دکتر غلام جوان دلویی

Morphologically, the lowest point of Tehran province is located in Varamin city with a height of 749 meters above sea level, and the highest point of the province is located in Tochal Heights with 4375 meters above sea level in Shemiranat city. The mega city of Tehran is also built on the alluvial fans at the foot hill of Alborz mountain, which are located on volcanic-sedimentary rocks of the third geological period (Cenozoic) that during the fourth geological period, it was affected by tectonic activities (Habibi and Horkad, 2014; Ali Beigi et al., 2015). High rates of erosion and sedimentation and urban development cause the destruction or burial of fault structures and their identification sign. Determining the boundary of geological structures is one of the most important and practical issues that has always been discussed in the various sub-branches of the earth sciences, including geophysics (Neawsuparp et al., 2005). Past tectonic earthquake studies have shown that the boundaries of geological structures are mostly identified by faults. In other words, the presence of faults is one of the indicators of active tectonic areas. Therefore, the study of faults to investigate seismicity in connection with the plans for the development of civil activities of cities, industrial towns and the scope of strategic facilities, the investigation of mineral potentials (minerals related to fractures and fault areas) and the detailed understanding of tectonic trends is very important. Here this method is used to calculate the location of seismic events that also presents the seismic nature of the fault processes and its geometry and depth structure in an area.In addition to reviewing aerial photographs and field survey, studying satellite images is one of the practical methods for identifying the trend of obvious faults and preparing maps of the fault system of different regions. In recent years, preparing airborne geophysical maps for hidden fault structures has become common. On the other hand, one of the most common methods for detecting hidden structures, including faults, is aerial magnetic studies, the interpretation and modeling of which has helped researchers in identifying subsurface faults or possible buried faults.It is worth mentioning that in some cases the boundary of the structures may not be associated with a fault. Also, there is a possibility that a fault structure does not have a noticeable magnetic signal. Therefore, the results of satellite images or aerial magnetometry do not necessarily lead to the identification of all hidden faults. In this research, it has been tried to process the aerial magnetometer data of Tehran province by different methods (e.g. reduction to the pole, directional derivatives, upward continuation, analytical signal, and horizontal gradient). Then put it on the fault map of the area and comparing the results, the degree of concordance of the trends of the faults in the region with the magnetic anomalies, magnetic bedrock type faults are identified. In the final stage, by placing a new layer of the seismicity map of the region, those active bedrock faults can be identified.The general results obtained in this research confirm that some of the active faults in the Tehran region are of the basement type, that the ability of these faults to cause large earthquakes is not far from expected, and this result is consistent with other recent seismological studies conducted by Soltani-Moghadam (2016), Ahmadzadeh et al. (2019) and Azqandi et al. (2023) and there is in very good agreement with their finalings.

Fault plane solution is one of the most important tools to determine the orientation of the stress field. The focal mechanism of earthquakes can be applied to determine the direction of rupture propagation, the structure of the fault and the stress field of the region. Dorouneh fault is the largest fault in Iran after the main Zagros fault with about 800 km length. The purpose of this study is to investigate the seismicity, the stress fields and the focal mechanism of earthquakes that have occurred across the three main segments western, middle and eastern parts of the Dorouneh fault. Therefore, the calculation of the focal mechanism is performed using the P-wave first-motion polarity. Also the stress situation of the events and the recognition of fault planes are presented in this research. Along this fault, the blocks have moved in both left and right directions, but certainly one of its last movements has had a right lateral motion. In this study, the waveforms recorded at the seismic stations of the National Seismological Center of Tehran University (IRSC), the National Center of Broadband Seismic Network of Iran belong to the International Institute of Earthquake Engineering and Seismology (IIEES) and seismic stations of Seismological Research Center at the Ferdowsi University of Mashhad were used. At first, the waveforms of each seismic event were combined with each other, and then the relocation of the events were determined based on new data set of this study (Figure 2). A number of high quality earthquake with a magnitude of more than 3 and an average depth of 14 km have been selected (their list is presented in table1) to calculate the fault plane solution.In order to calculate the mechanism of the recent earthquakes in the Khorasan region, interesting results have been obtained based on several methods (Assar Enayati, 1400). One of the common methods for estimating the mechanism of earthquakes, especially earthquakes with small magnitudes and at close distances from the epicenter, is the polarization of the first arrival of the P wave. Due to the dependence of the amplitude and polarization of the P wave on the focal mechanism, by determining the polarization of the first arrival of the seismic phase, the earthquake focal mechanism can be calculated. The results of focal mechanism solutions for significant events around Dorouneh fault show mostly left lateral strike slip motion which is consistent with the tectonic setting of the region. The difference in the focal mechanism of the events in the eastern and western parts of the fault is justified by the northward movement of the Lut block. The integration of data shows high accuracy in calculating the focal mechanism and more certainty about the results. Therefore, in the direction of the Dorouneh fault, the movements are both left-handed and right-handed from the seismic situation. The change in thefocal mechanism obtained from the seismic results, considering the stress axes changes, can represent the second and third order stress fields that balance the stress in this area today. The second-order stress can be related to continental rifting, isostasy adaptation, topography and deglaciation, and the third-order stress field can be related to the local stress source on a scale smaller than 100 km, which is influenced by the structural geometry, and interference between fault systems, topography and local density difference (Sheikh-ul-Islami et al., 2021).

Today, identifying new research trends in any scientific field is very important for researchers, universities and research institutes, research investors, industry, and scientific policymakers. Numerous studies have been conducted with scientometric approach in various branches of science (for example: Leydesdorff, 1987; Leydesdorff et al., 1994). Wegner and Leydesdorff (2003) examined the field of seismology in a study entitled "Seismology as a Dynamic and Distributed Field for Research" using the method of co-authorship and citation analysis between journals. The results of their study show that the scientific products of seismology are not different in terms of the degree of internationality compared to the older subject area of geophysics. Other studies in this field include the studies of Sagar et al. (2010), Wu et al. (2015), Amr (2018), Gizi and Putenza (2020) and He et al. (2021), which specifically examine a subfield of knowledge of Seismology (such as tsunamis, tectonic plates, studies related to a particular earthquake, or early earthquake-related warnings). The purpose of this study is to quantitatively and qualitatively evaluate the scientific products of Iran and the world in the Scopus citation database on the subject of Earthquake studies in the period 2019 to 2021. In this study, with the scientometric approach, VOSviewer software (Van Eck and Waltman, 2009, 2020) and co-occurrence analysis of keywords for scientific mapping and thematic exploring have been used.The present study shows that the number of researchers in the field of earthquakes, reported in the Scopus database, is equal to 112262 articles, which after being limited to 2019 to 2021, this number reached 15270 articles. In addition, the growth trend of research in the field of applied seismology in earth sciences has followed an exponential growth pattern and has grown significantly in the last three years. China, the United States, Japan, and Italy are ranked first to fourth in the world in research and production of scientific articles and are still at the forefront in the field of earthquake science and knowledge. A study of Iran's scientific production in comparison with other countries in two different periods shows that Iran, in the period 2007-2009 was not on the list of top 15 countries in the field of earthquake research, but in the last three years, it has ranked ninth and has reached almost the same level as Germany. However, there has been no significant change in other top countries, despite slight shifts in rankings.In addition, the number of articles by different research institutes in the field of earthquake knowledge in the period 2019-2021 is shown in Figure 6. As can be seen, most of the scientific output has been provided by Chinese research institutions, and several American and Asian universities have also contributed to producing earthquake knowledge in subsequent rankings. Most of the scientific products related to earthquakes in Iran are the results of research by researchers from the University of Tehran, the International Institute of Earthquake Engineering and Seismology (IIEES), and the Sharif University of Technology as the first to third ranks.The findings of this study are of great importance for directing suggestions and formulating technological research plans and projects to provide the ground for acquiring scientific authority of seismological knowledge in Asia. Therefore, the need to expand regional scientific cooperation in the policy-making of research institutes and researchers active in the field of earthquake sciences is inevitable to improve the scientific level of Iran among Asian and European countries.

In this study, coda wave decay parameter, coda Q, is evaluated using waveform data of three networks in the east and northeast of Iran based on the single-scattering method. The database includes 300 earthquakes with magnitudes in the range of 2.5-6.0 recorded in 2012 to 2020. The waveforms were gathered from the Iranain Seismological Center (IRSC) of the University of Tehran, National center of Broadband Seismic Network of Iran (BIN) at the International Institute of Earthquake Engineering and Seismology (IIEES) and Seismological Earthquake Research Center of the Ferdowsi University of Mashhad (FUMSN). The coda Q for the east-northeast of Iran was calculated as Qc = 125f 0.76 for a lapse time of 40s and optimal parameters of our database. We also evaluated coda Q based on parameters proposed by Havskov et al. (2016) as Qc = 90f 0.87 and as can be seen, the difference in the parameters leads to the different results. Furthermore, the effect of different parameters in estimating the quality factor of coda waves was investigated. The frequency dependence of the wave attenuation coefficient is evident in this region. Considering the 10-year interval of earthquakes used in the east and northeast of of Iran in this study, the obtained results indicate high seismicity rate and continuous seismic activity in the study area.   Recently some studies have been conducted to study the seismic wave propagation effects in this region. For example, Safari et al. (2020) investigated the attenuation of seismic waves in the Fariman region based on 122 local earthquakes recorded in a temporary dense seismic network of IIEES. Based on this research, the frequency relationship Qc = 66f 0.84 for a lapse time of 20s was obtained.The results of the quality factor studies depend on tectonic regime of the study area and various proccesing factors, such as: the lapse time, filter bandwidth, the window length, etc. Therefore, accurate comparison is only possible when similar parameters are considered in different studies.    We compared our results with several studies in different regions of  Iran and other parts of the world. The estimated values of Q0 in this area are in the same range of active regions of the world (Q0 <200) and is near to the results of studies conducted for another active regions of Iran. The results of our study are in good agreement with previous studies and indicate the strong frequency dependency in attenuation of seismic waves in northeast of Iran Plateaue. The observed small differences in coda Q estimates originate from differnet tectonic rigions and  processing parameters.

Recording, processing and identifying the parameters of independent earthquakes larger than Mw = 4 using advanced equipment, software and professional experts, can be calculated nowadays in less than 10 minutes automatically in the Iranian plateau. Double earthquake of November 14, 2021 with a small time difference (less than 90 seconds) occurred at a very close distance with magnitudes of 6.1 and 6.4, respectively. The calculation of the parameters of location, time and magnitude of the first event, in addition to the calculation of its focal mechanism parameters, was made possible with the help of semi-automatic or automatic software. However, the interference of the seismic phases of the first event with the second one in farther stations poses a serious challenge to the automatic and semi-automatic calculation of location, origin time, magnitude, as well as the parameters of the focal mechanism of the second event. In this study, by merging recorded seismograms and accelerograms in seismic stations within the country, the parameters of this double earthquake and their two main aftershocks with magnitudes of 5.1 and 5.4 have been calculated. In addition, the calculation of the focal mechanism of these four events is carried out based on the polarization method of the first P-wave polarity, the amplitude ratio of P and S waves and the modeling of seismic moment tensor. The results of this study show that according to the locations and focal mechanisms calculated for the double earthquake and both major aftershocks, the activity of the Handun basement fault, which is probably related to the formation of the Handun salt dome, caused double earthquakes of November 14, 2021 and its two main aftershocks in the northwest of Bandar-Abbas, south of Iran.

In this paper, we examined the influence of initial parametrization in the inversion of surface wave dispersion curves. First, the steps for choosing the most desirable parameters are described. Then, the influence of parametrization is investigated using two experimental approaches and also a systematic approach to find a consistent solution. The final results show that suitable values for initial parameters considering some basic principles and local site conditions can reduce the uncertainty in the final results. However, this uncertainty also strongly depends on a-priori information that could be implemented in the parametrization and also the inversion process.

Seismic velocity changes and shear wave anisotropy analysis can provide insights into deep structures. In multi-layered structures, cosine moveout pattern of radial component is observed for converted Ps phase. The method to calculate anisotropy parameters in layered structures has been developed by Ruempker et al. (2014). Some seismic stations do not have enough coverage in some azimuths, and we can split parameters (φ, δt) by fitting the best curve on Ps arrivals using the grid-search method. In this study, using synthetic data, the effect of the azimuth coverage is investigated and the sensibility of the results is also examined.

Attenuation of seismic waves is considered a very important characteristic of the wave propagation path because this physical parameter affects how the seismic waves propagate, and consequently knowing the amount of it is essential in accurate calculation of seismic source parameters, modeling and reducing seismic risk in seismic areas. Attenuation of seismic waves in an environment is the result of two physical processes, elastic and inelastic. In the elastic process, energy remains constant in the propagation medium; however, the amplitude of the waves may increase or decrease due to the geometrical spreading, multipath, and scattering. These factors depend on the type of wave, frequency, degree of heterogeneity and characteristics of the propagation medium. In the inelastic process, part of the energy of the seismic waves is converted to heat and the amplitude of the seismic waves decreases due to the loss of a part of the energy. In the inelastic process, factors such as inelastic properties of the environment and physical properties of the environment (wave velocity, density and temperature) play an important role. Not only the scattering and the intrinsic absorption are important factors in reducing the amplitude of direct waves, but they also affect the appearance of a seismogram.Decreasing the amplitude of seismic waves by increasing the propagation distance from the source and the frequency changes made in the time history of the earthquake is called attenuation. In general, the factors that weaken the waves and the energy emitted from the seismic source are reflection and passage of waves through the boundaries of the layers, multi-path, geometrical spreading, wave diffraction, attenuation and inherent absorption of waves due to heterogeneity in the propagation path. The attenuation of seismic waves is described by the dimensionless quantity of the quality factor Q, which indicates a decrease in the amplitude of the wave along the propagation path. This parameter is a function of frequency, seismic wave type, time window intended for seismic analysis, geological characteristics below the seismic recording site and tectonic activity of the region. Physically, Q is the ratio of wave energy to energy wasted in each cycle of oscillation. By examining and calculating the range of Q changes from the data processing of seismic waves emitted in the Earth's crust, the characteristics of its various parts can be realized. Parts of the Earth's crust that have very low attenuation have very high Q values, and parts with severe attenuation have very low Q values. Tectonically active regions have a relatively high heat flux, so they are more strongly adsorbed than other regions, so they have a lower Q value.The attenuation of coda waves, Qc, has been estimated in Fariman region, NE-Iran, using a single back-scattering model of S-coda envelopes. For this purpose, we used the time histories of 124 aftershocks of Do-Ghaleh Fariman earthquake (Mw6, 2017), recorded by local seismic network belong to International Institute of Earthquake Engineering and Seismology (IIEES). In this research, the frequency-dependent Qc values are estimated at central frequencies of 2, 4, 8, 16 and 24 Hz using different lapse time windows from10 to 60 s and the frequency-dependent relationships obtained for 30 s is Qc=(73±11) f (0.89±0.06). It is observed that the exponent n decreases and Qo increases as lapse time increases. Any increase of Q with depth or with distance from the seismic source to receiver would cause the increasing of coda-Q with lapse time. The average Qc values estimated and their frequency dependent relationships correlate well with a highly heterogeneous and highly tectonically active region. Our results regarding QC factor is the first study in this area and would be significant for reassessment seismic hazard and risk management in southern part of Khorasan Razavi.

The Mw 6.0 Do-Ghaleh Fariman earthquake occurred at 10:39 local time (06:09 GMT) on 2017 April 5, in 46 km away from Fariman city of Khorasan Razavi province in northeast Iran (Figure 1). The mainshock had a maximum Mercalli intensity of VIII (Severe) (Ahmadzadeh et al., 2018), and was felt by many people a radius of 200 km in eastern part of Iran. Despite the low population density, the earthquake caused widespread destruction, killing 2 people and injuring a further 100 people. Although many historical and instrumental destructive earthquakes have occurred in Great Khorasan, no evidences from large earthquakes reported in Fariman region. Immediately, after Do-Ghaleh Fariman earthquake, International Institute of Earthquake Engineering and Seismology (IIEES) decided to design an intensive seismic network around epicenter for monitoring aftershocks and seismological aspects studies. The IIEES local seismic network contains 16 velocitymeter (Lenartz 20 Sec) and 3 accelerometers (CMG-5TD Guralp with ±2g sensitivity) that deployed in the region for 40 days (Figure 1). The sampling rate of waveform data have been chosen at 200Hz for all seismic stations. Data acquisition is leading to 1500 aftershocks with high quality waveforms in this area. The IIEES velocity model is used as initial velocity model in Lotus12 program for optimizing velocity model in Fariman region. The optimum derived velocity model (as shown in table 4) is used for relocation of aftershocks. Figure 3 shows the location map of relocated aftershocks and seismic stations. The cross sections of well relocated events show a NW-SE dip direction (Figure 3).  To relocate the mainshock and to derive the fault plane solution we have retrieved all waveforms from seismic stations, both Iran Seismic center (ISC) belong to Institute of Geophysics at University of Tehran (IGUT) and Iran National Center of Broadband of Seismic Network belong to IIEES. For fault plane solution the first P-wave polarity method (Snoke et al., 1984) is used. The result of our relocation and fault plane solution of the main shock is shown in figure 5 & table 5 in comparison with other seismic agencies reports. To estimate the fault plane solutions of well-relocated aftershocks, we extracted 120 aftershocks with azimuthal gap less than 160°. The results of our fault plane solutions of 38 aftershocks with high quality are shown in figure 6 that have azimuthal gap less than 120° and recorded at least in 16 seismic stations. Focal mechanisms of 15 aftershocks are reversed which is numbered from 1 to 15 as shown in figure 6 and table 7. However, the rest of fault plane solutions show reverse mechanisms with strike slip component. Generally, the total average trend of reactivated fault, show NNW-SSE direction based on our study that is in good agreement with the trend and focal mechanism of Mozdoran fault (figure 6). Therefore, reactivation of the Mozdoran fault can be considered as main source of Do-Ghaleh Fariman Mw6 earthquake on April 5 2017. It should be noted that in some technical reports (e.g. Naimi, 2017) and old geological maps the final section of the Mozdoran fault is termed in Chah-Mazar fault.

One of the most seismically active parts of Iran is Zagros area. The basement-involved active fold-thrust belt of the Zagros in southwest Iran is underlain by numerous seismogenic blind basements thrust covered by the folded Phanerozoic sedimentary rocks. The present morphology of the Zagros active fold-thrust belt is the result of its structural evolution and depositional history: a platform phase during the Paleozoic; rifting in the Permian Triassic; passive continental margin (with sea-floor spreading to the northeast) in the Jurassic-Early Cretaceous; subduction to the north­east and ophiolite-radiolarite emplacement in the Late Cretaceous; and collision-shortening during the Neogene.Besides, there are a lot of different faults in Zagros, for example, the Main Zagros Reverse Fault (MZRF), the Main Recent Fault (MRF), the High Zagros thrust belt, the High Zagros Fault (HZF), and Mountain Front Fault (MFF). This study is focused on the last-mentioned one. The MFF flexure is introduced for the first time by Falcon (1961) and then is presented as the mountain front fault by Berberian and Tchalenko (1976)], which delimits the Zagros simple fold belt and the Eocene-Oligocene Asmari limestone outcrops to the south and southwest. The Mountain front fault (MFF), is a segmented master blind thrust fault with important structural topographic, geomorphic and seismotectonic characteristics. Therefore, the study and recognition of seismic parts of Iran are important. The aim of this study is to determine the focal mechanisms of Mountain Front Fault (MFF) at a latitude of 46 to 48.5 degree in Zagros. Due to the salt layers, large earthquakes rarely reach the surface. In such cases, the seismic method is an appropriate tool to understand the faulting mechanisms. By means of focal mechanisms, it is possible to gain information about the fault geometry and its related mechanism. The data used in this study are from International Institute of Earthquake Engineering, and Seismology (IIEES) and Institute of Geophysics of the University of Tehran (IGUT). Because of some wrong relocation, during this study relocated them to reach a well-relocated data base and better results. Getting the focal mechanism of an earthquake can occur in various ways. In this study, first, the waveform modeling by Isola software was used to find the focal mechanisms. To determine the accuracy of focal mechanism solutions obtained by waveform modeling, the polarity method was used to solve focal mechanisms. Besides, some of these earthquakes have also been reported by CMT. After determining focal mechanism solutions with the stated method, they were compared with CMT, and all the focal mechanism were mapped in the area so that the trend of this part of MFF can be recognized better. Because there are many earthquakes in this area, a reliable decision can be made. By looking at the maps, it is easily understandable that the trend in this part is obviously EW. Finally, the prevailing trend that obtained in the study area is found. Most of these earthquakes are trending EW. The study of 31 focal mechanisms in the area has permitted to constrain the faulting mechanism of MFF.

Peak ground acceleration is one of the most important factors that needs to be investigated in order to predict the devastation potential resulting from earthquakes in reconstruction sites. Besides, the maximum level of shaking control is subjected criteria that can be worth considering. In this research, a training algorithm based on gradient descent and Levenberg-Marquart (Train LM) were developed and employed by using strong ground motion records. The Artificial Neural Networks (ANN) algorithm indicated that the fitting between the predicted PGA values by the networks and the observed PGA values were able to yield high correlation coefficients of 0.78 for PGA.
From a deterministic point of view, the determination of the strongest level of shaking that is expected at a site has long been a significant consideration in earthquake engineering. Besides, knowledge of the maximum physically possible ground motions allows a meaningful truncation of the distribution of ground motion residuals, and as a result, leads to falling of the values computed in probabilistic seismic hazard analysis (Strasser and Bommer, 2009).
The peak ground acceleration parameter is often estimated by the attenuation of relationships and by using regression analysis. PGA is one of the most important parameters, often analyzed in studies related to damages caused by earthquakes (Gullo and Ercelebi, 2007). It is mostly estimated by the attenuation of equations and is developed by a regression analysis of powerful motion data.
Kerh and Chaw (2002) used software calculation techniques to remove the lack of certainties in declining relations. They used the mixed gradient training algorithm of Fletcher-Reeves’ back propagation error (Fletcher and Reeves, 1964). They applied three neural network models with different inputs including epicentric distance, focal depth and magnitude of the earthquakes. These records were trained and then the output results were compared with available nonlinear regression analysis.
In this article, to estimate strong ground motion acceleration component in an area, four artificial neural networks with different algorithms were used, including General Regression Neural Network (GRNN), Nonlinear Auto Regression neural network (NARX), Feed-Forward Back-Propagation error (FFBP) and General Feed-Forward Neural Network (GFFNN). Input vectors of neural networks include four parameters, which have key effects in occurrence of an earthquake in an area. The parameters include magnitude of moment, rupture distance of earthquake center, mechanism of faults, and ranking of site. Output vector has only one component: maximum peak ground acceleration for an earthquake in an area is used as a target output.
After different tests, GRNN network has maximum output correlation coefficient (0.87) and General Feed-forward Back-Propagation error neural network (FFBP) has the least (0.41). Besides, GRNN network had the least mean square error (0/014), and Back-Propagation network had 0.125. In this research, GRNN neural network is the best neural network, which can estimate possible peak acceleration more than 1g in an area.
Artificial neural networks are a set of non-linear optimizer methods which do not need certain mathematical models in order to solve problems. In regression analysis, PGA is calculated as a function of earthquake magnitude, distance from the source of the earthquake to the site under study, local condition of the site and other characteristics that are linked to the earthquake source such as slippery length and reverse, normal or wave propagation. In non-linear regression methods, non-linear relations that exist between input and output parameters are expressed as estimations, through statistical calculations within a specified relationship (Douglas, 2003).

Balouchestan Provinces. The epicenter (59.2E, 28.35 N) has been reported 52 kilometers away from the city of Mohammad Abad Rigan. Although there was no fault pointed on the geological maps in terms of the location of this earthquake, the aftershocks were recorded in two temporary seismological networks using 10 stations altogether from December 24, 2010 to January 24, 2011. In addition, the data recorded in the IIEES broadband seismic network was added to the mentioned data during the process. The goal of operating temporary seismic networks was aftershocks analysis in this area. Investigation and study of aftershocks behavior has done based on three component waveforms. This study contains three main parts. The first part is operation network, data gathering and preprocessing. In the second part, we try to locate and relocate aftershocks based on new database. The third part is fault pale solutions of aftershocks based on p-wave polarity technique. Locating over 500 aftershocks in the network, we recognized a fault with the length of 30 km, southwestnortheast strike and 32 NE trends. The most of aftershocks are located in a depth range of 2-15km; while a few earthquakes have greater depth to 23km. Investigation of the rate of aftershocks showed that the number of them decreased as time increased during three weeks. After that, the rate of aftershocks was increased for two weeks and finally another large earthquake happened in the area with magnitude of 6.3. Therefore, decomposing and distinguishing of aftershocks of first mainshock from foreshocks of the second mainshock is a great change here. In this study, we assume all events as aftershocks of first mainshock. Determining 28 focal mechanisms pertinent to the aftershocks as well as perpendicular sections on the aftershocks, we recognized the strike slip right - lateral fault, with a tensional component, dip 90 degree which met the surface. It i s worth noting that according to the geological evidence and comparison with the results obtained; this region has a complex structure. Also, it comprised some right - lateral parallel strike slip faults bringing about wrinkles in the given area. Our results are in good agreement with the geological and morphotectonic evidence. The mechanism and trend of the Mohammad Abad fault can be interpreted with the previous GPS measurements in eastern part of Iran.

In this article, we try to investigate the ambient noise characteristics based on amplitude, frequency content and its origin that were recorded on the broad-band seismic stations. To do this, we reviewed the technical literature from middle of 20th century noise studies until recent years. Moreover, cross correlation function of noise that is equivalent with the experimental green function is explained as the background study. For the first time, Campillo and Paul (2003) have calculated group velocity of Rayleigh and Love surface waves from waveforms of 101 teleseismic earthquakes recorded in the national Mexican seismic network. After that, the investigation into ambient noise for Green function analysis have been continued by Shapiro and Campillo (2004, 2005), Schuster et al. 2004), Snieder (2004), Bensen et al. (2007) and Wapenaar et al. (2013). They showed that it is possible to get the Green function between stations through calculating Cross Correlation Function of recorded ambient noise. Ambient noise is important since it does not dependent on occurred an earthquake. That’s why ambient noise is used widely in order to study inner structure of the ground between two seismic stations. It should be noted that the dynamic range and frequency content of the seismometers has important effect on the wide band of group velocity dispersion curves. In other words, the ambient noise recorded by means of short period sensors is useful to derive low period dispersion group velocity curves only. Therefore, we strongly suggest using broadband seismic stations to study surface wave analysis based on ambient noise. The next key factor to derive sharp experimental green function is optimum distance between two seismic stations. The shorter distance generates a high frequency green function which is due to shallow depth penetration of the energy. Therefore, the depth of target will define the distance between two seismic stations. However, the type of sensor can be important. Based on seismic wave propagation theory, the Rayleigh wave can be seen on vertical component and the Love wave can be seen on the horizontal components of a seismic station. Therefore, if one like to study dispersion curves of Rayleigh wave need to process vertical component of seismograms. Of course, in practice, using rotated horizontal component can generate sharp Love wave. The seven seismic broad-band stations located in the south-southeastern part of the country are selected for this research. The cross correlation method was used to calculate the experimental Green’s functions for pairs of seismic stations (BNDS CHBR, BNDSZHSF, BNDS-KRBR, BNDS-NASN, BNDS-TABS, and BNDS-SHRT). Dispersion curves of group velocities belonging to fundamental mode Rayleigh waves determined by frequency - time analysis. Thegeneral form of calculated dispersion curves is very similar to the earthquake dispersion curves. Besides, results of dispersion curves are comparable with the average global model. Our study, show the ability of ambient noise analysis for determining the earth's velocity structure. The results may prepare the basic curves for the seismic structure modeling like surface wave velocity structure and/or seismic surface wave tomography.

In this study, analysis is presented in two steps. In the first step, the theoretical S-wave displacement spectra, conditioned by frequency-independent Q, was fitted with the observed displacement spectra. Therefore corner frequency, moment magnitude and frequency-independent Q for each record were estimated simultaneously and the estimate of error is given in the root-mean-square sense over all the frequencies. In the second step, the corrected observed displacement from source effect was fitted with path term of Brune’s source model to estimate frequency dependent shear wave Quality factor. For comparison, Frequency dependent shear wave quality factor also is estimated from spectral decay method. The earthquake in Qom, 18 June 2007 (Ml=5.7), was the largest earthquake in the south of Tehran that recorded on strong motion acceleration stations. The data represented more than 40 accelerograms recorded from Kahak-Qom earthquake in the hypocentral distance range from 18 to 170 km. The source term obtained from inversion was analyzed to estimate various source parameters. Thereby, we estimated seismic moment (1.86*1024 dyne-cm), corner frequency (0.72 Hz), source radius (2.33 Km), fault slip (38 cm), source duration (1.5 sec), stress drop (12.3 bars) and moment magnitude (5.4), which are found to be consistent with the corresponding values reported in published studies. The path average value of Q is in the range Q=161 to 1652. The anelastic attenuation coefficient for the region as a whole is estimated in step 2 is Qs= 47f 0.71 in frequency range of 1 to 32 Hz. The frequency-independence attenuation for the study region shows that, in general, a Q value is significantly similar to the entire frequency range used than those found in other tectonic areas.