Institute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X24119980321--13083FAJournal Article19700101The released energies from the earthquakes occured during April 1967-February 1969 around
Sefid-Rud dam with 4Okm radius were analysed as a time series for modeling. The magnitudes of
the earthquakes are less than 4 in Richter scale, so thc time series is sufficient for the return
period. The monthly release of energy was obtained from the average of total energy release per
month and the model of Auto Regressive Moving Average (ARMA) is fitted to it. The model
parameters are determined from mathematical relations and based on the correlation of the
residuals, Port Monto and Akaike tests, the best model is recognized. This model is found to be
the first order, which applies less parameters, simple and is showing seismicity of the region.
Based on this model for the next 23 months the energy release and magnitude of the earthquakes
are simulated.
Since the biggest earthquake occured in this period has a magnitude 4, the simulation is
restricted to a maximum magnitude 4. The simulation of the earthquakes shows that in August
and October 1969 and in January 1971, an earthquake with magnitude of 3.5 to 4 would occur. It
is obvious, if we have longer series and bigger earthquakes, we would be able to simulate bigger
earthquakes. This simulation can compensate the lack of the earthquake records, due to
equipment defect.
For future seismicity of the region, the model is able to predict the seismicity of a month
having the related data for the previous 21 months. By applying the data of 22 months we can
predict the seismicity of the 23rd month which can be compared with the original data of 22nd and 23rd months. Finally by using 23 months original data, the prediction for the 24th month is
applicable. So by these three month prediction in this region the trend of seismicity in the near
future can be evaluated. The trend in this case is constant.The released energies from the earthquakes occured during April 1967-February 1969 around
Sefid-Rud dam with 4Okm radius were analysed as a time series for modeling. The magnitudes of
the earthquakes are less than 4 in Richter scale, so thc time series is sufficient for the return
period. The monthly release of energy was obtained from the average of total energy release per
month and the model of Auto Regressive Moving Average (ARMA) is fitted to it. The model
parameters are determined from mathematical relations and based on the correlation of the
residuals, Port Monto and Akaike tests, the best model is recognized. This model is found to be
the first order, which applies less parameters, simple and is showing seismicity of the region.
Based on this model for the next 23 months the energy release and magnitude of the earthquakes
are simulated.
Since the biggest earthquake occured in this period has a magnitude 4, the simulation is
restricted to a maximum magnitude 4. The simulation of the earthquakes shows that in August
and October 1969 and in January 1971, an earthquake with magnitude of 3.5 to 4 would occur. It
is obvious, if we have longer series and bigger earthquakes, we would be able to simulate bigger
earthquakes. This simulation can compensate the lack of the earthquake records, due to
equipment defect.
For future seismicity of the region, the model is able to predict the seismicity of a month
having the related data for the previous 21 months. By applying the data of 22 months we can
predict the seismicity of the 23rd month which can be compared with the original data of 22nd and 23rd months. Finally by using 23 months original data, the prediction for the 24th month is
applicable. So by these three month prediction in this region the trend of seismicity in the near
future can be evaluated. The trend in this case is constant.https://jesphys.ut.ac.ir/article_13083_25b4bd2dd3b33b95d153c742fa2133aa.pdfInstitute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X24119980321--13084FAJournal Article19700101On Novermber 20th, 1989, an earthquake with Ms=5.7 destroyed the Golbaf city in the Kerman province. To study the main shock and aftershocks, the Institute of
Geophysics, Tehran University, with cooperation of the Physics Department, Shahid Bahonar University of Kerman installed a temporary seismic network for about 40 days.
During this period more than 2500 events were recorded, among them 394 shocks were processed and located.
The epicenters of processed earthquakes were mostly distributed along the fault zone with 50 Ian length and 20 km width, and from 5 to 25 km depths. The mechanism
of main shock and the composite fault plane solution of aftershooks indicate thrusting, where the fault planes show a NW-SE striking with about 70° dip toward SW. It seems
that east parts of fault planes moved to the beneath its west partsOn Novermber 20th, 1989, an earthquake with Ms=5.7 destroyed the Golbaf city in the Kerman province. To study the main shock and aftershocks, the Institute of
Geophysics, Tehran University, with cooperation of the Physics Department, Shahid Bahonar University of Kerman installed a temporary seismic network for about 40 days.
During this period more than 2500 events were recorded, among them 394 shocks were processed and located.
The epicenters of processed earthquakes were mostly distributed along the fault zone with 50 Ian length and 20 km width, and from 5 to 25 km depths. The mechanism
of main shock and the composite fault plane solution of aftershooks indicate thrusting, where the fault planes show a NW-SE striking with about 70° dip toward SW. It seems
that east parts of fault planes moved to the beneath its west partshttps://jesphys.ut.ac.ir/article_13084_abb1ba290e6622c3b64f93f0d427ded6.pdfInstitute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X24119980321--13085FAJournal Article19700101In this study, based on the results obtained from laboratory measurements of compressional
and shear-wave velocities on 39 limestone rock samples in both dry and saturated states, a few
relationships have b<;,en found between physical properties of the rocks.
The data demonstrates simple systematic relationships between compressional and shear wave
velocities for both dry and saturated states. Also a few model theories have been used to predict
saturated velocities from dry velocities among those are Gassmann (1951) and Biot (1956)
theories and wyllie et al. (1956) and Raymer et al. (1980) relationships. The measurements also
show that the dry and saturated moduli decrease with increasing porosity. Our data show
excellent linear relationships between bulk and shear moduli normalised by density and VIn this study, based on the results obtained from laboratory measurements of compressional
and shear-wave velocities on 39 limestone rock samples in both dry and saturated states, a few
relationships have b<;,en found between physical properties of the rocks.
The data demonstrates simple systematic relationships between compressional and shear wave
velocities for both dry and saturated states. Also a few model theories have been used to predict
saturated velocities from dry velocities among those are Gassmann (1951) and Biot (1956)
theories and wyllie et al. (1956) and Raymer et al. (1980) relationships. The measurements also
show that the dry and saturated moduli decrease with increasing porosity. Our data show
excellent linear relationships between bulk and shear moduli normalised by density and Vhttps://jesphys.ut.ac.ir/article_13085_ed007980764920e79553a943bd59b8ad.pdfInstitute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X24119980321--13086FAJournal Article19700101Study of heat flow at the earth's surface is an important discipline of geophysics. Prior to the present work, such studies were limited only to southern Iran. In this
paper, bottom-hole temperatures of oil and gas wells in north central Iran, Kopeh Dagh, Caspian coastal plain, and Moghan plain are used for the first time to calculate
geothermal gradients; and the results are compared with those reported from the Zagros-Persian Gulf area. The range and pattern of gradient variations in Iran is more
complicated than what is represented in the global heat flow map. This intricatensess is a reflection of diverse tectonic histories of the different structural zones. In most parts
of northern Iran including Kopeh Dagh, Moghan Plain, and north central Iran gradient values are 25 °Ckm-1 or higher. For Gilan area in the Caspian coastal plain a value of 19 °Ckm-1 is obtained. There is no data for the Alborz Mountain Range yet, but considering crustal and upper mantle partial melting in the Quaternary, thermal
gradient values are expected to be at the high side of the above mentioned range or even higher. There is no geothermal data for southern central Iran, the
Sanandaj-Sirjan metamorphic belt and the Zagros thrust
zone. However, a more
complete set of data is available for the folded Zagros-Persian Gulf. Geothermal gradient is highly variable in the Zagros and contours generally stretch parallel to
structural trend, with values increasing to the south as the Moho depth decreases. Average thermal gradient is considerably higher in the eastern Zagros-Persian Gulf
relative to the area situated to the west of the Qatar-Kazeroon lineament. The regional thermal anomaly in the east coincides with the closely spaced salt domes, either
exposed or still unbreached. Salt domes not only cause more effective heat conduction, but also in the case of the Hormoz series, they have a great potential of radioactive
heat generation due to their remarkable enrichment in uranium. The anomalously high geothermal gradients is the reason why gaseous hydrocarbons are dominant in the
eastern Zagros-Persian Gulf region.Study of heat flow at the earth's surface is an important discipline of geophysics. Prior to the present work, such studies were limited only to southern Iran. In this
paper, bottom-hole temperatures of oil and gas wells in north central Iran, Kopeh Dagh, Caspian coastal plain, and Moghan plain are used for the first time to calculate
geothermal gradients; and the results are compared with those reported from the Zagros-Persian Gulf area. The range and pattern of gradient variations in Iran is more
complicated than what is represented in the global heat flow map. This intricatensess is a reflection of diverse tectonic histories of the different structural zones. In most parts
of northern Iran including Kopeh Dagh, Moghan Plain, and north central Iran gradient values are 25 °Ckm-1 or higher. For Gilan area in the Caspian coastal plain a value of 19 °Ckm-1 is obtained. There is no data for the Alborz Mountain Range yet, but considering crustal and upper mantle partial melting in the Quaternary, thermal
gradient values are expected to be at the high side of the above mentioned range or even higher. There is no geothermal data for southern central Iran, the
Sanandaj-Sirjan metamorphic belt and the Zagros thrust
zone. However, a more
complete set of data is available for the folded Zagros-Persian Gulf. Geothermal gradient is highly variable in the Zagros and contours generally stretch parallel to
structural trend, with values increasing to the south as the Moho depth decreases. Average thermal gradient is considerably higher in the eastern Zagros-Persian Gulf
relative to the area situated to the west of the Qatar-Kazeroon lineament. The regional thermal anomaly in the east coincides with the closely spaced salt domes, either
exposed or still unbreached. Salt domes not only cause more effective heat conduction, but also in the case of the Hormoz series, they have a great potential of radioactive
heat generation due to their remarkable enrichment in uranium. The anomalously high geothermal gradients is the reason why gaseous hydrocarbons are dominant in the
eastern Zagros-Persian Gulf region.https://jesphys.ut.ac.ir/article_13086_b1aa295c7f4199c747d40968b35e5a16.pdfInstitute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X24119980321--13087FAJournal Article19700101One of the steps in the seismic data processing is the tau-p transform analysis. The aspect of this transform is to improve resolution in seismic sections. The applications
of tau-p transform due to different useful aspects in seismic explorations contain: suppression or elimination of water reverberations and other multiples, velocity
analysis, migration and modeling, inversion, and noise attenuation.
In this paper, the linear and parabolic tau-p transforms are applied and considered on various models due to suppression or elimination of multiples and other unwanted
waves. These two kinds of transforms are compared with each other. Several computer
softwares developed in this research are designed to produce the synthetic seismic data. The data are then transformed to linear and parabolic tau-p for some seismic
processing. The direct waves, air waves, primary reflections, peg-leg multiples and water reverberations in two main software programs for two and more layer models are
considered. The results related to these two programs for six horizontal layers are exhibited.
A new filter is introduced and applied on the NMO corrected data in parabolic tau-p domain. Since arrival times of primaries are less than those of their multiples,
they have relative low tau and high p values; consequently, in parabolic tau-p domain, a linear corridor named as L-filter is chosen in a proper interval that contains desired
data. All data outside of this corridor is totally muted. By this procedure, multiples, air waves and direct arrivals are eliminated in tau-p domain. Then, by an inverse parabolic
tau-p the desired t-x data are obtained.One of the steps in the seismic data processing is the tau-p transform analysis. The aspect of this transform is to improve resolution in seismic sections. The applications
of tau-p transform due to different useful aspects in seismic explorations contain: suppression or elimination of water reverberations and other multiples, velocity
analysis, migration and modeling, inversion, and noise attenuation.
In this paper, the linear and parabolic tau-p transforms are applied and considered on various models due to suppression or elimination of multiples and other unwanted
waves. These two kinds of transforms are compared with each other. Several computer
softwares developed in this research are designed to produce the synthetic seismic data. The data are then transformed to linear and parabolic tau-p for some seismic
processing. The direct waves, air waves, primary reflections, peg-leg multiples and water reverberations in two main software programs for two and more layer models are
considered. The results related to these two programs for six horizontal layers are exhibited.
A new filter is introduced and applied on the NMO corrected data in parabolic tau-p domain. Since arrival times of primaries are less than those of their multiples,
they have relative low tau and high p values; consequently, in parabolic tau-p domain, a linear corridor named as L-filter is chosen in a proper interval that contains desired
data. All data outside of this corridor is totally muted. By this procedure, multiples, air waves and direct arrivals are eliminated in tau-p domain. Then, by an inverse parabolic
tau-p the desired t-x data are obtained.https://jesphys.ut.ac.ir/article_13087_d6174d5014edeb4978df44c37568314d.pdfInstitute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X24119980321--13088FAJournal Article19700101The 28th February, 1997, earthquake is the largest instrumentally recorded and the most destructive earthquake in Ardabil Province. It produced extensive damages and
heavy human lost. No significant surface rupture was observed in the field investigation. However, seismolog!cal evidence suggests that the rupture with a length of about 20 kill,
had a NW-SE trending left-lateral strike-slip mechanism. It was initiated in South-East and extended to North-West in a unilateral manner. The average stress drop was
estimated to be about 15 bar. The static displacement was calculated to be about 27cmThe 28th February, 1997, earthquake is the largest instrumentally recorded and the most destructive earthquake in Ardabil Province. It produced extensive damages and
heavy human lost. No significant surface rupture was observed in the field investigation. However, seismolog!cal evidence suggests that the rupture with a length of about 20 kill,
had a NW-SE trending left-lateral strike-slip mechanism. It was initiated in South-East and extended to North-West in a unilateral manner. The average stress drop was
estimated to be about 15 bar. The static displacement was calculated to be about 27cmhttps://jesphys.ut.ac.ir/article_13088_ffbc7553e61bc285625052cf87eb59cc.pdfInstitute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X24119980321--13089FAJournal Article19700101The Early to Middle Proterozoic Willyama Inliers in western New South Wales extend to the Curnamona section of the Olary Block in eastern South Australia. In
succession, these rocks consist of the Composite gneiss and migmatite Suite, the Quartzofeldespathic Suite, the Calcsilicate Suite, the Bimba Suite, and the Psammo
pelite Suite. The middle parts of the succession correlate stratigraphically to the units within the Broken Hill Block in New South Wales which host the well known Broken
Hill orebody. The Willyama Inliers in the Curnamona 1:250,000 sheet contain a magnetic marker horizon which consists of (i) The Quartzofeldespathic Suite, (ii) The
Calcsilicate Suite and (iii) The calcalbitite rocks (the gradation between the two Suites). This allows mapping these stratiform stratabound anomalous base metal horizons under
cover from latitude 32°S to 31°30'S and longitude 140_ to 141_ on the Kalabity and Mulyongari 1:100,000 sheets (7200 km2) using the magnetic data. The position of the non-magnetic, sulphidic and economic target, the Bimba Suite, can be deduced from the
location of the Quartzofeldespathic magnetic marker and the dip as determined from the magnetic modelling.
The magnetic marker, a distinctive feature on the magnetic maps, allows mapping of folds whose axes trend Northeast-Southwest and major shears which strike NW-SE and
NNE-SSW. The magnetic information indicates that the WilIyama rocks extend further north of the limited outcrop (latitude 32° OO'S) to latitude 31° 30'S; and to the Frome area (latitude 31 ° 00' S); and probably to the central area of the Curnamona Craton along the eastern part of the Benageri ridge. On the Curnamona 1 :250,000 sheet half
the magnetic anomalies arise from the Willyama rocks outcropping, near surface or covered. The magnetic maps indicate various types of granitic intrusions under cover.
The depth to the magnetic sources on the eastern three quarters of the Benageri 1:100,000 sheet in the Curnamona area is less than 350 metres and almost half of them are less than 200 metres deep. Such depths would not rule out exploitation of any orebodies which may be located in this prospective region. Magnetic interpretation shows that no willyama rocks are present at such relatively shallow depths in the western half of the benageti 1:100,000 sheet. This is cinsistent with the occasional drill hole data.The Early to Middle Proterozoic Willyama Inliers in western New South Wales extend to the Curnamona section of the Olary Block in eastern South Australia. In
succession, these rocks consist of the Composite gneiss and migmatite Suite, the Quartzofeldespathic Suite, the Calcsilicate Suite, the Bimba Suite, and the Psammo
pelite Suite. The middle parts of the succession correlate stratigraphically to the units within the Broken Hill Block in New South Wales which host the well known Broken
Hill orebody. The Willyama Inliers in the Curnamona 1:250,000 sheet contain a magnetic marker horizon which consists of (i) The Quartzofeldespathic Suite, (ii) The
Calcsilicate Suite and (iii) The calcalbitite rocks (the gradation between the two Suites). This allows mapping these stratiform stratabound anomalous base metal horizons under
cover from latitude 32°S to 31°30'S and longitude 140_ to 141_ on the Kalabity and Mulyongari 1:100,000 sheets (7200 km2) using the magnetic data. The position of the non-magnetic, sulphidic and economic target, the Bimba Suite, can be deduced from the
location of the Quartzofeldespathic magnetic marker and the dip as determined from the magnetic modelling.
The magnetic marker, a distinctive feature on the magnetic maps, allows mapping of folds whose axes trend Northeast-Southwest and major shears which strike NW-SE and
NNE-SSW. The magnetic information indicates that the WilIyama rocks extend further north of the limited outcrop (latitude 32° OO'S) to latitude 31° 30'S; and to the Frome area (latitude 31 ° 00' S); and probably to the central area of the Curnamona Craton along the eastern part of the Benageri ridge. On the Curnamona 1 :250,000 sheet half
the magnetic anomalies arise from the Willyama rocks outcropping, near surface or covered. The magnetic maps indicate various types of granitic intrusions under cover.
The depth to the magnetic sources on the eastern three quarters of the Benageri 1:100,000 sheet in the Curnamona area is less than 350 metres and almost half of them are less than 200 metres deep. Such depths would not rule out exploitation of any orebodies which may be located in this prospective region. Magnetic interpretation shows that no willyama rocks are present at such relatively shallow depths in the western half of the benageti 1:100,000 sheet. This is cinsistent with the occasional drill hole data.https://jesphys.ut.ac.ir/article_13089_ba09cfaa691aafe96b809633698260cc.pdfInstitute of Geophysics, University of TehranJournal of the Earth and Space Physics2538-371X24119980321--13090FAJournal Article19700101The Feb. 4, 1997 Bojnourd earthquake of M 6.8 occurred in a mountainous area, North-East Iran, and caused extensive destruction. Relatively a fewer human lives were
lost due to a strong foreshock. Field investigation and aftershocks distribution suggest a NW-SE faulting with a right-lateral strike-slip motion. Aftershock activity was
scattered indicating that the mainshock activated the nearby minor faults. Aftershocks extended to a length of 45km and a depth of 20km. The average stress drop was
estimated to be 20 bar and the static displacement was 35 em. Great destruction in the
affected area was mainly caused by poor seismic resistance of traditional adobe houses.
Well designed buildings in the epicentral region survived with minor damage. The ground-motion characteristics during the mainshock should be considered for the high
safety design of structures in the damaged area.The Feb. 4, 1997 Bojnourd earthquake of M 6.8 occurred in a mountainous area, North-East Iran, and caused extensive destruction. Relatively a fewer human lives were
lost due to a strong foreshock. Field investigation and aftershocks distribution suggest a NW-SE faulting with a right-lateral strike-slip motion. Aftershock activity was
scattered indicating that the mainshock activated the nearby minor faults. Aftershocks extended to a length of 45km and a depth of 20km. The average stress drop was
estimated to be 20 bar and the static displacement was 35 em. Great destruction in the
affected area was mainly caused by poor seismic resistance of traditional adobe houses.
Well designed buildings in the epicentral region survived with minor damage. The ground-motion characteristics during the mainshock should be considered for the high
safety design of structures in the damaged area.https://jesphys.ut.ac.ir/article_13090_da7556f2203ad933e47946017a439b81.pdf