فهرست مطالب سید کیوان حسینی

Due to the specific geographical and geological situation of Iran, the earthquake phenomenon imposes numerous human and financial losses on our country every year, and identifying areas prone to earthquakes and providing practical solutions are among the ways to reduce these losses. Also, by examining the impact of the subsidence phenomenon in the seismic process and reaching a comprehensive and practical model, it is possible to prevent and adjust the volume and scope of potential incidents rooted from this widespread hazard; noting that the relevant institutions have all the necessary regulations and standards for construction and safety regarding this process. The earthquake-prone areas which were subject to subsidence and earthquakes at the same time were reviewed. Conducting comprehensive and detailed studies in order to create a complete and scientific structure to identify and provide maps and updated information on the adaptation of the seismic situation and the subsidence of the country helps to prevent the occurrence of accidents and widespread loss of life and capital during these phenomena. In this regard, this study was planned aiming to investigate and assess the effect of subsidence on the seismicity trends of Varamin and Shahriar plains in Tehran region.

The current research aims to investigate the effect of subsidence rate changes on the seismicity trend using Sentinel-1 satellite data from 2014 to 2021. The studied area is in the southern part of the Alborz mountain range, namely Varamin Plain and Shahriar Plain which are located in the southern and western extremes of Tehran province, respectively. Due to the sensitivity of the research topic and to obtain more accurate results, a combination of digital information and hydrological data along with radar images of the area and field data were processed and analysed. Geological maps 1:50000, fault and seismicity 1:1000000 from the Geological Organization, topography 1:25000 from the National Mapping Organization, and seismic data from the years 1350 to 1400 were obtained from the Geophysics Institute of Tehran University and the International Research Institute of Seismology and Earthquake Engineering of Tehran. The data from 46 piezometer wells in the region from 2014 to 2021 were used for zoning and checking the underground water level. The satellite data of the Sentinel-1 sensor was used for interferometry to determine the subsidence rate of the region.

In the present study, the correction of the seismic catalog with standard techniques and the micro-seismic catalog showed that Varamin and Shahriar plains have subsidence rates of 65 and 54.5 cm per year, respectively, based on changes of 600,000 cubic meters per year in the volume of the aquifer. The studied case has led to the minimum stress changes in the area to the extent of 5 bar to 17 bar (equivalent to 500 to 1700 kilopascals). Also, the seismicity pattern of the area shows an increasing trend in the occurrence of subsequent earthquakes on one side, and a shortening of the seismic return period in the studied area on the other side.

The high consistency of the data trend in the distribution charts demonstrates the consistency of the subsidence trend and, subsequently, its effect on the seismicity trend of the studied area, which in turn indicates the effect of subsidence on the seismicity trend in the studied areas. The stress output resulting from loading shows a high increase in the stress of the area on one hand, and a decrease in pore pressure on the other hand. This is due to the decrease in the resistance of the soil in the studied area which manifests in the form of collapses and falling of structures and, with an emphasis on the extensive decrease in the strength of surface and subsurface layers, causes subsidence and intensification of subsidence in the region. To put it shortly, both of these phenomena will influence one another in an increasing cycle.

The shear wave quality factor is one of the key parameters for earthquake and engineering seismology studies. In the present study, this factor was investigated in the region of the 2012 Ahar-Varzaghan twin earthquakes. We used a generalized inverse method based on the shear wave windows of the aftershocks of these two earthquakes. 2860 records of broadband three-components and 540 records of short-period single-component from 1,650 aftershocks with a magnitude of 0.2 to 3.0 were used. The records of the aftershocks obtained within 29 days by a temporal seismic network by the Earthquake Research Center - Ferdowsi University of Mashhad at five broad-band and five short-period stations. Since the generalized inverse method needs a reference site to remove the source effect, the choice of the reference site was done using the results of the H/V spectral ratio method at the broad-band stations, as well as the topographic location of the stations. The frequency dependence of the was regressed in the range of 0.1 to 10 Hz and as Q_s=43 f^1.52 . This low value and high frequency-dependency can be attributed to the high heterogeneity of the crust and the active seismicity of the region.

Measuring of subsidence is often challenging due to the gradual occurrence in large-scale, and advanced measuring techniques are required. The first foresighted consequence of this catastrophic phenomenon is irreversible loss of aquifer reservoir. Subsidence is downward motion of the earth's surface with negligible horizontal vector component. Subsidence is occurring with different rates in many aquifers of the country constantly, because of excessive extraction of groundwater for years which causes lowering of the water table. Increasing the intensity of this phenomenon in recent years requires modern methods of measuring subsidence. InSAR technique can be strongly powerful that can extract vertical component in large extent, especially in areas with insufficient geodetic data. In this study, new Sentinel-1A imagery from 2014 to 2018 were used to examine the subsidence rate in the Kashmar and Khalil Abad plain. According to the high correlation between pair images, basic interferograms was calculated. Then, using SBAS method unnecessary phases were removed. Thereafter, the displacement phase was calculated and converted to the vertical component. Maximum subsidence rate is observed near the southwest suburb of Kashmar city and western part of Khalilabad plain. Results indicate that the Kashmar and Khalilabad plain was encountered maximum of 17 cm downward movement annually. Due to uneven and heterogeneous subsidence, the area has susceptibility for formation of longitudinal cracks. Final map can be used to control and manage water resources and prevent natural hazards and desertification

In this paper, the feedback or interaction between tectonic and surface processes in the Binaloud Mountains and Neyshabour plain has been investigated. To achieve this, we have used topographic data, recorded earthquake data provided by the Geophysical Institute of Tehran University (Mashhad center) and field surveying results. Surface processes affect the propagation of tectonic thrust wedges in orogenic belts. In regions tectonic processes have led to an increase in the surface slopes due to development of mountain highs, surface processes will justify the uplifted areas by smoothing the slopes, eventually shedding off a massive load of clastic sediments into the foreland basin. Because of their huge weight and volume, these sediments prevent the forward propagation of the wedge and therefore increase the accumulation rate of stress in the orogenic wedge. Also the increase of fault-plane dips in the orogenic wedge will make the slip along the fault planes hard or even impossible. Formation of out-of-sequence faults and back-rotation of preexisting thrust faults may be considered as results of these accumulated stresses. North Neyshaboor thrust fault is a later or secondary structure and can be considered as an out-of-sequence thrust because it cuts other thrust sheets and limbs of folds. Our research shows that the high volume of Paleogene/Neogen sediments in the Neyshabour foreland basin has prevented the forwards (southwestward) propagation of the Binaloud mountain range as the orogenic wedge. Releasing of the accumulated forces has therefore led to the development of the North Neyshaboor out-of-sequence fault and back-rotation of former thrust faults.

These days, hydrocarbon resources are one of the most important human needs. Therefore, it is necessary to use methods with high efficiency and low costs. Due to direct underground accessing, drilling is the most efficient method for subsurface studies. However, because of high cost and imperfect covering of the area under study, it is required to employ methods which provide better results. Seismography is one of the methods for collecting surface data, which exhibits an efficient model of reservoir characteristics. Seismic inversion is the method which enhances the resolution and accuracy of reservoir model by compiling seismic and well logging data. Impedance acoustic model results from inversion and indicates the variability of layers or fluid content. In this study, an impedance model was obtained using various inversion procedures, and porosity was then calculated. These procedures are post stack. Seismic, well logging data, and interpreted horizons were merged in Hendijan and Behregansar oil fields in the Persian Gulf. Seismic inversion was performed by band limited, sparse spike, and model based methods in Jahrom formation at a depth of about 2200m and a thickness of 300m. Finally, by comparison of the results, the model based method was introduced as the best one, because of the high correlation coefficient (99.65%) and low error (0.08)

The fractures are one of the structures, which can be used as a tool to unravel the tectonic processes in a region. The measurements of the fractures were conducted in the footwall and hanging wall of the North Neyshabour Thrust, which is one of the active faults of the region. We separated the fractures of the North Neyshabuor Thrust into tow sets of perpendicular and parallel to the fault, which suggests variations in tectonic condition. Clockwise rotation around vertical axis is the recent model, which is proposed for this region. Rotation model noted that the eastern part of NE Iran has been moving towards south and this magnitude increase towards the East. The southward movement of this region is in conflict with regional movement of the Iranian micro plate, which moves to the north. Increasing in elevation towards the east is caused by increasing in the shortening rate. Thus, a decrease in GPS vector towards the east suggests that the movement vector decreases towards the east. This does not indicate a decrease of shortening rate.