نشریه زمین شناسی محیط زیست
پیاپی 8 (پاییز 1388)

In 9 March 2008 an earthquake with ML=5.1 ouccered in the west of Aryan-Shahr city, southeast of Iran. Many villages destroyed by this earthquake. Primarily, the Sedeh fault with N76 trend was nominated as source of this earthquake. But the distribution of aftershock dispersals has been occurred in an ellipsoid district which is not superimposed on Sedeh Fault. The long axis of distribution ellipsoid of aftershocks (N120) is nearly perpendicular to the Sedeh Fault trend. The seismic network, installed by Institute of Geophysics (university of Tehran), recorded more than 100 aftershocks during 3 monthes. All data of 3 stations were processed, common aftershocks were separate, their parameters were determine and were drawn on fault map. Therefore distribution of aftershocks location and main shock geometry of causing fault is known. Based on investigation of aftershock epicenter dispersal and the interpretation of aeromagnetic data reveal the presence a blind fault (Ghesar fault) parallel to long axis of distributionellipsoid of aftershocks.

There are some active and quaterner faults in Tabas region such as Kalmard, Tabas, Nayband, Cheshme Rostam, Zenoghan, Ghoorichay, Anarak-Takhtnader and Ghadir that play role in seismicity of the region. Seismotectonic properties and seismicity effect estimatation of any sources is necessary for resistation of the cities. For this reason, amplification of alluvial sediments that affects the factors of strong ground motion such as acceleration, velocity and displacement, is important too. Earthquake zonation and risk analysis are important for Tabas city because of the city importance and existence of main industrial, economical centers and major ways in this city. Recorded earthquakes with Mb = 7.6represented that the region is tectonically active. Based on geophisic studies and active tectonic indexes and earthquake risk estimation of the region, possibility earthquake event with M=6, is 50%, for return period 75y. In the center of the city, maximum horizontal and vertical acceleration for return period 475y resulted from the potential earthquake, are 0.4g and 0.2 g, respectively.

The asymmetric ENE - WNW trending Inehvarzan - Dalichai anticline that is located in the East of Damavand city and on the East of Central Alborz. This anticline consists of late Precambrian - Paleozoic - Mesozoic sediments. North limb of this anticline is confined to the Dehnar - Mosha fault and southern branch of this fault. South limb anticline is limited to the several secondary faults. Morphotectonic investigations including geomorphic indexes, e.g. Smf, Facet%, Af, Vf, for determination of the relative tectonics activity class of this anticline are carried out. The analysis of these indices demonstrates that North limb anticline is more active than the South limb.

The analysis of distribution and characteristics of landslides triggered by earthquakes is important to understand the areas may be susceptible to landsliding in the next earthquakes. One of the most significant effects of the Manjil earthquake (M=7/7, 20/6/1990) was triggering landslides over an extensive area. In this study; the factors of these landslides such as slope, slope aspect, elevation, lithological unites and Arias intensity were investigated using GIS in an area close to the earthquake epicenter. In the next step, two indices called Susceptibility Index (SI) and Frequency Index (FI) presented to predict the location of future earthquake-induced landslides. Finally, landslides susceptibility in the study area has been rated based on these indices. The output of thisstudy can be used to predict landslide susceptible areas in the future earthquakes and to distinguish hazard zones in the overall study area.

Goosheh granitoid body is located to Sanandaj – Siran Zone (SSZ).The age of this granitoid mass is upper Eocene (priabonian).It consists of Syenogranite, Monzogranite and alkali granite. discriminant geochemical diagram show anorogenic characteristics of this intrusive mass. depletion in compatible element such as Cr, Ni and High Ga/AL, FeO/ MgO+Fe Ratio, and peraluminous index are characteristic of a type granit (crustal granit). This body have ()I = 0.7055 ± 0.004discrimination diagram show WPG for this body (A type granite). Rb-Sr Geochronology method obtaine age 41 ± 6ma (priabonian) for goosheh granitoid mass.

Cretaceous rock out crops in south east of Tehran and north west of Bibisharbanoo Mountains with 120 m in thickness composed of compact white limestone rocks and light red limestone rocks with Echinoderms and Braciupods and at the end of sequence thickness white or red calcareous layer with a lat of gastropods and foraminifer are completing this sequence. Field and microscopic (petrographic) studies led to tecognition 8 carbonate. Facieses A (bioclastice mudstone) with pelagic bioclasts. Facieses B (bioclastic wackston) with pelagic bioclasts. Facieses C (bioclastic packstone) with pelagic bioclasts. Facieses (A B C) indicates medium to relatively deep marine environments (open marine) Facieses D (bioclastic grindstone) and E (intraclastic grindstone)indicates high energy. Environment (barrier) Facieses F (bioclastic packs tone) with bentic bioclasts. Facieses G (bioclastic wacks tone) woth bentic bioclasts. Facieses H (peloid wacks tone) with bentic bioclast indicates lagoon environment. These facieses indicates a carbonate basinet in shape in shape homoclinal ramp.

In this study, geological information, results of petrophysical analysis and production data were used to determine reasons for water production from Asmari reservoir in Doroud Oil field and tried to present suitable methods for controlling water production.According to this study the main reason for high water production is due to coning. Low anisotropy (vertical-horizontal permeability ratio) and high drowdown pressure are the main reasons for water coning. Chocking back the wells is the first step to prevent water coning, however, utilizing dual completion and injection of gelpolymer are two remedial actions.

Due to carcinogenic and other hazardous effects of nitrate and nitrite this study has been done. The Objective of this study was survey of nitrate and nitrite concentration at well-waters in villages of Sari city in 2008-2009 and comparison them with standard levels. In this study, 152 water samples from 38 rural well-water supply facilities in each year have been surveyed. Nitrate and nitrite ions concentration were determined by DR-5000 spectrophotometer and then results have been analyzed by descriptive and analytical statistical methods using SPSS 16.Result showed nitrate and nitrite average concentrations respectively were 1.42 ± 0.571 and 0.004 ± 0.00141 mg/L in 1386 and their average concentrations were 1.24 ± 0.461 and 0.0081 ±0.0072 mg/L in 1387 respectively.Nitrate and nitrite average concentrations in the experimented samples were less than recommended permissible concentration level of WHO and water quality standard of Iran (10 and 1 mg/L respectively) and had no hygienic threat in region, But wastewater disposal in seepage wells may cause increase of nitrate and nitrite concentrations in the future.