Comprehensive Research in Earthquake Forecasting and Seismic Hazard Assessment

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Earth Sciences and Geography".

Deadline for manuscript submissions: closed (20 June 2023) | Viewed by 23225

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Special Issue Editors

O.Yu. Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Bol. Gruzinskaya str., 10, Build. 1, 123242 Moscow, Russia
Interests: earthquake; physics of seismic process; seismic hazard assessment; geophysics; earthquake prediction
Geophysics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
Interests: statistical seismology; seismic hazard assessment; applied geophysics; earthquake prediction

Special Issue Information

Dear Colleagues,

Despite some success, the issue of earthquake forecasting has yet to be resolved. Discussions in concerning the principal possibility of earthquake forecasting surface intermittently within the scientific community, especially in the short-term aspect. However, the bulk of these discussions were set in the Resolution of the General Assembly of the International Association of Seismology and Physics of the Earth’s Interior (IASPEI) in 2009 in Cape Town: "Resolution 4: Earthquake Forecasting and Predictability Studies - IASPEI RECOGNIZING the opportunities provided by recent developments in earthquake science and technology RECOMMENDS that research on forecasting and predictability of earthquakes, and the validation and comparative testing of prediction methods be supported".

However, it is not sufficient to correctly predict a future strong earthquake. It is necessary to provide a correct, scientifically substantiated assessment of the level of seismic danger, and the intensity of possible seismic shocks of a particular region, city and settlement. What should the administration of a megapolis do when it receives information about the likelihood of a strong earthquake? The problems of earthquake forecasting and seismic hazard assessment are closely connected to the issues of high-quality aseismic construction.

More than 12 years have passed since the IASPEI Resolution was adopted, and new earthquakes have occurred, expanding our knowledge about the physics of the seismic process, the physics of earthquake preparation processes, and searches for earthquake precursors. The obtained new data became the basis for the development of new models of ground behavior under the influence of seismic waves, providing initial information for the development and parameterization of models of earthquake zones and equations of ground motion prediction.

For the forthcoming Special Issue "Frontiers in Earthquake Forecasting and Seismic Hazard Reduction " of the MDPI Journal "Applied Sciences", we urge representatives of the scientific seismological community to share their results on the indicated topics in order to evaluate advancements in the earthquake forecasting and seismic hazard assessment, the state of the art of the problem, what to do, and in which direction to progress.

Researchers are invited to discuss results and the directions of further studies on the physics of the seismic process, from experiments in laboratory conditions to rock bursts in mines and seismically active regions during the preparation phase of strong earthquakes.

The development of earthquake forecasting models is being facilitated by the improvement of data and modeling inputs. Some modeling efforts are focused on short-term clustering of earthquakes, others on the time-varying probability of rupture of major fault sources, and others on the space–time–magnitude variation of the rate of earthquake occurrence in extended regions. Models can be statistical or physics based. Data input includes the past earthquake catalogue, known or inferred dates of previous fault ruptures, modeled physical variables such as stress accumulation and strain rates, and proposed precursory phenomena. Improved methods to test the performance of forecasting models are in development.

Contributions regarding all aspects of models designed to forecast earthquake occurrence in time and/or space are encouraged, and reports on the application of forecasts to inform the public or in support of earthquake countermeasures planning are welcome; articles on modern approaches to seismic hazard assessment and mitigation are also desired.

Prof. Dr. Alexey Dm. Zavyalov
Dr. Eleftheria E. Papadimitriou
Guest Editors

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Editorial

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2 pages, 165 KiB  
Editorial
Special Issue on Comprehensive Research in Earthquake Forecasting and Seismic Hazard Assessment
Appl. Sci. 2023, 13(20), 11564; https://doi.org/10.3390/app132011564 - 23 Oct 2023
Viewed by 554
Abstract
Dear Colleagues, [...] Full article

Research

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14 pages, 7092 KiB  
Article
Spatial Correlations of Global Seismic Noise Properties
Appl. Sci. 2023, 13(12), 6958; https://doi.org/10.3390/app13126958 - 08 Jun 2023
Cited by 2 | Viewed by 1333
Abstract
A study of global seismic noise during 1997–2022 was carried out. A property of waveforms known as the Donoho–Johnston (DJ) index was used, which separates the values of the wavelet coefficients into “small” and “large”. For each reference point in an auxiliary network [...] Read more.
A study of global seismic noise during 1997–2022 was carried out. A property of waveforms known as the Donoho–Johnston (DJ) index was used, which separates the values of the wavelet coefficients into “small” and “large”. For each reference point in an auxiliary network of 50 points, a time series was calculated with a time step of one day for the median of the values at the five nearest stations. In a moving time window of 365 days, correlations between the index values at the reference points were calculated. A decrease in the average values of the DJ-index and an increase in correlations were interpreted as a sign of an increase in global seismic danger. After 2011, there was a sharp increase in the maximum distances between reference points with large correlations. The high amplitude of the response of the DJ-index to the length of the day for 2020–2022 could predict a strong earthquake in the second half of 2023. The purpose of this study was to improve the mathematical apparatus for assessing the current seismic hazard according to the properties of seismic noise. Full article
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13 pages, 490 KiB  
Article
Incorporating Foreshocks in an Epidemic-like Description of Seismic Occurrence in Italy
Appl. Sci. 2023, 13(8), 4891; https://doi.org/10.3390/app13084891 - 13 Apr 2023
Cited by 4 | Viewed by 762
Abstract
The Epidemic Type Aftershock Sequence (ETAS) model is a widely used tool for cluster analysis and forecasting, owing to its ability to accurately predict aftershock occurrences. However, its capacity to explain the increase in seismic activity prior to large earthquakes—known as foreshocks—has been [...] Read more.
The Epidemic Type Aftershock Sequence (ETAS) model is a widely used tool for cluster analysis and forecasting, owing to its ability to accurately predict aftershock occurrences. However, its capacity to explain the increase in seismic activity prior to large earthquakes—known as foreshocks—has been called into question due to inconsistencies between simulated and experimental catalogs. To address this issue, we introduce a generalization of the ETAS model, called the Epidemic Type Aftershock Foreshock Sequence (ETAFS) model. This model has been shown to accurately describe seismicity in Southern California. In this study, we demonstrate that the ETAFS model is also effective in the Italian catalog, providing good agreement with the instrumental Italian catalogue (ISIDE) in terms of not only the number of aftershocks, but also the number of foreshocks—where the ETAS model fails. These findings suggest that foreshocks cannot be solely explained by cascades of triggered events, but can be reasonably considered as precursory phenomena reflecting the nucleation process of the main event. Full article
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11 pages, 2667 KiB  
Article
The 2022 Seismic Sequence in the Northern Adriatic Sea and Its Long-Term Simulation
Appl. Sci. 2023, 13(6), 3746; https://doi.org/10.3390/app13063746 - 15 Mar 2023
Cited by 1 | Viewed by 903
Abstract
We studied the long-term features of earthquakes caused by a fault system in the northern Adriatic sea that experienced a series of quakes beginning with two main shocks of magnitude 5.5 and 5.2 on 9 November 2022 at 06:07 and 06:08 UTC, respectively. [...] Read more.
We studied the long-term features of earthquakes caused by a fault system in the northern Adriatic sea that experienced a series of quakes beginning with two main shocks of magnitude 5.5 and 5.2 on 9 November 2022 at 06:07 and 06:08 UTC, respectively. This offshore fault system, identified through seismic reflection profiles, has a low slip rate of 0.2–0.5 mm/yr. As the historical record spanning a millennium does not extend beyond the inter-event time for the largest expected earthquakes (M6.5), we used an earthquake simulator to generate a 100,000-year catalogue with 121 events of Mw5.5. The simulation results showed a recurrence time (Tr) increasing from 800 yrs to 1700 yrs as the magnitude threshold increased from 5.5 to 6.5. However, the standard deviation σ of inter-event times remained at a stable value of 700 yrs regardless of the magnitude threshold. This means that the coefficient of variation (Cv=σ/Tr) decreased from 0.9 to 0.4 as the threshold magnitude increased from 5.5 to 6.5, making earthquakes more predictable over time for larger magnitudes. Our study supports the use of a renewal model for seismic hazard assessment in regions of moderate seismicity, especially when historical catalogues are not available. Full article
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12 pages, 6758 KiB  
Article
Evidencing Fluid Migration of the Crust during the Seismic Swarm by Using 1D Magnetotelluric Monitoring
Appl. Sci. 2023, 13(4), 2683; https://doi.org/10.3390/app13042683 - 19 Feb 2023
Cited by 3 | Viewed by 1244
Abstract
We applied multi–temporal 1D magnetotelluric (MT) surveys to identify space–time anomalies of apparent resistivity (ρa) in the upper lithosphere in the Antarctic Peninsula (the border between the Antarctic and the Shetland plates). We used time series over several weeks of [...] Read more.
We applied multi–temporal 1D magnetotelluric (MT) surveys to identify space–time anomalies of apparent resistivity (ρa) in the upper lithosphere in the Antarctic Peninsula (the border between the Antarctic and the Shetland plates). We used time series over several weeks of the natural Earth’s electric and magnetic fields registered at one MT station of the Universidad Nacional de Colombia (RSUNAL) located at Seymour–Marambio Island, Antarctica. We associated resistivity anomalies with contrasting earthquake activity. Anomalies of ρa were detected almost simultaneously with the beginning of a seismic crisis in the Bransfield Strait, south of King George Island (approximately 85.000 events were reported close to the Orca submarine volcano, with focal depths < 20 km and MWW < 6.9). We explained the origin of these anomalies in response to fluid migration near the place of the fractures linked with the seismic swarm, which could promote disturbances of the pore pressure field that reached some hundreds of km away. Full article
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18 pages, 3985 KiB  
Article
A Non-Extensive Statistical Physics View of the Temporal Properties of the Recent Aftershock Sequences of Strong Earthquakes in Greece
Appl. Sci. 2023, 13(3), 1995; https://doi.org/10.3390/app13031995 - 03 Feb 2023
Cited by 3 | Viewed by 1124
Abstract
Greece is one of Europe’s most seismically active areas. Seismic activity in Greece has been characterized by a series of strong earthquakes with magnitudes up to Mw = 7.0 over the last five years. In this article we focus on these strong [...] Read more.
Greece is one of Europe’s most seismically active areas. Seismic activity in Greece has been characterized by a series of strong earthquakes with magnitudes up to Mw = 7.0 over the last five years. In this article we focus on these strong events, namely the Mw6.0 Arkalochori (27 September 2021), the Mw6.3 Elassona (3 March 2021), the Mw7.0 Samos (30 October 2020), the Mw5.1 Parnitha (19 July 2019), the Mw6.6 Zakynthos (25 October 2018), the Mw6.5 Kos (20 July 2017) and the Mw6.1 Mytilene (12 June 2017) earthquakes. Based on the probability distributions of interevent times between the successive aftershock events, we investigate the temporal evolution of their aftershock sequences. We use a statistical mechanics model developed in the framework of Non-Extensive Statistical Physics (NESP) to approach the observed distributions. NESP provides a strictly necessary generalization of Boltzmann–Gibbs statistical mechanics for complex systems with memory effects, (multi)fractal geometries, and long-range interactions. We show how the NESP applicable to the temporal evolution of recent aftershock sequences in Greece, as well as the existence of a crossover behavior from power-law (q ≠ 1) to exponential (q = 1) scaling for longer interevent times. The observed behavior is further discussed in terms of superstatistics. In this way a stochastic mechanism with memory effects that can produce the observed scaling behavior is demonstrated. To conclude, seismic activity in Greece presents a series of significant earthquakes over the last five years. We focus on strong earthquakes, and we study the temporal evolution of aftershock sequences of them using a statistical mechanics model. The non-extensive parameter q related with the interevent times distribution varies between 1.62 and 1.71, which suggests a system with about one degree of freedom. Full article
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12 pages, 3201 KiB  
Article
Space–Time Variations of the Apparent Resistivity Associated with Seismic Activity by Using 1D-Magnetotelluric (MT) Data in the Central Part of Colombia (South America)
Appl. Sci. 2023, 13(3), 1737; https://doi.org/10.3390/app13031737 - 29 Jan 2023
Cited by 3 | Viewed by 1273
Abstract
In this work, we apply multi-temporal 1D-magnetotelluric (MT) surveys to estimate the space–time variations of the apparent resistivity ρa and correlate these changes with seismic activity in the central part of Colombia (South America). We use the time series of the Earth’s [...] Read more.
In this work, we apply multi-temporal 1D-magnetotelluric (MT) surveys to estimate the space–time variations of the apparent resistivity ρa and correlate these changes with seismic activity in the central part of Colombia (South America). We use the time series of the Earth’s natural electric and magnetic fields registered at two MT stations of the National University of Colombia Seismological Network (RSUNAL), located in the Eastern Andean Cordillera, in the central part of Colombia, over several days. Assuming that large earthquakes may generate these types of anomalies, we identified positive results for the Mesetas earthquake (Mw6.0, Lon = 74.184° W, Lat = 3.462° N, H = 13 km-depth, 24 December 2019, UTC 19:03:55), with anomalies registered eight hours before the mainshock. The depth at which the resistivity anomaly was identified coincides with the depth of the earthquake hypocenter. The origin of these anomalies may be associated with the migration of fluids due to the change in the stress regime before, during, and after the earthquake. We hypothesize that before the occurrence of an earthquake, the stress field generates pore pressure gradients, promoting alterations in fluid migration that change the resistivity of the upper crust. Full article
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14 pages, 2521 KiB  
Article
Modeling Locations with Enhanced Earth’s Crust Deformation during Earthquake Preparation near the Kamchatka Peninsula
Appl. Sci. 2023, 13(1), 290; https://doi.org/10.3390/app13010290 - 26 Dec 2022
Cited by 3 | Viewed by 1052
Abstract
In seismically active regions of the Earth, to which the Kamchatka peninsula refers, pre-seismic anomalies are recorded in different geophysical fields. One of such fields is the acoustic emission of rocks, the anomalies of which are recorded 1–3 days before earthquakes at the [...] Read more.
In seismically active regions of the Earth, to which the Kamchatka peninsula refers, pre-seismic anomalies are recorded in different geophysical fields. One of such fields is the acoustic emission of rocks, the anomalies of which are recorded 1–3 days before earthquakes at the distance of the first hundreds of kilometers from their epicenters. Results of joint acoustic-deformation measurements showed that growth of geoacoustic radiation intensity occurs during the increase in the level of deformations in rock masses by more than one order compared to the background values. Simulation studies of the areas with increased deformation are realized to understand the causes of anomalous acoustic-deformation disturbance occurrences before strong earthquakes. The model is based on the assumption that the Earth’s crust in the first approximation can be considered as a homogeneous isotropic elastic half-space, and an earthquake source can be considered as a displacements along a rectangular fault plane. Based on these assumptions, deformation regions of Earth’s crust were modeled during the preparations of two earthquakes with local magnitudes ML5 occurred on the Kamchatka Peninsula in 2007 and 2009. The simulation results were compared for the first time with the data of a laser strainmeter-interferometer installed at the Karymshina observation site (52.83 N, 158.13 E). It was shown that, during the preparation of the both earthquakes, the Karymshina observation site was within the region of shear deformations ≈107, which exceeded the tidal ones by an order. On the whole, simulation results corresponded to the results of the natural observations. Construction of an adequate model for the generation of acoustic-deformation disturbances before strong earthquakes is topical for the development of an early notification system on the threat of catastrophic natural events. Full article
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22 pages, 4323 KiB  
Article
Probabilistic and Scenario-Based Seismic Hazard Assessment on the Western Gulf of Corinth (Central Greece)
Appl. Sci. 2022, 12(21), 11152; https://doi.org/10.3390/app122111152 - 03 Nov 2022
Cited by 5 | Viewed by 2233
Abstract
The Gulf of Corinth (Central Greece) is one of the most rapidly extending rifts worldwide, with its western part being the most seismically active, hosting numerous strong (M ≥ 6.0) earthquakes that have caused significant damage. The main objective of this study was [...] Read more.
The Gulf of Corinth (Central Greece) is one of the most rapidly extending rifts worldwide, with its western part being the most seismically active, hosting numerous strong (M ≥ 6.0) earthquakes that have caused significant damage. The main objective of this study was the evaluation of seismic hazard through a probabilistic and stochastic methodology. The implementation of three seismotectonic models in the form of area source zones via a logic tree framework revealed the expected level of peak ground acceleration and velocity for return periods of 475 and 950 years. Moreover, PGA values were obtained through the stochastic simulation of strong ground motion by adopting worst-case seismic scenarios of potential earthquake occurrences for known active faults in the area. Site-specific analysis of the most populated urban areas (Patras, Aigion, Nafpaktos) was performed by constructing uniform hazard spectra in terms of spectral acceleration. The relative contribution of each selected fault segment to the seismic hazard characterizing each site was evaluated through response spectra obtained for the adopted scenarios. Almost all parts of the study area were found to exceed the reference value proposed by the current Greek National Building Code; however, the three urban areas are covered by the Eurocode 8 regulations. Full article
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16 pages, 1561 KiB  
Article
On the Omori Law in the Physics of Earthquakes
Appl. Sci. 2022, 12(19), 9965; https://doi.org/10.3390/app12199965 - 04 Oct 2022
Cited by 3 | Viewed by 2332
Abstract
This paper proposes phenomenological equations that describe various aspects of aftershock evolution: elementary master equation, logistic equation, stochastic equation, and nonlinear diffusion equation. The elementary master equation is a first-order differential equation with a quadratic term. It is completely equivalent to Omori’s law. [...] Read more.
This paper proposes phenomenological equations that describe various aspects of aftershock evolution: elementary master equation, logistic equation, stochastic equation, and nonlinear diffusion equation. The elementary master equation is a first-order differential equation with a quadratic term. It is completely equivalent to Omori’s law. The equation allows us to introduce the idea of proper time of earthquake source “cooling down” after the main shock. Using the elementary master equation, one can pose and solve an inverse problem, the purpose of which is to measure the deactivation coefficient of an earthquake source. It has been found for the first time that the deactivation coefficient decreases with increasing magnitude of the main shock. The logistic equation is used to construct a phase portrait of a dynamical system simulating the evolution of aftershocks. The stochastic equation can be used to model fluctuation phenomena, and the nonlinear diffusion equation provides a framework for understanding the spatiotemporal distribution of aftershocks. Earthquake triads, which are a natural trinity of foreshocks, main shock, and aftershocks, are considered. Examples of the classical triad, the mirror triad, the symmetrical triad, as well as the Grande Terremoto Solitario, which can be considered as an anomalous symmetrical triad, are given. Prospects for further development of the phenomenology of earthquakes are outlined. Full article
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18 pages, 7045 KiB  
Article
Variability in the Statistical Properties of Continuous Seismic Records on a Network of Stations and Strong Earthquakes: A Case Study from the Kamchatka Peninsula, 2011–2021
Appl. Sci. 2022, 12(17), 8658; https://doi.org/10.3390/app12178658 - 29 Aug 2022
Cited by 3 | Viewed by 1487
Abstract
A study of spatiotemporal variability and synchronization effects in continuous seismic records (seismic noise) on a network of 21 broadband seismic stations on the Kamchatka Peninsula was carried out in connection with the occurrence of strong earthquakes, M = 7.2–8.3. Data of 1-min [...] Read more.
A study of spatiotemporal variability and synchronization effects in continuous seismic records (seismic noise) on a network of 21 broadband seismic stations on the Kamchatka Peninsula was carried out in connection with the occurrence of strong earthquakes, M = 7.2–8.3. Data of 1-min registrations of the vertical movements velocity Earth’s surface were used for constructing time series of daily values of the generalized Hurst exponent α*, singularity spectrum support width ∆α, wavelet-based spectral exponent β, and minimum normalized entropy of squared orthogonal wavelet coefficients En for all stations during the observation period 2011–2021. Averaged maps and time-frequency diagrams of the spectral measure of four noise parameters’ coherent behavior were constructed using data from the entire network of stations and by groups of stations taking into account network configuration, volcanic activity and coastal sea waves. Based on the distribution maps of noise parameters, it was found that strong earthquakes arose near extensive areas of the minimum values of α*, ∆α, β, and the En maximum values advance manifestation during several years. The time-frequency diagrams revealed increased amplitudes of the spectral measure of the coherent behavior of the 4-dimensional time series (synchronization effects) before three earthquakes with Mw = 7.5–8.3 over months to about one year according to observations from the entire network of stations, as well as according to data obtained at groups of continental and non-volcanic stations. A less-pronounced manifestation of coherence effects diagrams plotted from data obtained at coastal and volcanic groups of stations and is apparently associated with the noisiness in seismic records caused by coastal waves and signals of modern volcanic activity. The considered synchronization effects correspond to the author’s conceptual model of seismic noise behavior in preparation of strong earthquakes and data from other regions and can also be useful for medium-term estimates of the place and time of seismic events with Mw ≥ 7.5 in the Kamchatka. Full article
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18 pages, 5321 KiB  
Article
Statistical and Comparative Analysis of Multi-Channel Infrared Anomalies before Earthquakes in China and the Surrounding Area
Appl. Sci. 2022, 12(16), 7958; https://doi.org/10.3390/app12167958 - 09 Aug 2022
Cited by 2 | Viewed by 1165
Abstract
Abundant infrared remote sensing images and advanced information processing technologies are used to predict earthquakes. However, most studies only use single long-wave infrared data or its products, and the accuracy of prediction is not high enough. To solve this problem, this paper proposes [...] Read more.
Abundant infrared remote sensing images and advanced information processing technologies are used to predict earthquakes. However, most studies only use single long-wave infrared data or its products, and the accuracy of prediction is not high enough. To solve this problem, this paper proposes a statistical method based on connected domain recognition to analyze multi-channel anomalies. We extract pre-seismic anomalies from multi-channel infrared remote sensing images using the relative power spectrum, then calculate positive predictive values, true positive rates and probability gains in different channels. The results show that the probability gain of the single-channel prediction method is extremely low. The positive predictive value of four-channel anomalies is 41.94%, which is higher than that of single-channel anomalies with the same distance threshold of 200 km. The probability gain of the multi-channel method is 2.38, while that of the single-channel method using the data of any channel is no more than 1.26. This study shows the advantages of the multi-channel method to predict earthquakes and indicates that it is feasible to use multi-channel infrared remote sensing images to improve the accuracy of earthquake prediction. Full article
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32 pages, 19153 KiB  
Article
Analyzing the Correlations and the Statistical Distribution of Moderate to Large Earthquakes Interevent Times in Greece
Appl. Sci. 2022, 12(14), 7041; https://doi.org/10.3390/app12147041 - 12 Jul 2022
Cited by 3 | Viewed by 1294
Abstract
Seismic temporal properties constitute a fundamental component in developing probabilistic models for earthquake occurrence in a specific area. Earthquake occurrence is neither periodic nor completely random but often accrues into bursts in both short- and long-term time scales, and involves a complex summation [...] Read more.
Seismic temporal properties constitute a fundamental component in developing probabilistic models for earthquake occurrence in a specific area. Earthquake occurrence is neither periodic nor completely random but often accrues into bursts in both short- and long-term time scales, and involves a complex summation of triggered and independent events (ΔT). This behavior underlines the impact of the correlations on many potential applications such as the stochastic point process for the earthquake interevent times. In this respect, we intend firstly to determine the appropriate magnitude thresholds, Mthr, indicating the temporal crossover between correlated and statistically independent earthquakes in each 1 of the 10 distinctive sub-areas of the Aegean region. The second goal is the investigation of the statistical distribution that optimally fits the interevent times’ data for earthquakes with MMthr after evaluating the Gamma, Weibull, Lognormal and Exponential distributions performance. Results concerning the correlations analysis evidenced that the temporal crossover of the earthquake interevent time data ranges from Mthr 4.7 up to Mthr 5.1 among the 10 sub-areas. The distribution fitting and comparison reveals that the Gamma distribution outperforms the other three distributions for all the data sets. This finding indicates a burst or clustering behavior in the earthquake interevent times, in which each earthquake occurrence depends upon only the occurrence time of the last one and not from the full seismic history. Full article
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13 pages, 1613 KiB  
Article
Preliminary Study on the Generating Mechanism of the Atmospheric Vertical Electric Field before Earthquakes
Appl. Sci. 2022, 12(14), 6896; https://doi.org/10.3390/app12146896 - 07 Jul 2022
Cited by 2 | Viewed by 1608
Abstract
Precursor signals for earthquakes, such as radon anomalies, thermal anomalies, and water level changes, have been studied in earthquake prediction over several centuries. The atmospheric vertical electric field anomaly has been observed in recent years as a new and valuable signal for short-term [...] Read more.
Precursor signals for earthquakes, such as radon anomalies, thermal anomalies, and water level changes, have been studied in earthquake prediction over several centuries. The atmospheric vertical electric field anomaly has been observed in recent years as a new and valuable signal for short-term earthquake prediction. In this paper, a physical mechanism of the atmospheric vertical electric field anomaly before the earthquake was proposed, based on which the Wenchuan earthquake verified the correctness of the model. Using Monte Carlo simulations, the variation of the radon concentration with height before the earthquake was used to simulate and calculate the ionization rates of radioactive radon decay products at different heights. We derived the atmospheric vertical electric field from −593 to −285 V/m from the surface to 10 m before the earthquake by solving the system of convection-diffusion partial equations for positive and negative particles. Moreover, negative atmospheric electric field anomalies were observed in both Wenjiang and Pixian before the Wenchuan earthquake on 12 May, with peaks of −600 V/m in Pixian and −200 V/m in Wenjiang. The atmospheric electric field data obtained from the simulation were shown to be in excellent concordance with the observed data of the Wenchuan earthquake. The physical mechanism can provide theoretical support for the atmospheric electric field anomaly as an earthquake precursor. Full article
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18 pages, 5140 KiB  
Article
How Useful Are Strain Rates for Estimating the Long-Term Spatial Distribution of Earthquakes?
Appl. Sci. 2022, 12(13), 6804; https://doi.org/10.3390/app12136804 - 05 Jul 2022
Cited by 4 | Viewed by 1913
Abstract
Strain rates have been included in multiplicative hybrid modelling of the long-term spatial distribution of earthquakes in New Zealand (NZ) since 2017. Previous modelling has shown a strain rate model to be the most informative input to explain earthquake locations over a fitting [...] Read more.
Strain rates have been included in multiplicative hybrid modelling of the long-term spatial distribution of earthquakes in New Zealand (NZ) since 2017. Previous modelling has shown a strain rate model to be the most informative input to explain earthquake locations over a fitting period from 1987 to 2006 and a testing period from 2012 to 2015. In the present study, three different shear strain rate models have been included separately as covariates in NZ multiplicative hybrid models, along with other covariates based on known fault locations, their associated slip rates, and proximity to the plate interface. Although the strain rate models differ in their details, there are similarities in their contributions to the performance of hybrid models in terms of information gain per earthquake (IGPE). The inclusion of each strain rate model improves the performance of hybrid models during the previously adopted fitting and testing periods. However, the hybrid models, including strain rates, perform poorly in a reverse testing period from 1951 to 1986. Molchan error diagrams show that the correlations of the strain rate models with earthquake locations are lower over the reverse testing period than from 1987 onwards. Smoothed scatter plots of the strain rate covariates associated with target earthquakes versus time confirm the relatively low correlations before 1987. Moreover, these analyses show that other covariates of the multiplicative models, such as proximity to the plate interface and proximity to mapped faults, were better correlated with earthquake locations prior to 1987. These results suggest that strain rate models based on only a few decades of available geodetic data from a limited network of GNSS stations may not be good indicators of where earthquakes occur over a long time frame. Full article
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