2003 Altai earthquake

Tectonic setting

The Altai Mountains form the most northerly part of the complex zone of collision between the Indian and Eurasian plates, contributing 7 mm per year of the total 35 mm per year of convergence between the two plates, according to estimates from GPS data. The main structures accommodating this convergence are northwest–southeast trending right lateral strike-slip faults with subordinate west–east trending thrust faults, associated with the ends of the strike-slip structures. Most previous seismicity in the area in the instrumental era are dextral strike-slip in type. Only one thrust fault event () has been observed trending parallel to the Altai chain in this period.

Earthquake

The total length of the fault rupture was about 60 km, based on observations of surface rupture, although the extent of aftershocks suggest that the rupture at depth was somewhat longer. This earthquake had components of right-lateral strike-slip and reverse movement in a segmented fault zone which had not been previously recognized. Based on field observations and the analysis of InSAR data, the fault responsible for the earthquake dips steeply to the northeast. Further analysis of the three–dimensional distribution of aftershocks, however, suggest that the fault zone is sub-vertical, extending down to a depth of 17 km. Modelling of the observed InSAR fringe pattern is consistent with at least three fault segments moving during the earthquake. The two segments to the northwest moved with dominantly right-lateral strike-slip, with a component of reverse movement. The most southeasterly segment had a pure reverse slip displacement.

Damage

Between 99 and 300 houses were destroyed, along with 1,942 other buildings affected. It was the strongest earthquake in this region since an estimated magnitude 7.7 earthquake on 20 December 1761.

Ground effects

Landslides affected the Kosh-Agachsky and Ust'-Ulagan Districts.

References

References

1. Dorbath, C.. (2008). "Geological and Seismological Field Observations in the Epicentral Region of the 27 September 2003 Mw 7.2 Gorny Altay Earthquake (Russia)". Bulletin of the Seismological Society of America.
2. (2007). "Combining InSAR and seismology to study the 2003 Siberian Altai earthquakes—dextral strike-slip and anticlockwise rotations in the northern India–Eurasia collision zone". [[John Wiley & Sons.
3. "M7.3 Respublika Altay, Russian Federation Earthquake of 27 September 2003". United States Geological Survey.
4. ISC. (2016). "ISC-GEM Global Instrumental Earthquake Catalogue (1900–2012)". [[International Seismological Centre]].
5. National Geophysical Data Center / World Data Service (NGDC/WDS). (1972). "Significant Earthquake Database". [[National Geophysical Data Center]], [[National Oceanic and Atmospheric Administration.
6. (September 4, 2009). "PAGER-CAT Earthquake Catalog". United States Geological Survey.