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In this paper we present new and review already existing landslide and earthquake data for a large part of the Tien Shan, Central Asia. For the same area, only partial databases for sub-regions have been presented previously. They were compiled and new data were added to fill the gaps between the databases. Major new inputs are products of the Central Asia Seismic Risk Initiative (CASRI): a tentative digital map of active faults (even with indication of characteristic or possible maximum magnitude) and the earthquake catalogue of Central Asia until 2009 that was now updated with USGS data (to May 2014). The new compiled landslide inventory contains existing records of 1600 previously mapped mass movements and more than 1800 new landslide data. Considering presently available seismo-tectonic and landslide data, a target region of 1200 km (E–W) by 600 km (N–S) was defined for the production of more or less continuous geohazards information. This target region includes the entire Kyrgyz Tien Shan, the South-Western Tien Shan in Tajikistan, the Fergana Basin (Kyrgyzstan, Tajikistan and Uzbekistan) as well as the Western part in Uzbekistan, the North-Easternmost part in Kazakhstan and a small part of the Eastern Chinese Tien Shan (for the zones outside Kyrgyzstan and Tajikistan, only limited information was available and compiled). On the basis of the new landslide inventory and the updated earthquake catalogue, the link between landslide and earthquake activity is analysed. First, size–frequency relationships are studied for both types of geohazards, in terms of Gutenberg–Richter Law for the earthquakes and in terms of probability density function for the landslides. For several regions and major earthquake events, case histories are presented to outline further the close connection between earthquake and landslide hazards in the Tien Shan. From this study, we concluded first that a major hazard component is still now insufficiently known for both types of geohazards – and even totally unknown for most giant landslides: the time information. Thus, dating rockslides and any large mass movement is a crucial factor in order to better constrain related hazards. Second, we highlight the role of coupled hazards in the Tien Shan – inside the mountain range the largest disasters were caused by earthquake-triggered landslides and massive earth flows. Therefore, it is of prime importance for these mountain regions to complement single hazard assessment by coupled hazard scenarios. On the basis of these scenarios, risk evaluations may then be completed considering direct impacts on artificial dams, hydropower schemes, mining and road infrastructure as well as remote effects from possible dam breaches and mobilisation of mining and nuclear waste storages. Basic hazard and risk components are partly analysed in this paper and partly in a companion paper ‘Tien Shan geohazards database: Landslide susceptibility and impacts’. |
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