Recurrence Time Of Earthquakes Research Articles

Review and Update on Some Connections between a Spring-Block SOC Model and Actual Seismicity in the Case of Subduction Zones.

The self-organized critical (SOC) spring-block models are accessible and powerful computational tools for the study of seismic subduction. This work aims to highlight some important findings through an integrative approach of several actual seismic properties, reproduced by using the Olami, Feder, and Christensen (OFC) SOC model and some variations of it. A few interesting updates are also included. These results encompass some properties of the power laws present in the model, such as the Gutenberg-Richter (GR) law, the correlation between the parameters a and b of the linear frequency-magnitude relationship, the stepped plots for cumulative seismicity, and the distribution of the recurrence times of large earthquakes. The spring-block model has been related to other relevant properties of seismic phenomena, such as the fractal distribution of fault sizes, and can be combined with the work of Aki, who established an interesting relationship between the fractal dimension and the b-value of the Gutenberg-Richter relationship. Also included is the work incorporating the idea of asperities, which allowed us to incorporate several inhomogeneous models in the spring-block automaton. Finally, the incorporation of a Ruff-Kanamori-type diagram for synthetic seismicity, which is in reasonable accordance with the original Ruff and Kanamori diagram for real seismicity, is discussed.

A Continuous 13.3-Ka Paleoseismic Record Constrains Major Earthquake Recurrence in the Longmen Shan Collision Zone

Thrust collision zones with low slip rates along the plate boundary are significant areas of stress accumulation and prone to develop more destructive earthquakes with longer recurrence intervals. Such regions are often classified as low seismic risk if they lack continuous records of large earthquakes, such as the eastern Tibetan Plateau before the 2008 Mw 7.9 Wenchuan earthquake. Here, we provide a continuous seismic record in the Longmen Shan thrust fault zone spanning 13,000 years based on detailed investigation of the soft-sediment deformation structures and seismites in the Lixian lacustrine sequence. The recurrence time of large earthquakes (M ≥ 8.1) is 1,200 years, which is significantly shorter than the previous estimate of 2,000–6,000 years. The Maoxian-Wenchuan fault is the main fault that triggered the deformation in the Lixian lacustrine sediments. In addition, earthquake recurrence in the warm period is more frequent than that in the cold period, which should arouse our attention for the seismic study of tectonically active regions.

High resolution morphometric analysis of the Cordone del Vettore normal fault scarp (2016 central Italy seismic sequence): Insights into age, earthquake recurrence and throw rates

We investigated the late Quaternary throw distribution of the main normal fault that ruptured during the Mw 6.5 2016 earthquake in central Italy by means of a high-resolution structure-from-motion (SfM)-derived Digital Surface Model (DSM). We focused on a key area along the Cordone del Vettore fault (CDV), which is part of the Vettore-Bove fault system (VBFS). The CDV displays a prominent compound post-glacial scarp that allowed the reconstruction of the along-strike cumulative throw distribution. We propose a geometric approach to calculate the CDV fault throw distribution from the reconstruction of a displaced glaciation-related erosional surface, used as a geomorphic marker, and a series of closely spaced cross profiles. The proposed calculation accounts for both the slip vector direction and the degraded scarp top, including field data on fault dip angles. Following this approach, we recognized two scarps with a minimum average fault throw of ~21 m and ~35 m for this section of the investigated fault strand.The correlation with the possible post-LGM (Last Glacial Maximum) deglaciation phases of the erosional surface suggests a minimum scarp age of 25–27 ka cal BP. Such an age provides a reasonable CDV fault throw rate of ~0.8 mm/a, comparable with known long-term throw rates of the VBFS and active Apennines normal faults. By comparing the reconstructed long-term Cordone del Vettore throw distribution with the 2016 coseismic one, ~24 2016-like surface faulting events are required to generate the main cumulative scarp, under the assumption of constant slip per event. This, along with the age of the scarp, yields an average earthquake recurrence time interval of ~1100 a. These results suggest the presence of multiple regional markers that correlates with different LGM (if not pre-LGM) major glacial phases, whose erosional processes allow the preservation of pre-existing bedrock fault scarp remnants.

Modelling the large earthquakes recurrence times along the North Aegean Trough Fault Zone (Greece) with a physics-based simulator

SUMMARYThe recurrence time of large earthquakes above a predefined magnitude threshold on specific faults or fault segments is one of the key parameters for the development of long-term Earthquake Rupture Forecast models. Observational data of successive large earthquakes per fault segment are often limited and thus inadequate for the construction of robust statistical models. The physics-based earthquake simulators are a powerful tool to overcome recurrence data limitations by generating long earthquake records. A physics-based simulator, embodying well known physical processes, is applied in the North Aegean Trough (NAT) Fault Zone (Greece). The application of the simulation is implemented, after defining a five segment source model, aiming at the investigation of the recurrence behaviour of earthquakes with Mw ≥ 6.5 and Mw ≥ 7.0. The detailed examination of the 544 Mw ≥ 6.5 earthquakes included in the simulated catalogue reveals that both single and multiple segmented ruptures can be realized along the NAT. Results of statistical analysis of the interevent times of Mw ≥ 6.5 and Mw≥ 7.0 earthquakes per participating segment to the related ruptures indicate the better performance of the Brownian Passage Time renewal model in comparison to exponential model. These results provide evidence for quasi-periodic recurrence behaviour, agreeing with the elastic rebound theory, instead of Poissonian behaviour.

Probabilistic modeling and predicting mean recurrence time of major earthquakes in Bangladesh

Probabilistic modeling and predicting mean recurrence time of major earthquakes in Bangladesh

Micro- and nano-porosity of the active Alpine Fault zone, New Zealand

Abstract. Porosity reduction in rocks from a fault core can cause elevated pore fluid pressures and consequently influence the recurrence time of earthquakes. We investigated the porosity distribution in the New Zealand's Alpine Fault core in samples recovered during the first phase of the Deep Fault Drilling Project (DFDP-1B) by using two-dimensional nanoscale and three-dimensional microscale imaging. Synchrotron X-ray microtomography-derived analyses of open pore spaces show total microscale porosities in the range of 0.1 %–0.24 %. These pores have mainly non-spherical, elongated, flat shapes and show subtle bipolar orientation. Scanning and transmission electron microscopy reveal the samples' microstructural organization, where nanoscale pores ornament grain boundaries of the gouge material, especially clay minerals. Our data imply that (i) the porosity of the fault core is very small and not connected; (ii) the distribution of clay minerals controls the shape and orientation of the associated pores; (iii) porosity was reduced due to pressure solution processes; and (iv) mineral precipitation in fluid-filled pores can affect the mechanical behavior of the Alpine Fault by decreasing the already critically low total porosity of the fault core, causing elevated pore fluid pressures and/or introducing weak mineral phases, and thus lowering the overall fault frictional strength. We conclude that the current state of very low porosity in the Alpine Fault core is likely to play a key role in the initiation of the next fault rupture.

Frictional Strengthening Explored During Non‐Steady State Shearing: Implications for Fault Stability and Slip Event Recurrence Time

AbstractOn natural faults that host repeating slip events, the inter‐event loading time is quite large compared to the slip event duration. Since most friction studies focus on steady‐state frictional behavior, the fault loading phase is not typically examined. Here, we employ a method specifically designed to evaluate fault strength evolution during active loading, under shear driving rates as low as 10−10 m/s, on natural fault gouge samples from the Waikukupa Thrust in southern New Zealand. These tests reveal that in the early stages of loading following a slip event, there is a period of increased stability, which fades with accumulated slip. In the framework of rate‐ and state‐dependent friction laws, this temporary stable phase exists as long as slip is less than the critical slip distance and the elapsed time is less than the value of the state variable at steady state. These observations indicate a minimum earthquake recurrence time, which depends on the field value of the critical slip distance and the background slip rate. We compare estimates of minimum earthquake recurrence times with the recurrence times of repeating large earthquakes on the Alpine Fault in southern New Zealand and repeating small‐magnitude earthquakes on the San Andreas Fault system in California. We find that the observed recurrence times are mostly longer than the predicted minimum values, and exceptions in the San Andreas system may be explained by elevated slip rates due to larger earthquakes in this region.

Different probabilistic models for earthquake occurrences along the North and East Anatolian fault zones

Turkey is bounded by the two of the most active fault zones: the North Anatolian Fault Zone (NAFZ) and the East Anatolian Fault Zone (EAFZ). Therefore, Turkey has experienced several great earthquakes (M > 7.0) in these fault zones. These earthquakes caused huge devastation on buildings and roads as a result of landslides and liquefaction. Because of these huge effects, we aim to evaluate earthquake hazards by calculating the conditional probability of an earthquake with three probabilistic models (Weibull, gamma, and lognormal) in three selected regions along the NAFZ and EAFZ. For this purpose, the model parameters were calculated by using maximum likelihood estimates from the earthquake (Mw ≥ 5.5) recurrence times that occurred between 1900 and 2016 in the study regions. The fitting of model and data were tested with the log-likelihood value, Akaike information criterion, and the Kolmogorov-Smirnov minimum distance criterion. The lognormal model is the best-fit model for three regions according to the Kolmogorov-Smirnov distance criterion while the gamma is the best for region 3 according to the other two test criteria. The gamma model gives the highest probability value (> 0.80) for all regions, and lognormal results reach the values > 0.90 for region 1 (t = 0, τ = 11), for region 2 (t = 0, τ = 7), and for region 3 (t = 0, τ = 11). These results indicated that the short-time-period earthquake probabilities are high in the study regions. On the other hand, this study will be very useful for assessing the seismic risk and constituting the disaster mitigation plans of the study regions.

Gutenberg–Richter’s b Value and Earthquake Asperity Models

The Gutenberg–Richter (G–R) relationship can be derived as the Gibbs distribution. For a given earthquake set (all earthquakes in a given region, time period, magnitude range, tectonic settings) the Gibbs probability density function for magnitudes, with a given b value in its exponent, is the most uniform distribution under the constraints of the magnitude range and mean value. Therefore, it represents our limited knowledge about the system output: the only pieces of information are the mean value and the magnitude range. Honest earthquake forecasts can be based on such a distribution, since it represents all and only available information about the seismic system. The b value can change among different earthquake sets (in time, space, magnitude ranges, or tectonic settings), since it is related to earthquake rupture dynamics, or seismic source characteristics. The relationship between the b value and the exponent $$\beta$$ in the rupture area vs. maximum slip scaling, $$A\propto D^{\beta }$$, results from viewing earthquake recurrence time in connection with the slip budget. This makes a link between earthquake statistics (the G–R law) and physics (fault characteristics). Specifically, the relationship enables us to explain different ranges of b values at megathrust faults, in dependence on interplate asperity and coupling distributions, as well as on amounts of sediments and fluids in subduction channels. The approach differs from common interpretations of the G–R law in that the b value becomes a field variable, not a constant. It is always the Gibbs distribution for a given magnitude range that we use due to our ignorance about the system outcome, and it is the b value that variates, depending on our knowledge about the system physics. This is important for seismic forecasts, which are mostly based on the G–R relationship. First, because the physical processes leading to the largest earthquakes can be revealed by observing the b value variations. Second, because earthquake generation process can be thought of as sampling with constraints, where the b value and the magnitude range are the constraints.

Tsunami deposits refine great earthquake rupture extent and recurrence over the past 1300 years along the Nankai and Tokai fault segments of the Nankai Trough, Japan

Study of prehistoric to medieval-age tsunami deposits along a riverbank site near the eastern Nankai Trough, central Japan, show that, not only did Tokai earthquakes occur with a higher frequency than previously thought, but that contemporaneous ruptures of the Tokai and Nankai fault segments were also more common. The site revealed a ∼1-km long coast-normal cross section of the strand plain and exposed four sandy tsunami deposits, each of which indicates inundation over 2 km inland of the coast. Radiocarbon dating of previously studied and newly discovered deposits in the region indicates a shorter recurrence time for Tokai earthquakes and clarifies their linkage with Nankai earthquakes. We attribute the younger two tsunami deposits to the 1498 and 1096 CE Tokai earthquakes. The older two deposits confirm the occurrence of the Tokai earthquakes in 887 CE and in the latest 7th century. These events are not reliably recorded in historical documents in the Tokai region but were noted in the Nankai area. The 887 CE earthquake likely represents a full-length rupture of the Tokai and Nankai segments, as was the case for the 1707 CE earthquake. Integrated with the previous studies, these new results show that nine Tokai earthquakes occurred over the last 1300 years, the oldest in the latest 7th century, and in 887, 1096, 1361, 1498, 1614, 1707, 1854 and 1944 CE. Recalculated recurrence intervals range from 90 to 265 years. Except for the 1498 Meio Tokai earthquake, the Tokai earthquakes occurred simultaneously with Nankai earthquakes.

Contemporary deformation and seismicity analysis in Southwest Japan during 2010–2018 based on GNSS measurements

A significant amount of work has been conducted in the Japanese islands on high-precision positioning, surveying, natural disaster mitigation, reference frame, and datum definitions; however, there is substantial scope for exploring the current seismotectonic activity of Japan, which would provide further awareness of disaster management. The short recurrence time of great inter-plate earthquakes and well-recorded geodetic observations provide one of the best examples to analyze the combination of contemporary deformation and seismic intensity in Southwest (SW) Japan. In the current study, we analyzed three districts of SW Japan which include mainly Kyushu district and parts of Chugoku and Shikoku districts. We predicted Global Navigation Satellite System (GNSS) measurements based on Amurian-fixed reference frame (AREF) velocities with the help of singular spectrum analysis (SSA) method and examined the regional deformation from April 01, 2010 to December 31, 2018. In addition, we analyzed the earthquakes clustered calculated by the nearest neighborhood distance method, which showed prominently bimodal seismicity of SW Japan and revealed the existence of two statistically distinct earthquake populations. The events inside a cluster were normally close to their nearest neighbors, whereas events from distinct clusters were comparatively aloof from each other. Finally, the paper provides the spatial strain and rotational rate variation for selected seismotectonic districts that are in relatively good agreement with the seismic deformation inferred from earthquake focal mechanisms. We believe that our integrated approaches would provide a better insight into the active deformation of SW Japan.

Evaluating earthquake-induced rockfall hazard near the Dead Sea Transform

Abstract. We address an approach for rockfall hazard evaluation where the study area resides below a cliff in an a priori exposure to rockfall hazard, but no historical documentation of rockfall events is available and hence important rockfall hazard parameters like triggering mechanism and recurrence interval are unknown. We study the rockfall hazard for the town of Qiryat Shemona, northern Israel, situated alongside the Dead Sea Transform, at the foot of the Ramim escarpment. Numerous boulders are scattered on the slopes above the town, while pre-town historical aerial photos reveal that boulders had reached the location that is now within town limits. We use field observations and optically stimulated luminescence dating of past rockfall events combined with computer modeling to evaluate the rockfall hazard. For the analysis, we first mapped the rockfall source and final downslope stop sites and compiled the boulder size distribution. We then simulated the possible rockfall trajectories using the field observed data to calibrate the simulation software by comparing simulated and mapped boulder stop sites along selected slopes, while adjusting model input parameters for best fit. The analysis reveals areas of high rockfall hazard at the southwestern quarters of the town and also indicates that in the studied slopes falling blocks would stop where the slope angle decreases below 5–10∘. Age determination suggests that the rockfalls were triggered by large (M>6) historical earthquakes. Nevertheless, not all large historical earthquakes triggered rockfalls. Considering the size distribution of the past rockfalls in the study area and the recurrence time of large earthquakes in the region, we estimate a probability of less than 5 % to be affected by a destructive rockfall within a 50-year time window. Here we suggest a comprehensive method to evaluate rockfall hazard where only past rockfall evidence exists in the field. We show the importance of integrating spatial and temporal field observations to assess the extent of rockfall hazard, the potential block size distribution and the rockfall recurrence interval.

Re-estimate of Major Earthquake Activity in Surrounding Areas after the MS 6.6 Jinghe Earthquake in Xinjiang, 2017

According to theory, earthquakes may produce disturbances in surrounding areas and affect the major earthquake occurrence rate of surrounding faults. The MS 6.6 Jinghe Earthquake on 9th August, 2017 occurred in the Tienshan Seismic Belt where there is much tectonic activity and many strong earthquakes occur. The impact of this earthquake on major earthquake activity of surrounding areas is worth studying. This paper attempts to combine two models: the Brownian passage-time (BPT) model, which describes the quasi-periodic recurrence of major earthquakes, and the Coulomb Failure Stress model, which describes rock failure on faults. The amount of change in the rate of major earthquake occurrence caused by a nearby earthquake was calculated, and changes in major earthquake activity in the surrounding areas after the Jinghe Earthquake were re-estimated. There are few differences in major earthquake occurrence rate change by stress disturbances calculated with the BPT model or the Coulomb Failure Stress model. Calculation results are consistent with actual earthquake cases. The 2017 Jinghe Earthquake increased major earthquake activity on the Boluokenu Fault and Yili Basin North Fault, and the expected major earthquake recurrence times of the two faults were advanced by 11 years and 59 years, respectively. Conclusions of this paper provide a reference for time-dependent seismic hazard assessments in related areas.

Have we seen the largest earthquakes in eastern North America?

The assumed magnitude of the largest future earthquakes, Mmax, is crucial in assessing seismic hazard, especially for critical facilities like nuclear power plants. Estimates are made using various methods and often prove too low, as for the 2011 Tohoku, Japan, earthquake. Estimating Mmax is particularly challenging within tectonic plates, where large earthquakes are infrequent, vary in location and time, and often occur on previously unrecognized faults. For example, it is unclear whether the short historical record includes the largest possible earthquakes along the eastern continental margin of North America. We explore this issue by generating synthetic earthquake histories and sampling them over a few hundred years. Due to the short histories, the maximum magnitudes appearing most often in a sub-catalog, Mmaxa, are often smaller than the maximum magnitude in the parent catalog, Mmaxp, that can occur. Future earthquakes along the continental margin may thus be significantly larger than those observed to date. More generally, these simulations demonstrate that the largest earthquake in a catalog likely reflects a combination of catalog length, a region’s earthquake productivity, and relative proportion of small to large events. For regions with low seismicity, small variations in b value, the ratio of large to small events, due to sampling has a significant impact on the expected recurrence times of large magnitude earthquakes. Although the precise likelihood of observing Mmaxp depends on the distribution of recurrence times, a catalog shorter than an earthquake’s mean recurrence time will likely not contain an event of that size. As a result, Mmax cannot always be reliably estimated from earthquake catalogs.

Introducing stochastic recurrence interval to classification algorithms for identifying asperity patterns

The introduction of stochastic earthquake recurrence times in feature vector is attempted for the identification of asperities in the area of Hokkaido, Japan, using machine learning algorithms. Seismicity attributes, feature selection algorithms, and class balancing techniques were used. The stochastic attributes of earthquake density in space, b-value, and the earthquake recurrence intervals were set as asperity identifiers. The study area was divided into 422 subareas, and in each one of them the aforementioned attributes were estimated for each subarea. For increasing the method efficiency a feature selection algorithm was utilized to indicate which of the selected attributes have the potential to contribute to the identification of asperities. A feature vector is presented, combining the attributes mentioned above, and well-known machine learning algorithms were used to identify the asperities locations. The performance of the method was tested with the 10-fold cross-validation technique and was found sufficient in means of F1 score.

Chilean megathrust earthquake recurrence linked to frictional contrast at depth

Fundamental processes of the seismic cycle in subduction zones, including those controlling the recurrence and size of great earthquakes, are still poorly understood. Here, by studying the 2016 earthquake in southern Chile—the first large event within the rupture zone of the 1960 earthquake (moment magnitude (Mw) = 9.5)—we show that the frictional zonation of the plate interface fault at depth mechanically controls the timing of more frequent, moderate-size deep events (Mw 8.5). We model the evolution of stress build-up for a seismogenic zone with heterogeneous friction to examine the link between the 2016 and 1960 earthquakes. Our results suggest that the deeper segments of the seismogenic megathrust are weaker and interseismically loaded by a more strongly coupled, shallower asperity. Deeper segments fail earlier (~60 yr recurrence), producing moderate-size events that precede the failure of the shallower region, which fails in a great earthquake (recurrence >110 yr). We interpret the contrasting frictional strength and lag time between deeper and shallower earthquakes to be controlled by variations in pore fluid pressure. Our integrated analysis strengthens understanding of the mechanics and timing of great megathrust earthquakes, and therefore could aid in the seismic hazard assessment of other subduction zones. The recurrence time of megathrust earthquakes in Chile may be controlled by frictional contrasts at depth, according to analyses of stress build-up and release related to the December 2016 southern Chile earthquake.

Holocene Event Record of Aysén Fjord (Chilean Patagonia): An Interplay of Volcanic Eruptions and Crustal and Megathrust Earthquakes

AbstractIn the first months of 2007, the Aysén region in southern Chile was affected by a crustal seismic swarm. Its largest earthquake (Mw 6.2) occurred in April and had its epicenter in Aysén Fjord. Seismic intensities became so high that hundreds of onshore mass movements were triggered, several of which entered into the fjord, resulting in mass transport deposits (MTDs) preserved at the fjord bottom. Here we present a Holocene record of paleo‐earthquakes in the previously unstudied Patagonian fjordland based on MTD stratigraphy. High‐resolution seismic data retrieved using two different seismic systems (sparker and TOPAS) reveal multiple older MTDs on different stratigraphic levels. Correlation of the seismic stratigraphy with sedimentological data obtained from a long Calypso core (MD07‐3117) allows conclusion on the seismic origin of these deposits. Additionally, radiocarbon dating permits constructing an age model, validated by tephrochronology, providing an age for the different MTD levels. We thus present a highly detailed paleoseismological history of the Aysén region, including at least six major Holocene earthquakes, one of which is likely related to a known megathrust earthquake. Other earthquakes are related to activity of the Liquiñe‐Ofqui Fault Zone (LOFZ), forming the main source of seismic hazard in the area. We can infer a general average recurrence time for LOFZ earthquakes of ~2,100 years in the vicinity of Aysén Fjord with clustered events during the early and late Holocene. Finally, we argue that cascading events (causal link between volcanic and seismic events) may be a frequent phenomenon along the LOFZ.

Time-dependent seismic hazard analysis for the Greater Tehran and surrounding areas

This study presents a time-dependent approach for seismic hazard in Tehran and surrounding areas. Hazard is evaluated by combining background seismic activity, and larger earthquakes may emanate from fault segments. Using available historical and paleoseismological data or empirical relation, the recurrence time and maximum magnitude of characteristic earthquakes for the major faults have been explored. The Brownian passage time (BPT) distribution has been used to calculate equivalent fictitious seismicity rate for major faults in the region. To include ground motion uncertainty, a logic tree and five ground motion prediction equations have been selected based on their applicability in the region. Finally, hazard maps have been presented.

STATISTICS OF EARTHQUAKE RECURRENCE TIME IN NORTH AEGEAN TROUGH

The determination of recurrence time of strong earthquakes of certain magnitude on a specific fault or fault segment is an important component of seismic hazard assessment. The occurrence of these earthquakes is neither periodic nor completely random but often clustered in time. This fact in connection with their limited number inhibits a deterministic approach for recurrence times calculation and thus application of stochastic processes is required. For recurrence times determination in the area of North Aegean, all the available information on strong earthquakes (historical and instrumental) with M6.0 is collected. Given that source parameters of historical events contain larger uncertainties, reassessment of their focal parameters before the application of stochastic processes is necessary, which was performed by applying the method of Bakun and Wentworth (1997). The reasses sed catalogue was divided into three data sets, according to the strong events spatial distribution and their association with distinctive fault segments. Three statistical distributions (Weibull, inverse Gaussian, lognormal) were applied and evaluated with the Anderson–Darling test and the Akaike and Bayesian Information Criteria. The Weibull distribution exhibited better performance in two out of three data sets and the Inverse Gaussian distribution in the third. With given distributions the occurrence probabilities were calculated for strong events above a certain magnitude and for certain time interval.

Space-time assessing of the earthquake potential in recent years in the Eastern Anatolia region of Turkey

In this study, a statistical analysis is carried out to reveal the current earthquake potential in the Eastern Anatolia region of Turkey. For this purpose, a space-time assessing based on the recent changes in Gutenberg-Richter b-value, seismic quiescence Z-value, cumulative moment, annual probability and recurrence time of earthquakes is achieved. Temporal variation of b-value indicates that average b-value decreased from 1.25±0.02 between 2002 and 2010 to 1.08±0.02 between 2011 and 2015. A clear quiescence in the seismic moment in recent years may be a clue foretelling the occurrence of an intense event. Annual probability of the earthquakes between 3.5 and 4.0 magnitude levels exhibits a value equal to and larger than 30. Recurrence time of the earthquakes has a value between 2.0 and 3.0 years for magnitude level of 6.0, and a value between 6.0 and 7.0 years for magnitude level of 7.0. A significant decrease in b-value and clear quiescence anomalies in Z-value at the beginning of 2015 are observed in the several same regions. These areas cover the Central Anatolia Fault Zone, Malatya and Ovacık faults, the southeastern part of the Eastern Anatolia Fault Zone, and the junction of the Eastern Anatolia and Dead Sea Fault Zones. In these anomaly regions, a decreasing trend in b-value may be an indicator of stress increases and an increasing trend in Z-value may show the quiescence areas before the next earthquake occurrences. As a remarkable fact, these areas in the Eastern Anatolia region may be interpreted as one of the most likely locations for the major earthquakes in the future.