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Himalayan Geology, Vol. 31
(2), 2010, pp. 167-168, Printed in India
SERC School: Fifth Module on Tectonics - Climate Change interaction and
Paleoseismology
Summary: Under SERC School of the DST, Government of India five courses were
sanctioned entitled “Crustal deformation and tectonic geomorphology”. The
first four courses were organized at the Indian Institute of Technology,
Kanpur (Organizers: Dr. Rajiv Sinha and Prof. S.K. Tandon), C-MMACS,
Bangalore (Organizers: Dr. M. Mukul), Wadia Institute of Himalayan Geology,
Dehradun (Organizers: Dr. A.K. Dubey and Dr. R. Jayangondaperumal), and R.
R. Lalan College, Bhuj, Gujarat (Organizers: Dr. L.S. Chamyal, Dr C. P.
Rajendran and Dr. M. Thakkar). The final fifth module proposed on
“Climate-Tectonics Interaction and Paleoseismology of active faults” was
organized at Sikkim Manipal Institute of Technology campus at Rang Po,
Sikkim from 27th May to 10th June, 2009 by Dr. R.Jayangondaperumal (WIHG,
Dehradun) and Dr. B. Senthil Kumar (IISc, Bangalore). The course was
designed to expose the participants to geology of the NE Himalaya
“Tectonics-Climate Change interaction and Paleoseismology”.
The course was attended by 25 participants from various universities,
research institutes and IIT‘s from 27th May to 10 June, 2009. The faculty
for the courses included Drs. L. S. Chamyal, V.C. Thakur, C.P. Rajendran,
V.P. Rao, A.K. Dubey, N. Juyal, M. Mukul, Pradeep Srivastava, Vikrant Jain,
V. Singh, Santanu Bose, B. Senthil Kumar, and R. Jayangondaperumal.
Since the main objective of the fifth SERC module was to train the
participants in field techniques, 10 days of field work including trenching
of active faults was oragnised at Chalsa. The participants were taught the
various approaches that can be employed in mapping geomorphic surfaces like
fans, terraces in determining rates of erosion and uplift, and
reconstructing the past geometry of tectonically active landscapes.
The field training was confined to vicinity of the North and South Kalijohar
Thrusts. The field training included structural mapping, terrace mapping
through handy station (portable version of the Total Station (EDM) designed
by Nakata), identification of tectonic and fluvial landforms, tectonic
scarps, and site selection for trenching. The landforms and scarp profile
were mapped by stick line method (using Brunton compass and a stick of known
length) and by using a TRUPULUSE mounted on a tripod (designed by Prof.
Nakata). Data collected in the field using stick line method and handy
station were used to generate topographic maps and scarp profiles by the
participants. Based on the scarp profile and topographic map, participants
were trained for selecting a suitable site for trenching (Figs. 1 and 2).
A trench was excavated (50m length x 5m depth x 6m width) normal to the
NW-SE striking scarp at a plantation site (Pani Jhora) near Chalsa (Figs. 1,
2 and 3). Trenching across the scarp exposed a fault with a minimum of 6 m
displacement. A grid (1 x 1 m) in trench wall after scrapping and cleaning
was used to analyze the exposed structure and stratigraphy (Fig. 2). Three
student groups made partial trench logs by placing graph paper and mylar on
top of a map board. After completion of the exercise, suitable sites for
sampling of datable materials for AMS (C-14 - Accelerator Mass Spectrometer
dating) and OSL techniques, to constraint the age of the earthquake, was
shown to the participants, who collected 8 OSL and 13 AMS samples. The
samples are expected to bracket the age of an earthquake preserved in the
trench. The age results also have potential to extend the spatial extent of
the AD 1100 earthquake reported by Upreti et al. (2000) and Lave et al.
(2005). Kumar et al. (in press) have described large to great event after
studying a trench to the east of the present trench. However their age
constraints are wide-spread and do not allow with confidence a correlation
with the AD 1100 event. The excavated trench can provide estimates of
co-seismic displacement, shortening and vertical separation associated with
the seismic event.
References
Lave, J., et al. (2005) Evidence for a Great Medieval Earthquake (~1100
A.D.) in the Central Himalayas, Nepal, Science, v.307, pp.1302"1305.
Nakata, T., et al. (1998) First successful paleoseismic trench study on
active faults in the Himalaya, EOS, Trans., v.79(45), F615.
Upreti, B. N., et al. (2000) The latest active faulting in Southeast Nepal,
paper presented at Proceedings Active Fault Research for the New Millenium -
Hokudan International Symposium and School on Active Faulting, Awaji Island,
Hyogo Japan.
Kumar, Senthil, Wesnousky, Steven G., Jayangondaperumal, R., Nakata, T.,
Kumahara, Y., and Singh, Vimal. (in press) Paleoseismological evidence of
surface faulting along the northeastern Himalayan front, India: Timing,
Size, and Spatial Extent of Great Earthquakes. (JGR, in press).
R. Jayangondaperumal, WIHG, Dehradun
Senthil Kumar Babu, IISc, Bangalore
Course Director
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