Seismotectonic-Geologic Hazards Zoning of Iran

Mehran Arian

doi:10.15446/esrj.v19n1.40664

Abstract

Seismotectonic-geologic hazards zoning map of Iran is drawn based on deterministic seismic hazards evaluation using the seismicity records, structural trends, tectonic settings, fault ruptures and neotectonics activities in Iran. This map has been prepared to indicate the seismotectonic-geologic hazards of Iran. It contains the earthquake hazards parameters such as b value and Mmax for the nineteen seismotectonic provinces. Furthermore, Moho discontinuity depth, seismogenic layer depths and seismic rates for all provinces are investigated. The majority of deformation in Iran has been concentrated in the continental crust of the country. Zagros and Alborz experience deep earthquakes that are an indication of existence of the thick-skinned tectonics. Finally, some provinces such as Piranshahr- Borojen, East Iran, Naien- Rafsanjan and East Alborz, which include main suture zones of Iran, have faced high seismic hazards. ResumenEste estudio se realizó con el fin de preparar un mapa zonal de amenazas seismotectónicas y geológicas de Irán con base en la evaluación de amenazas sismícas deterministas a través de los registros sísmicos, las tendencias estructurales, las configuraciones tectónicas, las rupturas de fallas y la actividad neotectónica en Irán. Este mapa contiene los parámetros de amenaza sismológica como los valores b y Mmax para las 19 provincias sismotectónicas del país. Además, se investigó la profundidad de la Discontinuidad de Mohorovičić, las capas sismogénicas profundas y las clasificaciomes sísmicas para todas las provincias. La mayoría de la deformación de Irán está concentrada en la corteza continental del país. Las provincias de Zagros y Alborz experimentan terremotos profundos que indican la existencia de una configuración tectónica de capa gruesa. Finalmente, algunas provincias como Piranshahr-Borojen, Este de Irán, Naien-Rafsanjan y Este de Alborz, que incluyen las principales zonas de sutura de Irán, han enfrentado grandes riesgos sísmicos.

Highlights

Materials and MethodsThe deterministic assessment of the seismotectonic-geologic hazards of Iran involves specifying the magnitude ranges and dominant mechanism of earthquakes that might bring about destructive effects on the regions and main cities
Each seismotectonic province has a range of seismogenic layer depths and dominant mechanism of earthquakes, as these are related to tectonic settings, neotectonics activities, Mechanical Stratigraphy and deformational models of crust
From tectonics point of view, this province contains the Maiamay- Taibad marginal back arc basin, south- eastern part of Great Kavir- Urmieh lake foreland basin and South Great Kavir folded and thrust belt (Fig. 1). The latter case is the result of the collision between the northern part of East-Central Iran miniplate and southeastern part of North-Central Iran miniplate.There are many salt diapirs that have been formed by tectonic forces (Arian, 2012, Asadian and Arian 2009, Pourkermani and Arian, 1997) Focal mechanisms of several earthquakes are thrusting and dextral strike-slip faulting in the eastern part and sinistral strike slip faulting and thrusting in western part such as Garmsar (Ms=5.1, 2007)

Summary

Materials and Methods

The deterministic assessment of the seismotectonic-geologic hazards of Iran involves specifying the magnitude ranges and dominant mechanism of earthquakes that might bring about destructive effects on the regions and main cities. Regional tectonics (Qorashi and Arian, 2011) was integrated with seismologic data to prepare the seismotectonic-geologic hazards of Iran. The Seismotectonic- geologic hazards map is identified based on the physiographic-tectonic zoning map of Iran’s sedimentary basins (Arian, 2013). These basins described the locations of different structural units of Iran (Fig. 1). In this study, based on updated catalogue of significant and damaging Iranian earthquakes, a new seismotectonic -geologic hazards zoning map has been proposed.

AND DISCUSSION

CONCLUSIONS