Page 34 - Jabalpur_EQ

Selsmological Aspects
Chapter 2

in a broad sense is defined
on the premises of the protocontinents the seismicity The seismicity
with low intracontinental seismicity.
by the three protocontinents, moderately
to increase from the nuclei towards peripheries forming
appears
active seismic zones along the protocontinental margins and weak zones (e.g
lineaments and rifts).
of the Peninsular India to block tectonics
Khattri (1994) attributes the seismicity to this
with a strain field being caused by the Indian plate motion. According
hypothesis the earthquakes are expected to occur at the boundary of two blocksS.
The significant number of faults are either in the NE or NW direction in the Pen-
insular India which might have given rise to many seismicity zones. Based on the
alignment of epicenters and spatial distribution of earthquakes, ten seismicity
zones have been identified (Fig. 2-6). These zones are almost linear and define the
boundaries of regions with no seismicity (stable zones).

The compressional strain responsible for the seismicity of the Peninsular India is
due to the collision of Indian plate with the Eurasiar1 plate. Also, the upper crust,
which is usually the seismogenic layer has thinned out at some places in the Pen-
insula to less than 10 km, due to the compressional strain and high heat flow
(Kaila et al. 1989). Therefore, the Indian Peninsula is not likely to support a sig
nificant accumulation of strain. The occurrence of moderate earthquakes like
Koyna (1967), Latur (1993) and Jabalpur (1997) is most probably due to compres-

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20
20
BAY
N
-- OF
ARABIAN BENGAL
SEA
-
-

62
92

Figure 2-6. Seismicity zones based on block tectonics (Khattri 1994).

Jabalpur Earthquake of May 22, 1997 24