JOURNAL OF THE EARTH
Year:2008 | Volume:3 | Issue:3|Papers Count:10

The area under investigation is the part of Fars (eastern Zagros) between Kazeron and Razak faults and investigation of its tectonic position is the main aim of this Paper. In order to this, results of previous workers have compiled together. In the other hand, geologic and seismic data have integrated with geophysical data and interpretations.Therefore, it appears that formation of high zones and embayments are the results of basement configuration and its magnetic anomalies are adapted on structural boundaries.Finally, according to all evidence, Razak, Nezam Abad, Sabzposhan and Kareh Bas faults are basement faults.

This manuscript presents an attenuation relationship of peak ground acceleration (PGA) derived from Hormozgan strong motion data for hard rock, soft rock, soil and soft soil sites and an acceleration map of Hormozgan province (Southern Iran) on this data. For this purpose 370 records in Hormozgan Province (Southern Iran) between 1973 and July 2007 are selected.The database is compiled for earthquakes having body wave magnitude (Mb) and PGA values ranging between 3 and 7, and 5 and 748 gal respectively, and distances to epicenter are between 2 and 279 Km. From the regression analysis of the data, an attenuation equation for PGA, considering hard rock, soft rock, soil and soft soil conditions is developed. In this study, We have suggested an equation for prediction of PGA values. In addition, an equation between body wave magnitude and surface wave magnitude (Ms) and also a relationship between faults rupture length and surface wave magnitude of Hormozgan Province data is developed.

In the southwest of Hafthar village, there is a deposit of Quartzite (Top Quartzite) inside the Paleozoic sediments. The layers of this deposit are parallel with the general layering of the area. This contains the upper part of the lalun. The footwall is red Lalun sandstone and the handing wall is dark Milla limestone. Strike and dip of the Quartzite layers differ from place to place due to the tectonics.The Quartize Ore Contains 85% Quartze, 10% Feldspar, some Amphibole and Mica (Soricite). There are also few grains of clay minerals and iron oxid in the ore. The average grade of ore is as the following: SiO2=93.78%, AL2 O3 =1.55%, Fe2 O3=0.22%.To use this ore for the glass industry, ore dressing tests were carried on this ore (crushing, grading, calcinations). The result was almost good.The silice grade has increased up about 4%, Aluminum oxide decreased about 0/75% and iron oxide increased a little.After ore dressing this ore can be used for glass and other industries.

For study on the stresses performance in Ahar area, some samples were taken from outcrop structures including faults, folds and joints in this area. Drawing and studying rose diagrams, contour line and examining the state of the stresses in the area under study, indicates that the existing structures are formed in compressional tectonic regim with dextral strike-slip component. General seismotectonic considerations of Ahar range up to 300 km radious has performed. In this case the most important earthquakes which cover the studied region with the most important faults in this region and its environment are introduced.

The late Devonian Jeirud Formation was studied in the southern flank of Aynehvarzan -Dalichai anticline (Seyed Abad section). In the studied section the Jeirud Formation is underlain by the early Cambrian Lalun Formation (with erosional surface) and disconformably overlain by the early Carboniferous Mobarak Formation. These sediments have deposited in a siliciclastic /carbonate system in a beach-barrier island environment. The Jeirud Formation consists of three facies groups, seven main facies and twenty one siliciclastic and carbonate facies. These facies groups have included tidal flat subarkose and sandy dolomite, lagoonal sandy dolomite and mudstone and shale, barrier quartzarenite, sub litharenite and microconglomerate. The deposits of Jeirud Formation have sedimented in southern divergent margin of paleothetys. This stratigraphic section consists of two sedimentary sequence of Kaskaskia mega sequence.

In this research, the alluvium thickness and its accordance with district wells data are studied in Shahr-e-Kord city using surface microtremores and shear wave velocity. Shear wave velocity measurements are performed in 20 profile and surface microtremores sampling in 25 stations. The shear wave velocity and alluvium natural period maps are plotted in GIS media and finally, the alluvium thickness is calculated using Dubri formula.Comparing the results with the alluvium thickness in the wells shows that the two methods are in proper accordance. Therefore, this method can be used in the preliminary studying of alluvium thickness determination.

Iran exposes to natural disasters because of its geographical position. Iran settles on Alpian-Himalaya seismic belt and its populous regions are mostly comforted in active tectonic parts of it. Excessive human and cost losses during recent catastrophic earthquakes, Rudbar, Bam, Buiin Zahra and etc., indicate the necessity of seismic studies of residential, industrial and cultural parts of country.Regarding large earthquakes happened in and around Qom province and its being in the vicinity of Tehran province encouraged us to study seismotectonics and seismicity of Qom. Studying local and teleseismic data shows that southwest of the province is more seismically active than other parts. This study can be used for next considerations to seismic zoning and microzoning of Qom.

This paper presents a probabilistic hazard assessment of Ilam region in Zagros mountain, western Iran.Zagros is one of the most seismically active parts of Alpine-Himalayan seismic belt. We got a catalogue containing historical and instrumental, complete for magnitudes greater 4. To account for seismicity of regions near Ilam, area under study was extended and fault map then seismotectonic map was obtained.Considering seismic pattern in area, potential seismic sources were detected and modeled as volume sources. Using probabilistic method and choosing attenuation relationship, we obtained peak ground acceleration on bedrock in sites for exceedence probability 64%, 10% and 2% and life time 50 years.Considering four relatively hazard level, we zoned Ilam to four zones as high danger part, relatively high danger, intermediate and low seismic hazard level.