The field of natural hazards research has a rich history in geography, appropriately so because it involves conflicts between physical processes and human systems. Natural events occur without direct human effect and endanger his social life. Events that enforce average annual up to 150000 human damages and more than 140 milliard dollars financial damages on counties and especially developing countries. Among all the natural disasters, the earthquake is one of the most serious ones. It brings tremendous economic losses and deaths of people, as well as the enormous effects on the harmonious and continuous development of society. Iran is an event ism country in the world. In this field look at the recent decades earthquakes statistics that reveal average once in every five years.

Gilan province is located in south western of Caspian Sea in mountainous area of Talesh and central Alborz range that endure many earthquakes up today. The most ancient earthquake ever occurred in this area refers to Marlik civilization which is located near Rudbar – Rostam Abad. One of the recent earthquake in the 20^th century in this area is Rudbar earthquake in 21 Jun 1990 with magnitude Ms = 7.7 Richter that caused many destruction. In one hand according to complex tectonic of central Alborz and in the other hand locating Gilan in the south west of Caspian sea that demonstrate many seismic activities, it illustrates as a result that this area is one of the active high potential seismic area of Iran.

The current study is aimed at investigating the earthquake vulnerability of rural and urban settlements of Gilan province. To this end, Euclidean distant analysis and raster overlay have been conducted in GIS. To run the procedure, the first step is to calculate distance (pixels in 86 m dimension) between province and active and inactive fault line based on Euclidean analysis distance in Arc Map. The next step is aimed at standardizing the calculated distances using Raster Calculator Command. The, zoning of earthquake vulnerability of Gilan into five zones (based on active/inactive faults) is the primary goal. As a matter of fact, standardization leads to fuzzy maps. Standard score (distance) is calculated by dividing each score by sum of the scores. The next step tries to categorize zoning map and to translate Raster map into vector one in order to calculate the area of each risk category. Finally, overlay of urban and rural layers base on zoning map may help us analyze seismic hazard urban and rural regions of Gilan province.

Results have shown that 40.72 % of total area of Gilan province are in 15 km distance from active fault. Also, 21.51 % of total area of Gilan province are in 15 to 30 km distance from active fault. Additionally, 64.45 % of total area of Gilan province are in less than 8 km distance from inactive fault (Table 1).



Table 1. Seismic hazard zonation according to faults




Probability of earthquake hazard
Distance to fault lines
Relative area


Active Faults
Passive Faults
Active Faults
Passive Faults


Very low risk
0-20
60-76
32-42
7.29
1.42


Low risk
20-40
45-60
24-32
13.82
3.96


Medium risk
40-60
30-45
16-24
16.66
8.13


High risk
60-80
15-30
8-16
21.51
22.04


Very high risk
80-100
0-15
0-8
40.72
64.45


sum
-
100






According to seismic hazards due to active faults, 18 cities out of 51 urban regions are severely vulnerable to earthquake. Accordingly, 67.20 % of Gilan urban population are located at high-risk zone. Seismic hazard zoning map based on active faults have indicated that 20 cities are highly vulnerable to earthquake. (Table 2)



Table 2. Investigating the risk of earthquake in urban areas of Guilan province




Probability of earthquake hazard
urban Settlement
Population (2011)
Relative population frequency (percent)


Active Faults
Passive Faults
Active Faults
Passive Faults
Active Faults
Passive Faults


Very low risk
0-20
3
1
135846
17106
1.14
9.07


Low risk
20-40
6
4
86133
144021
9.62
5.75


Medium risk
40-60
10
8
739095
754968
50.43
49.37


High risk
60-80
14
18
380908
273137
18.24
25.44


Very high risk
80-100
18
20
155188
307938
20.57
10.37


sum
51
1497170
100






Seismic studies on rural settlement of Gilan province have indicated that 1350 rural out of 2925 rural residences are severely vulnerable to earthquake because they are near to active faults. These regions are the habitat of 24.9 % of the total rural population. Zoning map based on inactive faults have shown that 1679 rural regions are vulnerable to earthquake (Table 3).



Table 3. Probability of earthquake hazard in rural settlements




Probability of earthquake hazard
Rural Settlement
Population (2011)
Relative population frequency (percent)


Active Faults
Passive Faults
Active Faults
Passive Faults
Active Faults
Passive Faults


Very low risk
0-20
162
42
54240
30236
5.51
3.07


Low risk
20-40
379
147
183718
92018
18.68
9.35


Medium risk
40-60
481
291
255412
176183
25.96
17.91


High risk
60-80
553
766
245392
340448
24.95
34.61


Very high risk
80-100
1350
1679
244942
344819
24.90
35.05


sum
2925
983704
100






Studies have claimed that the majority of rural and urban regions of Gilan province are severely earthquake-prone. It is due to geographic and natural features of the mentioned province. To this end, some recommendations are given:


Meticulous supervision on safety of building from the stage of plan-making to administration which have to be based on engineering principles for earthquake-prone cities including Baresar, Ataqur, Asalem, Haviq, and Roodbar which are next to active faults
Prevention of formation of suburbs and towns on southern and northern parts of Gilan because these parts are really vulnerable to earthquake
Prediction of temporary accommodation in central Gilan because this part is less vulnerable to earthquake
To equip buildings, hospitals, schools, and other buildings located in big cities including Rasht, Bandar-E Anzali, Fuman, and Lahijan with facilities required in case of earthquake
To hold training courses in rural and urban parts of the mentioned province to make residents prepared for earthquake and for emergency evacuation
To prioritize reformation of old and historical buildings in Rasht because Rasht is mostly laden with old buildings which are really vulnerable to earthquake