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Land subsidence induced by soil consolidation is one of the natural hazards that occur gradually. This phenomenon has reached its critical state in most regions of Iran. Factors affecting subsidence are groundwater level depletion, land cover, soil type, elevation, slops gradient, rock bed depth, etc. The causes of subsidence should be investigated so that decisions could be based on the real characteristics of the region. Decrease in groundwater level is one of the most important factors that influences subsidence but due to the complexity of the relationship between subsidence and other factors, a direct linear relationship between groundwater level and subsidence cannot be considered. The study aimed to investigate the relationship between subsidence and groundwater changes through relationship between the two parameters in the period 2014 to 2018 in Isfahan. In this regard, the time series of radar interferometry and the time series of water levels of piezometric wells in the Isfahan were studied. The results show that in 12% of the wells, no correlation exists, in 9%, poor positive ignorable correlation, in 12%, fair positive correlation, in 48%, significant positive correlation, in 6%, poor negative ignorable correlation, in 4% fair negative correlation and in 9% there is a strong and negative significant correlation between the subsidence rate and the groundwater level. Correlation values show the complexity of the relationship between subsidence and water level depletion. Therefore, the relationship between subsidence and its causative factors requires more detailed studies and comprehensive models. [ABSTRACT FROM AUTHOR]

Seismic interferometry is a method that allows the retrieval of the seismic response at one receiver from a virtual source at the position of another receiver. In recent years, seismic interferometry has become a common tool in seismological studies. With continuous recording data in seismic stations, new opportunities are available to seismologists to present new hypotheses and studies. Continuous data contains ambient noise which has random amplitudes and phases and can propagate in all possible directions, so by using ambient noise, it is possible to retrieve responses between two seismic stations. In most applications, long-duration vertical and horizontal components of continuous time series recorded at two stations are cross-correlated to approximate the Green's function between the two stations. After stacking all available data for each station's pairs, group velocity dispersion curves are measured using multiple-filter analysis for each EGF signal. In our research, group velocity dispersion measurements are used for tomography. The radial anisotropy can be inferred from the Love-Rayleigh (L-R) discrepancy, that is, from the difference between the travelling speeds of horizontally and vertically polarized surface waves. Seismic anisotropy in the Earth's crust is the signature of past and ongoing crustal deformation. Thus, observation of this anisotropy reflects the nature and distribution of the deformation bearing on the crustal rock. In conventional seismic tomography techniques, it is necessary to determine the dimensions of grids or other parameters such as smoothing and damping. A two-step inversion algorithm is employed to solve the tomographic inverse problem. In this study, transdimensional tomography is applied, which adapts to a non-uniform data coverage without requiring any arbitrary regularization such as damping or smoothing. It is a one-step non-linear tomographic algorithm. The algorithm is rooted in a Bayesian framework using Markov chains with reversible jumps. The study area in this research is the Central Alborz area (latitude 34.5-38 N degrees and longitude 48.5-54.5 E degrees). We process all available contentious vertical and horizontal seismic data from the Iranian Seismological Center (IRSC) and the International Institute of Earthquake Engineering and Seismology (IIEES) in this region for the three years from 2013 through 2016. Also, we use data from earthquakes with magnitude above 3.5, which were recorded on these stations between 2006 and 2016. The results obtained from seismic tomography and radial anisotropy show the possibility of separation between different tectonic seismic regions based on the velocity anomalies and radial anisotropy. Moreover, radial anisotropy shows the cooled Damavand magma at a depth of about 20 km. [ABSTRACT FROM AUTHOR]

Land subsidence as a hydrogeomorphology event is currently occurring dangerously in many plains of the country due to uncontrolled groundwater extraction from water bearing layers, and accordingly monitoring and studying this phenomenon seems to be necessary. In this study, land subsidence rate of the Najafabad aquifer was determined through the Differential Radar Interferometry (DInSAR) processing of the ASAR and PALSAR radar data and the results were validated by comparying with the differential leveling and groundwater level drowdown data. Processing of the ASAR sensor data estimates the land subsidence in the Najafabad plain at an average annual subsidence rate of 6.7 cm and a total of 41 cm during 6 years period and processing of the PALSAR data suggests an annual rate of 7.7 cm and total subsidence of 30 cm during 4 years period. Most of the occured displacements are related to the Tiranchi, Koushk, Ghahderijan, Goldasht and Falavarjan cities. The simultaneous groundwater level data with acquisition date of the radar satellite images between 2002 and 2014 shows a drawdown ranging from 0.5 to 46.5 meters in the south and east to north of the Najafabad city consistent with the estimated land subsidence areas.The DInSAR processing of the PALSAR data has led to a more accurate results with higher spatial resolution. Results of the radar data processing can be employed for the hazard zonation directly utilized for management and planning of control and preventive measures. [ABSTRACT FROM AUTHOR]

The persistent scattering interferometry (PSI) technique is a valuable tool in displacements' monitoring of earth's surface. The persistent scattering interferometry (PSI) based on persistent scatterrer (PSInSAR) is one of the techniques used to reduce constraints (temporal and spatial incoherency). It is based on persistent scatterer and monitor displacement of only the pixels with timely-constant properties of scatterer. In order to detect and monitor landslides, two time series SAR data sets including PALSAR ascending images from 2007 to 2010 and ASAR images from 2003 to 2010 with C-band and L-band wavelength were applied, respectively. Also, the PSI technique was implemented in a landslide near Noghol village, Padena, Semirom of Isfahan province. The results revealed that both PALSAR and ASAR data set were efficient in identifying Noghol landslide. The results obtained from ASAR and PALSAR images processing (with the values of 1253 mm and 1578 mm in two stages of time 4 and 7 years, respctively) were compared. The obtained vertical displacement's rate of the landslide by using ASAR data was more suitable because of its descending orbit. However, PALSAR images that indetified more persistent scatterrer points were better in the detection of the landslide area. The results of GPS and PSInSAR techniques revealed that landslide displacement values and aspect were the same, confirming 135 centimeters of displacement to the west aspect. Finally, a combination of radar data in two different passes provided the possibility of monitoring the mechanism of landslide and its movement direction. [ABSTRACT FROM AUTHOR]