Satellite image interpretation, geologic mapping, and paleoseismic trenching are
used to investigate the Trans-Yamuna active fault system in the northwestern Doon Valley
of the Indian Himalayan foothills. This east-west fault system is subparallel to and crosses
the Main Boundary thrust near the structural transition from the Nahan salient to the
Dehra Dun reentrant. The Trans-Yamuna active fault system may terminate to the east at
a lateral ramp of the Main Boundary thrust. A south-side-up, relatively linear fault trace
with variable fault dips suggests that the fault system is high-angle reverse with a
component of strike-slip. It is subdivided into the Sirmurital, Dhamaun, and Bharli faults,
which probably connect at depth. The Dhamaun fault is exposed where it cuts the late
Holocene upper Bhatrog terrace deposit of the Giri River. A paleoseismic investigation of
the Sirmurital fault at another Giri River terrace did not expose the fault, but it suggests
that late Holocene terrace deposits there may be folded into a syncline parallel to fault
strike. The fold axis of the syncline continues into bedrock to the west. Earthquakes in
1905, 1803, or perhaps earlier may have been the source of folding of the fine-grained
sediments within this terrace deposit. The Trans-Yamuna active fault system is a
secondary hangingwall fault that may accommodate some strain release above the
decollement during large-magnitude earthquakes. Strike-slip motion may be related to the
lateral translation of the Karakoram fault block and east-west extension of the southern
Tibet block as a result of oblique convergence between the Indian and Eurasian plates in
the northwest Himalaya. / Graduation date: 1999
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/33684 |
| Date | 09 October 1998 |
| Creators | Oatney, Emily M. |
| Contributors | Yeats, Robert S. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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