Seismic Hazard in Mountainous Areas
Seismic Hazard and Earthquake Induced Landslides Probability in Mountainous Areas
Tech Area / Field
- ENV-MRA/Modelling and Risk Assessment/Environment
- OBS-GEO/Geology/Other Basic Sciences
- OBS-NAT/Natural Resources and Earth Sciences/Other Basic Sciences
3 Approved without Funding
Institute of Geology, Earthquake Engineering and Seismology, Tajikistan, Dushanbe
- NORSAR, Norway, Kjeller\nUniversity of Liege, Belgium, Angleur\nGeoForschungsZentrum Potsdam, Germany, Potsdam
Project summaryThe Project aim. Within the framework of this project it is planned to develop an up-to-date quantitative approach for the estimation of earthquake impacts on the triggering earthquake induced landslides in the mountain areas. The study will be applied to the area that is most affected both by earthquake and landslide hazards in Tajikistan. It is a Garm area, between the junction of the Obihingoy and Surhob rivers and the Kyrgyz Republic border. This area is exposed to both a high seismic hazard and a high susceptibility to landslide hazard on one hand, and includes densely populated areas in the mountains on the other hand. Therefore, it is chosen as a pilot study area for the development an up-to-date methodology for estimation of the multi hazards risk for seismically active mountain areas, not only in Tajikistan, but for all Central Asia mountain regions, and possibly worldwide.
Current status. Seismic hazard assessment for Central Asia was conducted in the past at a small scales (1:5000000 - 1:1000000) and averaging of earthquake parameters resulted in the loss of regional particularities of seismic events. In Tajikistan, the current Map of General Seismic Zoning was made in 1978, and has never been "off the mark" with regard to the measured seismic effects within the territory of Tajikistan. However, other facts give rise to serious concern about the applicability of such map: actually, this map provides predictions mainly aimed at ensuring safety of buildings and structures with respect to the impact of seismic ground shaking. The World’s experience indicates that most losses of human lives and considerable material damages in the mountain regions are associated with effects of secondary earthquake consequences: landslides, rockslides, debris flows and soil liquefaction. Dramatic examples, when people lost their lives not directly due to the seismic shaking, but mainly as a result of landslides, rockslides or debris flows, are given by such earthquakes in Tajikistan as Karatag in 1907 (M=7.4), Sarez in 1911 (M=7.4), Faizabad in 1930 (M=6.4) and in 1943 (M=6.7), Khait in 1949 (M=7.4), Hissar in 1989 (M=5.5) The importance of the topic is further highlighted by the most recent catastrophic event in May 12, 2008, the Wenchuan earthquake in China (M=7.8), which damaged 1803 dams and reservoirs, and triggered tens of thousands of landslides over an area of many thousands of square kilometers, killing thousands of people.
The existing seismic hazard maps in terms of intensity of shaking in MSK64 scale don’t take into account such consequences though above examples indicate the importance of such analysis. Most accurate results of the seismic impact assessment provides the probabilistic seismic hazard approach (PSHA) with using up-to-date ground motion prediction equations (GMPE) to estimate the spectral accelerations with given exceedance probability of calculated values. For the landslides the dynamic seismic loads can be estimated more accurately when the first resonance frequency of the massive of the loose deposits on the slope is taken into account. PSHA allows us to compute accelerations at a given spectral frequency that equal to the resonance frequency of the massive of the loose deposits on the slope like most unstable its part.
The project’s influence on progress in this area. The project methodology and techniques of estimation the earthquake induced landslides for mountainous areas will be based on the up-to-date GIS database compilation and analysis, modern seismic hazard and landslide hazard estimation technique that will be worked out during the Project implementation and allows us to provide more accurate assessment of real seismic impact for population and property.
The participants’ expertise. The scientists involved in this project have many years of considerable experience to work in seismically active mountainous areas where they did not only study seismicity, but also other natural hazards especially landslides, rock falls and debris flows, including earthquake triggered events. They took part in some international projects (CASRI, TIPAGE, GEM, TIPTIMON and others). Some information is available on the Internet web-site http://www.ingeos.tj.
Expected results and their application. The final output of this project will be a new verified methodology and approach of multi-hazard analysis, which is applicable in seismically active mountainous regions and allows a more accurate estimation of combined seismic and landslide hazard for areas, which have a high risk for property and population. The results of such an assessment for the seismically active mountainous country in Central Asia will improve the safety of the population and contribute to the sustainable development of the economy. In addition, the created GIS database will provide manifold information on those areas that are most at risk for seismic and landslides hazards allowing the profound selection of areas and which would require more detailed analyses and monitoring because of the high risk affecting important industrial and social infrastructure. The GIS database as well the final results will be accessible through the Institute’s web-site – www.ingeos.tj.
Scope of activities. The following activities will be implemented in the frame of the Project:
- collecting the geological, seismological and meteorological data including information about active faults, seismic catalogues, slope failures, as well as on the most important industrial and social structures in the pilot area (hospitals, schools, villages, main infrastructures like roads, bridges, power lines and so on);
- creating up-to-date GIS database for further analysis;
- using recent satellite imagery and DEM (digital elevation model) for upgrading the existing information about landslides and infrastructure;
- creating the seismic hazard maps based on up-to-date PSHA methodology and techniques (spatial analysis of the seismic events and seismic sources, using modern ground motion prediction equations – GMPEs - for estimation the seismic impacts);
- analyzing the slope failures and their connection with the most active seismic sources;
- analyzing the triggering effects of strong earthquakes for slopes stability;
- identifying the first resonance frequencies for the loose deposits on the most characteristic slopes in the study area with the help of instrumental data (portable seismic stations) (Nakamura’s test) for analysis their seismic stability;
- creating of the maps of seismic impacts with given spectral accelerations and given exceedance probabilities for calculated values ;
- based on the collected data, their analysis and finding develop the appropriate methodology and techniques for estimation the probability of the earthquake induced landslides in the mountain areas;
- creating of the probability map of earthquake induced landslides for the Project area;
- based on the Project results, recommendations are provided for the national authorities for a safer land-use in mountainous areas;
- presentation of the Project’ results to the international scientific community.
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