DETECTION OF EARTHQUAKE HAZARD IN SOUTHWEST PENINSULAR INDIA - SPURT OF VARIOUS UNUSUAL GEOLOGICAL INCIDENTS Presented by Dr. Daya Shanker Assistant Professor Department of Earthquake Engineering Indian Institute of Technology Roorkee, Roorkee, India CTBTO(S&T2011) June 08-10, 2011 Natural Disasters would keep happening, we cannot avoid them, so lets prepare ourselves. Join our effort to build a Disaster Management Information D. SHANKER 1 , H.N. Singh 2 , John Mathai 3 V.N. Neelakandan 3 A. Kumar 2 1 Department of Earthquake Engineering, Indian Institute of Technology Roorkee, e-mail: [email protected]2 Department of Geophysics, Banaras Hindu University, Varanasi 221 005, INDIA 3 Centre for Earth Science Studies, P.B. No. 7250, Akkulam Trivandrum-695 031, INDIA
Slide 1DETECTION OF EARTHQUAKE HAZARD IN SOUTHWEST PENINSULAR INDIA
- SPURT OF VARIOUS UNUSUAL GEOLOGICAL INCIDENTS
Presented by Dr. Daya Shanker
Assistant Professor Department of Earthquake Engineering
Indian Institute of Technology Roorkee, Roorkee, India
CTBTO(S&T2011) June 08-10, 2011
Natural Disasters would
effort to build a Disaster
Management Information
D. SHANKER 1, H.N. Singh 2, John Mathai3 V.N. Neelakandan3
A. Kumar2
2Department of Geophysics, Banaras Hindu University, Varanasi 221
005, INDIA
3Centre for Earth Science Studies, P.B. No. 7250, Akkulam
Trivandrum-695 031, INDIA
State boundary
Kerala
ºº
9º
º
10º
9º
77
& Colour rain F Bubbling/gas emission % W ell water colour
change
W avy Motion
Kasaragod
Kannur
Kozhikode
Malappuram
Kalpetta
Kochi
Alleppey
Palakkad
Trichur
Kollam
Kottayam
Trivandrum
Pathanamthitta
Painavu
The city is underlain by significant thickness of sedimentary
formations of which thickness and geological conditions are known
and it would help establish empirical relationships between the
site amplifications and basin configuration
Fig. 1: Map of Kerala state showing general geology and tectonic
features along with the affected regions by all the unusual
geological incidents that have occurred during February to November
2001.
No rth
*K a n n u r
* K o z h i k o d e
*
*
*
*
A l l e p p e y
*
M a l a p p u r a m
* K o l l a m
* K o t t a y a m
*
*
*
P a t h a n a m t h
P a l a k k a dNo rth
1 2
1 1
7 6
T a m i l N a d
7 5 7 6 7 7
1 1
K i l o m e t e r s
8 0
1 2
R i v e r s
D i s t r i c t b o u n d a r y
I N D I A
K e r a l a
S t a t e b o u n d a r y
C o a s t a l l i n e
L i n e a m e n t D y k e s
LAKSHADEEP SEA
R e c e n t T e r t i a r y L a t e r i t e P r e c a m b r i a n C
r y s t a l l i n e & A s s o c i a t e d I n t r u s i v e s W
a t e r b o d y
7 5
A l l I n c i d e n t s ( F e b - N o v 2 0 0 1 )
G e o l o g y a n d T o f K e r a l a
Kerala is an integral segment of the South Indian Shield and
tectonically very stable landmass. The region comprises Precambrian
crystalline rocks, metamorphosed to the granulite grade under high
temperature and pressure conditions. The dominant rock type is
massive charnockite, a medium to coarse grained ortho-pyroxene
bearing anhydrous granulite, and is texturally very compact. The
rocks are variably weathered and lateritised up to 5 m of laterite
capping at places.
Unusual Geological Incidents in Kerala During 2001
Seismicity
1. Micro-earthquake Activity (EQ)
2. Building Cracks (BC) 3. Ground Fissures (GF) 4. Land Subsidence
(LS) 5. Well Collapse (WC) 6. Trees/Bushes Shaking (TBS) 7.
Bubbling/ Muddying and
Gas Emission (BMG)
8. Wavy Motion in Well Water (WM) 9. Well Water Level Increase
(WLI) 10. Well Water Level Decrease (WLD) 11. Well/ Pond Dry
(WD)
12. Leaf Fall (LF) 13. Coloured Rain (CR) 14. Well Water Colour
Change (WWC)
Fig. 2a: Unusual geological incidents that have occurred in Kerala
state during 2001.
February-02 March 2001 June-November 2001
Micro-earthquake Activity (EQ) Building Cracks (BC) Ground Fissures
(GF) Wavy Motion in Well Water (WM) Well Water Level Increase (WLI)
Well Water Level Decrease (WLD) Trees/Bushes Shaking (TBS)
Micro-earthquake Activity (EQ) Building Cracks (BC) Ground Fissures
(GF) Wavy Motion in Well Water (WM) Well Water Level Increase (WLI)
Well Water Level Decrease (WLD)
Well/ Pond Dry (WD) Bubbling/ Muddying and Gas Emission (BMG) Land
Subsidence (LS) Well Collapse (WC) Leaf Fall (LF) Coloured Rain
(CR) Well Water Colour Change (WWC)
Fig.2b: Unusual geological incidents and their active phases that
have occurred in Kerala state during 2001.
Active Phases of Unusual Geological Incidents in Kerala During
2001
Fig. 3: Histograms showing district wise (a) and incident wise (d)
number of various unusual geological incidents that have occurred
in Kerala state during 1996 to November 2001; January to March, and
April to November 2001. District wise (b & c) and incident wise
(e & f) distribution of individual incident occurred during
January to March, and April to November are also shown as radar
chart. The distribution patterns show that the incidents during
January to March (b) were confined to certain districts only
whereas the activity during April to November (c) were spread
almost throughout the state (Abbreviations: EQ (micro-earthquakes);
WM (wavy motion in well water); WLI (well water level increase);
TBS (trees/bushes shaking); WLD (well water level decrease); BC
(building cracks); GF (ground fissures); WC (well collapse); BMG
(bubbling/ muddying and gas emission); LS (land subsidence); WD
(well/ pond dry); LF (leaf fall); WWC (well water colour change);
CR (coloured rain); TRV (Trivandrum); KOL (Kollam); PAT
(Pathanamthitta); ALE (Alleppey); KOT (Kottayam); IDU (Idukki); ERN
(Ernakulam); TRI (Trichur); PAL (Palakkad); MAL (Malappuram); CAL
(Calicut); KAN (Kannur); KAS (Kasaragod); WAY (Wayanad)).
0
25
50
75
100
125
nts
TRV KOL PAT ALE KOT IDU ERN TRI PAL MALCAL KAN KASWAY
Districts (south to north)
1996 to Nov 2001 Jan to Mar 2001 April to Nov 2001
a
Trivandrum Kollam
ts
BC BMG CR EQ GF TBS WM LS LF WC WLD WD WLI WWC Incidents
1996-Nov 2001 Jan-Mar 2001 April-Nov 2001
d
LF
WC
WLD
WD
WLI
WWCf
Fig. 4: Temporal distribution (daily occurrence) of all the unusual
geological incidents (a) that have occurred in Kerala from (1)
September 1996 to November 2001; (2) 2000 to November 2001; (3)
January to November 2001; (4) January to March 2001; and (5) April
to November 2001. Temporal patterns of individual fourteen
incidents that have occurred from February to November 2001are
shown in Figure b. Vertical lines are histograms of daily number,
and solid curves are the cumulative number of the incidents. The
distribution pattern clearly indicates that the spurt in activities
has taken place in two active phases starting from February and
June, and are separated by a quiescence period of about three
months. The active phase from February to 02 March has shorter
duration as compared to the active phase started from 01 June
2001.
6-Sep-96 18-Jul-97 29-May-98 9-Apr-99 18-Feb-00 29-Dec-00 9-Nov-01
0
10
20
30
40
10
20
30
40
10
20
30
40
10
20
30
40
10
20
30
40
Cumulative Number of Incidents
F-M: February to March 2001 J-N: June to November 2001
a
0
5
10
15
0
5
10
15
0
5
10
15
0
5
10
15
0
5
10
15
0
16
32
0
5
10
15
0
5
10
15
0
5
10
15
0
5
10
15
0
5
10
Trees/Bushes Shaking Well Collapse
Building Cracks Land Subsidence
Time (days)
b
Fig. 5: Cumulative number of individual total incidents with time
that have occurred in Kerala from September 1996 to November 2001
(a); January to March 2001 (b); January 2000 to November 2001 (c);
April to November 2001 (d); January to November 2001 (e) and June
to November 2001 (f). Prior to February 2001, only a few
earthquakes have occurred which include both the moderate sized
earthquakes of 12 December 2000 and 7 January 2001 around
Irattupettah in Kottayam district. Spurt in unusual geological
incidents have taken place mainly in two active phases starting
from February and June 2001 during which a total of 14 different
types of incidents have occurred. The active phases beginning from
February and June are separated by a quiescence phase of about
three months duration (03 March to 31 may 2001). (Abbreviations: EQ
(micro-earthquakes); WM (wavy motion in well water); WLI (well
water level increase); TBS (trees/bushes shaking); WLD (well water
level decrease); BC (building cracks); GF (ground fissures); WC
(well collapse); BMG (bubbling/ muddying and gas emission); LS
(land subsidence); WD (well/ pond dry); LF (leaf fall); WWC (well
water colour change); CR (coloured rain)).
0
70
140
210
C um
ul at
iv e
N um
C um
ul at
iv e
N um
C um
ul at
iv e
N um
C um
ul at
iv e
N um
C um
ul at
iv e
N um
C um
ul at
iv e
N um
ts
WM BC WLI EQ GF WLD TBS WC CR WD LS LF WWC BMG
Temporal Distribution of Individual Incident
Sept.1996-Nov. 2001
a
Fig. 6: Map of Kerala state showing spatial (a) and temporal (b)
distribution of various unusual geological incidents that have
occurred from September 1996 to November 2001. A total of 14
different types of incidents have occurred during the period which
are shown over the major geological features, drainage and
lineament patterns of the state. Most of these geological incidents
have occurred from February to November 2001. Arrows indicate the
time of either increase in the number of continuing incidents or
onset of new incidents (Abbreviations: EQ (micro-earthquakes); WM
(wavy motion in well water); WLI (well water level increase); TBS
(trees/bushes shaking); WLD (well water level decrease); BC
(building cracks); GF (ground fissures); WC (well collapse); BMG
(bubbling/ muddying and gas emission); LS (land subsidence); WD
(well/ pond dry); LF (leaf fall); WWC (well water colour change);
CR (coloured rain).
K a s a r a g o d
K a n n u r
K o z h i k o d e
M a l a p p u r a m
K a l p e t t a
K o c h i
A l l e p p e y
P a l a k k a d
T r i c h u r
K o l l a m
K o t t a y a m
T r i v a n d r u m
P a t h a n a m t h i
P a i n a v u
º1 0
K e r a l a
S t a t e b o u n d a r y D i s t r i c t b o u n d a r y C o a s t
a l l i n e
R e c e n t
L i n e a m e n t D y k e s
R i v e r s
º 7 6º7 5
T A M I L N A
LA K
S H
A D
E E
P S
E A
T e r t i a r y L a t e r i t e P r e c a m b r i a n C r y s t a l
l i n e & A s s o c i a t e d I n t r u s i v e s W a t e r b o
d y
9º
K i l o m e t e r s
8 0
2 W M
I n c i d e n ( 1 9 9 6 - 2 0
Longitude (º E)
C um
ul at
iv e
N um
LS LF WWC BMG
Sept.1996-Nov. 2001
)
Fig. 7: Map of Kerala state showing spatial (a) and temporal (b)
distribution of various unusual geological incidents that have
occurred from January to November 2001. A total of 14 different
types of incidents have occurred during the period. Most of these
geological incidents have occurred from February to November 2001
and the weekly rates of occurrence of individual incident during
the period is shown in Figure c. Arrows indicate the time of either
increase in the number of continuing incidents or onset of new
incidents (Abbreviations: EQ (micro-earthquakes); WM (wavy motion
in well water); WLI (well water level increase); TBS (trees/bushes
shaking); WLD (well water level decrease); BC (building cracks); GF
(ground fissures); WC (well collapse); BMG (bubbling/ muddying and
gas emission); LS (land subsidence); WD (well/ pond dry); LF (leaf
fall); WWC (well water colour change); CR (coloured rain).
a
Cu mu
lat ive
N um
ide nts
WM BC WLI EQ GF WLD TBS WC CR WD LS LF WWC BMG
Temporal Distribution of Individual Incident
Jan.- Nov. 2001
K a n n u r
K o z h i k o d e
M a l a p p u r a m
K a l p e t t a
K o c h i
A l l e p p e y
P a l a k k a d
T r i c h u r
K o l l a m
K o t t a y a m
T r i v a n d r u m
P a t h a n a m t h i
P a i n a v u
º1 0
K e r a l a
S t a t e b o u n d a r y D i s t r i c t b o u n d a r y C o a s t
a l l i n e
R e c e n t
L i n e a m e n t D y k e s
R i v e r s
º 7 6º7 5
T A M I L N A
LAKSH AD
EEP SEA
T e r t i a r y L a t e r i t e P r e c a m b r i a n C r y s t a l
l i n e & A s s o c i a t e d I n t r u s i v e s W a t e r b o
d y
9º
K i l o m e t e r s
8 0
C R
W L I
h
I n c i d e n ( J a n - N o v 2
0
2
4
6
8
Incidents
W ee
kly R
ate of
oc cu
rre nc
e EQ GF BC TBS WLI WM WLD WC CR WD LS LF WWC BMG
c
Fig. 8: Spatial (a) and temporal (b) distribution of various
unusual geological incidents that have occurred in Kerala state
from January to March 2001. During this period, a total of seven
different types of incidents (micro-earthquakes, wavy motion, water
level increase, water level decrease, shaking of trees/ bushes,
ground fissures, and building cracks) have occurred, which are
mostly clustered in Calicut, Malappuram and Palakkad districts in
the north; and Trivandrum, Kollam and southern parts of Alleppey
districts in the south. Arrows indicate the time of either increase
in the number of continuing incidents or onset of new incidents
(Abbreviations: EQ (micro- earthquakes); WM (wavy motion in well
water); WLI (well water level increase); TBS (trees/bushes
shaking); WLD (well water level decrease); BC (building cracks); GF
(ground fissures).
K a s a r a g o d
K a n n u r
K o z h i k o d e
M a l a p p u r a m
K a l p e t t a
K o c h i
A l l e p p e y
P a l a k k a d
T r i c h u r
K o l l a m
K o t t a y a m
T r i v a n d r u m
P a t h a n a m t h i
P a i n a v u
º1 0
K e r a l a
S t a t e b o u n d a r y D i s t r i c t b o u n d a r y C o a s t
a l l i n e
R e c e n t
L i n e a m e n t D y k e s
R i v e r s
º 7 6º7 5
T A M I L N A
LAKSH AD
EEP SEA
T e r t i a r y L a t e r i t e P r e c a m b r i a n C r y s t a l
l i n e & A s s o c i a t e d I n t r u s i v e s W a t e r b o
d y
9º
K i l o m e t e r s
8 0
C R
W L I
22
22
2
I n c i d e n ( J a n - M a r 2
Longitude (º E)
Cu mu
lat ive
N um
Jan.-March 2001
)
Fig. 9: Spatial (a) and temporal (b) distribution of various
unusual geological incidents that have occurred in Kerala state
from April to November 2001. During this period, a total of 13
different types of incidents (including all the incidents except
trees/ bushes shaking during January to March) have occurred, which
are distributed throughout the state irrespective of geology and
topography. Arrows indicate the time of either increase in the
number of continuing incidents or onset of new incidents
(Abbreviations: EQ (micro-earthquakes); WM (wavy motion in well
water); WLI (well water level increase); WLD (well water level
decrease); BC (building cracks); GF (ground fissures); WC (well
collapse); BMG (bubbling/ muddying and gas emission); LS (land
subsidence); WD (well/ pond dry); LF (leaf fall); WWC (well water
colour change); CR (coloured rain).
a
K a n n u r
K o z h i k o d e
M a l a p p u r a m
K a l p e t t a
K o c h i
A l l e p p e y
P a l a k k a d
T r i c h u r
K o l l a m
K o t t a y a m
T r i v a n d r u m
P a t h a n a m t h i
P a i n a v u
º1 0
K e r a l a
S t a t e b o u n d a r y D i s t r i c t b o u n d a r y C o a s t
a l l i n e
R e c e n t
L i n e a m e n t D y k e s
R i v e r s
º 7 6º7 5
T A M I L N A
LAKSH AD
EEP SEA
T e r t i a r y L a t e r i t e P r e c a m b r i a n C r y s t a l
l i n e & A s s o c i a t e d I n t r u s i v e s W a t e r b o
d y
9º
K i l o m e t e r s
8 0
C R
2 W M
( A p r i l - N o v I n c i d e n
0
70
140
210
280
350
420
Cu mu
lat ive
N um
ide nts
WM BC WLI EQ GF WLD TBS WC CR WD LS LF WWC BMG
Temporal Distribution of Individual Incidents
April to Nov. 2001
b
Fig. 10: Cumulative number of individual unusual geological
incidents in Kerala that have occurred from January to November
2001 (a); January to March 2001 (b); and April to November 2001
(c). The distribution patterns clearly indicate two sets of active
phases separated by a quiescence phase for about 3 months from
March to May 2001. The spurt in activity had taken place in the
beginning of February with occurrence of seven different types of
incidents over the preceding normal background, and it continued
till March 02 beyond which the activity reduced to background till
May end. The second active phase had initiated with well collapse
incident followed by 12 additional incidents and continued till
November with reduced frequency. (Abbreviations: EQ
(micro-earthquakes); WM (wavy motion in well water); WLI (well
water level increase); TBS (trees/bushes shaking); WLD (well water
level decrease); BC (building cracks); GF (ground fissures); WC
(well collapse); BMG (bubbling/ muddying and gas emission); LS
(land subsidence); WD (well/ pond dry); LF (leaf fall); WWC (well
water colour change); CR (coloured rain)).
C um
ul at
iv e
N um
BC
EQ
GF
TBS
WM
WLD
WLI
b
0
42
84
126
168
210
1-Jan-2001 2-Mar-2001 1-May-2001 30-Jun-2001 29-Aug-2001
28-Oct-2001
BC BMG CR EQ GF TBS WM LS LF WC WLD WD WLI WWC
a
0
42
84
126
168
210
1-Apr-2001 16-May-2001 30-Jun-2001 14-Aug-2001 28-Sep-2001
12-Nov-2001
BC BMG CR EQ GF TBS WM LS LF WC WLD WD WLI WWC
Well Collapse
Coloured Rain
Time (days)
Time (days)
Fig. 11: Spatial distribution of earthquakes in Kerala state that
have occurred since historical past till April 2002 (a). It is
evident from temporal patterns that number of earthquakes have been
very low prior to 1983 and there is gradual increase in the
seismicity in the recent past which is confined to certain
localities. Seismicity in Kerala state occurred from 2000-April
2002 (b); and 2001- April 2002 (c) show its significant
fluctuations in two active phases from February to 02 March, and
August to September 2001. Magnitude relationships of
micro-earthquakes occurred during February to November 2001 (d)
indicates that the magnitude of none of the earthquakes exceeded
3.5, and this active phase is preceded by two moderate sized
earthquakes of 12 December 2000 and 07 January 2001 of M 5 &
4.8 respectively.
d
Kerala
Recent
*
19001994
a
0
2
4
M ag
nit ud
Nu mb
er of
Ea rth
qu ak
Nu mb
er of
Ea rth
qu ak
)
Fig. 12: Spatial (a) and temporal patterns (b) of earthquakes in
Kerala state that have occurred from 1900 to April 2002. During
this period, most of the earthquakes are clustered in eight
localities as delineated in the map. Temporal distribution is
restricted till April 2002 and patterns of seismicity variation are
shown from 1900 to April 2002 (b) and 1978 to April 2002 (c).
Histograms of daily number of earthquakes are also shown in both
the figures. a and b denotes active phases of recent seismicity in
Kerala from February to March, and from June to November 2001
respectively.
a
Karunagapalli
Ambalapuzha
Mararikulam
Kerala
Nu mb
er of
E art
hq ua
ke s
b
1978 1981 1984 1987 1990 1993 1996 1999 Time (years)
Nu mb
er of
E art
hq ua
Cumulative (1978-April 2002)
A
B
c
Fig. 13: Seismicity of Kerala from 1996 to April 2002 (a). Only
three earthquakes have occurred during 1996 to 2000 which include
recent largest earthquake of M 5 on 12 December 2000 around
Irattupettah in Kottayam district. Temporal patterns of seismicity
from 1996-April 2002 (b); 2000-April 2002 (c); and 2001- April 2002
(d) show significant fluctuations of seismicity in two active
phases from February to 02 March, and August to September 2001.
Histograms of daily and cumulative number of earthquakes are shown
in these figures. The active phase starting from February 2001 is
preceded by two moderate sized earthquakes of 12 December 2000 and
07 January 2001 of M 5 & 4.8 respectively.
La titu
de (º
Kerala
Recent
*
2000
2001
a
0
10
20
30
40
Nu mb
er of
Ea rth
qu ak
Nu mb
er of
Ea rth
qu ak
a
Fig. 14: Spatial (a) and temporal (b & c) distribution of daily
number of well collapse incident that have occurred from June to
November 2001 in Kerala state. The incident is mostly confined in
southern districts, Malappuram and Calicut with sparse distribution
in remaining parts of the state. It is evident that there was no
well collapse incident prior to June (b), and the spurt in incident
had taken place from the beginning of June which continued till
November with reduced rate. Maximum occurrences is recorded during
the third week of June 2001 (WC: well collapse).
Longitude (º E)
K a n n u r
K o z h i k o d e
M a l a p p u r a m
K a l p e t t a
K o c h i
A l l e p p e y
P a l a k k a d
T r i c h u r
K o l l a m
K o t t a y a m
T r i v a n d r u m
P a t h a n a m t h i
P a i n a v u
º1 0
K e r a l a
S t a t e b o u n d a r y D i s t r i c t b o u n d a r y C o a s t
a l l i n e
R e c e n t
L i n e a m e n t D y k e s
R i v e r s
º 7 6º7 5
T A M I L N A
LAKSH AD
EEP SEA
T e r t i a r y L a t e r i t e P r e c a m b r i a n C r y s t a l
l i n e & A s s o c i a t e d I n t r u s i v e s W a t e r b o
d y
9º
K i l o m e t e r s
8 0
1 0 W C
W e l l C o l l ( J u n e - N o v
0
9
18
27
36
Nu mb
er of
W ell
C oll
ap se
b
) a
Fig. 15: Spatial distribution of affected regions (a) and temporal
patterns due to well collapse incident that have occurred from June
to November 2001 in Kerala state. District wise distribution of
percent of well collapses shown in the radar chart (b) indicate
that maximum collapses have occurred in Malappuram district (~25%
of the total) followed by Trivandrum, Kollam, Alleppey, Kottayam,
Calicut and Palakkad districts. It is evident that the spurt in the
incident that had initiated from 01 June with a weekly frequency of
about eight well collapses, which increased to a maximum of 57
during the third week of June beyond which the rate reduced slowly
to normal till the end of November 2001 (c).
Longitude (º E)
W e l l C o l l a p s e ( J u n - N o v 2 0 0 1 )
A l l I n c i d e n t s ( F e b - N o v 2 0 0 1 )
A f f e c t e d R U n u s u a l G e o l o a n d W e l l
K a s a r a g o d
K a n n u r
K o z h i k o d e
M a l a p p u r a m
K a l p e t t a
K o c h i
A l l e p p e y
P a l a k k a d
T r i c h u r
K o l l a m
K o t t a y a m
T r i v a n d r u m
P a t h a n a m t h i
P a i n a v u
º1 0
K e r a l a
S t a t e b o u n d a r y D i s t r i c t b o u n d a r y C o a s t
a l l i n e
R e c e n t
L i n e a m e n t D y k e s
R i v e r s
º 7 6º7 5
T A M I L N A
LAKSH AD
EEP SEA
*
K i l o m e t e r s
8 0
0
10
20
30
40
50
60
1 4 7 10 13 16 19 22 25 Time (weeks from 01 June to 30 November
2001)
Nu mb
er of
W ell
C oll
ap se
c
Fig. 17: Typical forms of well collapses and other related
incidents that have occurred in Kerala from June to November 2001,
and associated geological conditions (Photographs by Dr. H.N. Singh
and Mr. John Mathai).
Plate 6 Date: 19 July 2001 Location: Nedumkunnam, Kottayam district
Lateritic midland, gentle slope, charnockite basement; dried in few
hours; bubbled initially; Seepage continues T.D.: 8 m; DTWT: 6 m;
Age: > 30 yrs
Plate 7 Date: 18 July 2001 Location: Nedumkunnam, kottayam district
Lateritic midland, gentle slope, charnockite basement; bubbling
continued for 11 days T.D.: 5 m; DTWT: 3.8 m; Age: > 20
yrs
Plate 8 Date: July 19, 2001 Location: Changanacherri, Kottayam
district Alluvial plain, basement (not known) Ground depression in
unconsolidated sandy loam about 50 cm diameter DTWT (nearby well):
1.5 m
Plate 9 Location: Kuttikkanam, Idukki district Minor fault plane;
N-S trend; dip to east; associated with NNW-SSE Kerala
lineament
Plate 1 Date: 15 June 2001 Location: Arumanur, Kottayam district
Floodplain of Minachil River, sandy alluvium; shallow basement;
rings slipped by 0.6 m; bubbling observed before collapse; T.D.: 8
m; DTWT: 4 m; Age: > 40 yrs
Plate 2 Date: 14 June 2001 Location: Kaviyur, Pathanamthitta
district Floodplain of Manimala River, almost flat, sandy alluvium;
rings slipped by about 2 m; upper strata relatively intact;
muddying and bubbling observed before collapse T.D.: 8 m; DTWT: 4
m; Age: > 10 yrs
Plate 3 Date: 15 June 2001 Location: Ullala, Kottayam district,
coastal alluvium Well lined with laterite blocks collapsed totally;
bubbling seen before collapse T.D.: 5 m; DTWT: 1.5 m (water seen
close to the surface); Age: >30 yrs
Plate 4 Date: 24 July 2001 Location: Chempazhanthi, Trivandrum
district; Lateritic midland, gentle slope, base lithomarge; rings
slipped by 2.4 m suddenly; T.D.: 11 m; DTWT: 4.6 m Present depth:
8.2 m; Age: 40 yrs; rings: 10 yrs
Plate 5 Date: 05 July 2001 Location: Iverkala, Pathanamthitta
district Lateritic midland- gentle slope, base lithomarge Vertical
collapse: 1.5 m; Age: > 15 years (Photo courtesy: Malayala
Manorama Daily)
Fig. 18: Typical forms of well collapses that have occurred in
various parts of Kerala from June to November 2001 (pictures by Dr.
H.N. Singh & Mr. John Mathai).
Typical Forms of Well Collapses
Various Forms of Ground Deformations in Kerala During 2001 Building
Cracks/ Displacement of Wooden Beam
K in
ar ap
al la
m / K
ol le
ng od
(P al
ak ka
Kollengod (Palakkad)Nilambur (Malappuram)
Fig 19. Building cracks, displacement of the wooden beam and ground
fissures observed in various parts of the Kerala state during
February to March 2001. The pictures of ground fissures and
building cracks/ displacement of wooden beams presented here are
from Malappuram and Palakkad districts where extensive ground
deformations in various forms have occurred during the period. Some
ground fissures were measured more than 500 m long especially in
Mamgara area in Nilambur. Multiple ground cracks observed in
Chittur Taluk occupy the epicentral tract of Coimbatore earthquake
of 1900 (pictures by Dr. H.N. Singh).
Fig. 16: Cumulative Number of unusual geological incidents occurred
in Kerala from January to November (a); and cumulative rainfall
pattern recorded at eight observatories in Kerala state from March
to August 2001 as against normal for the same periods (b). The
total rainfall during June to August 2001 is compared with the
total rainfall during the same period in the high rainfall year of
1991 (Source: IMD rainfall data for 2001 as reported in
Mathrubhoomi daily; Normal rainfall and the rainfall for the 1991
is taken from Hand Book on Watershed based development, State
Planning Board Publication, December 1999). Several incidents have
occurred during the period of scanty rainfall and hence there is no
positive correlation between rainfall and occurrence of unusual
geological incidents.
a
0
42
84
126
168
210
5
10
15
20
25
BMG
WWC
TBS
WLD
LS
WD
LF
0
1000
2000
3000
March-May
1991
2001
0
1000
2000
3000 Actual 2001 Normal 2001 June-August 2001 (total) June-August
1991
June 2001
August 2001
Ra inf
all In
ten sit
y ( mm
Rainfall Monitoring Stations
Untimely Leaf Fall
Field pictures showing untimely leaf fall which have occurred
during the monsoon period from June to November 2001 in Kollam and
Trivandrum districts in Kerala. Similar phenomena are also observed
in Malappuram and Trichur districts. This incident has taken place
during the active period of other unusual geological incidents such
as well collapses, earthquakes, wavy motion in well water etc
(Pictures by John Mathai).
o N
K a s a r a g o d
a
K o z h i k o d e
M a l a p p u r a m
K o c h i
K o l l a m
K o t t a y a m A l l e p p e y
T r i v a n d r u m
Eo
P a l a k k a d T r i c h u r
P a i n a v u
P a t h a n a m t h i t S t a t e b o u n d a r y D i s t r i c t b
o u n d a r y C o a s t a l l i n e
R e c e n t
L i n e a m e n t D y k e s
R i v e r s
T e r t i a r y L a t e r i t e P r e c a m b r i a n C r y s t a l
l i n e & A s s o c i a t e d I n t r u s i v e s W a t e r b o
d y
*0 4 0
K i l o m e t e r s
8 0
1 2
1 1
I N D I A
7 5 7 6 7 7
7 5
1 0
K A R N A T A K A
LA K
SH A
D E
E P
SE A
1 0
F B M G W L D
( J a n - N o v 2 0 0 1 ) W a t e r L e v e l F l u
0
25
50
75
100
C um
ul at
iv e
N um
Time (days)
Fig. 18: Spatial (a) and temporal (b) Pattern of WM, WLI, WLD, WD
and BMG that have occurred in Kerala state
K a s a r a g o d
K a n n u r
K a l p e t t a
K o z h i k o d e
K o c h i
K o t t a y a m
A l l e p p e y
K o l l a m
M a l a p p u r a m
P a l a k k a d
T r i c h u r
P a i n a v u
P a t h a n a m t h i t
T r i v a n d r u m
LA K
S H
A D
E E
P S
E A
K i l o m e t e r s
8 0
L a t e r i t e
D y k e s L i n e a m e n t
R e c e n t T e r t i a r y
K e r a l a
I N D I A
C o a s t a l l i n e
R i v e r s W a t e r b o d y
S t a t e b o u n d a r y D i s t r i c t b o u n d a r y
P r e c a m b r i a n C r y s t a l l i n e & A s s o c i a t e
d I n t r u s i v e s
K a r n a t a k a a
7 6
1 0
o
o
1 2 1 2
W L F
W W C
&
&
& &
& &
&
&
& &
&&
& &
&
&
&
&
&
&
& &
&
&&
&&
& & &
&
&& &&
& &
& &
&
&& &
&&& &&&&&
& &&
&&
&& & &
&&&
& &
&
&&
&
&
&
& &
& & &
& &
&
&&&& &
%
%
%%%
% %
%
%
ul at
iv e
N um
Time (days)
Spatial (a) and temporal (b) patterns of CR LF,WWC that have
occurred in Kerala during June to november 2001. All these
Incidents have occurred during II active Phase and coincide on time
scale. Duration Of these incidents is observed to be shorter as
compared to other incidents during the Same period
Fig. I-1: Spatial (a, b & c) and temporal (d) patterns of all
the incidents that have occurred in Kerala during Janauary to
November 2001.
K a s a r a g o d
K a n n u r
K o z h i k o d e
M a l a p p u r a m
K a l p e t t a
K o c h i
A l l e p p e y
P a l a k k a d
T r i c h u r
K o l l a m
K o t t a y a m
T r i v a n d r u m
P a t h a n a m t h i t
P a i n a v u
LAKSHADEEP SEA
K i l o m e t e r s
8 0
1 2
1 1
D y k e s L i n e a m e n t
R e c e n t T e r t i a r y L a t e r i t e
C o a s t a l l i n e
R i v e r s S t a t e b o u n d a r y D i s t r i c t b o u n d a r
y
7 5
1 0
K e r a l a
T a m i l N a
K a r n a t a k a
P r e c a m b r i a n C r y s t a l l i n e & A s s o c i a t e
d I n t r u s i v e s W a t e r b o d y
1 1
1 0
1 2
W D
W M E Q
%
%
%%%
% %
%
%
" "
"
"
"
"""""
"
""
E a s t
U n u s u a l G e o I n c i d e n t s i n
( J a n - N o v 2 0 0
a
BC BMG
0 20 40 60 80 100 120
Trivandrum Kollam
Pathanamthitta Alleppey
Kottayam Idukki
Ernakulam Trichur
Palakkad Malappuram
Calicut Kannur
Kasaragod Wayanad
Di str
ict s
20
40
20
40
Cumulative Number of Incidents
K a n n u r
K o z h i k o d e
M a l a p p u r a m
K a l p e t t a
K o c h i
A l l e p p e y
P a l a k k a d
T r i c h u r
K o l l a m
K o t t a y a m
T r i v a n d r u m
P a i n a v u
P a t h a n a m t h i t t
No rth
R i v e r s
D i s t r i c t b o u n d a r y
I N D I A
K e r a l a
S t a t e b o u n d a r y
C o a s t a l l i n e
L i n e a m e n t D y k e s
LAKSH AD
EEP SEA
R e c e n t T e r t i a r y L a t e r i t e P r e c a m b r i a n C
r y s t a l l i n e & A s s o c i a t e d I n t r u s i v e s W
a t e r b o d y
1 2
1 1
K a r n a t a k a
T a m i l N a d
7 7
K i l o m e t e r s
8 0
1 2
1 1
" I
B u i l d i n g C r a c k s ( B C ) G r o u n d F i s s u r e s ( G
F )
II
( J a n - N o v 2 0 0 1
G r o u n d F i s s u B u i l d i n g C r
a K a s a r a g o d
K a n n u r
K o z h i k o d e
M a l a p p u r a m
K a l p e t t a
K o c h i
A l l e p p e y
P a l a k k a d
T r i c h u r
K o l l a m
K o t t a y a m
T r i v a n d r u m
P a i n a v u
P a t h a n a m t h i t t a
No rth
R i v e r s
D i s t r i c t b o u n d a r y
I N D I A
K e r a l a
S t a t e b o u n d a r y
C o a s t a l l i n e
L i n e a m e n t D y k e s
LAKSH AD
EEP SEA
R e c e n t T e r t i a r y L a t e r i t e P r e c a m b r i a n C
r y s t a l l i n e & A s s o c i a t e d I n t r u s i v e s W
a t e r b o d y
1 2
1 1
K a r n a t a k a
T a m i l N a d
7 7
K i l o m e t e r s
8 0
1 2
1 1
L F W W C
B M G
%
%
%%%
% %
%
%
" "
"
"
"
"""""
"
""
II II
U n u s u a l G e o I n c i d e n t s i n K
( J a n - N o v 2 0 0 1 )
a
Comparison
K a n n u r
K o z h i k o d e
K a l p e t t a
K o c h i
A l l e p p e y
T r i c h u r
M a l a p p u r a m
K o l l a m
K o t t a y a m
T r i v a n d r u m
P a l a k k a d
P a i n a v u
)
)
)
)
)
)
)
)
) )
)
)
)
R i v e r s
D i s t r i c t b o u n d a r y
I N D I A
K e r a l a
S t a t e b o u n d a r y
C o a s t a l l i n e
L i n e a m e n t D y k e s
LAKSH AD
EEP SEA
R e c e n t T e r t i a r y L a t e r i t e P r e c a m b r i a n C
r y s t a l l i n e & A s s o c i a t e d I n t r u s i v e s W
a t e r b o d y
1 2
1 1
K a r n a t a k a
T a m i l N a d
7 7
K i l o m e t e r s
8 0
1 2
1 1
No rth %
T B S W L D
L S B M G
W W C
U n u s u a l G e o l I n c i d e n t s i n K
( 1 9 9 6 - 2 0 0 1 )
I
II
a K a s a r a g o d
K a n n u r
*
*
K a l p e t t a *
*
A l l e p p e y
*
*
*
M a l a p p u r a m
K o l l a m *
K o t t a y a m *
T r i v a n d r u m *
P a l a k k a d *
P a i n a v u
*
* R i v e r s
D i s t r i c t b o u n d a r y
I N D I A
K e r a l a
S t a t e b o u n d a r y
C o a s t a l l i n e
L i n e a m e n t D y k e s
LAKSH AD
EEP SEA
R e c e n t T e r t i a r y L a t e r i t e P r e c a m b r i a n C
r y s t a l l i n e & A s s o c i a t e d I n t r u s i v e s W
a t e r b o d y
1 2
1 1
K a r n a t a k a
T a m i l N a d
7 7
K i l o m e t e r s
8 0
1 2
1 1
No rth
W C
I
W e l l C o l l a p ( J u n e - N o v e m b e r
a
Comparison
( J u n e - N o v . 2 0 0 1 )
A l l I n c i d e n t s ( F e b . - N o v . 2 0 0 1 ) W e l l C o l
l a p s e
U n u s u a l G e o l o g i c a n d W e l l C o l l a
A f f e c t e d R e g iK a s a r a g o d
K a n n u r
*
*
K a l p e t t a *
*
A l l e p p e y
*
*
*
M a l a p p u r a m
K o l l a m *
K o t t a y a m *
T r i v a n d r u m *
P a l a k k a d *
P a i n a v u
*
* R i v e r s
D i s t r i c t b o u n d a r y
I N D I A
K e r a l a
S t a t e b o u n d a r y
C o a s t a l l i n e
L i n e a m e n t D y k e s
LAKSH AD
EEP SEA
R e c e n t T e r t i a r y L a t e r i t e P r e c a m b r i a n C
r y s t a l l i n e & A s s o c i a t e d I n t r u s i v e s W
a t e r b o d y
1 2
1 1
K a r n a t a k a
T a m i l N a d
7 7
K i l o m e t e r s
8 0
1 2
1 1
No rth
b K a s a r a g o d
K a n n u r
*
*
K a l p e t t a *
*
A l l e p p e y
*
*
M a l a p p u r a m
K o l l a m *
K o t t a y a m *
T r i v a n d r u m *
P a l a k k a d *
P a i n a v u
*
* R i v e r s
D i s t r i c t b o u n d a r y
I N D I A
K e r a l a
S t a t e b o u n d a r y
C o a s t a l l i n e
L i n e a m e n t D y k e s
LAKSH AD
EEP SEA
R e c e n t T e r t i a r y L a t e r i t e P r e c a m b r i a n C
r y s t a l l i n e & A s s o c i a t e d I n t r u s i v e s W
a t e r b o d y
1 2
1 1
K a r n a t a k a
T a m i l N a d
7 7
K i l o m e t e r s
8 0
1 2
1 1
No rth
A l l I n c i d e n t s
E a r t h q u a k e s ( F e b . - N o v . 2 0 0 1 )
( F e b . - N o v . 2 0 0 1 )
E a r t h q u a k e s
E a r t h q u a k e s ( A p r i l - N o v . 2 0 0 1 )
( F e b . - M a r c h 2 0 0 1 )
( F e b - N o v 2 0 0 1
A f f e c t e d R e g U n u s u a l G e o l o g i
a n d E a r t h q u a
a
Comparison
K a n n u r
*
*
K a l p e t t a *
*
A l l e p p e y
*
*
M a l a p p u r a m
K o l l a m *
K o t t a y a m *
T r i v a n d r u m *
P a l a k k a d *
P a i n a v u
*
* R i v e r s
D i s t r i c t b o u n d a r y
I N D I A
K e r a l a
S t a t e b o u n d a r y
C o a s t a l l i n e
L i n e a m e n t D y k e s
LAK SH
AD EEP SEA
R e c e n t T e r t i a r y L a t e r i t e P r e c a m b r i a n C
r y s t a l l i n e & A s s o c i a t e d I n t r u s i v e s W
a t e r b o d y
1 2
1 1
K a r n a t a k a
T a m i l N a d
7 7
K i l o m e t e r s
8 0
1 2
1 1
N or
th
G r o u n d F i s s u r e s B u i l d i n g C r a c k s
A l l I n c i d e n t s
B u i l d i n g C r a c G r o u n d F i s u
A f f e c t e d R e
( F e b - N o v 2 0 0 1
c K a s a r a g o d
K a n n u r
*
*
K a l p e t t a *
*
A l l e p p e y
*
*
M a l a p p u r a m
K o l l a m *
K o t t a y a m *
T r i v a n d r u m *
P a l a k k a d *
P a i n a v u
*
* R i v e r s
D i s t r i c t b o u n d a r y
I N D I A
K e r a l a
S t a t e b o u n d a r y
C o a s t a l l i n e
L i n e a m e n t D y k e s
LAK SH
AD EEP SEA
R e c e n t T e r t i a r y L a t e r i t e P r e c a m b r i a n C
r y s t a l l i n e & A s s o c i a t e d I n t r u s i v e s W
a t e r b o d y
1 2
1 1
K a r n a t a k a
T a m i l N a d
7 7
K i l o m e t e r s
8 0
1 2
1 1
N or
th F e b . - N o v . 2 0 0 1
W a v y m o t i o n
A l l I n c i d e n t s
T r e e s / B u s h s h a k i n g , W e l l d r y , W a t e r l e v
e l i n c r e a s e
A f f e c t e d R e g T r e e s / b u s h s h a G r o u n d w a t e
r
I n c i d e n t s
d
Comparison
*K a n n u r
* K o z h i k o d e
*
*
*
*
A l l e p p e y
*
M a l a p p u r a m
* K o l l a m
* K o t t a y a m
*
*
*
P a t h a n a m t h
No rth
1 2
1 1
7 6
T a m i l N a d
7 5 7 6 7 7
1 1
K i l o m e t e r s
8 0
1 2
R i v e r s
D i s t r i c t b o u n d a r y
I N D I A
K e r a l a
S t a t e b o u n d a r y
C o a s t a l l i n e
L i n e a m e n t D y k e s
LAK SH
AD EEP SEA
R e c e n t T e r t i a r y L a t e r i t e P r e c a m b r i a n C
r y s t a l l i n e & A s s o c i a t e d I n t r u s i v e s W
a t e r b o d y
7 5
) 1 9 9 6 - 2 0 0 0 2 0 0 1 - A p r 2 0 0 2
E a r t h q u a k e s
S e i s m i c i t y o ( 1 9 9 6 - A p r i l 2
2 0 0 0 2 0 0 1
a *
K a s a r a g o d
K o z h i k o d e
T r i c h u r
P a l a k k a d
K a l p e t t a
M a l a p p u r a m
P a i n a v u
A l l e p p e y
K o c h i
K o t t a y a m
P a t h a n a m t h
K o l l a m
T r i v a n d r u m
R i v e r s
D i s t r i c t b o u n d a r y
I N D I A
K e r a l a
S t a t e b o u n d a r y
C o a s t a l l i n e
L i n e a m e n t D y k e s
LAK SH
AD EEP SEA
R e c e n t T e r t i a r y L a t e r i t e P r e c a m b r i a n C
r y s t a l l i n e & A s s o c i a t e d I n t r u s i v e s W
a t e r b o d y
1 2
E a s t
K i l o m e t e r s
8 0
No rth
1 1
7 7
1 1
1 2
1 0
)
)) )
) ) )
)
)
)
)
:
:
:: : :
:
:
: :::
::
:
:
: :
: :
) :
E a r t h q u a k e s A p r - N o v 2 0 0 1 F e b - M a r 2 0 0 1 1
9 8 4 - J a n 2 0 0 1
1 9 9 4 1 9 0 0
S e i s m i c i t y o ( 1 3 4 1 - 2 0 0 1 )
1 9 8 82 0 0 1 2 0 0 0
(1341-April 2002)
E a s t
E a r t h q u a k e s
1 9 5 0 - 1 9 7 4 1 9 7 5 - 1 9 9 9
B a c k g r o u n d 1 9 0 0 - 1 9 4 9
2 0 0 0 - A p r i l 2 0 0 2 1 9 0 0 - A p r i l 2 0 0 2
( 1 9 0 0 - 2 0 0 2 ) S e i s m i c i t y o
C o a s t a l l i n e
L i n e a m e n t D y k e s W a t e r b o d y R i v e r s
1 0 1 0
1 1
D i s t r i c t b o u n d a r y S t a t e b o u n d a r y
I N D I A
K e r a l a
1 21 2
*K a r n a t a k a
T a m i l N a d
LAKSH AD
EEP SEA
K i l o m e t e r s
0 4 0 8 0
*
*
*
K a n n u r
K a l p e t t a
*K o z h i k o d e
P a l a k k a d
*
*
*
M a l a p p u r a m
T r i c h u r
K o c h i*
* *
*
*
*
*
P a i n a v u
P a t h a n a m t h i
1 9 0 01 9 9 4
2 0 0 1
a
*K a n n u r
* K o z h i k o d e
*
*
*
*
A l l e p p e y
*
M a l a p p u r a m
* K o l l a m
* K o t t a y a m
*
*
*
P a t h a n a m t h
No rth
1 2
1 1
7 6
T a m i l N a d
7 5 7 6 7 7
1 1
1 2
R i v e r s
D i s t r i c t b o u n d a r y
I N D I A
K e r a l a
S t a t e b o u n d a r y
C o a s t a l l i n e
L i n e a m e n t D y k e s
LAKSH AD
EEP SEA
R e c e n t T e r t i a r y L a t e r i t e P r e c a m b r i a n C
r y s t a l l i n e & A s s o c i a t e d I n t r u s i v e s W
a t e r b o d y
7 5
K i l o m e t e r s
0 4 0 8 0
7 7
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2 0 0 1 - A p r 2 0 0 2
E a r t h q u a k e s
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2 0 0 0
( J a n . - 2 0 0 0 - A p S e i s m i c i t y o
2 0 0 1 2 0 0 0
a
Comparison
2.7
2.8
2.9
3.0
S ei
sm ic
E ne
rg y
R el
ea se
Number of earthquakes
(x 1
0 2
0 er
M 5
M 5
M 4.5
M 4.3
M 5
M 4.8
M 6
Temporal patterns of microearthquake activity (EQ) and well
collapse (WC) incidents in Kerala that have occurred from January
to November 2001. Note that the spurt in seismic activity had taken
place in two active phases starting from the beginning of February
and from the last week of August 2001 and are separated by a long
quiescence period of 6 months whereas spurt in well collapse
activity had initiated from the beginning of June when there was no
seismic activity.
N um
Monthly Number Cumulative
B C
Kerala Region
A: Normal Seismicity B: Precursory Swarm C: Gap Events/ period D:
Mainshock and afterhsocks
0
20
40
60
80
Daily Cumulative
N um
A: Normal Seismicity B: Precursory Swarm C: Gap Events/
period
C o a s t a l l i n e
L i n e a m e n t D y k e s W a t e r b o d y R i v e r s
1 1
N or
E a s t
D i s t r i c t b o u n d a r y S t a t e b o u n d a r y
I N D I A
K e r a l a
1 21 2
*K a r n a t a k a
T a m i l N a
LA K
SH A
D E
E P
SE A
K i l o m e t e r s
0 4 0 8 0
*
*
*
K a n n u r
K a l p e t t a
*K o z h i k o d e
P a l a k k a d
*
*
*
M a l a p p u r a m
T r i c h u r
K o c h i*
* *
*
*
*
*
P a i n a v u
)
))
)
) ) )
)
)
)
)
:
:
:: : :
:
:
:
::: ::
:
:
: :
: :
1 9 0 0 - 1 9 8 3 E A R T H Q U A K E S
F e b - M a r . 2 0 0 1 A p r - N o v . 2 0 0 1
1 9 8 4 - J a n . 2 0 0 1
I n c i d e n t s ( F e b - N o v . 2 0 0 1 )
I N C I D E N T S ( J a n - N o v . 2 0 0 1 )
S e p t . - N o v . J u n . - A u g . M a r . - M a y J a n . - F e
b . B a c k g r o u n d
1 9 9 4 1 9 0 0
2 0 0 0 / 2 0 0 1 1 9 8 8
P o t e n t i a l A r e f u t u r e s e i s m i c
A Model showing an elliptical area (dotted) trending east-west in
the Central Kerala region is delineated as potential zone for the
probable location of future significant earthquake using the most
direct manifestations of various unusual geological incidents
during 2001( land deformation, ground water anomalies in open
wells, past and recent seismic events and fault zones, and
available historical seismicity data since 1900),
Conclusions • A total of 612 unusual geological incidents at 499
different locations have occurred in Kerala state from February to
November 2001.
•A database is created incorporating all the important occurrence
features related to these incidents and spatio-temporal patterns
are studied. No such incidents prior to February 2001 and beyond
November 2001 are observed in the state.
.Under normal geological conditions, such widespread unusual
geological incidents can not occur in a region. No surficial
causative factor such as rainfall activity during 2001 was found to
play role in triggering these incidents.
Conclusions (Contd………..) • Peculiar character of temporal patterns
(short duration) and widespread occurrence of these incidents
without showing spatio-temporal inter- relationships indicate that
the incidents are caused by a single causative factor of internal
geodynamic processes in Kerala region. •Enhanced seismic activity
during February- March and August-October 2001 also indicate
towards the vital role of internal geodynamic processes in
triggering these incidents. •In short, except three incidents
(coloured rain, well water colour change and untimely leaf fall),
the remaining incidents can be considered as macroscopic precursors
(under the category of land deformation) to an impending large
earthquake in Kerala.
Conclusions (Contd………..) •Similar to some of these incidents had
occurred in China and its surrounding areas prior to large
earthquakes and have been regarded as earthquake precursors.
•The present chain of events, if viewed in terms of the dilatancy
diffusion model, can be manifestations of preparatory stage of an
earthquake.
•Based on Sudden spurt in various unusual geological incidents and
seismic activity during Feb. to Nov. 2001 and past significant
earthquakes, a potential area trending east- west and enclosed by
latitude 10.7-10,90 N and longitude 76.0-76.80 E have been
delineated for the impending large earthquake.
Slide Number 1