Time Of Earthquake Occurrence Research Articles

Analisis Bahaya Bencana Gempa Bumi di Wilayah Kabupaten Pesisir Selatan

This study aims to determine the earthquake hazard levels in Pesisir Selatan Regency, West Sumatra Province, by identifying the Peak Ground Acceleration (PGA) values and the distribution of earthquake hazard levels. The type of research used is quantitative descriptive analysis and spatial analysis. The method employed in this study is Probabilistic Seismic Hazard Analysis (PSHA). To determine the Peak Ground Acceleration values, parameters such as earthquake location, occurrence time, and earthquake magnitude are used. For determining the earthquake hazard distribution, data on Ground Amplification Factor (GAF) is utilized. The results of this study show that the distribution of Peak Ground Acceleration in the study area ranges from 0.17 g to 0.93 g. The value of 0.17 g is found in Koto XI Tarusan District, while the highest value is observed in Silaut District. Additionally, the distribution of earthquake hazard levels shows that areas with low hazard level cover 697.04 km², moderate hazard level covers 4150.49 km², and high hazard level covers 1201.81 km². This study provides earthquake hazard maps that can be used for mitigation and planning in the region.

Research on rescue priority based on high spatiotemporal resolution mobile positioning data

Estimate the key rescue areas of earthquake accurately, which is of great significance for deploying rescue forces and implementing rescue activities in post-earthquake scientifically.This paper based on the idea of first zoning, then classification, and then prioritizing rescue, taking the core area of Tangshan City as the study area, based on urban road data and mobile positioning data, combined with GIS methods to achieve street level rescue zoning, k-means clustering analysis is used to classify rescue sectors, and personnel burial model is used to conduct rescue priority classification.The results indicate that rescue priority is closely related to the time of earthquake occurrence. When the earthquake occurs between 18pm and 7pm in the next day, the number of priority rescue sector at level I and II is the highest. When the earthquake occurs between 8am and 11am on weekends, the number of priority rescue sector in residential areas increases, while the number of priority rescue zone decreases in workspace areas. This study provides refined rescue zoning and priority grading in the early stages of disaster relief with the absence of disaster information, which will help to assist in decision-making for professional force dispatch.

Unveiling Temporal Cyclicities in Seismic b-Values and Major Earthquake Events in Japan by Local Singularity Analysis and Wavelet Methods

Studying the temporal characteristics of earthquake activity contributes to enhancing earthquake prediction capabilities. The seismic b-value is a key indicator describing the relationship between seismic frequency and magnitude. This study investigates the correlation between the occurrence of major earthquakes and seismic b-values using earthquake activity records in Japan from 1990 to 2023. Local singularity analysis and wavelet analysis of earthquake frequency and b-value time series reveal significant 5-year periodic features in seismic activity in Japan. Furthermore, our research identifies that this periodicity is also prominent in major earthquakes with magnitudes of 7 and above. Additionally, through a detailed analysis of the cross-correlation between seismic b-values and the occurrence time of major earthquakes, we uncover a notable pattern: major earthquakes often occur approximately two years after the peak of seismic b-values. This discovery offers a new perspective on earthquake prediction and may play a crucial role in future earthquake early warning systems.

Spatio-temporal characterization of earthquake sequence parameters and forecasting of strong aftershocks in Xinjiang based on the ETAS model.

In this paper, the Integrated Nested Laplace Algorithm (INLA) is applied to the Epidemic Type Aftershock Sequence (ETAS) model, and the parameters of the ETAS model are obtained for the earthquake sequences active in different regions of Xinjiang. By analyzing the characteristics of the model parameters over time, the changes in each earthquake sequence are studied in more detail. The estimated values of the ETAS model parameters are used as inputs to forecast strong aftershocks in the next period. We find that there are significant differences in the aftershock triggering capacity and aftershock attenuation capacity of earthquake sequences in different seismic regions of Xinjiang. With different cutoff dates set, we observe the characteristics of the earthquake sequence parameters changing with time after the mainshock occurs, and the model parameters of the Ms7.3 earthquake sequence in Hotan region change significantly with time within 15 days after the earthquake. Compared with the MCMC algorithm, the ETAS model fitted with the INLA algorithm can forecast the number of earthquakes in the early period after the occurrence of strong aftershocks more effectively and can forecast the sudden occurrence time of earthquakes more accurately.

Feasibility Study on Earthquake Prediction Based on Impending Geomagnetic Anomalies

By deploying a magnetic monitoring network in the earthquake-prone areas of Sichuan, China, and conducting long-term observations, processing, and analysis of real-time geomagnetic data, it can be observed that the pre-earthquake geomagnetic anomalies are highly correlated with the occurrence time of earthquakes. We propose a novel algorithm that obtains a new quantity by accumulating geomagnetic anomaly energy to eliminate external environmental interference and take its gradient as a measure for predicting the occurrence time of an earthquake. Through observations of a large amount of geomagnetic data, it is confirmed that the proposed method can be used to predict the occurrence time of earthquakes with about 75% to 85% accuracy. Conclusions: The geomagnetic anomaly phenomenon can be accurately observed and recorded before an impending earthquake, and it has been confirmed by data that using this observation makes imminent earthquake prediction a practical prediction method.

A new method for coseismic offset detection from GPS coordinate time series

Currently, the extraction of coseismic offset signals primarily relies on earthquake catalog data to determine the occurrence time of earthquakes. This is followed by the process of differencing the average GPS coordinate time series data, with a time interval of 3 to 5 days before and after the earthquake. In the face of the huge amount of GPS coordinate time series data today, the conventional approach of relying on earthquake catalog data to assist in obtaining coseismic offset signals has become increasingly burdensome. To address this problem, we propose a new method for automatically detecting coseismic offset signals in GPS coordinate time series without an extra earthquake catalog for reference. Firstly, we pre-process the GPS coordinate time series data for filtering out stations with significant observations missing and detecting and removing outliers. Secondly, we eliminate other signals and errors in the GPS coordinate time series, such as trend and seasonal signals, leaving the coseismic offset signals as the primary signal. The resulting coordinate time series is then modeled using the first-order difference and data stacking method. The modeling method enables automatic detection of the coseismic offset signals in the GPS coordinate time series. The aforementioned method is applied to automatically detect coseismic offset signals using simulated data and the Searles Valley GPS data in California, USA. The results demonstrate the efficacy of our proposed method, successfully detecting coseismic offsets from vast amounts of GPS coordinate time series data.

Improving the Estimation of the Occurrence Time of an Impending Major Earthquake Using the Entropy Change of Seismicity in Natural Time Analysis

This article is focused on a new procedure concerning a more accurate identification of the occurrence time of an impending major earthquake (EQ). Specifically, we first recapitulate that, as was recently shown [P. Varotsos et al., Communications in Nonlinear Science and Numerical Simulation 125 (2023) 107370], natural time analysis of seismicity supplemented with the non-additive Tsallis entropy Sq leads to a shortening of the time window of an impending major EQ. This has been shown for the Tohoku mega-EQ of magnitude M9 that occurred in Japan on 11 March 2011, which is the largest event ever recorded in Japan. Here, we also show that such a shortening of the time window of an impending mainshock can be achieved for major, but smaller EQs, of the order of M8 and M7. In particular, the following EQs are treated: the Chiapas M8.2 EQ, which is Mexico’s largest EQ for more than a century that took place on 7 September 2017 near the coast of Chiapas state in Mexico, the 19 September 2017 M7.1 EQ that occurred within the Mexican flat slab, and the M7.1 Ridgecrest EQ on 6 July 2019 in California.

Pre-quake frequency characteristics of Ms ≥7.0 earthquakes in mainland China

In this study, natural orthogonal expansion was performed on earthquake frequencies to compute the pre-quake frequency fields of 9 Ms ≥7.0 earthquakes in mainland China from 1980 to 2020. The temporal and spatial pre-quake anomalies of these earthquakes were extracted from their frequency fields. We found that the majority of pre-quake temporal anomalies (i.e., variations exceeding two-times the absolute mean square error) of a strong earthquake are condensed within the first four frequency fields, and typically comprise multiple components. The temporal factor of the first frequency field usually accounts for the largest proportion of these anomalies (40%–60% of the entire field). Most Ms ≥7.0 earthquakes exhibited long-term anomalies 5–8 years before their occurrence; some presented medium-term anomalies 1–2 years prior to the quake, and only a few presented short-term and imminent anomalies (≤3 months before the quake). Anomalous seismic hazard zones have high-gradient turning points in regional frequency-field contour maps, and the epicenters of strong earthquakes are often located in areas containing active faults that have contour values. Through the comparison of seismic frequency field and the traditional method of regional seismic activity frequency (3 months), it is shown that the frequency-field time factor has the advantages of diversified and rich abnormal information. The slope comparison between the frequency field and the cumulative frequency curve shows that the frequency anomaly time of the two is consistent, and the conclusion is reliable. Therefore, the seismic frequency method can predict the occurrence time and location of strong earthquakes, which is closer to the predictable seismic model.

Order Parameter and Entropy of Seismicity in Natural Time before Major Earthquakes: Recent Results

A lot of work in geosciences has been completed during the last decade on the analysis in the new concept of time, termed natural time, introduced in 2001. The main advances are presented, including, among others, the following: First, the direct experimental verification of the interconnection between a Seismic Electric Signals (SES) activity and seismicity, i.e., the order parameter fluctuations of seismicity exhibit a clearly detectable minimum when an SES activity starts. These two phenomena are also linked closely in space. Second, the identification of the epicentral area and the occurrence time of an impending major earthquake (EQ) by means of the order parameter of seismicity and the entropy change of seismicity under time reversal as well as the extrema of their fluctuations. An indicative example is the M9 Tohoku EQ in Japan on 11 March 2011. Third, to answer the crucial question—when a magnitude 7 class EQ occurs—whether it is a foreshock or a mainshock. This can be answered by means of the key quantities already mentioned, i.e., the order parameter of seismicity and the entropy change of seismicity under time reversal along with their fluctuations. The explanation of the experimental findings identified before major EQs is given in a unified way on the basis of a physical model already proposed in the 1980s.

Role of Antecedent Rainfall in the Earthquake-Triggered Shallow Landslides Involving Unsaturated Slope Covers

Different soil cover saturation has a significant effect in influencing slope stability conditions of weathered covers under earthquake-induced shaking. Here we analyze the Montecilfone, Italy (2018), case history, an Mw 5.1 earthquake that revealed an exceptionality in the spatial distribution of the surveyed earthquake-induced shallow landslides. This feature can be justified as intense rainfall occurred in the epicentral area before the seismic event, contributing to increasing the saturation and the weight of the soil covers. To verify the effective influence of antecedent rainfall as a preparatory factor in the earthquake triggering of soil covers, stability conditions for both static and dynamic scenarios were validated by reconstructing different saturation conditions related to a rainfall event that occurred before the earthquake. Soil cover surveying was performed within a 150 km2 area to output its spatial distribution in terms of their compositional features and thickness, whose variability was constrained through empirical models. Based on laboratory test results, 1D infiltration numerical models were performed through the Hydrus-1D free domain software to estimate the saturation degree of the soil cover and the water infiltration depth, taking as a reference the intensity of the rainfall event. Soil cover sequential charts of water content were obtained at different depths and times up to those recorded at the time of earthquake occurrence by the performed numerical modelling. Safety factors (SFs) of the slope covers were quantified assuming an unsaturated condition in the slope stability equation. The outputs reveal that pore pressure spatial distribution in the unsaturated medium infers on the earthquake-induced scenario of shallow landsliding, demonstrating its role as a preparatory factor for earthquake-induced shallow landslides.

Comparasion Model Analysis Time of Earthquake Occurrence in Indonesia based on Hazard Rate with Single Decrement Method

The purpose of this studi is to find an expectations and variability as estimators of the risk of earthquakes occurring in each province in Indonesia. Indonesia is a country that prone to natural disasters, especially earthquakes and tsunamis. The earthquake disaster damage the buildings and casualties. The risk of loss from earthquakes can be transferred using insurance. Insurance companies certainly need an analysis to estimate the probability of an earthquake occurring at a certain location and time. Hazard rate has an important role in the prediction theory of the process of earthquakes. The hazard rate can be known by the single decrement method. After the hazard rate is known, the survival function and the distribution function of the cumulative distribution of earthquake data in Indonesia will be known to look for expectations and variability as estimators of the risk of earthquakes occurring in each province in Indonesia. The data used in this study is earthquake that happen in Indonesia categorized as destructive earthquake minimum 5 magnitude. We used the data to compare a hazard function using linear model, quadratic model, cubic model and exponential. First, we plot and then using each models find the standard error. The best model suggest for Indonesia prediction Time of Earthquake Occurrence using an exponential model.

Predictive capacity of topological measures in evaluating seismic risk and resilience of electric power networks

Electric Power Networks (EPNs) play a fundamental role in the wellbeing of modern societies and recovery of societal functions after an earthquake. Risk and resilience analyses may identify useful network characteristics to improve EPN response and recovery during and after a severe seismic event. This work computes different functional measures in order to: (i) estimate the actual risk and resilience of EPNs; and (ii) evaluate the predictive capacity of different topological measures (TMs) relative to the EPN earthquake risk performance. The analysis is carried out on the Chilean EPN at the national, regional and substation level, by using a detailed model of the network. EPN operation was modeled using the DC optimal power flow model from the time of earthquake occurrence until full system recovery using the Seismic Probabilistic Risk Assessment framework. Seismic risk and resilience estimations of Energy Not Supplied (ENS) and number of hours with ENS have been correlated with six network TMs. Linear correlation results show that TMs provide, in general, limited insight into the criticality of the Chilean EPN. In spite of that, the strongest correlation was observed for the degree TM. Moreover, the Damage Consequence Index confirmed the rather uniformly distributed seismic risk along the country.

Double event joint location method considering P-wave arrival time system errors

Microseismic (MS) source location is a core technology in MS monitoring that helps to infer the mechanical state of the rock mass and prevent dynamic disasters. However, when considering P-wave arrival time system errors (PATSEs), conventional location methods encounter the problem of high inversion dimensions and do not consider the influence of large P-wave arrival time errors. Therefore, we proposed a low-dimension double event joint location (DEJL) method that considers the PATSEs and introduces data field theory to reduce the influence of large P-wave arrival time errors. First, the P-wave travel-time equation of double events was constructed to eliminate the earthquake occurrence time and PATSEs, and the high-dimension inversion was reduced to a set of equations containing only six parameters. Then, 2000 P-wave arrival time combinations from more than six sensors were selected, and a Newton iterative based algorithm was proposed to solve the location point of each combination. Finally, the location point with the largest potential value of the data field was considered as the location result. The Institute of Mine Seismology acquisition system, placed in the Yongshaba mine in Guizhou Province, China, was selected to conduct the tests. P-wave arrival time datasets were obtained from two synthetic locations and eight blasting events. The results showed that the average location error of the blasting events using the proposed method is 32.59 m, which is lower than that of the homogeneous velocity-based location results. Thus, we determined that the proposed method offers a good MS location accuracy and broad application potential.

Tidal Influence on Seismic Activity During the 2011–2013 El Hierro Volcanic Unrest

AbstractThe El Hierro volcanic unrest started in July 2011, with an increase in observed seismicity rates and surface deformation. After the initial onset, hypocenters migrated southward through September 2011, culminating in a submarine eruption beginning on October 10, 2011 and finishing in February 2012. The seismic activity continued, with remarkable periods of unrest through 2012 and 2013. The most significant episodes of seismic activity during this unrest are related to magma migration at depth. In this work, we compute tidal stress for each earthquake, at its hypocenter depth, and assign them a tidal stress phase angle. We have found statistically significant correlations between the occurrence of earthquakes and tidal stress phase angles, corresponding mainly to increasing tidal stress change rates. We found primarily that the magnitude of vertical and E‐W horizontal tidal stress values and their changing rates with time were correlated with earthquake occurrence times. We also found that there is no correlation between tides and seismicity at times with no observed surface displacements, suggesting that tidal modulation might be related to overpressure during migration of magma. Tidal modulation changes with depth and the influence of ocean‐loading tides is stronger than the influence of solid Earth tides. Our results support the hypothesis that tidal stress may modulate the seismicity during volcanic unrest, particularly during shallow depth magma migration.

Identification of radon anomalies induced by earthquake activity using intelligent systems

The temporal variability of soil radon concentration of tectonically active origin is considered a potential earthquake precursor. However, the reliable identification of radon anomilies possibly induced by earthquake activity is still enigmatic. The present study applies intelligent algorithms such as artificial neural networks (ANN), multiple linear regressions (MLR) and decision trees (DT) for an improved and more reliable identification of radon anomalies of the tectonically active origin in northern Pakistan. The dataset utilized in the present investigation includes the soil radon concentration and associated meteorological parameters recorded at a seismically active location in northern Pakistan. The recorded dataset is subdivided into seismically active (SA) and stable (NSA) periods using a time window of ±7 days around the time of earthquake. The NSA dataset is utilized for the training/cross-validation of intelligent algorithms using three input (meteorological factors) and one output parameter (radon). The trained intelligent models are then used to simulate the expected radon level during the SA periods based on the measured environmental parameter. The discrepancy (Q) between the simulated and measured radon is utilized to identify statistically significant (x¯±2σ) radon anomalies. Our results reveal that all the employed intelligent algorithms show a significant deviation in Q values around the time of earthquake occurrence. Furthermore, comparative analysis suggests that ANN performs better than the other techniques. In conclusion, our study paves the way for the possible use of radon in designing an optimized strategy for earthquake forecasting.

Lower Ionospheric turbulence variations during the intense tectonic activity in Eastern Aegean area

This paper may be considered as an additional approval of the way the tectonic activity affects the lower Ionosphere. The results of our investigation, on the occasion of the recent East Aegean tectonic activity, indicate that the High - Frequency limit, fo, of the ionospheric turbulence content, increases as the site and the time of the earthquake occurrence is approaching, pointing to the earthquake location.We conclude that the Lithosphere Atmosphere Ionosphere Coupling (LAIC) mechanism through acoustic or gravity wave could explain this phenomenology, as a result of a the frequency differential damping of the propagating turbulent in the ionosphere. Proper use of this result may lead to a method of earthquake hazard mitigation using the byproducts of the Global Positioning Network (actually Total Electron Contain, TEC, estimations) which are available freely.

Increased radon concentration in Katalekhor tourist cave during an earthquake compared with 10 years of follow-up data

On May 27, 2008, a strong earthquake of magnitude 5.3 Richter hit Zanjan province. The radon concentration has been measured and registered at the time of earthquake occurrence at 10:48 local time inside the Katalekhor cave being situated at suburb of Zanjan city. After this event, it was planned to measure and analyze the radon concentration in the same year (2008) and 10 years after the earthquake (2018) by using passive methods and the results have been presented. Real time observations show an increase of five times in radon concentration when earthquake happened comparing to normal condition.

Analysis of Time Dynamical Features in Intraplate Versus Interplate Seismicity: The Case Study of Iquique Area (Chile)

The intraplate and interplate seismic catalogues of Iquique (Chile) area were investigated by using seismological (b value of the Gutenberg–Richter law), fractal (Allan Factor and detrended fluctuation analysis) and topological (Horizontal Visibility Graph) methods. The two catalogues show different stress state indicated by the different b value, larger for the intraplate seismicity. The interplate seismicity shows significant time-clustering behavior of the earthquake occurrence times at large time scales, while the time distribution of the intraplate earthquakes seems to be featured by random fluctuations without any significant sign of time-clustering. Different role seems to be played by aftershocks in the two investigated seismic zones, revealed by the different time distribution of the aftershock-depleted catalogue of the intraplate zone, which remains Poissonian for most of the time scales, and the interplate zone that still keeps its clustering phenomenon but at higher timescales, thus shortening its clustering time scale range. Furthermore, the interevent times of the interplate catalogue are characterized by persistent dynamics even after removing the aftershocks, while uncorrelated fluctuations characterize the behavior of interevent intervals of the whole as well as aftershock-depleted intraplate catalogue. Additionally, the magnitudes of both catalogues are characterized by time-reversibility before and after the aftershock removal; while the interevent times of intraplate catalogue change their status from time-irreversibility to time-reversibility after removing the aftershocks. The obtained results seem to evidence a different role played by the aftershocks in the intraplate and interplate zones, that needs to be further explored.

Retrospective and forward prediction of next strong earthquakes in oceanic ridges and trenches using probabilistic models

Earthquake occurrence and recurrence depend on number of factors beyond mere observations. These include seismotectonic nature of the region, spreading rate of the ridge or subduction of plates causing the trench, active or otherwise nature of the fault on crust (on land), stress-strain regime, and so on. In this work, the recurrence and expected times of next strong earthquakes (M ≥ 6) in the oceanic ridges and trenches were computed using gamma and lognormal probabilistic models. Summing the occurrence times of last strong earthquakes and these recurrence times, expected times of the next strong earthquakes were retrospectively and forwardly predicted. The expected times of the next strong earthquakes retrospectively predicted correlated with the recorded strong earthquakes in the earthquake catalog of the Advance National Seismic System (ANSS) hosted by the Northern California Earthquake Data Centre, USA, for the period of 1978–2017 in a readable format. The successful prediction of the expected times of the next strong earthquakes retrospectively is an indication that the expected times of the next strong earthquakes forwardly predicted in the regions of study will be positive. However, since the occurrence and recurrence of earthquakes depend on many factors, it is therefore important to note that it may not always be accurate to predict future earthquakes from retrospective perspective. Nonetheless, this work is a good effort, and it has thrown up some interesting results.

Source characterizations of the New Cairo earthquake, Egypt

The New Cairo region was hit by a moderate size earthquake (Mw = 4.18) on midday Monday, 31st December 2018 that was felt throughout the greater Cairo region without any reported damage. The source mechanism solution and moment tensor inversion exhibit a normal fault with a minor strike-slip component. The NW-fault plane is the preferred rupture plane consistent with the geological and tectonic settings of the region. The dynamic source parameters have calculated, assuming a simplified circular source model, by using displacement spectra. The obtained source parameters are included average seismic moment is 2.41E+15 N-m, rupture radius of 0.46 Km, stress drop is 10.9 MPa, relative displacement is 0.012 cm, and energy releases are 1.2E+18 Erg. According to “Scholz” (1990), the studied earthquake might be considered as an intraplate type-(II) earthquake that related to plate boundaries. In the present study, the thermal infrared data is used to derive Land Surface Temperature (LST) as a precursory analysis for this earthquake. The results indicated that there was a correlation between LST with precursor seismic activity before the time of the New Cairo earthquake occurrence.