Risk Analysis of Urban Settlements against Earthquake Hazard in Lorestan Province

Earthquake is of natural hazards which its occurrence mostly causes great damages .. Geographical distribution of earthquakes in Iran indicates that 66 percent of the land of Iran is faced with earth quake risk, which 90 percent of the population lives in these areas. However, the cities of Iran are seriously vulnerable against earthquakes with 5.5 and 6 Richter. Lorestan province forms part of Zagros Mountains and in general 50.83 percent of Iran's earthquake has happened in this mountains. Hence Lorestan has  faced with destructive earthquake with a high mortality. This  part of Iran has been  classified as the areas with strong earthquakes. Also recording a great number of earthquake Epicentesr during the last century and happening destructive earthquakes in the province, indicates that faults are active in this area.   One of the most destructive earthquake occurred in Iran around a hundred years ago in 1287 Hijri –at Solar Silakhor Doroud area This province with a population density of 62 persons per square kilometer has about 2.65 percent of the population that is considered as populated area. The objectives of the present study includes  the spatial distribution pattern  of the province's cities and population  and study the  spatial distribution of the cities and urban population of Lorestan province regarding the earthquake risk. In this paper, for the study of spatial pattern of major cities of the province ,  "gravity or specifying separation point "has been used,  the results indicate that  the major urban centers of the  province have almost been scattered as organic. On the other hand the frequency of water main faults at the margins of faults is the main factor for locating  cities and villages in this province. Therefore majority of the residential areas have been located at the faults area and are faced with great damages and are vulnerable.
Based on the  results obtained from  zoning maps indicate that  about six percent of the province population  are located at very high risk zone, 23 percent of the population in high risk area and 56 percent are located in the middle zone.