University of Tehran PressJournal of the Earth and Space Physics2538-371X30120040320Attenuation relationships of seismic intensity in IranAttenuation relationships of seismic intensity in Iran10873FAAliMoradiInstitute of Geophysics, University of Tehran0000-0002-0836-9027NoorbakhshMirzaeiInstitute of Geophysics, University of TehranMehdiRezapourInstitute of Geophysics, University of TehranJournal Article19700101The isoseismal maps for 22 earthquakes in different regions of Iran were analyzed to study the attenuation of seismic intensity with the distance from the epicentre under a certain surface wave magnitude (Ms). The attenuation relationships were derived by using an iterative least squares fit procedure. These equations were derived from more basic concepts assuming that the intensity is proportional to the logarithm of seismic energy density at any location empirically. The isoseismal maps are elongated in the direction of local structural trend of causative faults. Therefore, attenuation relationships for the main direction of fault, transverse to it and average attenuation were derived. <br />Ia =11.564 + 0.943M — 2.508Ln(Ra + 33) a = 0.79 Ra <200km along the main direction of fault <br />Ib= 9.469 + 0.717M —2.121Ln(Rb + 13) a = 0.49 Rb I = 11.926 + 0.831M — 2.7Ln(R + 22) a = 0.49 R<167km average attenuation Where M is the surface wave magnitude and I is the intensity at a distance R(km) from the epicenter. <br />The attenuation of seismic intensity in Iran is faster than the East and West of China and Sicily and Calabria in Italy, apart from different tectonic characteristics of these regions.The isoseismal maps for 22 earthquakes in different regions of Iran were analyzed to study the attenuation of seismic intensity with the distance from the epicentre under a certain surface wave magnitude (Ms). The attenuation relationships were derived by using an iterative least squares fit procedure. These equations were derived from more basic concepts assuming that the intensity is proportional to the logarithm of seismic energy density at any location empirically. The isoseismal maps are elongated in the direction of local structural trend of causative faults. Therefore, attenuation relationships for the main direction of fault, transverse to it and average attenuation were derived. <br />Ia =11.564 + 0.943M — 2.508Ln(Ra + 33) a = 0.79 Ra <200km along the main direction of fault <br />Ib= 9.469 + 0.717M —2.121Ln(Rb + 13) a = 0.49 Rb I = 11.926 + 0.831M — 2.7Ln(R + 22) a = 0.49 R<167km average attenuation Where M is the surface wave magnitude and I is the intensity at a distance R(km) from the epicenter. <br />The attenuation of seismic intensity in Iran is faster than the East and West of China and Sicily and Calabria in Italy, apart from different tectonic characteristics of these regions.https://jesphys.ut.ac.ir/article_10873_d8a19fc42b05b559fec609a60b7c7b39.pdfUniversity of Tehran PressJournal of the Earth and Space Physics2538-371X30120040320--10874FAJournal Article19700101The migration process removes the effect of wave propagation from the recorded seismic data. As an application of this operator, seismic events will move towards their correct positions, diffractions have to collapse and dipping events have to move to their correct subsurface locations.
In this article different algorithms of the migration operator have been considered and applied on real data. Based on the results, the Kirchhoff migration, which is the most common algorithm, was chosen and used to apply for pre-stack depth migration on real data. The data obtained from an oil field in the southern part of Iran. Subsequently the obtained results were comparedThe migration process removes the effect of wave propagation from the recorded seismic data. As an application of this operator, seismic events will move towards their correct positions, diffractions have to collapse and dipping events have to move to their correct subsurface locations.
In this article different algorithms of the migration operator have been considered and applied on real data. Based on the results, the Kirchhoff migration, which is the most common algorithm, was chosen and used to apply for pre-stack depth migration on real data. The data obtained from an oil field in the southern part of Iran. Subsequently the obtained results were comparedhttps://jesphys.ut.ac.ir/article_10874_ec698306c39c2fb225e5d03803195d1e.pdfUniversity of Tehran PressJournal of the Earth and Space Physics2538-371X30120040320--10875FAJournal Article19700101In conventional seismic reflection technique to improve the signal to noise ratio processing steps perform in common midpoint (CDP) gathers. To remove the effects of the offset normal move out correction, the operator does not perform well through reflectors which have intersecting dips beneath the surface. In this case, the dip move out operator will be able to remove the effect of the dip. All the known dip-move out (DM0) algorithms that are not integral methods require seismic data to be sorted in regularly sampled constant-offset sections. Sometimes sorting data is time consuming and difficult. In contrast, DM0 in shot profiles can be applied directly to shot records. The shot-DMO operator is space- variant and time-variant. After a logarithmic transformation the time and the space coordinates, the operator becomes time-invariant and space-invariant. In this paper, shot-DMO operator was used for a 2-D seismic line of central Iran. Field data show that the shot-DMO method yields stacked sections better than stacked sections with f-k DM0 for constant- offset sections.In conventional seismic reflection technique to improve the signal to noise ratio processing steps perform in common midpoint (CDP) gathers. To remove the effects of the offset normal move out correction, the operator does not perform well through reflectors which have intersecting dips beneath the surface. In this case, the dip move out operator will be able to remove the effect of the dip. All the known dip-move out (DM0) algorithms that are not integral methods require seismic data to be sorted in regularly sampled constant-offset sections. Sometimes sorting data is time consuming and difficult. In contrast, DM0 in shot profiles can be applied directly to shot records. The shot-DMO operator is space- variant and time-variant. After a logarithmic transformation the time and the space coordinates, the operator becomes time-invariant and space-invariant. In this paper, shot-DMO operator was used for a 2-D seismic line of central Iran. Field data show that the shot-DMO method yields stacked sections better than stacked sections with f-k DM0 for constant- offset sections.https://jesphys.ut.ac.ir/article_10875_5508c827fd828aafcaf5916e8eaa30e3.pdfUniversity of Tehran PressJournal of the Earth and Space Physics2538-371X30120040320--10876FAJournal Article19700101https://jesphys.ut.ac.ir/article_10876_47cb9892a61163945dfc0a10206f8504.pdfUniversity of Tehran PressJournal of the Earth and Space Physics2538-371X30120040320--10877FAJournal Article19700101In quantitative and qualitative assessment of the numerical algorithms for barotropic primitative equations, comparision with the real atmosphere can not be used as the main criterion to determine the accuracy of the algorithms. This holds particularly for limited-area applications when boundary conditions add to the difficulties of determining the true solution. The complexity comes from a combinations of the barotropic primitive model error, the numerical algorithm error, and errors in the way data are assimilated to the model. It is thus necessary to use ever increasingly our dynamical knowledge of the behavior of the solutions of the barotropic primitive, or shallow water, equations in the process of determining the accuracy of numerical algorithms. A useful approach here is to study balanced (vortical) and imbalanced (gravity waves) parts of the flows, and their interaction. In spite of the limitations faced when working with real-atmosphere data, such study can uncover some important information on the working of the algorithms. Having this objective in mind, the present paper is devoted to the study of spatio-temporal behavior of balanced and imbalanced parts in three numerical algorithms for the regional barotropic primitive equation. The algorithms are: the potential enstrophy conserving Eulerian algorithm of Sadoumy (1975), and two algorithms derived from Sadoumy’s algorithm by simply changing the prognostic variables from :momentum-geopotential height to (i) Rossby potential vorticity (PV), divergence, geopotential height, (ii) PV, divergence, and ageostrophic vorticity. In the latter two algorithms, PV is solved by a standard semi-Lagrangian method using piecewise bicubic interpolation and the other prognostic variables are solved by the proper use of Sadoumy’s algorithm for momentum components and geopotential height. Compared with the Eulerian algorithm of Sadourny, the PV-based algorithm shows a marked improvement in the representation of both balanced and imbalanced parts of the flow.In quantitative and qualitative assessment of the numerical algorithms for barotropic primitative equations, comparision with the real atmosphere can not be used as the main criterion to determine the accuracy of the algorithms. This holds particularly for limited-area applications when boundary conditions add to the difficulties of determining the true solution. The complexity comes from a combinations of the barotropic primitive model error, the numerical algorithm error, and errors in the way data are assimilated to the model. It is thus necessary to use ever increasingly our dynamical knowledge of the behavior of the solutions of the barotropic primitive, or shallow water, equations in the process of determining the accuracy of numerical algorithms. A useful approach here is to study balanced (vortical) and imbalanced (gravity waves) parts of the flows, and their interaction. In spite of the limitations faced when working with real-atmosphere data, such study can uncover some important information on the working of the algorithms. Having this objective in mind, the present paper is devoted to the study of spatio-temporal behavior of balanced and imbalanced parts in three numerical algorithms for the regional barotropic primitive equation. The algorithms are: the potential enstrophy conserving Eulerian algorithm of Sadoumy (1975), and two algorithms derived from Sadoumy’s algorithm by simply changing the prognostic variables from :momentum-geopotential height to (i) Rossby potential vorticity (PV), divergence, geopotential height, (ii) PV, divergence, and ageostrophic vorticity. In the latter two algorithms, PV is solved by a standard semi-Lagrangian method using piecewise bicubic interpolation and the other prognostic variables are solved by the proper use of Sadoumy’s algorithm for momentum components and geopotential height. Compared with the Eulerian algorithm of Sadourny, the PV-based algorithm shows a marked improvement in the representation of both balanced and imbalanced parts of the flow.https://jesphys.ut.ac.ir/article_10877_0865fd19f407149e3a6a70c6ab86434a.pdfUniversity of Tehran PressJournal of the Earth and Space Physics2538-371X30120040320--10878FAJournal Article19700101Snowmelt-runoff simulation is an important concern in different aspects of snowy watershed management. But data scarcity is often an obstacle in such a simulation. Inadequate data has restricted the modelers to employ simpler methods. The present paper is aimed at modeling ungauged snowy catchments with more complicated methods, wherein the required data has been generated. For this objective the SWAT (Soil and Water Assessment tool), Degree-Day, SRM, and SNOW17 are identified for detailed evaluations, which are combinations of temperature, temperature-radiation and energy budget based methods. These methods have been programmed and linked with the SWAT model so as to take advantage of SWAT weather data generation capability, and also to ensure uniformity in evaluation of the snowmelt algorithms. Off line performance evaluation of these selected modules has been carried out for the Ammameh watershed in Iran. The results show better performance of the energy budget method using synthesized data, compared with solely simple temperature-based method.Snowmelt-runoff simulation is an important concern in different aspects of snowy watershed management. But data scarcity is often an obstacle in such a simulation. Inadequate data has restricted the modelers to employ simpler methods. The present paper is aimed at modeling ungauged snowy catchments with more complicated methods, wherein the required data has been generated. For this objective the SWAT (Soil and Water Assessment tool), Degree-Day, SRM, and SNOW17 are identified for detailed evaluations, which are combinations of temperature, temperature-radiation and energy budget based methods. These methods have been programmed and linked with the SWAT model so as to take advantage of SWAT weather data generation capability, and also to ensure uniformity in evaluation of the snowmelt algorithms. Off line performance evaluation of these selected modules has been carried out for the Ammameh watershed in Iran. The results show better performance of the energy budget method using synthesized data, compared with solely simple temperature-based method.https://jesphys.ut.ac.ir/article_10878_69b16b84b7bd0417c15a39d9d0977198.pdfUniversity of Tehran PressJournal of the Earth and Space Physics2538-371X30120040320--10879FAJournal Article19700101A microgravity investigation was conducted on an excavated foundation located in the Technical University of Tehran. The aim was the detection of subsurface cavities or other anomalous conditions that threaten the stability of the foundation. The survey consists of 420 gravity stations. The positive coarse grain alluvium saturated by surplus water and negative cavity anomalies have been detected based on the Bouguer and second vertical derivative maps. The depth of the sources have also been determined. To confirm the results an inversion 2D-modelling is also applied to residual anomalies. Some of the shallow accessible anomalies have been confirmed in the field by excavation.A microgravity investigation was conducted on an excavated foundation located in the Technical University of Tehran. The aim was the detection of subsurface cavities or other anomalous conditions that threaten the stability of the foundation. The survey consists of 420 gravity stations. The positive coarse grain alluvium saturated by surplus water and negative cavity anomalies have been detected based on the Bouguer and second vertical derivative maps. The depth of the sources have also been determined. To confirm the results an inversion 2D-modelling is also applied to residual anomalies. Some of the shallow accessible anomalies have been confirmed in the field by excavation.https://jesphys.ut.ac.ir/article_10879_61a552855b8b20819ab3c9a1baaded2b.pdfUniversity of Tehran PressJournal of the Earth and Space Physics2538-371X30120040320--10880FAJournal Article19700101Travel time inversion has been used in this study in order to obtain a velocity model. This velocity model has been used in a depth migration algorithm afterwards.
To achieve this purpose three main steps are as follows: picking phases, forward modeling, inverse modeling and finally using an appropriate depth migration algorithm to apply to the data.Travel time inversion has been used in this study in order to obtain a velocity model. This velocity model has been used in a depth migration algorithm afterwards.
To achieve this purpose three main steps are as follows: picking phases, forward modeling, inverse modeling and finally using an appropriate depth migration algorithm to apply to the data.https://jesphys.ut.ac.ir/article_10880_064810850b276e23c3b2ecc5705172b7.pdfUniversity of Tehran PressJournal of the Earth and Space Physics2538-371X30120040320--10881FAJournal Article19700101https://jesphys.ut.ac.ir/article_10881_7b66328e94a0f3af7a759f5d2f74da9d.pdf