Institute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X26120000320--13091FAJournal Article19700101This study presents the results of seismic hazard mapping and
ground motion assessment for central Alborz region in Iran. The results have been based on historical seismicity, recurrence statistics and probabilistic ground motion analysis. The seismicity parameters were calculated by Weichert Maximum Likelihood Method. Seismic
hazard was assessed as maps for 10% and 64% probability of exceedance in 50 years. The estimated values for peak ground
acceleration were 0.53g and 0.19g for the above probability levels respectively in the region 48.5E to 54.5E and 34.5N to 37.5N.
Because of low amount of data and uncertainty of location, time and magnitude of the historical events, estimated value also contains uncertainty. The results of this study show importance of estimating slip rate of faults for more accurate studies in the futureThis study presents the results of seismic hazard mapping and
ground motion assessment for central Alborz region in Iran. The results have been based on historical seismicity, recurrence statistics and probabilistic ground motion analysis. The seismicity parameters were calculated by Weichert Maximum Likelihood Method. Seismic
hazard was assessed as maps for 10% and 64% probability of exceedance in 50 years. The estimated values for peak ground
acceleration were 0.53g and 0.19g for the above probability levels respectively in the region 48.5E to 54.5E and 34.5N to 37.5N.
Because of low amount of data and uncertainty of location, time and magnitude of the historical events, estimated value also contains uncertainty. The results of this study show importance of estimating slip rate of faults for more accurate studies in the futureInstitute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X26120000320--13092FAJournal Article19700101Institute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X26120000320--13093FAJournal Article19700101Thermal conductivity of rocks for accurate estimation of geothermal heat flux is important. Here we introduce the desgin and
construction of a newly built system based on the principle of steady state heat conduction using divided bars method.
The system is computer controlled and has been calibrated using standard quartz samples. Typical error in the system is about one
percent which is mainly due to the way the sample is positioned in the system. For proper positioning, one must use a conductive greace
to generate good contacts between the sample and the rods.
Measurements of a few rock samples from Iran, give thermal conductivites which are within the reported values by others. The geothermal heat flux based on these measurements and the geothermal gradients from different parts of Iran, show that its mean value varies between 45 and 70 mW/m2, for these regions.
Variations in geothermal gradient along the depth of same wells may also indicate the variations in rock with different thermal conductvities.Thermal conductivity of rocks for accurate estimation of geothermal heat flux is important. Here we introduce the desgin and
construction of a newly built system based on the principle of steady state heat conduction using divided bars method.
The system is computer controlled and has been calibrated using standard quartz samples. Typical error in the system is about one
percent which is mainly due to the way the sample is positioned in the system. For proper positioning, one must use a conductive greace
to generate good contacts between the sample and the rods.
Measurements of a few rock samples from Iran, give thermal conductivites which are within the reported values by others. The geothermal heat flux based on these measurements and the geothermal gradients from different parts of Iran, show that its mean value varies between 45 and 70 mW/m2, for these regions.
Variations in geothermal gradient along the depth of same wells may also indicate the variations in rock with different thermal conductvities.Institute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X26120000320--13094FAJournal Article19700101Compressional and shear wave velocities have been measured in three orthogonal directions in cubic samples of three groups of rocks
in both dry and water-saturated states under low axial stress.
The three groups of rocks consist of seven granite samples taken
from Bandarabbas, six sandstone samples from Chabahar and fifteen andesite samples from Oromieh. Thomsen's three dimensionless anisotropy parameters E, Y and £5 have been calculated for each sample. The results show that for all three groups of rocks the
assumption of elliptical anisotropy is justified. Also it is observed that
for all of the rocks the elastic constants, Young's moduli, Poisson's
ratios and bulk moduli in saturated samples are greater than corresponding values in dry samples.Compressional and shear wave velocities have been measured in three orthogonal directions in cubic samples of three groups of rocks
in both dry and water-saturated states under low axial stress.
The three groups of rocks consist of seven granite samples taken
from Bandarabbas, six sandstone samples from Chabahar and fifteen andesite samples from Oromieh. Thomsen's three dimensionless anisotropy parameters E, Y and £5 have been calculated for each sample. The results show that for all three groups of rocks the
assumption of elliptical anisotropy is justified. Also it is observed that
for all of the rocks the elastic constants, Young's moduli, Poisson's
ratios and bulk moduli in saturated samples are greater than corresponding values in dry samples.Institute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X26120000320--13095FAJournal Article19700101Institute of Geophysics has established a digital telemetric seismic
network in Tehran region since 1997. Wealth of data from recorded
local earthquakes create an opportunity to image crust and upper mantle in the region. We proposed to study velocity and interface structure of
the crust and upper mantle in the Tehran region using local earthquakes. As a fITst step we obtained a 1-D velocity model by analysis of the
travel-time curves for nearly 20000 P-wave arrival times from 2900 local earthquakes. Recorded earthquakes were classified along the
five separate profiles, and corresponding travel-time curves were analyzed. In addition, a 3-D ray tracing forward modeling code was
written in order to refine model parameters. The results indicate a two-layer crust in the study area. Compressional wave velocity of the first layer is 6.05 km/s and that of second layer is 7.01 km/s. Depths for Conrad and Moho discontinuities were obtained 16 and 46 km
respectively, which well correlates with the results of the previous gravimetric crustal studies. Since, it was difficult to pick arrival time of the direct shear waves, we could not determined the shear wave velocity for the first layer in the crust, but it found to be 3.90 and 5.20 km/s for
the second layer of the crust and the Moho, respectivelyInstitute of Geophysics has established a digital telemetric seismic
network in Tehran region since 1997. Wealth of data from recorded
local earthquakes create an opportunity to image crust and upper mantle in the region. We proposed to study velocity and interface structure of
the crust and upper mantle in the Tehran region using local earthquakes. As a fITst step we obtained a 1-D velocity model by analysis of the
travel-time curves for nearly 20000 P-wave arrival times from 2900 local earthquakes. Recorded earthquakes were classified along the
five separate profiles, and corresponding travel-time curves were analyzed. In addition, a 3-D ray tracing forward modeling code was
written in order to refine model parameters. The results indicate a two-layer crust in the study area. Compressional wave velocity of the first layer is 6.05 km/s and that of second layer is 7.01 km/s. Depths for Conrad and Moho discontinuities were obtained 16 and 46 km
respectively, which well correlates with the results of the previous gravimetric crustal studies. Since, it was difficult to pick arrival time of the direct shear waves, we could not determined the shear wave velocity for the first layer in the crust, but it found to be 3.90 and 5.20 km/s for
the second layer of the crust and the Moho, respectivelyInstitute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X26120000320--13096FAJournal Article19700101Presence of a conductive body in a magnetic field causes inductive currents to now in the body. The secondary magnetic field of this currents adds to the primary magnetic field. The receiver then respor.ds to the resultant of the arriving primary and secondary fields, so that the response differs in both phase and amplitude.
In the VLF method the primary electromagnetic field has
frequency of 5 to 30 KHz, and is received as a plane wave at the measuring point. In this paper we are using the VLF method in the
area of a copper mine (Ghaleh Zary copper mine) located 180 kIn south of the city of Birjand.
Measurements were carried out along 21 east-west profiles and the usual methods were used in the interpretation of data. The VLF results agree well with both geological information and the results of
IP measurements.Presence of a conductive body in a magnetic field causes inductive currents to now in the body. The secondary magnetic field of this currents adds to the primary magnetic field. The receiver then respor.ds to the resultant of the arriving primary and secondary fields, so that the response differs in both phase and amplitude.
In the VLF method the primary electromagnetic field has
frequency of 5 to 30 KHz, and is received as a plane wave at the measuring point. In this paper we are using the VLF method in the
area of a copper mine (Ghaleh Zary copper mine) located 180 kIn south of the city of Birjand.
Measurements were carried out along 21 east-west profiles and the usual methods were used in the interpretation of data. The VLF results agree well with both geological information and the results of
IP measurements.Institute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X26120000320--13097FAJournal Article19700101The susceptibility and magnetic anisotropy of the volcanic rocks of
Damavand volcano lacated in NE of Tehran, Iran and their relationships with petro fabric, geology and strain have been studied.
For this purpose the susceptibility of several sampels from six sites of the north Emamzadeh Ali stream which is located in NE of
Tehran was measured and then magnetic fabric was computed.
Measurement of susceptibility and computation of its anisotropy
have been done on the basis of second order tensor which was defind
for susceptibility ellipsoid and its anisotropy. The dominant strain of the region is determined by considering the correspondence of the susceptibility ellipsoid with the strain ellipsoid. The direct estimating methods of strain ellipsoid are very hard comparing to this method. Other advantage of the method used in this study is to correlate the geology and petrology maps. The results show a number of linear relationships between various parameters of the magnetic fabric.The susceptibility and magnetic anisotropy of the volcanic rocks of
Damavand volcano lacated in NE of Tehran, Iran and their relationships with petro fabric, geology and strain have been studied.
For this purpose the susceptibility of several sampels from six sites of the north Emamzadeh Ali stream which is located in NE of
Tehran was measured and then magnetic fabric was computed.
Measurement of susceptibility and computation of its anisotropy
have been done on the basis of second order tensor which was defind
for susceptibility ellipsoid and its anisotropy. The dominant strain of the region is determined by considering the correspondence of the susceptibility ellipsoid with the strain ellipsoid. The direct estimating methods of strain ellipsoid are very hard comparing to this method. Other advantage of the method used in this study is to correlate the geology and petrology maps. The results show a number of linear relationships between various parameters of the magnetic fabric.Institute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X26120000320--13098FAJournal Article19700101We present numerical solution of the equations of motion of the driven spring-block model with stick-slip dynamics. The system
consists of an array of N masses which describes the statistical and dynamical properties of dissipative systems. Here, we mostly emphasise the very low and very high velocity regimes. We show that
there is a clear shift in distribution of the slip-force when we move f_om low velocity regime to intermediate and then to high velocity regime. This changing behaviour is dependent to the behaviour of S
type in intermediate velocity and to Inverse-Gaussian distribution in high values of velocity.We present numerical solution of the equations of motion of the driven spring-block model with stick-slip dynamics. The system
consists of an array of N masses which describes the statistical and dynamical properties of dissipative systems. Here, we mostly emphasise the very low and very high velocity regimes. We show that
there is a clear shift in distribution of the slip-force when we move f_om low velocity regime to intermediate and then to high velocity regime. This changing behaviour is dependent to the behaviour of S
type in intermediate velocity and to Inverse-Gaussian distribution in high values of velocity.Institute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X26120000320--13099FAJournal Article19700101In shallow seismic survey source generated coherent noises have a wide range of spectral overlap with seismic signals. Consequently, conventional band-pass filtering could not suppress them. Their elimination requires the implementation of some special techniques that
may not commonly used for this purpose. The K-L decomposi- tion
technique treats each trace as a data vector, and computes a set of
uncorrela ted
principal
component
traces
from
an
eigenvalue
decomposition of the matrix of zerlag cross-covariance of the given multi-trace input data set. The principal component traces are arranged in order of decreasing energy content, i. e. the signal with the largest variance will appear as first principal component and so on.
Subsequently, the input record are reconstructed utilizing only the information contained in a specified selection of the principal component
traces, those associated with large eigenvalues. This amounts to reconstruction of the coherent energy present in the input data seLIn
this study the K-L transformation technique was applied on 96-trace shot records of 3-D seismic survey flattened on the air wave, then the first
fIVe of the 96 principal components were used to estimate the air wave components of the records. The technique was found an effective way of eliminating air waves from engineering-scale 3-D seismic shot records.In shallow seismic survey source generated coherent noises have a wide range of spectral overlap with seismic signals. Consequently, conventional band-pass filtering could not suppress them. Their elimination requires the implementation of some special techniques that
may not commonly used for this purpose. The K-L decomposi- tion
technique treats each trace as a data vector, and computes a set of
uncorrela ted
principal
component
traces
from
an
eigenvalue
decomposition of the matrix of zerlag cross-covariance of the given multi-trace input data set. The principal component traces are arranged in order of decreasing energy content, i. e. the signal with the largest variance will appear as first principal component and so on.
Subsequently, the input record are reconstructed utilizing only the information contained in a specified selection of the principal component
traces, those associated with large eigenvalues. This amounts to reconstruction of the coherent energy present in the input data seLIn
this study the K-L transformation technique was applied on 96-trace shot records of 3-D seismic survey flattened on the air wave, then the first
fIVe of the 96 principal components were used to estimate the air wave components of the records. The technique was found an effective way of eliminating air waves from engineering-scale 3-D seismic shot records.Institute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X26120000320--13100FAJournal Article19700101Ice initiation in clouds, a most important field of meteorological
research during the last 50 years, has been of special interest to cloud
modification scientists. However, despite many success in this field there remains numerous ambiguities in the ice nucleation process.
One of the most important source of ice production within clouds is Hallett-Mossop (H-M) ice multiplication process. In this research
work, The H-M process was analyzed at a relatively constant rime surface temperature (Ts =: -5°C) and liquid water content (L we =: 0.93 gm-3) over a high range of updraught velocities than before (from 1.5 to 12 ms-l) with a rotating rod appratus with radii of either
15 or 25 em.
Experiment detected a local maximum of about 35 to 40 splinters per mg of rime close to 3 ms-l. In addition, for the first time it was detected that there is a maximum rate of 60 to 70 splinters per mg of rime at updraught velocity of 6 ms-I, Possibly due to a combination of
rime texture change from feathery to kernel and the ice shell-fracture process. It was found that the radial acceleration at constant updraught velocity did not have significant effects on splinter
production.Ice initiation in clouds, a most important field of meteorological
research during the last 50 years, has been of special interest to cloud
modification scientists. However, despite many success in this field there remains numerous ambiguities in the ice nucleation process.
One of the most important source of ice production within clouds is Hallett-Mossop (H-M) ice multiplication process. In this research
work, The H-M process was analyzed at a relatively constant rime surface temperature (Ts =: -5°C) and liquid water content (L we =: 0.93 gm-3) over a high range of updraught velocities than before (from 1.5 to 12 ms-l) with a rotating rod appratus with radii of either
15 or 25 em.
Experiment detected a local maximum of about 35 to 40 splinters per mg of rime close to 3 ms-l. In addition, for the first time it was detected that there is a maximum rate of 60 to 70 splinters per mg of rime at updraught velocity of 6 ms-I, Possibly due to a combination of
rime texture change from feathery to kernel and the ice shell-fracture process. It was found that the radial acceleration at constant updraught velocity did not have significant effects on splinter
production.Institute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X26120000320--13101FAJournal Article19700101Laboratory experiments have a specific significance in mInIng exploration to detemine electrical properties of rock specially in the intended parameters in IP procedure.
For the time being, IP geophysical procedure receives a specific significance in metallic ore deposits exploration. However, separation
of IP anomalies of massive from disseminated mineralization
according to the measured IP amounts with common procedures isn't possible. This research has been done on measurement of polarizability in the Taknar copper ore deposits. on the basis of laboratory experiment, polarizability has been measured in three
normal directions (A, B, C), and then the mean apparent polarizability in different time after cut off has been calculated. As a result of this operations, a model is presented on which by measuring apparent polarizability and then their mean in two early and late time after cut off (e. g. one 0.5 and the other 17 seconds after electricity
cut off and calculation of _ 17 ratio) We can separate the anomalies
TI 0.5
of the mineralizations.
The ratio specimens in massive mineralization is dramatically larger than disseminated mineralization. This result is used in mining exploration. It's necessary to state that the mean for apparent polarizability in 0.5 second after electricity cut off for massive and disseminated mineralization have a relatively high and approximately near each other amounts and so if only TJ 0.5 is measured, separation
between the apparent polarizability anomalies from the minerali¬zation point of view is not possible.Laboratory experiments have a specific significance in mInIng exploration to detemine electrical properties of rock specially in the intended parameters in IP procedure.
For the time being, IP geophysical procedure receives a specific significance in metallic ore deposits exploration. However, separation
of IP anomalies of massive from disseminated mineralization
according to the measured IP amounts with common procedures isn't possible. This research has been done on measurement of polarizability in the Taknar copper ore deposits. on the basis of laboratory experiment, polarizability has been measured in three
normal directions (A, B, C), and then the mean apparent polarizability in different time after cut off has been calculated. As a result of this operations, a model is presented on which by measuring apparent polarizability and then their mean in two early and late time after cut off (e. g. one 0.5 and the other 17 seconds after electricity
cut off and calculation of _ 17 ratio) We can separate the anomalies
TI 0.5
of the mineralizations.
The ratio specimens in massive mineralization is dramatically larger than disseminated mineralization. This result is used in mining exploration. It's necessary to state that the mean for apparent polarizability in 0.5 second after electricity cut off for massive and disseminated mineralization have a relatively high and approximately near each other amounts and so if only TJ 0.5 is measured, separation
between the apparent polarizability anomalies from the minerali¬zation point of view is not possible.