International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004 
  
Figure 1 a) Fault plane solutions of Mongolian earthquakes (After Bayasgalan, 1999). First motion solutions in cyan, Harvard CMT 
solutions in blue, body waveform modelling solutions from other studies in magenta and Bayasgalan (1999) in red. The numbers 
indicate the date of seismic event. The letters in white box stands for GA- Gobi Altay, G-TS- Gobi Tien Shan; MA - Mongolian 
Altay; STB — Shargyn Tsagaan Basin. The box in red corresponds to the study area. b) Mosaic of ASTER images used in the 
structural interpretation of the Shargyn Basin. Red lines show faults along prominent morphological boundaries. 
active tectonics, specifically active thrust faulting. The writers 
however, relate these terraces to younger active mountain 
fronts, formed much later than the older currently inactive ones. 
  
95° 00" " 05730 
Figure 2. Mosaic of ASTER images of the Shargyn Basin; red 
lines indicate faults. Field evidence shows most of the faults in 
the basin to be thrust fault, with some marked by left lateral 
shear. 
The Shargyn Fault 
One of the best-exposed sub latitudinal fault zones in the study 
area is the fault system of the Shargyn fault (Figs. Ib and 3; see 
also Fig. 4), which defines the northern margin of the Shargyn 
Basin. It is clearly visible from both ASTER and Landsat TM 
images because of its prominent topographical features. The 
fault is characterized by linear or curvi-linear principal 
displacement zone in map view. The eastern continuation of this 
fault branches and curves, as en echelon fault. 
The Shargyn fault bounds the southern end of Darviyn Nuruu 
range and forms an arc on the north side of the Shargyn Basin. 
A clear scarp can be delineated from both Landsat TM and 
ASTER images for distance of 55 km. At approximately, 30 km 
east of Tajgar Bulag up to the Hoit Shargyn River (Fig. 3) it is 
marked by a scarp facing north and crossing young alluvial 
deposits. At places the height of the scarp reaches 2.0 — 2.5 m, 
but along much of this segment its height is only 1.0 to 1.5 m. A 
number of earthquakes were recorded in the Shargyn fault zone 
in the past, but they are of low magnitude and not higher than 
M- 6. The fault plane solution for this event shows nearly pure 
strike-slip faulting: left lateral on a plane striking 81? 
(Bayasgalan, 1999). Field check reveals a clear left-lateral 
displacement, structurally controlled by river or stream 
deflections. 
Latitudinal oriented large ridges between the Tajgar Bulag and 
Sonduultai village appear to be pressure ridges also indicating 
left lateral slip (See Figure 4). These include a line of frontal, 
elongated hills along strike-slip fault protruding above the 
piedmont zone. They are separated from the main massif by a 
wide elongated depression. But, there are also many 
morphological features and tracts that seem to occupy thrusting 
and reverse component along the fault. Farther east along the 
Buural Mountain, the fault is marked both by a prominent scarp 
and by a wide zone (10 to 20m) of highly fractured, and 
brecciated rock. Baljinnyam et al: (1993) measured southward 
dips of 35° to 55° in bedrock exposures and small (~1 m), but 
consistent, left lateral offsets of divides between dry streambeds 
on the north side of Buural Mountain. The offsetting of streams 
and the alignment of morphological features are very 
conspicuous. The drag effect implies a left-lateral sense of 
displacement along the neotectonic fault. Dense distribution of 
faults also characterize the Buural Mountain massif where step- 
like, short, parallel and persistent faults trending NE-SW are 
evident. Farther west along the foot of Darviyn Nuruu range, the 
fault is marked both by a triangle shaped mountain facets and 
by a wide zone (20 to 100 m) of highly fractured, mylonizated 
and brecciated rocks along the fault zone. Although this part 
seems to indicate an ancient fault scarp, there are recent and old 
alluvial fans uplifted at the mountain front that might be 
suggestive of earthquake been concentrated on discrete fault 
zones (or mountain building been concentrated on distinct 
mountain fronts). The morphology of a segmented alluvial fan 
may be used as an indicator of active tectonics because the fan 
form may reflect varying rates of tectonics processes, such as 
faulting, uplift, tilting and folding along and adjacent to the 
mountain front. In the case of the current research, the youngest 
segments found near the mountain front such as on top of an 
alluvial fan on the eastern end of the Darviyn Nuruu Mountain 
front would be associated with active uplifting. But far away to 
the west from Yamaat Ulaan Uul Mountain, youngest fan 
segments are far away from mountain front and are 
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