Showing 3 results for Alborz
M Mirabedini, M Aghatabay,
Volume 16, Issue 42 (5-2015)
Abstract
Baladeh-Kojour earthquake of May 28th, 2004 is one of the largest earthquakes in vicinity of Tehran, occurred in the northern part of the Alborz range. In this research, spatial variation of fractal parameters has been studied to estimate the seismic pattern of the study area. In order to draw the spatial variation maps, b-value, correlation dimension of epicentral and temporal distribution of earthquakes, De and Dt have been calculated for the data sets of before and after the mainshock, separately. The results show that before the earthquake, these parameters have low values in the eastern side of the mainshock epicenter. It seems that these low values before the earthquake may arise due to clusters of events with larger magnitude and small events after it. Seismic rate has decreased in the surroundings of the mainshock (seismic quiescence). After the mainshock, the lowest values of b-value and Dt is seen in the epicentral and western part of the mainshock. These low values are due to aftershock clustering and stress release, took placed just after the mainshock and during the aftershock sequence. Intensity increasing is observed in the shake map of earthquake. The De parameter is low after the mainshock occurrence. Low b-value and high De indicate high level of seismic activity in the region. The obtained results show the fractal parameters sensitivity to spatial and temporal clustering of earthquakes. Therefore, these parameters can be used as an indicator for seismic precursory patterns of major earthquakes.
Volume 18, Issue 48 (2-2007)
Abstract
A major part of structural studies is the analysis of elements of fold style. In this paper, the elements of main folds style in the Alborz – Central, Iran border zone, were investigated. In this respect, cylindricity, symmetry, style of a folded surface, style of a folded layer and style of a folded multilayer were evaluated. Finally, fold style characteristics and young history of folding in the studied area were indentified. In addition, two main mechanisms (Buckle and Detachment Folding) were distinguished.
Volume 18, Issue 48 (2-2007)
Abstract
Shekarnab intrusion is a part of an extensive magmatism in the Central Alborz Tectonic Zone of Iran. This intrusive body, which is mostly composed of monzonitic, gabbroic and syenitic lithologies, was intruded within green tuffs of the Karaj formation. These plutonic rocks show geochemical alkaline-potassic affinity and in the case of aluminum saturation index, they could be classified as meta-aluminous rocks. These rocks show Nb negative anomaly, enrichment of LILE and are depleted in HFSE. The spider and discrimination diagrams demonstrate that the parent magma of the plutonic intrusion could be related to a subduction zone and have emplaced in an active continental margin. Based on geochemical analysis of trace and major elements, as well as field and petrographical studies, it could be suggested that crystal differentiation has played an important role in lithological diversity of this intrusive body.
