakes energy with local maximums of the correlation coefficient between RVA and LgΣE parameters. The area, including the earthquake epicenters that generated such an emanation response at monitoring stations, is in the form of an ellipse extended in the northeastern direction – along the main fault structures of the BRZ. The obtained results, besides confirming the previously proposed model of radon field formation in the Baikal Region under the influence of external and internal forces, provide the for the identification of further stable precursors of strong earthquakes based on a comprehensive analysis of data from a branched emanation monitoring network.

Depth to the bottom of lithospheric magnetic sources beneath north-eastern Eurasia: lithospheric thermal regime and relation to seismicity

For north-eastern Eurasia (60—70° N, 90—180° E), the bottom depth of the lithospheric magnetoactive layer is estimated using the centroid method based on two-dimensional spectral analysis of the lithospheric magnetic field. The lithospheric magnetic field within the study region is described by the EMAG2v3 global model. The obtained results show that maximum values ( 50 km) of the depth to the bottom of lithospheric magnetic sources are observed almost everywhere under the Siberian platform north of 65° N. Minimum depth values (30 km) are traced under the Koryak-Kamchatka fold belt and the Okhotsk-Chukotka volcanogenic belt. Under the Verkhoyansk-Kolyma fold belt, different maximums (up to 40 km) and minimums (up to 30 km) of the bottom depth are seen. Assuming that magnetite is a main magnetic mineral in the continental lithosphere, our distribution of the bottom depth evidences for the eastward lithospheric heating — from the Siberian platform to the Koryak-Kamchatka fold belt. The revealed tendency is confirmed by independent geophysical data. Comparison of the obtained results with a distribution of epicenters of regional earthquakes (M ≥ 4.0, 1962—2020) shows that most sources of strong earthquakes (M ≥ 6.0), registered during the instrumental period of observation, are confined to zones in which a sharp change in the depth to the bottom of lithospheric magnetic sources occurs.

Preliminary Results of the Seismicity Monitoring Experiment around the 2019 Mw5.4 Earthquake Epicenter in the Central South China Sea Basin

Preliminary Results of the Seismicity Monitoring Experiment around the 2019 Mw5.4 Earthquake Epicenter in the Central South China Sea Basin

Displacement and damage analysis of earth dams during the 2023 Turkiye earthquake sequence

The earthquake sequence that occurred on 6 February 2023 in Turkiye caused significant damage to various infrastructures including geostructures such as dams. A total of 17 earth dams within a 200-km radius of the earthquake epicenter experienced varying degrees of damage, ranging from minor (∼2 cm) to major (up to ∼150 cm) deformations. As study of these reveals that the damaged dams are located within the closest distance to the fault of less than 30 km, with an average value of ∼12 km. This study specifically focuses on the seismic displacement analysis of the 17 damaged dams, utilizing the sliding block methods. The recorded motion data was analyzed using the kriging technique to estimate the spectral response at the dam sites. Moreover, the recorded ground motions were scaled to the resonant period of the dam site to estimate acceleration time history. The findings reveal that the rigid block analysis can provide an average estimation of seismic displacement with a relative error of less than 44%. The results of the damage analysis indicate that seven dams reached the ultimate limit state and two dams experienced the serviceability limit state. Moreover, the univariate and multivariate fragility functions are developed to estimate seismic probabilistic analysis of earth dams based on the observed data and the limit states. The results show that the selection of a single intensity measure (IM) and a combination of IMs can affect the predicted probability of failure. The findings provide an insight into the resilience assessment of dams and other geosystems during this strong earthquake.

Modeling spatial distribution of earthquake epicenters using inhomogeneous Log-Gaussian Cox point process

Modeling spatial distribution of earthquake epicenters using inhomogeneous Log-Gaussian Cox point process

Preliminary Evaluation of Traffic Resilience against Potential Earthquake in Penang Island

When an earthquake occurs in a neighboring country close to Malaysia, such as Indonesia, the tremor can be felt by Malaysians, especially states located along the Straits of Malacca. The epicenter of an active earthquake in the Indian Ocean near northwestern Sumatra, Indonesia triggered a tsunami in December 2004 that hit Penang Island and killed dozens of people and caused minor property damage especially the transportation system. A Quantum Geographic Information System (QGIS), Open Street Maps (OSM), Online Questionnaire Survey, and Literature Review were used to evaluate the preliminary traffic resilience in Penang Island. The presence of fault lines and traffic networks from the secondary data were identified and integrated using GGIS and OSM. The contour results showed that the red zone (most affected) and yellow zone (less affected) were mostly located in the northeast district and the upper half in the southwest district while only a small part was covered with the green zone (not affected) in the southwest district of Penang Island. The factors influencing humans in responding during an earthquake were panic and fear from the point of view of history and general knowledge, as well as announcements and evacuations by the government as the highest votes by online questionnaire survey. Preliminary, the traffic networks with higher probability being affected in the events of earthquake are identified so that further study for the traffic resilience can be carried out.

Investigating ultra-low frequency emissions and total electron content anomalies as earthquake precursors in Sumatra (2019–2020)

Ultra-low frequency (ULF) emissions and total electron content (TEC) anomalies are potential earthquake precursors for short-term earthquake prediction. This study comprehensively examines ULF emissions and TEC anomalies associated with the Sumatra earthquakes spanning 2019–2020. Precursor ULF emissions are identified through the polarization power ratio calculations involving Z-component and H-component geomagnetic data, meticulously recorded by the Magnetik Acquisition Data System (MAGDAS). Employing the Single Station Function Transfer technique, ULF anomalies directed toward the epicenter of earthquakes are recognized as reliable precursors. Among the 29 earthquakes scrutinized, 25 were heralded by ULF emissions acting as precursors. Among these, 15 instances solely exhibited ULF emissions, unaccompanied by TEC anomalies, while the remaining ten were linked to TEC anomalies. The investigation of TEC anomalies employs advanced autocorrelation techniques rooted in the analysis of correlation coefficient deviations. TEC anomalies are meticulously acquired from the observations of the Sumatran GPS Array (SuGAr) stations. Furthermore, this study illuminates a positive correlation (R = 0.65) between the lead time of ULF emissions and TEC anomalies. Moreover, the frequency of ULF emissions and TEC anomalies also showcases a direct relationship with earthquake magnitude. Heightened frequencies of ULF emissions and TEC anomalies as earthquake precursors correspond to more significant magnitudes in ensuing earthquakes. The outcomes of this research significantly augment the understanding of employing ULF emissions and TEC anomalies as effective earthquake precursors in the context of Sumatra.

Green’s Function, Earthquakes, and a Fast Ambient Noise Tomography Methodology

Green’s function plays an important role in the relationship of a future strong earthquake epicenter to the average earthquake potential score. In the frame of the latter, the fractal dimension of the unified scaling law for earthquakes naturally arises. Here it is also shown to be a cornerstone for the development of a new ambient noise tomography methodology, which is applied for example to the west coast of Central Greece. In particular, we show that a fast and reliable 3D shear velocity model extraction is possible without the need for a large amount of data, great-circle propagation assumptions, or the intermediate step of inverting for group velocity maps. The tomography results are consistent with previous studies conducted in the neighboring region.

The first 30 min hidden aftershocks of the 2022 September 17, ML 6.4, Guanshan, Taiwan earthquake and its seismological implications

The first 30 min of the aftershock sequence following the 2022 September 17, ML 6.4, Guanshan, Taiwan earthquake is investigated by the back-projection (BP) method. Based on the Automatic Gain Control (AGC) to process individual earthquake record and sort waveforms by epicentral distance, 80 events are identified near the Guanshan earthquake epicenter to verify its temporal variation. However, most of these events cannot clearly image by the BP method to determine its spatial locations for its small amplitude and short time separation. In total, 29 aftershocks are imaged by this study to identify its spatial locations during this time period. The relocated events are compared with the Central Weather Bureau (CWB) rapid report catalogue. Only 5 events have been reported by the CWB rapid report catalogue. These unreported hidden aftershocks are identified to distribute surrounding the epicenter and extended to the east. This extracted information of hidden aftershocks is crucial for assessing the potential for future large aftershocks and estimating the associated seismic hazards in a given region, and provide extra message to evaluate the source physics in general.

Analysis of the Value of Maximum Ground Acceleration in Earthquake Disaster Mitigation Efforts on the Lan

The Aceh region itself has a location that is within the scope of the Sumatran fault, areas on active faults can experience a high possibility of earthquakes. Earthquake epicenters on the mainland can occur due to shifts in the Sumatran fault which is indicated by the number of earthquakes along the fault and generally has shallow depths. The research was conducted to determine the value of the earthquake acceleration on the ground around the East Aceh Alue Genteng bridge. The results of this study found that the magnitude of the earthquake can affect the level of acceleration of the earthquake that occurs, the acceleration of the earthquake increases with the magnitude of the earthquake. Based on the results of calculating the acceleration of the earthquake using magnitude 7, 5 SR-9.3 SR, the earthquake acceleration occurred significantly and continues to increase. Earthquake acceleration data is one of the important data that can be used in earthquake mitigation such as in planning strong building structures that are able to withstand loads caused by earthquakes.

Predictors of Uptake of Rotavirus Vaccination Amongst Disadvantaged Communities in Pakistan.

Introduction. Pakistan has the highest childhood mortality associated with diarrheal diseases. The objective of this study is to identify underlying factors contributing to lack of knowledge among mothers regarding vaccine's efficacy in the prevention of diarrhea. Methodology. Secondary data was analyzed from a cross-sectional household survey in Northern Pakistan of eligible households having under-2-year children. Univariate and multivariate logistic regression analyses were carried out. Results. Only 30% of the mothers had knowledge regarding diarrhea prevention by vaccine. The main factors found significantly correlated with this knowledge were mother's education, distance of households from EPI centers, immunization status of children, counseling regarding clean drinking water and hygiene, provision of ORS, and antenatal care services by LHWs. Conclusion. Women's literacy, access to care and LHW services are important for improving awareness and acceptance of vaccines for vaccine preventable diseases including diarrhea. Policy makers need to focus on improved monitoring and reprioritization of undermined services by LHWs.

A Deep Attention Model for Onsite Estimation of Earthquake Epicenter Distance and Magnitude

A Deep Attention Model for Onsite Estimation of Earthquake Epicenter Distance and Magnitude

Risk Factors of Community Acquired Pneumonia among Under Five Children in a Tertiary Level Hospital in Rajshahi

Introduction: Community acquired pneumonia (CAP) top the list of causes of under five children mortality in the world. Proper assessment of these risk factors and controlling them may help decrease the morbidity and mortality in under-five children suffering from CAP in Bangladesh and thereby help in improving the quality of life of our future generation. Objective: To assess the risk factors of CAP among under five children ( 2-59 months ) in a tertiary level hospital in Rajshahi. Materials and methods: This is a case control study which was carried out in the department of Pediatrics and EPI center of Rajshahi Medical College Hospital, RMCH from January 2017 to December 2018 to determine the risk factors of CAP among under five children. For this study, total 246 children, aged 2 months to 59 months, were selected by purposive sampling technique. 123 were cases who were taken from indoor and 123 were healthy controls who were taken from out patients department & EPI centre. After taking written consent from guardians, history was taken and physical examination was done. All informations were recorded in a predesigned data sheet. Chi-square test and odds ratio were used to demonstrate level of significance. Results: Among 246 children greater number of patients of both group were male and came from rural area. Cases were predominant under 12 months and came from lower socioechonomic status. A statistically significant association was found between social class and CAP (<0.001), father’s literacy was inversely related to CAP (p value <0.001). Types of housing, ventilation of living room , overcrowding, types of fuel and cookers used for cooking, parental smoking , malnutrition, history of diarrhea and presence of anemia , prematurity and low birth weight were significantly associated with CAP ( p value <0.05) . Conclusion: Proper assessment of these risk factors and controlling them may help decrease the morbidity and mortality in under-five children suffering from CAP in Bangladesh and thereby help in improving the quality of life of our future generation. TAJ 2023; 36: No-2: 145-153

Double resonance in seismo-lithosphere-atmosphere-ionosphere coupling

nvestigations into causal mechanisms behind anomalous pre-earthquake phenomena are considered a promising way of earthquake prediction. Numerous promising channels for seismo-lithosphere-atmosphere-ionosphere coupling have been proposed; however, predicting earthquakes remains a great challenge in the scientific society. Short-period ground vibrations exhibiting frequency characteristics similar to natural frequencies caused by strata failure resonance have recently been detected using tiltmeters embedded in magnetometers prior to earthquakes. These vibrations originate from regions near the epicentres of forthcoming earthquakes and can be simultaneously detected by broadband seismometers and ground-based global navigation satellite system (GNSS) receivers. Unlike the total electron contents (TECs) obtained from orbiting satellites, the vibrations and the identifiable TEC perturbations in data from geostationary satellites of the BeiDou Navigation System share frequencies prior to earthquakes. However, the causal relationship between the vibrations and TEC perturbations remains unclear due to a gap in data observations between the lithosphere and ionosphere. To address this issue, an instrumental array was established to monitor vibrations and perturbations in the lithosphere, atmosphere, and ionosphere. Observational data from the array partially fill the gap, and analytical results show that ground vibrations, air pressure, magnetic fields, and TEC data shared a common frequency of approximately 5 × 10–3 Hz (5 mHz) before major earthquakes. This suggests that the resonant ground vibrations trigger atmospheric resonance before earthquakes. Therefore, the double resonance (crustal and atmospheric resonance) model is a new explanation for the observed anomalies in multiple geophysical parameters in the lithosphere, atmosphere, and ionosphere. Retrieving resonant signals from multiple sources of observational data is a significant challenge, but once this issue is overcome, double resonance may contribute to practical earthquake prediction.

Lower Ionospheric variations during the intense tectonic activity in the broader area of Greece on October of 2020

In this paper, we investigate the Lower ionospheric variations from TEC observations during the intense seismic activity of October 2020 in the area of Greece. The data were analysed using both, statistical analysis of TEC variations in order to detect uneven gross variations and Discrete Fourier analysis in order to investigate the TEC turbulence. The results of this investigation indicate that the High-Frequency limit fo of the ionospheric turbulence content, increases as aproaching the occurrence time of the earthquake, pointing to the earthquake epicenter, in accordance with our previous investigations. We conclude that the Lithosphere Atmosphere Ionosphere Coupling, LAIC, mechanism through acoustic or gravity waves could explain this phenomenology. In addition, the statistical analysis shows an excess greater than 3𝜎 from the mean TEC values, one and seven days before the earthquake. Since no major disturbance of the geomagnetic field occured during these days, we conclude that we probably observed precursory ionospheric variations in accordance to analogous findings from the variation of VH/VHF electromagnetic wave propagrations over strong earthquake areas.

Lower-ionosphere anomalies prior to strong earthquakes that occurred in north-central mainland Greece on March 2021 as revealed by multi-method analysis of VLF sub-ionospheric propagation data

In this work we present the multi-method analysis of very low frequency (VLF) data, acquired by the radio receiver with call name UWA, located in Athens (Greece), in the University of West Attica, focusing on two strong ( ) earthquakes (EQs) that occurred in north-central mainland Greece sequentially, on 3 and 4 March 2021, with very close epicenters. Specifically, we used the data acquired from seven VLF transmitters located in Europe, North/North-West to UWA, and their propagation paths include the specific EQs epicenters. We analyzed these data using multiple analysis methods in order to investigate for possible EQ-related anomalies, taking also into account all the other possibly ionosphere-influencing extreme events that occurred during the studied period. Especially, we applied the “nighttime fluctuation method” (NFM), as well as, the “terminator time method” (TTM) in order to reveal any statistical anomaly in the nighttime amplitude recordings of VLF sub-ionospheric propagation data within 15 days before each one examined EQs. Also, we calculated the scalogram (wavelet power spectrum over time) using Morlet mother wavelet of the same nighttime data searching for possible imprints of wave-like structures during the same time period. In terms of criticality analysis, first we applied the “natural time” (NT) analysis method to the daily-valued NFM VLF propagation quantities, and subsequently applied the “method of critical fluctuations” (MCF) to the raw nighttime amplitude VLF recordings, to check for any criticality signatures up to two weeks before the examined EQs. Taking into account all the above-mentioned analysis results, we conclude that there are multiple indications that the lower ionosphere was indeed disturbed due to the preparation processes of the above-mentioned EQs, offering different types of seismogenic indications.