seismic surveillance of himalaya-an indian...
TRANSCRIPT
Seismic Surveillance of Himalaya-An Indian Initiative
SHYAM S. RAINational Geophysical Research InstituteHyderabad, INDIA
The Great Himalayan Earthquakes
Geological Sections
Eastern Nepal
WesternNepal &Kumaon
Nepal Seismic Network
Seismicity pattern
Density Distribution of Epicenters
HFT
MBT
MTMCT
STD
77.5 78 78.5 79 79.5 80 80.5 8129
29.5
30
30.5
31
31.5
MRG
BNK
GTH
SRP
PKHHLG LTA
JLM
GHT
OKM
TMN
KLSNTI
Harsil
Uttarkashi
NewTehri
NarendraNagar
Mana
NainiTal
Bageshwar
Pithoragarh
MCT
MTMunsiyari
MCT
RT
Indian Seismic Network
76.5 77 77.5 78 78.5 79 79.5 80 80.5 8128
28.5
29
29.5
30
30.5
31
31.5
NDINPL
GRG
NDA
MRT
RKEKTD
DKL
MRGPPL
BNKSYT
GTHKSL
SRPNAL
PKHLNSHLGALI
LTA
TMNJLM
KSPNTI
GHT
OKM
HFTMBT
MT
MCT
STD
MCT
MT
RT
Indian Seismic Network(Apr 2005 – Dec 2006)
Geometry of MHT and MOHO
Gw1.6
Gw1.0
baz 30-40, del 60-65,
MBT MCT GHCLesser Himalaya
MHT
MOHO
(* Distances computed with reference to Kotdwar station )
MBT MCT
KTD DKLMRG
PPL BNKSYT GTH KSL SRP NAL
PKH HLGALI
LTA
JLM
0 20 40 60 80 100 120 140 1600
1000
2000
3000
Alt
(m)
0 20 40 60 80 100 120 140 160Dist (km)
-60
-40
-20
0
Dep
th(k
m)
~ 200
~ 50
?
?
GHC
Geometry of MHT and MOHO
Velocity Models
MRG
BNK
KSL
Velocity Models
NAL
HLG
LTA
Velocity Models
LESSER HIMALAYA HIGHER HIMALAYA
78 78.5 79 79.5 80 80.5 8129
29.5
30
30.5
31
HFT
MBT
MT
MCT
STD
Seismic SstationsEarthquakes
Seismicity in Uttaranchal Himalaya(July 2005 – Feb 2006)
020
4060
80
Dep
th(k
m)
40 60 80 100 120 140 160 180 200 220 240 260 280
Distance (km)
MOHO
KTD DKL MRG PPL BNK SYT GTH KSL SRP NAL PKH LTA JLM
HFT MBT MT MCT STD
Seismic Depth Section
MHT
Ground Acceleration Modelling
Ground Acceleration
Earthquake source
Fault Property= *
Wave propagation*
( ) ( ) ( )[ ]risiI
N
iim tttutS
RRCtU −−⎟⎟⎠
⎞⎜⎜⎝
⎛=∑
=
*1
Here u¨(t) is the recorded acceleration (EGF) corresponding to subfault i.
Ci is the ratio of the stress drop in the i-th fault to that of the small aftershock event.
Ri is the distance of the i-th fault to the surface station and R is the hypocentral distance between the station and the source of the aftershock.
The shear-wave travel time tsi from i-th fault to the station can be computed from the velocity model
Empirical Green's Function Approach
0 50 100-5
0
5x 10-4
time (s)
acc
(m/s
/s)
ali-e
0 50 100-5
0
5x 10-4
time (s)
acc
(m/s
/s)
ali-n
0 50 100-2
0
2x 10-4
time (s)
acc
(m/s
/s)
ali-z
0 50 100-1
0
1x 10-3
time (s)
acc
(m/s
/s)
ght-e
0 50 100-1
0
1x 10-3
time (s)
acc
(m/s
/s)
ght-n
0 50 100-5
0
5x 10-4
time (s)
acc
(m/s
/s)
ght-z
0 50 100-2
0
2x 10-3
time (s)
acc
(m/s
/s)
nal-e
0 50 100-2
0
2x 10-3
time (s)
acc
(m/s
/s)
nal-n
0 50 100-1
0
1x 10-3
time (s)
acc
(m/s
/s)
nal-z
Recorded Ground AccelerationRecorded Ground Acceleration
ModelledModelled Ground Acceleration Ground Acceleration (for M=8)(for M=8)
