Application of geodetic leveling data on recent fault activity in Central Alborz, Iran

Abstract In this paper, geodetic leveling data in three lines across the Central Alborz range have been utilized to analyse recent activities of the range major faults. These data gathered by National Cartographic Center of Iran in three times during the past 22–32 yr. Mathematical modeling is applied to remove systematic errors from the raw leveling data. The vertical movement (uplift or subsidence) rate is estimated from height differences of benchmarks during geodetic leveling data times. The results show that the average uplift in Central Alborz during data times varies from 17.0 ± 0.9 to 18.1 ± 0.9 mm in the hangingwall of the major North Tehran and Mosha faults, respectively. The lower values of the uplift across the faults are taken as an account for the faults locking during the data times and their possible seismic potential. Evaluation of the uplift rate for the major faults under study in Central Alborz indicates the reduction of vertical uplift from west to east along the main proven faults like the Mosha Fault. The rate of uplift in the hangingwall of the Mosha Fault decreases from 0.921 ± 0.283 (mm yr− 1) (20.3 ± 0.905 mm 22 yr−1) in west to the rate of 0.508 ± 0.228 (mm yr−1) (11.7 ± 1.031 (mm 23 yr−1)) in east. The unusual subsidence anomalous in some benchmarks is considered as the effect of geological features such as Karst phenomena. Moreover, comparison on the rate of vertical movement across the Central Alborz shows the greater uplift in the southern flank (10.4 ± 0.9 mm) with respect to its northern flank (6.3 ± 0.9 mm) during the data times. This interpretation is in agreement with Global Positioning System studies that indicates a progress of young deformation in Central Alborz toward the range southern hillside.