Central Asia (CEA)

Summary

The Global Hazard Mosaic covereage of Central Asia (Kazakhstan, Kyrgyzstan, Tajikistan, Uzbekistan, and Turkmenistan) comes from the Earthquake Model Central Asia (EMCA; Ullah et al., 2013 and www.emca-gem.org), a Global Earthquake Model regional program coordinated by the German Research Centre for Geosciences (GFZ). The model was originally developed for the OpenQuake (OQ) engine.

Information about the OQ model versions and input files can be found on the Results and Dissemination page.

Interactive Viewer

The viewer below depicts the seismic sources and hazard results in terms of PGA for a return period of 475 years. Click on the menu in the upper right corner to select the layer.

Tectonic overview

Central Asia is a transitional region between the northern ranges of the Indo-Asian, Iranian and Caucasian active orogenic belts and the stable Eurasian interior. Range-bounding thrust faults are present through the southern part of this area, and some very large strike-slip faults such as the Talas-Fergana fault in between the Tien Shan and Pamir ranges can extend for a great distance into the more stable areas to the north. Strain rates are moderately high for continental orogens in the area, though the distributed nature of the deformation means that slip rates on individual faults rarely exceeds a few mm/yr. Nonetheless, seismicity from the early instrumental period (late 1800s and early 1900s) and paleoseismologic studies indicate that large, slowly-slipping faults are capable of hosting great (M 7.5-8.3) earthquakes, which are fortunately infrequent.

Basic Datasets

Please refer to Ullah et al., 2013.

Hazard Model

Seismic Source Characterisation

The source model consists of a single logic tree branch using area sources that model seismicity at depths < 50 km. In some cases, "super zones" were required in order to include enough data to assign occurrence parameters.

Ground Motion Characterisation

The original publication (Ullah et al., 2013) computes hazard in terms of MSK-64 intensity. The ground motion model logic tree below was assembled by the GEM Secretariat.

Results

Hazard curves were computed with the OQ engine for peak ground acceleration (PGA) and spectral acceleration (SA) at 0.2s, 0.5s, 1.0s, and 2s. The computation was performed on a grid of 55968 sites (spaced at approximately 10 km) with reference site conditions corresponding to a shear wave velocity in the upper 30 meters (Vs30) of 760-800 m/s.

The hazard map for PGA corresponding to a 10% probability of exceedance in 50 years (475 year return period), can be seen using the interactive viewer. For a more comprehensive set of hazard and risk results, please see the GEM Visualization Tools.

References

Ullah, Shahid, Dino Bindi, Marco Pilz, Laurentiu Danciu, Graeme Weatherill, Elisa Zuccolo, A. Issuk, N. Mikhailova, Kanat Abdrakhmatov, and Stefano Parolai. "Probabilistic seismic hazard assessment for Central Asia." Ann. Geophys. 58, no. 1 (2015): 0103S.