The consequential destructions that are brought by earthquakes are often devastating and dreadful. The number of casualties involved during an earthquake always reach the thousands. Aside from the tragic and enormous lose of human lives, the other effects associated with earthquake are also quite catastrophic, such as the devastation to the city's infrastructure, the economical and social structure of the affected region, just to list a few.
Statistical analysis of data shows that there are on average, about 150 earthquakes with magnitude 6 or higher occur each year on a global scale, which is equivalent to approximately 1 devastating earthquake strikes once every 3 days. Also, there are about 20 earthquakes with magnitude 7 or higher occur annually world wide. Those stastistical data mentioned above may not be very appealing to you. However, you have to realize the fact that for each of those potentially damaging earthquakes, the number of casualties are very significant, often on the interval between a few and a dozen thousands, not to mention the other damages and losses.
The list below summarizes the most significant hazards that are posed by the occurance of earthquakes.
Ground shaking: the most apparent effect from an earthquake to the landscape is the shaking of the ground. The ground typically shakes with an acceleration of 0.1 ĘC 0.35g (1 g=9.8m/s2). This is caused by the surface wave near the epicenter of the earthquake, and accounts for the collapses of most man-made structure and yields the most fatalities during most of the earthquake. The intensity of the ground shake, however, depends on several factors such as the geological condition of the affected zone, the magnitude of the earthquake and the distance from the epicenter. The collapses of buildings are the most hazardous to the victims of earthquakes. Aside from the intensity of the ground shake, the buildings' resistance to the collapse also varies from one to another, based on a variety of factors. The design and material used for a particular building account for the most resistance of the building to the ground shake. Generally speaking, structures that are made with concrete and masonry are very prone to the collapses since they are very brittle, on the other hand, structures made with wooden materials and steel are less prone to the collapses. Moreover, in some earthquake prone regions, the buildings are designed and constructed with strict building codes in order to stand the shake of the ground and therefore reduce the risk from the earthquake.
Ground rupture: some severe earthquakes can also cause the ground to rupture, thus the buildings near the rupture zone are usually destroyed.
Fire: fire is considered as one of the secondary hazards associated with an earthquake. The collapses of man-made structures during an earthquake can often knock down flammable, explosive and combustible materials, which ultimately yield severe major fires. Moreover, water pipelines and electric power supplies are also very vulnerable against earthquakes. This hinders the communication, evacuation and fire-distinguishing processes that occur at the affected zone.
Liquefaction: this is a process where the shaking causes the unconsolidated land base to become water-saturated, thus causes buildings to fall down as landslide occurs as a result of liquefaction.
Tsunami: earthquakes that occur beneath sea level and near the coastal regions can trigger tsunami. The mechanism of the formation of tsunami caused by an earthquake is similar like the earthquake, however, we do not provide detail regarding its formation here.
Disease and epidemic: as water pipes are broken as a result of earthquake, water in the reservoir can often become infected. The disease can be spread out soon and turn into an epidemic level if no proper treatment and evacuation are met soon.