disasters of earthquake in the Nation's progress explain
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ults, or by the movement of magma in volcanic areas. Smaller earthquakes occur frequently, but annually, only as many as 18–20 reach a magnitude above Ms 7. Approximately 40 disastrous earthquakes have occurred since the end of the twentieth century, and the total death toll is nearly 1.7 million. This number is about 50% of all victims of natural disasters. Most earthquakes (80%) occur in the oceans, mainly in the subduction zones. Earthquakes occurring in such regions have a frelatively large magnitude and they are also deep. These earthquakes can cause tsunamis. Continental earthquakes are less frequent than those in the ocean and they occur mainly on the boundaries of continental plates or the boundaries of active blocks (Johnston and Schweig 1996, China Earthquake Administration 2005).
Like other disasters, earthquakes and tsunamis can be sudden, seriously destructive, and create long-lasting social, environmental, and economic problems. However, compared with weather-related or biological disasters, damage from earthquakes is multiplied by the impossibility of accurate and timely forecasting, and afterwards by difficulty in timely response and rescue efforts.
Earthquake disaster risk zonation is an important tool in earthquake disaster prevention. Most developed countries have accurate and detailed earthquake disaster zoning and risk assessment maps. However, it is necessary to continue to evaluate the potential dangers of earthquakes by improving theory and methodology of risk assessment, based on seismic activity and active fault monitoring. It is also crucial to document disaster-caused changes, disaster degree, risk, and loss estimations (Long and Zelt 1991, Ma 2005, Liu 2007, Liu et al. 2007).
Engineering analysis for structural collapse prevention and deformation of buildings in the event of a major earthquake must be implemented everywhere. Related research must continue to be carried out on the seismic structure of active faults, mechanisms of earthquake generation, assessment of potential earthquake activity, and potential losses.
The suddenness and destructiveness of earthquakes often result in rescue decisions being delayed, chaotic, unplanned, and unscientific, thus resulting in even greater loss. It is critical to improve the means and methods of rescue in all countries. In order to improve the capabilities of emergency response and rescue, research should comprehensively review emergency rescue systems, rapid disaster-evaluation technologies, communications, and decision-making methods (Shen et al. 2003, Qu et al. 2004, Wang et al. 2008). There is also a great need for improved early warning systems. The lack of such a system resulted in the long-distance devastating damage following the Indian Ocean tsunami of 2004.
A systematic assessment of emergency and assistance needs before an earthquake would serve in determining the disaster extent, quantify assistance needed, and establish a disaster-planning database and disaster-needs forecast. The resulting disaster aid model could help to rapidly make decisions on the level of required assistance within 2–3 hours after large-scale earthquakes and an hour after middle-small-scale earthquakes. For example, the Ms 8.0 Wenchuan earthquake resulted in a large number of deaths and injuries as well as disruption of electricity, communications, transportation lines, and water supplies. Figure 1 shows the appearance of Beichuan County Town before and after the earthquake. Major difficulties were encountered in the response time for rescue and disaster-relief operations because of the unknown situation on-site. The Chinese Academy of Sciences, in cooperation with other organizations, used remote-sensing techniques to immediately assist with disaster relief. Through acquiring, processing, interpreting, and analyzing remote-sensing data, a series of reports on disaster reduction were immediately submitted for earthquake assistance and disaster relief at all government levels. Additionally, digital earth technologies, such as using Google Earth immediately after the earthquake to acquire spatial information of the disaster area, played a crucial role in assisting scientists to understand geological structures and plan for the subsequent further studies (Guo 2009, 2009a, 2009b, 2010a).
Figure 1. Beichuan County Town of Wenchuan earthquake area in May 2008. Left: oblique photo before the earthquake; Right: 3-D airborne remote-sensing image after the earthquake.
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