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 CSIR Fourth Paradigm Institute

(Formerly CSIR Centre for Mathematical Modelling and Computer Simulation)

A constituent laboratory of Council of Scientific & Industrial Research (CSIR).

Ministry of Science and Technology, Government of India.

Events Calendar

Ph. D. Oral Examination/Viva-voce of Ms. Silpa K
Friday 04 June 2021, 11:00am - 12:30pm
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Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002

Multi-scale Modelling Programme, CSIR - Fourth Paradigm Institute (CSIR-4PI)

PhD Thesis Oral Examination/Viva-Voce

A study on Indian plate seismogenesis using kinematic slip distribution models of selected earthquakes

by Silpa K
AcSIR Reg.No.10PP14J45002

Date/Time: Friday, 4 th June 2021, 11:00 AM

Venue: Online Google Meet:

The lithospheric stress accumulated due to relative plate motions is mostly accommodated at plate
boundary fault interface zones and is evident from dense and destructive seismic activity there.
Unlike these plate interface earthquakes, there are infrequent large intraplate event occurrences
within the continental/oceanic interiors and sinking slabs, and this study, in particular, looks at
their seismogenic characteristics. These earthquakes can be highly destructive due to their shallow
source. They generate a very high amount of ground shaking and can occur as a complete surprise
at regions with no known seismic history. Interestingly, at times, this class of events is reported
from areas where strain rates are low, yet destructive. Off and on, large magnitude earthquakes
with complex slip histories are also globally noticed. It is observed that these within the plate
earthquakes show links with the plate boundary ruptures in the vicinity. With this background, this
study particularly focuses on the Indian plate intraplate deformation, paying attention towards its
stable continental region (SCR), diffuse Wharton zone, outer-rise region of the Andaman Nicobar
subduction and sinking slab interiors of the Indo-Burmese and Himalayan collision regions. The
mode of investigation involves the usage of the teleseismic kinematic finite-fault simulations with
supportive stress-inversion models. Results on the Indian SCR region indicate seismogenic features
with compact singular asperity breakage within the Indian crust. Models suggest that even faults
without any previous or repetitive activity can also fail in a low-strained and pre-stressed Indian
SCR. Likewise, Northern Wharton Basin models favour faulting on ∼ESE-WNW oriented active
shear structures. This study confirms that the centroid depths at this region lie within the 600 0 C
isotherm. Still, occasionally the seismic slip can extend up to ∼750 0 C isotherm, indicating brittle
nature at the upper mantle. A depth-wise variation in the stress field, from shallow oblique-normal
faulting to deeper oblique-reverse indicates the direct control of plate bending or slip-partitioning
effects on the Northern Wharton tectonics. Similar analysis on the outer-rise region of Andaman-
Nicobar subduction reveals active deformation due to slab bending effects and the possible influence
of northward drag of the Indian plate stresses at North, South and Little Andaman regions. Mod-
els indicate extensive stress field rotations after the 2004 Mw 9.2 Sumatra-Andaman megathrust
earthquake, which has resulted in a mixed response of seismicity within the slab and the nearby
Wharton Basin. Co-seismic and post-seismic model comparisons indicate a strong correlation with
co-seismic stress relief zones and regions of rapid post-seismic reloading. Similarly, results suggest
a cold caramel slab at the Sikkim Himalaya region and further adds that the slab tearing could be
the reason for the lower crustal deeper earthquakes. Likewise, the study infers that the lateral shear
due to the northward drag of Indian plate and slip partitioning within the slab could explain the
slab earthquakes in the Indo-Burmese Arc.

Location Online Google Meet: