Geology Reference
In-Depth Information
A
Megathrust Trench
B
C
South
Tibet
Ganges plain Siwaliks Lesser Himalaya
GreaterHimalaya
South Tibet
100 km
STD
MFT
MBT
MCT
STD
Lesser
Himalaya
MCT
Greater
Himalaya
0
trench
site
pr
esen
tly lo
cked
(slip
in la
rge e
arthq
uake
s)
MBT
20
Siwaliks
MFT
current
seismicity
40
Ganges
plain
60
trench
site
-50
0 50
Distance from the Main Frontal Thrust (km)
100
150
200
Orogenic Section
Structure Map
Fig. 6.31
Megathrust earthquakes in the Himalayan continental collision.
A. Excavation across the scarp of the Himalayan megathrust in eastern Nepal. A cumulative slip of
∼
17 (+5/−3) m deforms the
overlying units that date from
∼
1100 BP. Note the bedrock uplift in the hanging wall. B. Simplified cross-section of the Himalaya
showing the creeping zone along the sole thrust in the north that generates current seismicity beneath the Greater Himalaya, and the
presently locked sole thrust underlying the Lesser Himalaya and breaking the surface at the Main Frontal Thrust (MFT). Elastic strain
currently accumulating in the Greater Himalaya is proposed to be transferred to the MFT during megathrust earthquakes. MCT: Main
Central Thrust; MBT: Main Boundary Thrust; STD: South Tibetan Detachment. C. Location map of the cross-section (B) and the trench
site (A) with respect to major Himalayan structures. Modified after Lavé
et al.
(2005).
