Seismic hazards and risk assessment for the mountain areas

Great progress has been made in seismology, earthquake engineering and the assessment of the risks of seismic hazards. Unfortunately, seismic hazards and seismic risk are not diminishing but are increasing in direct proportion to human activities in seismically sensitive areas. These activities are known to exert an effect on the upper part of the lithosphere. Activities of particular concern are rapid oil and gas production, mining, the construction of large reservoirs and the production of dangerous chemicals. The increased seismic risk is of concern in the construction of nuclear power stations and similar structures. Even small earthquakes can cause landslides, rocks falls and mud flows which are a threat to such structures. The mountainous areas constitute a fragile environment where human activity can increase the risk and hazard of natural disasters. Furthermore, the study of earthquakes in the mountainous regions of Tajikistan, has shown that the majority of casualties and property damage are caused by the secondary consequences and not by the earthquakes themselves. Such secondary consequences include landslides, falling rock, mud flows and floods. The Sarez earthquake in 1911, the Khait earthquake in 1949 and the Hissar earthquake in 1989 provide vivid examples of how earthquakes have provoked landslides and mud flows the result of which has been much loss of life. In Tajikistan, where 93% of the territory is covered by mountains and where landslides, falling rocks and mudflows are particularly prevalent, these secondary effects are of great concern, The Institute of Earthquake Engineering and Seismology of the Academy of Sciences of the Republic of Tajikistan has developed maps of the seismic risk in the mountain regions. These maps show the active zones of tectonic rock faults along with the landslides, rock falls and mud flows that have occurred. In general, the seismicity that has existed in the past is present today and will be present in the future. Seismic hazard zones can be discerned in photographs taken from satellites. By mapping seismic hazards and combining this with information about natural hazards we can estimate the risk to a territory of the secondary consequences of earthquakes. Using this method the risk of injury and property damage could be reduced.