Investigation of human settlements located in the active fault zone (the study of Kerman province)

.Pacific and Alpine-Himalayan belts are two major seismic zones in the world, and Iran is situated in the middle of the Alpine-Himalayan belt. The presence of numerous active faults has made Kerman province one of the earthquake-prone regions. The Kohbanan, Lekarkoh and Naiband faults in the north of Kerman, the Gok and Shahdad faults in the center and the Bam and Sabzevaran faults in the south of the province are the most prominent faults in the region. What is important about the fault is the magnitude of the possible earthquake due to the movement of the fault and the seismic power of a fault. Determining the zone and width of the fault is very important for settlements and villages with cities. The existence of the city and thousands of villages in the fault zone or within a radius of a few kilometers in the region, which is at risk of earthquakes and the dangers caused by it, and the determination of the faults zone. In this research, an attempt is made to determine the boundaries of the faults by studying and investigating the location of the faults in the region, while measuring the seismic power of the active and important faults, according to the fault mechanism. It has also been introduced and identified areas and areas favorable for earthquakes. Therefore, the main goal of the current research is to determine the urban and rural settlements located in the fault zone according to the fault mechanism.



Methodology

The research method is descriptive-analytical and is a type of applied research that identifies residential centers located in the area of active faults zone in Kerman province. Data collection tools in this study include written documents, statistical data (quantitative and qualitative statistics), visual documents and field studies. Also, topographic maps, geology, digital elevation model (DEM), altitude maps, slope maps, major and minor fault maps, regional earthquake maps, urban points maps and rural points maps were used in the research. Research Society: Regional faults, Urban and rural residential areas. Software used: GIS, Global mapper, Google Earth.



Fig1: Flowchart of research stages

Results and Discussion

The investigations and studies performed in this work confirmed that Kerman Province is a tectonically active region. The presence of numerous seismically active major faults and the occurrence of too many earthquakes in the province have made it a seismically active site in Iran. In general, the regional faulting systems follow some northwest – southeast and north/northwest – south/southeast trends, which is in agreement with the regional tectonic setting. In this respect, the Kuhbanan, Gok(Golbaf), Rafsanjan, Shahr-e-Babak, Bam, Boloord, and Davaran Faults exhibited the first trend, while the Lakar-Kooh, Sabzevaran(Jiroft), Nayband, and Anar Faults followed the second trend. In principle, the studied faults showed some dextral reverse directions. Accordingly, the Kuhbanan, Lakarkuh, Gok, Bam, Lalezar, Rafsanjan and Davaran Faults were a dextral reverse fault, the Nayband Fault was a strike-slip dextral feature, the Sabzevaran, Anar and Ravar Faults were dextral, and the Rayn Fault was reversed. In terms of activity, the Kuhbanan, Gok, Sabcevaran, Lale-Zar, Rafsanjan, and Rayn Faults were active, while the other faults were either semi-active or inactive. An important thinking to note about a fault is the magnitude of the probable earthquake upon the fault movement. A very significant hazard associated with an earthquake event is the possible rupture at the fault on the ground surface, which can be addressed only through previous recognition of the hazard and respecting the fault zone by banning any construction activity within the zone. The fault zone refers to an area around a seismically active fault wherein ground displacement and, possibly, rupture occur or are likely to occur upon later earthquakes. In the present research, statistical analysis was performed to calculate the seismic potential of different active faults across the studied area. According to the modified equation of Mohajer-Ashjaee for the Iranian faults, all of the studied active faults exhibited seismic potentials (Ms) above 7. Moreover, the map of the fault setback zone was prepared for the active faults across the region considering the fault type and the faulting mechanism using the geographic information system (GIS). Next, superimposing the fault zone map onto the map of the populated urban and rural areas, the situation of different cities and villages to the studied faults was investigated.

Conclusion

In the present work, once finished with identifying and investigating the active faults across the region, statistical analyses were used to calculate their seismic potential followed by investigating the adverse historical fault-driven earthquakes across the region considering the fault movement direction(dextral,normal,reversed) to prepare a map of the fault zone using the latter method. Subsequently, the fault zone map was superimposed on the populated urban and rural areas to identify the areas exposed to the risk of earthquake. The survey of urban and rural areas of Kerman province shows that 27 cities and 2266 villages are located within one kilometer of faults in the region, as well as 43 cities and 7095 villages located within one to five kilometers of faults in the region. Among them, the cities of Kohbanan, Kianshahr, Hajdak and Barwat are right in the fault zone, and the city of Golbaf is 200 meters away from the fault zone, as well as hundreds of villages are located right in the active faults zone, which is at risk of earthquakes and the dangers caused by it, hence the observance of security Buildings from design to implementation based on engineering principles are very necessary for earthquake-prone areas.