Journal of Economic Geology (Feb 2021)
Analysis of correlation of Neotectonic and seismicity in Bakharden-Quchan zone
Abstract
Introduction Two fundamental goals are followed in this paper: 1- Active neotectonics of the Kopeh Dagh Mountains particularly in its central part that is called the Bakharden-Quchan Zone in NE Iran for special features of faulting and role of faults within this zone in the collision between Arabia-Eurasia plates. 2- Seismicity hazards of faulting to recognize the relationship between asperities and earthquakes through analyzing the correlation of fractal dimension and b-value parameters. The Kopeh Dagh Mountain is accommodating a large portion of northward motion of central Iran with respect to Eurasia, involving a major right- lateral strike-slip fault system in its central part (the Bakharden-Quchan Zone). This fault system corresponds to the northeastern boundary of the Arabia-Eurasia collision and can be considered to be a lithospheric scale tectonic feature. The Kopeh Dagh Mountain forms a linear intercontinental fold-thrust belt trending NW-SE between the stable Turan platform and central Iran (Afshar Harb, 1979; Hollingsworth et al., 2006; Shabanian et al., 2009; Shahidi et al., 2013). Materials and methods This research uses both historical and instrumental seismicity data along with observations from Landsat 7 satellite imageries, topographic data (SRTM), field observations and mathematical fractal dimension (D) model plus integral mathematical functions to find a logical correlation between tectonic movements, asperities and earthquakes in different active zones. Results There is an array of active right-lateral strike-slip faults in the central part of the Kopeh Dagh Mountain which obliquely cut the range and produce offsets of several Kilometers in the geological structures. These faults all end in thrusting and link to blind faults, revealed by the uplifts and incision of the Late Quaternary terraces. These faults have rotated around their vertical axes and can account for several Kilometers of the N-S shortening. They are responsible for major destructive earthquakes in both 19th and 20th centuries and represent important seismic hazards for populous regions of NE Iran. These faults also require several Kilometers along-strike extension that is taken up by the westward component of motion between south Caspian sea basin, Shahrood fault system and both Eurasia and central Iran (Hollingsworth et al., 2006; Shabanian et al., 2009; Bretis et al., 2012). Discussion The Bakharden-Quchan faults have identifiable ends, where they turn into thrusting and link to blind faults. The fault changing mechanism to reverse has caused increase of stress, shortening by thrusting in their end bending. Structural relation faults between this zone and the Binaloud Mountain through Meshkan transfer zone which is the major motion engine of this zone to put it constantly under neotectonic stresses for convergence of Arabia-Eurasia plates since the last Alpine orogeny phase. Most of the seismic activities of this zone could provide us with precious data on crust tension distribution through microseismic and computing parameters of b-value, fractal dimension (D) and mapping of local stresses. In neotectonic active zone b Acknowledgment We thank the Department of Geology of Shahrood Azad Islamic University and acknowledge support of the respectable editor and reviewers of the Journal of Economic Geology and thank them for their constructive suggestions on alterations to the manuscript. References Afshar Harb, A., 1979. The stratigraphy, tectonics and petroleum geology of the Kopeh Dagh region, Northern Iran. Ph.D. thesis, Royal school of Mines, London, England, 17 pp. Aki, K., 1981. Source and scatering effects on the spectra of small local earthquakes. Bulletin of the Seismological Society of America, 71(6): 1687–1700. Bretis, B., Grasemann, B. and Conradi, F., 2012. An Active Fault Zone in the Western Kopeh Dagh (Iran). Austrian Journal of Earth Sciences, 105(3): 480–192. Hollingsworth, J., Jackson, J., Walker, R., Gheitanchi, M.R. and Bolourchi, M.J., 2006. Strike-slip faulting, rotation, and along-strike elongation in the Kopeh Dagh mountains, NE Iran. Geophysical Journal International, 166(3): 1161–1177. King, G., 1983. The accommodation of large strains in the upper lithosphere of the earth and other solids by self-similar fault systems: the geometrical origin of b-value. Pure and Applied Geophysics, 121(5–6): 761–815. Shabanian, E., Siame, L., Bellier, O., Benedetti, L. and Abbassi, M.R. 2009. Quaternary slip rates along the northeastern boundary of the Arabia-Eurasia collision zone (Kopeh Dagh Mountains, Northeast Iran): Geophysical Journal International, 178(2): 1055–1077. Shahidi, A., Nazari, H. and Ghaemi, F., 2013. Structure of Iran-Kopeh Dagh. Mining and Geology Organization of Iran, Tehran, 197 pp. Wiemer, S. and Wyss, M., 2002. Mapping spatial variability of the frequency-magnitude distribution of earthquakes. Advances in Geophysics, 45: 259–302.
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