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| Titel |
Contemporary surface ruptures in the zone of the Baikal-Mondy fault (Baikal rift system): dynamics of formation and origin |
| VerfasserIn |
Vladimir Sankov, Aleksei Sankov, Marina Lebedeva, Sergey Ashurkov, Anna Parfeevets |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250098032
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| Publikation (Nr.) |
 EGU/EGU2014-13669.pdf |
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| Zusammenfassung |
| Sublatitudinal Baikal-Mondy (Tunka) left-lateral strike-slip fault accommodates
North Mongolia submeridional rift basins opening (Darkhad and Khubsugul). It is
the connecting link between the central and south-western parts of the Baikal rift
system. We investigated the present-day activity of faulting on southern border of
Mondy basin, which is due to their position at the junction of east-west trending
active faults of the Baikal-Mondy fault system with submeridional structures of
Khubsugul basin. The investigated area is characterized by high seismic activity. The
epicenter of one of the strongest Mondy earthquake 1950 (Mw = 7.0) is located within
the Mondy basin. Reconstruction of Late Cenozoic tectonic stress field shows a
predominance of strike-slip deformation regime with NW-SE direction of the minimum
compression axis and NE-SW direction of the maximum compression axis, which
correlates with the present-day stress field derived from the data on earthquake focal
mechanisms.
On the top of the southern shoulder of Mondy basin a series of extended NE trending
surface ruptures that cut the crust of weathering and bedrock across the local watershed were
discovered. The rupture length reaches 180 m, width ruptures bedrock reaches 0.6 m. In the
bedrock tectonic microfractures of NW and NE directions are dominated, but the NW
trending surface ruptures are not observed.
In the area of contemporary ruptures the geodetic measurements were carried out in the
period 2009-2013. The results of processing the measurement data on the local testing ground
showed that most divergent baselines undergoes extension with maximum values reaching 30
mm/year. The block experienced elongation in all directions, but the morphology of ruptures
suggests that the main direction of stretching is NW-SE. The intensity of cracks opening
decreases markedly with time. According to eyewitnesses known that active crack
opening at about 100 mm/year started 4 years before Kultuk earthquake (27.08.2008,
Mw = 6.3), the epicenter of which was located near the southern tip of the Baikal
basin.
The existence of centimeter level deformations is confirmed using of differential
SAR interferometry method. A pair of images taken with an interval of 2 years
highlighted the linear zone of active deformation in the centimeter level. The length
of the structure is about 4 kilometers. The offset along the Line-of-Sight (LOS)
direction is from 18 to 42 mm, which corresponds to the vertical displacement
of 22 to 50 mm, or a horizontal displacement of 32 to 74 mm (Lebedeva et al.,
2013).
Along with the described ruptures we discovered normal faults with an amplitude greater
than 2 m, which can be traced along the submeridional local watershed. The length of the
normal faults reaches 800 m. The morphology and position of these faults can be attributed to
their sackung structures.
We conclude that the detected current surface ruptures have complex origins and develop
under the influence of endogenous (tectonic) and exogenous forces. They founded along NE
trending ancient tectonic structures within wide strike-slip zone and main direction of
opening corresponds to the direction of extension of paleo- and present-day stress field.
According to the dynamics of ruptures opening, the main phase of their formation is
connected with stage of Kultuk earthquake preparation. As for geodetic data the block is
stretched in all directions, it can be assumed that, by analogy with closely spaced sacking |
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