Estimation of earthquake disasters and losses
Assessment of earthquake disasters and secondary disasters is the great significance for the reduction of risk, resource allocation and emergency response planning of a region. By storing and analyzing geological structure information, GIS can be used to predict the ‘scenario’ of earthquake occurrence and estimate the potential losses caused by earthquakes in the region. In addition, GIS also provides a powerful tool to analyze the spatial distribution of disaster severity and help the government allocate emergency response resources when earthquakes actually occur.
The spatial distribution of various information, such as geological structure, should be considered comprehensively in earthquake disaster assessment, which usually includes the following steps (Fig. 14-9)：
Estimation of earthquake disaster: It is necessary to identify the seismic source point, establish the model of earthquake occurrence and seismic wave propagation at that point, and finally get the final vibration intensity according to the soil conditions on the surface.
Estimation of secondary earthquake disasters: Secondary earthquake disasters include liquefaction, landslides, faults, etc. To evaluate these disasters, it is necessary to collect geological structure information of the corresponding areas and calculate the intensity and duration of surface movement and the occurrence of these disasters in the course of previous earthquakes.
Estimation of damage to buildings: It is necessary to collect the distribution of buildings and lifelines in the seismic area, and then build damage models for each building, which is a function of the intensity of ground vibration and potential secondary disasters.
Estimation of losses that can be measured by money and not by money: Losses that can be measured by money include the repair and reconstruction of damaged buildings, while losses that cannot be measured by money include casualties. Estimating these losses requires corresponding socio-economic information. In addition, different models are needed to determine the costs of garbage removal and resettlement, unemployment, mental impacts and other long-term or short-term impacts.
Figure 14-9: Assessment process of seismic loss
As shown in the figure above, a variety of spatial information, such as geological structure, architecture and so on, are used in seismic loss assessment. Therefore, GIS is an ideal tool for seismic loss assessment. Fig.14-10 and Fig.13-11 both describe the process of using GIS for seismic loss assessment.
Figure 14-10: GIS-based seismic loss assessment process (1)
Figure 14-11: GIS-based seismic loss assessment process (2)
Usually, the intensity of ground motion can be calculated according to the location of the earthquake source and the propagation formula of seismic wave. Secondary disasters and damage to buildings should be calculated according to the relevant maps, and the financial and non-financial losses can be evaluated based on the results of the above calculation. In the process of analysis, because the intensity of earthquake and the degree of damage attenuate with the distance from the source, the buffer zone calculation model should be used. While in the calculation of money loss and non-money loss, because multiple factors should be considered, the superimposed composite model should be used.