The Doruneh fault system with more than 700 km length, after the main Zagros fault, is known as the largest fault in Iran. In this research, this fault system is divided into 3 main parts because the mechanisms of its different parts are different. The western part is reported to have a left lateral strike-slip mechanism with a reverse component, the middle part is a left lateral strike-slip mechanism, and the eastern part is reported to have a reverse mechanism. In this study, Seismicity parameters and their temporal and spatial changes along this fault system are analyzed using seismic data collected from 1980 to 2023 and based on the maximum likelihood method. In this regard, the temporal changes of b-value shows two significant drops, which indicate two relatively strong Torbat-e Heydarieh earthquakes in 2010 and the Fariman earthquake in 2017. Despite the fact that the scientific community is not yet able to accurately predict earthquakes, according to the studied method and with the continuous monitoring and analysis of various earthquake parameters, especially b-value, it is not far from expected to predict the occurrence of possible earthquakes in the future.

Most of the areas of the Iranian Plateau are high Seismicity regions and there is a considerable difference between them. These differences in the eastern Iranian Plateau including the Lut block compared to the surrounding areas are so substantial that can be studied independently. A brief look at the seismic maps of this region shows that around the Lut block, the activity of strike-slip and reverse faults has caused many and devastating earthquakes but in the inner parts, it can be considered as a small rigid plate regarding the relative stability. In this research, using the most updated catalog as the main source, a catalog of 1760 historical and instrumental declustered earthquakes was provided for the area bounded in 56.5°-61°E and 28°-35.5°N in eastern Iran. The data was divided into a historical part and four instrumental parts of 1900 to 1963, 1964 to 1999, 2000 to 2005 and 2006 to 2022. Using the maximum curvature method for each of the four time intervals, the data completeness thresholds were determined to be 5.7, 4.7, 4 and 3.1, respectively. The Seismicity parameters were estimated taking into account the uncertainty of the magnitudes. Substantially, the estimated b-value is equal to 1.06 and the mean annual occurrence rate for magnitude equal or greater than 3.1 is 58. The maximum magnitude of the earthquakes is estimated to be 7.9, which indicates the high Seismicity of the region. The probability of annual exceedance for different magnitudes is estimated for the return periods of 50, 475, and 2475 years. Comparing the results of this study with the results of the other studies performed based on the same data and the same method for the Central-East Iran seismotectonic province confirms that the Seismicity of the Lut block and its margin can be determined independently from the other parts of the Central-East Iran seismotectonic province.

The Bakharden-Quchan Faulted Zone is located in central Part of thrusted-folding belt of kopeh Dagh in NE border of Iran-Turkmenistan with array of active right lateral strike-slip faults by trending NW-SE that their ends have bent to joint blind faults in thrusts. Mechanism changing faults to reverse have caused to increase stress, shortening by thrusting in their ends bending. Most of the historical and instrumental earthquakes have distributed around faulted system of Bakharden-Quvhan Zone. Seismicity results of this zone with microseismics and computing parameters of b-value, fractal dimension (D) and mapping of local stresses distribution could have achieved us precious data on crust tension distribution, mechanism faults and system fault changes during time and place of probable occurrence future earthquakes. In neo-tectonic active zone b < 0/6 to 1/1 and D changes between zero to 2. If b< 0/6 and D closes to zero, faults and earthquakes will concentrate in asperities with high rate of stress but if b> 0/6 and D closes to 2 faults and earthquakes will scatter in whole of zone with low rate of stress. Occurrence of major earthquakes are not far away expectation in edge of asperities although there is a possibility that they gradually loss energy to get inactive because the seismology way of releasing energy in these faults is, when group of faults approach to motion threshold are increased b-values and other group of faults are accumulating energy, so their b-values are decreased.

In this research, the spatial correlation between the variables representing Bouguer gravity anomaly and Seismicity in Iran is evaluated. For this purpose, the gravity anomalies and Seismicity data of this region have been analyzed statistically as well as geostatistically, for the period 1975-2021. Based on the findings of this study, it can be concluded that the significant correlation observed between the variables of gravity anomaly variations and the Seismicity-related variables, especially the variables related to the frequency of earthquake occurrences, suggests that the gravity anomaly variations can be considered as an affective factor in seismic activity of this region.The Iranian Plateau is one of the most seismically active regions on the Earth because of its geologic and tectonic setting. This plateau is marked by high topography relief and also by great changes in gravitational and isostatic anomalies across it. Many researchers have studied the variations of gravitational anomalies across Iran, and some have pointed to the relationships between these anomalies and Seismicity in this region. The Bouguer gravity anomaly is obtained by making the necessary corrections to measurements taken directly from the ground stations, and well reflects the deep density variations in the crust. This anomaly can also clearly show changes in crustal thickness in different regions, such that areas with high crustal thicknesses show negative anomalies and areas with low crustal thicknesses show positive anomalies.In this study, at first, the study region was divided into rectangles with dimensions of 0.5 by 0.5 geographical degrees and then the variables related to the Seismicity and gravity anomalies were calculated and computed for each cell. Pearson correlation coefficients between these variables were computed and validated using statistical software Minitab (ver. 16.2.2). Also, maps representing the spatial distribution pattern of these variables were prepared. The remarkable similarity between the spatial patterns of variations of these variables indicates a strong correlation between the Bouguer gravity anomaly and Seismicity in this region. The Pearson correlation coefficient values calculated between the variables also confirm this correlation. These values indicate that both variables of average Bouguer anomaly and the range of variations of this anomaly show a significant positive correlation with the Seismicity-related variables. This degree of correlation is stronger for the variable of the Bouguer anomaly variation and moreover, this variable is more correlated with the Seismicity variables associated with the frequency of earthquakes. In the next step, variograms were prepared.     The results obtained show that among the Seismicity-related variables of the region, the b Seismicity parameter (from the Gutenberg-Richter relation) has more spatial variability and show high spatial autocorrelation up to long distances. On the other hand, the other variables related to earthquake frequency and magnitude of earthquakes show less spatial autocorrelation. The variograms provided for the two variables representing the bouguer anomaly also show remarkable similarity to the Seismicity-related diagrams. This similarity is more pronounced for the variable of the Bouguer anomaly variation. The remarkable similarities of the variograms, along with the similarities of the spatial distribution maps of these variables, may indicate a close relationship between these two series of variables. Finally, it can be concluded that gravitational forces, especially forces caused by isostatic imbalances, can play an important role in the process of earthquake occurrences in Iran.

North-western Iran (Azerbaijan province), one of the most seismic regions of the country, has experienced many seismic events during its long history. The recent dual earthquake with Mw = 6:4 and Mw = 6:3 struck the Ahar-Varzaghan area in Azerbaijan province in 2012.8.11 and caused a lot of fatalities. In this paper, the varieties of several seismic parameters, such as the b-value of the Gutenberg-Richter relation and standard deviation, Z, have been investigated to explore the temporal and spatial changes of Seismicity patterns. Calculating and comparing these data before and after the occurrence of earthquake demonstrate some information about anomaly preceding main shocks. Temporal variations of b-value show a clear decrease before the 2012 Ahar- Varzaghan dual earthquakes. Considering the spatial changes in the b-values, it is possible to recognize a zone with abnormal low b-values around the epicenter of these events. The variation of the b and Z-values around the epicenter shows preparedness of the region before the occurrence of the main shock of Ahar-Varzaghan earthquake.

In the present study, we investigate some statistical features of earthquake precursors, namely the variations of the b-value and Z-value parameters in time and space, before the occurrence of MN≥5.0 earthquakes in northeast Iran. Based on the literature, the b-value of the Gutenberg–Richter distribution is connected to the field of seismic stress, so that it decreases linearly with increasing differential stress and vice versa. Still, a high differential stress at later stages of an earthquake cycle causes failure of large patches. The Z-value parameter is also associated with seismic quiescence periods which imply the regional preparedness for the occurrence of strong earthquakes.    It is worth mentioning that our study covers ten MN≥5.0 target earthquakes that occurred between 2010 and 2022. However, due to the large number of target earthquakes, the text body is focused on one of the events accompanied with all investigated anomalies, namely the 2015 Kashmar MN 5.2 earthquake.    In order to study the anomalies of seismic parameters, an earthquake catalog, reporting post-2006 MN≥0.3 events, was extracted from the Iranian Seismological Center. As the raw catalog includes small size events, it was preprocessed via removing possible non-tectonic events. These events, being mostly quarry blasts, have been statistically recognized by an unrealistic increase in the number of events during working hours (i.e. 6.00 to 16:00 O’clock). Accordingly, the Rq method, implemented in the ZMAP software package, has been used for removing possible quarry blasts. The estimation of seismic parameters has been done by assuming the Poisson distribution of the occurrence of earthquakes. Therefore, dependent events (i.e. aftershocks and foreshocks) were also eliminated from the used catalog, using a declustering procedure. However, in the case of the 2015 Kashmar earthquake, the de-quarrying and declustering procedures remove 6859 events out of 22143. Having estimated the magnitude of completeness (Mc) for the region of the Kashmar earthquake, we removed earthquakes with magnitudes less than Mc=1.8. Furthermore, as earthquake catalogs commonly involve in a sort of temporal fluctuation of Mc which is mostly due to increase in the number of seismographs over time, the stability of Mc=1.8 for the region has also been checked. In total, the residual catalog includes 7606 MN≥1.8 earthquakes over the Kashmar region.    Our results indicate that at least one of the investigated anomalies can retrospectively be observed prior to all target earthquakes. Still, in some cases both anomalies can simultaneously be detected in the space and time domains. Moreover, the results show that regions characterized by both b-value≤1.0 (after experiencing a temporally decreasing trend of b-value) and Z-value≥3.0 are most prone areas for future MN≥5.0 earthquakes. Furthermore, it has been found that there exists a significant correlation between the explored anomalies, so that the correlation coefficient is higher than 0.6 for some cases. In conclusion, our results confirm that temporal and spatial variations of Seismicity parameters can somehow be interpreted as effective indicators for the areas prone to earthquakes with significant earthquakes.

Background and Objectives: The occurrence of natural disasters can be considered one of the most important concerns of human life, especially for the people of developing countries. The existence of natural disasters in Iran has made Iran one of the top 10 countries in the world in terms of disasters. Analysis of seismic data shows that almost every 5 years, on average, an earthquake with a magnitude of 7 (such as the Saravan and Sarpol-e-Zahab-Kermanshah earthquakes) occurs in Iran and has serious effects on human society. In this study, the parameters of strong ground motion in the Sarpol-e-Zahab area have been analyzed with a special focus on its crisis. Material and methods: In order to evaluate the return period of the earthquake in this fault system, two preliminary relationships of Gutenberg-Richter and the final distribution of the Kijku-Sellovel method have been used. In order to study Seismicity and seismic hazard analysis, after studying the geology of the study area, the tectonics and Seismicity of the region were studied. After that, a tectonic seismic model was prepared from this zone to better determine the nature of Seismicity. Then, the seismic source database of the study area was defined and entered into EZ-frisk software for further analysis. Results: The magnitude of the earthquakes based on the Gutenberg-Richter and Kijku-Sellovel methods has shown that the magnitude of the earthquake in the 475-year return period is 6. 9Ms and 7. 0Ms, subsequently. A magnitude of more than 7. 8 is not expected in this region based on the Gutenberg-Richter method. On the other hand, the values of acceleration on the side where the fault slope is (northeast of the fault), have higher values than on the opposite side. In addition, the maximum acceleration of the earthquake in the position of the mountain frontal fault is estimated 0. 75 gal. Conclusion: Therefore, considering the importance of the study area (geologically), the existence of active and important faults in this region, as well as political-security threats, the existence of spatial exchanges and links on both sides of the border, and the underdevelopment of study and planning in the field of crisis management of this region seems necessary. Also, according to the results of the earthquake return period in this region, raising the level of urban environment flexibility against the stresses caused by the crisis and minimizing the time of rehabilitation and resilience of cities are among the most important factors that should be considered in planning and managing cities.

Alborz is a narrow, long and high elevated mountain belt that participates in a part of motion between Arabia and Eurasia. Central Alborz is the site of historical and recent large earthquakes. Considering fast expansion of the cities located in this zone and their socio-economical activities, there is a great need for different Seismicity studies. Several active faults that are usually from mountain bordering type and are parallel to the mountain belt trend have been already identified. These faults are mostly compressional or have a great compressional component, so with longer return periods and thus stronger earthquakes. In this paper a short but clear geoscientific picture of Central Alborz will be given and then some Seismicity characteristics just like spatio-temporal distribution and changes, b-value changes and fractal dimension will be studied. Based on the results b-value reduces with depth and also before some great regional earthquakes. Meanwhile fractal dimension is near 2 that may reflect the planer distribution of seismic sources in this region.

Reservoir-triggered Seismicity (RTS) is a phenomenon, which has been observed in several large dam projects all over the world, especially for the reservoirs which are constructed in seismically active regions. Practically all the territory of the Republic of Armenia is characterized as the high seismic active area. A review of reservoir triggered Seismicity in Armenia shows that it mainly occurs in large dams which are located near active faults. In this paper it has been shown that the number of microearthquakes increases after Tolors reservoir operation, cause changes of seismic regime in the observed regions. The correlation of Seismicity and water level in Tolors reservoir allows assuming the influence of long-term harmonious changes of water level on the seismic activity in the region.

Iran exposes to natural disasters because of its geographical position. Iran settles on Alpian-Himalaya seismic belt and its populous regions are mostly comforted in active tectonic parts of it. Excessive human and cost losses during recent catastrophic earthquakes, Rudbar, Bam, Buiin Zahra and etc., indicate the necessity of seismic studies of residential, industrial and cultural parts of country.Regarding large earthquakes happened in and around Qom province and its being in the vicinity of Tehran province encouraged us to study seismotectonics and Seismicity of Qom. Studying local and teleseismic data shows that southwest of the province is more seismically active than other parts. This study can be used for next considerations to seismic zoning and microzoning of Qom.