Estimation of Coda Waves Attenuation for NW Himalayan Region using Local Earthquakes
IR@C-MMACS: CSIR-Centre for Mathematical Modelling and Computer Simulation, Bangalore
View Archive Info| Field | Value | |
| Title |
Estimation of Coda Waves Attenuation for NW Himalayan Region using Local Earthquakes
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| Creator |
Parvez, Imtiyaz A
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| Subject |
Computational Seismology
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| Description |
The attenuation of seismic wave energy in NW Himalayas has been estimated using local
earthquakes. Most of the analyzed events are from the vicinity of the Main Boundary Thrust (MBT)
and the Main Central Thrust (MCT), which are well-defined tectonic discontinuities in the Himalayas.
The time-domain coda-decay method of a single backscattering model is employed to calculate
frequency dependent values of Coda Q (Qc). A total of 36 local earthquakes of magnitude range 2.1 to
4.8 have been used for Qc estimation at central frequencies 1.5, 3.0, 6.0, 9.0, 12.0 and 18.0 Hz
through eight lapse time windows from 25 sec to 60 sec starting at double the time of the primary Swave
from the origin time. The estimated average frequency dependence quality factor gives the
relation, Qc=158f1.05, while the average Qc values vary from 210 at 1.5 Hz to 2861 at 18 Hz central
frequencies. The observed coda quality factor is strongly dependent on frequency, which indicates
that the region is seismic and tectonically active with high heterogeneities.
The variation of the quality factor Qc has been estimated at different lapse times to observe its
effect with depth. The estimated average frequency dependent relations of Qc vary from 85f1.16 to
216f0.91 at 25 sec to 60 sec lapse window length respectively. For 25 sec lapse time window, the
average Qc value of the region varies from 131±36 at 1.5 Hz to 2298±397 at 18 Hz, while for 60 sec
lapse time window its variation is from 285±95 at 1.5 Hz to 2868±336 at 18 Hz of central frequency.
The variation of Qc with frequency and lapse time shows that the upper crustal layers are seismically
more active compared to the lower lithosphere. The decreasing value of the frequency parameter with
increasing lapse time shows that the lithosphere acquires homogeneity with depth.
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| Publisher |
CSIR Centre for Mathematical Modelling and Computer Simulation
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| Date |
2004-09
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| Type |
Monograph
NonPeerReviewed |
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| Format |
application/pdf
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| Identifier |
http://cir.cmmacs.ernet.in/196/1/rrcm0404.pdf
Parvez, Imtiyaz A (2004) Estimation of Coda Waves Attenuation for NW Himalayan Region using Local Earthquakes. Technical Report. CSIR Centre for Mathematical Modelling and Computer Simulation, C-MMACS,Bangalore 560037,India. (Unpublished) |
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| Relation |
http://cir.cmmacs.ernet.in/196/
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