ORIGINAL ARTICLE

Estimation of Qp and Qs of Kinnaur Himalaya

Naresh Kumar & Shonkholen Mate &

Sagarika Mukhopadhyay

Received: 19 April 2013 /Accepted: 9 September 2013 /Published online: 2 October 2013# Springer Science+Business Media Dordrecht 2013

Abstract The attenuation characteristics of the Kinnaurarea of the North West Himalayas were studied usinglocal earthquakes that occurred during 2008–2009.Most of the analyzed events are from the vicinity ofthe Panjal Thrust (PT) and South Tibetan DetachmentThrust, which are well-defined tectonic discontinuitiesin the Himalayas. The frequency-dependent attenuationof P and S waves was estimated using the extended codanormalization method. Data from 64 local earthquakesrecorded at 10 broadband stations were used. The codanormalization of the spectral amplitudes of P and Swaves was done at central frequencies of 1.5, 3, 6, 9,and 12 Hz. Qp increases from about 58 at 1.5 Hz to706 at 12 Hz, and Qs increases from 105 at 1.5 Hz to1,207 at 12 Hz. The results show that the quality factorsfor both P and Swaves (Qp andQs) increase as a functionof frequency according to the relation Q=Qo f

n, where Qo

is the corresponding Q value at 1 Hz frequency and “n”is the frequency relation parameter. We obtainedQp=(47±2)f

(1.04±0.04) and Qs=(86±4)f(0.96±0.03) by

fitting power law dependency model for the estimatedvalues of the entire study region. The Q0 and n valuesshow that the region is seismically very active and thecrust is highly heterogeneous. There was no systematic

variation of values ofQp andQs at different frequenciesfrom one tectonic unit to another. As a consequence,average values of these parameters were obtained foreach frequency for the entire region, and these wereused for interpretation and for comparison with world-wide data. Qp values lie within the range of valuesobserved for some tectonically active regions of theworld, whereas Qs values were the lowest among thevalues compared for different parts of the world. Qs/Qp

values were >1 for the entire range of frequenciesstudied. All these factors indicate that the crust is highlyheterogeneous in the study region. The high Qs/Qp

values also indicate that the region is partially saturatedwith fluids.

Keywords Attenuation . Kinnaur Himalaya . Codanormalization .Qp

.Qs

1 Introduction

The energy of the seismic wave propagating throughthe earth decays due to geometrical spreading, intrinsicattenuation, and scattering attenuation. The seismicenergy is converted to heat by intrinsic attenuationdue to anelastic absorption and scattering attenuationredistributes the energy at random heterogeneitiespresent in the earth (Aki 1969, 1980; Aki and Chouet1975; Tsujiura 1966; Singh and Herrmann 1983;Frankel and Wennerberg 1987; Sato and Fehler 1998;Mukhopadhyay and Tyagi 2008; Mukhopadhyay et al.2010). Attenuation of seismic waves in the lithosphere

J Seismol (2014) 18:47–59DOI 10.1007/s10950-013-9399-7

N. KumarWadia Institute of Himalayan Geology,General Mahadeo Singh Road, Dehradoon 248001, India

S. Mate : S. Mukhopadhyay (*)Department of Earth Sciences,IIT Roorkee, Roorkee 247667, Indiae-mail: sagarfes@iitr.ernet.in

is an important property of the Earth. For studying theregional earth structure and seismotectonic activity of aregion, knowledge of this property is required(Hoshiba 1993; Del Pezzo et al. 1995; Bianco et al.2002). This knowledge is also useful for earthquakehazard assessment (Pulli 1984; Havskov et al. 1989;Anderson et al. 1996; Mukhopadhyay and Tyagi 2007)and studying source parameters (Abercrombie 1997).Attenuation characteristic of a region is represented bythe quality factor, Q, which measures the deviationfrom perfect elasticity. It is defined as (Knopoff andHudson 1964):

2π=Q ¼ −ΔE=E

where ΔE is the energy lost in one cycle of vibrationcaused by passing of seismic wave through some partof the Earth, and E is the total energy available in aharmonic wave. The quality factor can be estimatedusing decay rate of direct P (Qp), S (Qs), coda of localearthquake, or Lg wave amplitude (Aki 1969; Sato andFehler 1998; Yoshimoto et al. 1993; Mukhopadhyay andTyagi 2007, 2008; Mukhopadhyay and Sharma 2010a;Mukhopadhyay et al. 2006, 2008, 2010; Mohamed et al.2010; Rahimi et al. 2010; Singh et al. 2011).

Attenuation of seismic waves is attributed to intrin-sic and scattering mechanism. Intrinsic attenuation iscaused by small-scale crystal dislocations, frictionalheating, and viscous drag between rock matrix andinterstitial fluids (Goric and Muller 1987; Akinci andEydogen 2000; Giampiccolo et al. 2006). Scatteringattenuation represents loss of energy of a direct wavecaused by reflection, refraction, and conversion due toexistence of heterogeneities (Sato and Fehler 1998).The earth has heterogeneities at different scales,starting from microscopic to continental scale. Theseare mainly due to the tectonic processes such asfaulting, folding, large-scale crustal movements asso-ciated with plate tectonics. Variation in deposition ofsedimentary rocks and magma/lava flow also lead toheterogeneity. These factors lead to wide variations inrock properties that cause velocity perturbations in theEarth (Sato and Fehler 1998).

The quality factor (inversely proportional to attenu-ation) of P (Qp) and S (Qs) waves give us informationof the characteristics of the Earth medium throughwhich these waves propagate. In the present work,extended coda normalization method is used for esti-mation of Qp and Qs of Kinnaur Himalayas (Fig. 1).

Data from 64 local earthquakes recorded at 10 broad-band stations (Fig. 1) are used for this purpose. Theresults are compared with available results of differentparts of the world and interpreted.

2 Geology and tectonic setting

The convergence of the northward dipping Indian plateunder the Eurasian plate formed the Himalayas withIndian Tsangpo-suture zone (ITZ) representing the lineof collision between India and Eurasia. This ongoingconvergence movement has resulted in a high level oftectonic activity, which has developed ITZ, South TibetanDetachment (STD), Main Central Thrust (MCT), MainBoundary Thrust (MBT), and Himalayan Frontal Thrust(HFT) as prominent thrusting (faulting) boundaries in theHimalayas. All these major thrust faults are suggested toroot into a low-angle detachment, the Main HimalayanThrust (Schelling and Arita 1991). The Himalayan orogenhas four major tectonostratigraphic units: the TethyanHimalaya, the Higher Himalayan Crystalline, the LesserHimalaya, and the Siwalik Himalaya. These are boundedby north-dipping crustal scale fault systems describedabove as STD, MCT, MBT, and HFT (Le Fort 1975;

76 77 78 79

30

31

32

33

STD

PTMBF

HFT CT

JT

MBT

HFT

STD

LOSR

KAZAHURLING

KHAB

MUDHPULGA

BANJAR

SAHARAN

RACKCHHAM

SPILLO

Fig. 1 General seismotectonic map of Kinnaur Himalayas.MBF Main Boundary Fault, HFT Himalayan Frontal Thrust,JT Jutogh thrust, STD Southern Tibetan Detachment, PT PanjalThrust. Earthquake epicenters are plotted as circles; trianglesrepresent recording stations

48 J Seismol (2014) 18:47–59

Seeber and Armbruster 1981; Burg and Chen 1984;Burchfiel et al. 1992). Siwalik Himalaya is separated fromthe Himalayan Foreland Basin by HFT. In addition, thereare many localized thrusts, faults, folds, and minor linea-ments present in different parts of the Himalayas (Najmanet al. 2004).

In the present study region, along with MBF andHFT, the Jutogh Thrust (JT) and Panjal Thrust (someconsider it to be the MCT), are well-known tectonicfeatures. The study region show prominent discontinu-ities as shown in Fig. 1. Prior to the Himalayan orog-eny, the MBT was formed as a normal fault during anextensional phase in NW Himalayas (Dubey et al.2001). From a variety of geological features, thereactivation of MBF and HFT during the Quarternaryhas been inferred, which is still active. As it is revealedby subsequent evolution of the foredeep marked byintra-basin boundary faults during Quarternary period,the Himalayan foothill region has been experiencingneotectonic activity. Ni and Barazangi (1984) observedfrom the fault plane solutions that the thrust faultingwith strike–slip motion occur along gently northwarddipping planes in NW Himalayas. Thiede et al. (2006)

opined that the Indian plate is underthrusting theEurasian plate at a shallow angle in the NS to NNE-SSW direction, indicated by thrust faulting focal mech-anism, and there is a surface of decollement at whichmost of the seismicity is concentrated.

3 Data set and analysis

In 2008, a dense local seismic network of 10 stations wasinstalled in the Kinnaur region of NWHimalaya (Fig. 1),which provided the required data set. The data are of thelocal earthquakes that occurred during the period 2008–2009. The stations have three component broadbandinstruments with frequency band 1/240 Hz to 20 Hz,sampling rate of 100 samples/s and natural period of240 s. The data are recorded by Taurus digitizationhaving dynamic range of 138 dB and synchronized withGPS for highly accurate timing. This region has experi-enced a strong (M7.0) earthquake in 1975 and has highseismic activity north of the well-known high Himalayanseismic belt. This is the only region in the Himalaya thatis having so high seismicity north of STD.

Fig. 2 An example ofseismograms recorded atvarious stations for an earth-quake that occurred on 09/01/2009 (magnitude 3.1).Epicentral distance to vari-ous stations and stationcodes are mentioned alongthe traces. Vertical arrowsindicate P and S arrival times

J Seismol (2014) 18:47–59 49

P and S waveform data of 64 earthquakes (Fig. 1)recorded by these stations have been analyzed. Figure 2

shows some examples of seismograms used in thisanalysis. These earthquakes are located using recently

BNJR

0123456789

10

0 50 100 150 200Distance (Km)

f=1.5HzQp=65

0123456789

10

0 50 100 150 200Distance (Km)

f=1.5HzQs=113

0123456789

10

0 50 100 150 200Distance (Km)

f=3HzQp=121

0123456789

10

0 50 100 150 200Distance (Km)

f=3HzQs=209

0123456789

10

0 50 100 150 200Distance (Km)

f=6HzQp=392

0123456789

10

0 50 100 150 200Distance (Km)

f=6HzQs=679

0123456789

10

0 50 100 150 200Distance (Km)

f=9HzQp=512

0123456789

10

0 100 200Distance (Km)

f=9HZQs=885

0123456789

10

0 50 100 150 200Distance (Km)

f=12 HzQp=706

0123456789

10

0 50 100 150 200Distance (Km)

f=12 HzQs=1207

a HURL

0123456789

10

0 50 100 150 200Distance (Km)

f=1.5HzQp=72

0123456789

10

0 50 100 150 200Distance (Km)

f=1.5HzQs=105

0123456789

10

0 50 100 150 200Distance (Km)

f=3HzQp=196

0123456789

10

0 50 100 150 200Distance (Km)

f=3HzQs=247

0123456789

10

0 50 100 150 200Distance (Km)

f=6HzQp=286

0123456789

10

0 50 100 150 200Distance (Km)

f=6HzQs=402

0123456789

10

0 50 100 150 200Distance (Km)

f=9HzQp=362

0123456789

10

0 50 100 150 200Distance (Km)

f=9HzQs=543

0123456789

10

0 50 100 150 200Distance (Km)

f=12HzQp=571

0

2

4

6

8

10

12

0 50 100 150 200Distance(Km)

f=12HzQp=787

b

Fig. 3 Normalized amplitudes versus distance for P and S waves for the stations (a) Banjar, (b) Hurling, and (c) Saharan. “f” representsfrequency in Hertz. The least square line fit and estimated Qp and Qs values are also shown in the plots

50 J Seismol (2014) 18:47–59

developed one-dimensional velocity model (Kumaret al. 2009) for the adjoining region of Kangra-Chamba. The events were located using SEISAN soft-ware (Havskov and Ottemoeler 2005). The coda mag-nitude for this data set varies between 1.9 and 3.2, anddepth of focus varies between 5 and 24 km. The

epicentral distance range varies between 8 and100 km. The estimatedQp andQs values were comparedwith those observed in different parts of the world.

4 Methodology and analysis

Aki (1980) proposed a single station method of esti-mating attenuation in which direct S-wave amplitude isnormalized by coda amplitude measured at a fixed timeand at the same frequency. It is called coda normaliza-tion method. The basis for the method is the fact thatcoda envelopes show a decay rate that is independentof source–receiver distance (Aki and Chouet 1975;Rautian and Khalturin 1978; Fehler and Sato 2003).The effect of source, site, and instrument can be elim-inated, and data from many earthquakes can be com-bined to obtain a stable estimate of attenuation.Yoshimoto et al. (1993) extended the method to deter-mine Q for P and S waves at the same time by com-paring P, S, and coda amplitudes of events at differenthypocentral distances. This method has been used forestimating Qp and Qs values for Kinnaur Himalaya.

The basic idea of this method stands on the propor-tionality among the coda amplitude (Ac), the sourcespectral amplitudes of S waves (As) and P waves (Ap) ata given frequency f as:

Ac f ; tcð ÞαAs fð ÞαAp fð Þ ð1Þ

where f is the frequency in Hertz and tc is the referencelapse time measured from the source origin time. Thelapse time is chosen to be greater than two times the S-travel time. The first proportionality implies thatAc( f,tc) is independent of the hypocentral distance(Aki 1980). The second proportionality is deducedfrom the assumption that the ratio of P to S wavesource spectra is constant for a small range of magni-tudes. In this method, the source effects, commoninstrument effect, and site responses are removed bynormalizing the direct wave spectra to those of coda.The S wave as well as P wave energy recorded at astation for a given earthquake depends on magnitude,source mechanism as well as path effects. By carryingout coda normalization, the effect of magnitude isremoved. By combining data of many earthquakes,the effect of source mechanism is averaged out to a

SRHN

0123456789

10

0 50 100 150 200Distance (Km)

f=1.5HzQp=70

0123456789

10

0 50 100 150 200Distance (Km)

f=1.5HzQs=120

0123456789

10

0 50 100 150 200Distance (Km)

f=3HzQp=157

0123456789

10

0 50 100 150 200Distance (Km)

f=3HzQs=247

0123456789

10

0 50 100 150 200Distance (Km)

f=6HzQp=242

0123456789

10

0 50 100 150 200Distance (Km)

f=6HzQs=388

0123456789

10

0 50 100 150 200Distance (Km)

f=9HzQp=428

0123456789

10

0 50 100 150 200Distance (Km)

f=9HzQs=626

0123456789

10

0 50 100 150 200Distance (Km)

f=12HzQp=532

0123456789

10

0 50 100 150 200Distance (Km)

f=12Qs=765

c

Fig. 3 (continued)

J Seismol (2014) 18:47–59 51

large extent. Even if we do not take the average of N–Sand E–W component, it will still average out the neteffect of source mechanism. The fact that we have

taken earthquake data with very small magnitude alsohelps, as the effect of source mechanism will not be assevere as that for larger magnitude earthquakes.

0

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Qp

f(Hz)

BNJR

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Qs

f(Hz)

BNJR

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Qp

f(Hz)

HURL

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Qs

f(Hz)

HURL

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f(Hz)

KAZA

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f(Hz)

KAZA

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Qp

f(Hz)

KHAB

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Qs

f(Hz)

KHAB

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Qp

f(Hz)

LOSR

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f(Hz)

LOSR

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Qp

f(Hz)

MUDH

0

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0 5 10 15

Qs

f(Hz)

MUDH

0

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0 5 10 15

Qp

f(Hz)

PULG

0

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0 5 10 15

Qs

f(Hz)

PULG

0

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0 5 10 15

Qp

f(Hz)

RKCH

0

200

400

600

800

1000

1200

1400

0 5 10 15

Qs

f(Hz)

RKCH

Fig. 4 Plot ofQp versus frequency f(Hz) andQs versus f(Hz) for different stations. Station codes are shown on top of each figure. Verticallines represent error bars

52 J Seismol (2014) 18:47–59

On the basis of the proportionality mentionedabove, using seismograms from earthquakes of differ-ent epicentral distances, Qp andQs can be calculated asfollows:

lnAp f ; rð ÞrAc f ; rð Þ

� �¼ −

πfQp fð ÞV p

r þ c1 fð Þ ð2Þ

lnAs f ; rð ÞrAc f ; rð Þ

� �¼ −

πfQs fð ÞV s

r þ c2 fð Þ ð3Þ

where Ap( f,r) and As( f,r) are the amplitude spectra ofthe direct P and S waves at the hypocentral distance r(km), respectively. Vp and Vs are the P and S wavevelocities, respectively, and c1( f ) and c2( f ) are con-stants for a given frequency. We take Vp=6 km/s andVs=3.47 km/s for this analysis. The geometricalspreading factor is taken to be r−1 when r ≤ hm and1/√(rhm) for r>hm, where hm is equal to twice thethickness of the crust (Herrmann and Kijko 1983;Ma’hood et al. 2009; Singh et al. 2012). In the studyarea, hm varies between 100 and 120 km (Rai et al.

2006). As maximum hypocentral distance is about100 km, we can take geometrical factor to be r−1

without much error in estimated Qp and Qs values.de Lorenzo et al. (2013) have shown that even ifgeometrical spreading factor varies from 1 by a verysmall amount, it can significantly affect the estimatedQp and Qs values. For Umbria-Marche (Italy), theyobserved that by simultaneously inverting for Qp, Qs

as well as corresponding geometrical spreading fac-tors, the estimated Qp and Qs values were systemat-ically smaller compared to those estimated assuminglinear geometrical factor. We have assumed a lineardependence of amplitude of waves on geometricalfactor and find that the data show very good fit(Fig. 3). We plan to carry out simultaneous inversionfor Qp, Qs, and geometrical factors in future to seewhether it significantly affects the estimated Qp andQs values or not.

By plotting the values obtained for the data shownon the left-hand side of Eqs. (2) and (3) against thehypocentral distance for different earthquakes andthen by fitting a straight line by least-square method,we can estimate Qp and Qs from the slopes of theselines. The P wave analysis is based on the vertical (Z)component seismograms and the S wave analysis isbased on N–S component seismograms as the maxi-mum amplitudes of S waves are nearly equal in boththe N–S and E–W components. On the filteredseismograms, we measured the spectral amplitudesof the direct P and S waves in a 2.56 s time windowstarting from the onset of P and S waves, respective-ly. After a lot of trial, this value was chosen for theavailable data set to ensure that, in the P wave win-dow, S wave contamination does not occur and all thetime windows have same duration. Coda-spectral am-plitude Ac( f,tc) is calculated for a 2.56-s time windowat tc=T0+45 s where the lapse time tc should be twicethat of the S wave travel time or greater (Aki andChouet 1975; Rautian and Khalturin 1978) and T0 isthe origin time of an earthquake.

Filtered seismograms were analyzed to evaluatefrequency dependent Q. Each seismogram was dig-itally bandpass filtered using a phaseless four-poleButterworth filter with five passbands of 1–2, 2–5, 4–8,6–12, and 9–15 Hz with central frequencies of 1.5, 3, 6,9, and 12 Hz. The bandwidths were chosen to maintainrelative constant bandwidth. Half values of the peak-to-peak amplitudes represent Ap( f, r) and As( f, r), respec-tively. Coda-spectral amplitude Ac( f, tc) was measured

0

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0 5 10 15

Qp

f(Hz)

SPLO

0

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0 5 10 15

Qs

f(Hz)

SPLO

0

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600

800

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1200

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0 5 10 15

Qp

f(Hz)

SRHN

0

200

400

600

800

1000

1200

1400

0 5 10 15

Qs

f(Hz)

SRHN

Fig. 4 (continued)

J Seismol (2014) 18:47–59 53

from the root mean squares (rms) coda amplitude of theN–S component for each frequency band.

5 Results and discussions

The natural logarithm of normalized P (Eq. 2) and S(Eq. 3) amplitudes are plotted with respect to the epi-central distance for data of all the earthquakes recordedat a given station for a given frequency. Figure 3 showsthese plots for both P and S wave data set for threestations (BNJR, HURL, and SRHN) out of the tenstations of the network and for all the central frequen-cies used in this analysis. We have applied least-squares fitting to minimize the sum of the absolutedeviations of the differences between data and dataestimated by the model. The slopes of the best-fitted

lines are used to estimate Qp and Qs using the follow-ing relations [from Eqs. (2) and (3)]

Slope ¼ −πf

Qp V pforPwave ð4Þ

Slope ¼ −πf

Qs V sfor S wave ð5Þ

For calculation of above parameters, amplitude datafor a given station was considered only whensignal/noise ratio for coda was >2. Figure 3 shows thatscatter in data points is small, i.e., the data quality isgood. This also means that the small scatter in data isan indication that data are well fitted by the model withan assumption of geometrical spreading factor of r−1.However, the estimated Qp and Qs values may showsome change if nonlinear geometrical spreading factoris considered as suggested by de Lorenzo et al. (2013).The estimated Qp and Qs values for different stations atdifferent frequencies are shown in Fig. 4. The error inestimated Qp and Qs values are small (Table 1).

The values of Qp and Qs for the Kinnaur regionincrease with increasing frequency. This indicates thefrequency-dependent nature of the Q (Fig. 4). It in-creases from about 58 at 1.5 Hz to 706 at 12 Hz for Qp

and 105 at 1.5 Hz to 1,207 at 12 Hz forQs, respectively.Figure 5a and b shows plots of values of Qp and Qs,respectively, for 1.5 Hz at different station locations. Itis observed that no systematic variation with tectonic/

Table 1 Average values of Qp and Qs along with their standarddeviations at different central frequencies

f (Hz) Qp ±ΔQp Qs ±ΔQs Qs/Qp

1.5 69.2 3 128.5 5 1.84

3 152.9 9 237.7 13 1.55

6 300 19 486.5 28 1.62

9 453.8 16 697.5 40 1.54

12 614 19 937.4 50 1.53

QP=(47±2)f(1.04±0.04) QS=(86±4)f

(0.96±0.03)

Values of Qs/Qp and the frequency relations are also shown

76 77 78 79

30

31

32

33

STD

PT

MBF

HFT CT

JT

MBT

HFT

STD

LOSR

KAZAHURLING

KHAB

MUDHPULGA

BANJAR

SAHARAN

RACKCHHAM

SPILLO65

72

79

59

66

6187

81

5870

76 77 78 79

30

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33

STD

PTMBF

HFT CT

JT

MBT

HFT

STD

LOSR

KAZAHURLING

KHAB

MUDHPULGA

BANJAR

SAHARAN

RACKCHHAM

SPILLO113

105

151

136

124

124151

148

113120

a b

Fig. 5 Values of a Qp and b Qs at 1.5 Hz mentioned beside the station locations

54 J Seismol (2014) 18:47–59

geologic features occur for these parameters. Similarresults are also obtained for Qp and Qs at other fre-quencies. Besides, the variation in these parameters at agiven frequency is not very large from one station toanother. Hence, average values of these parameters ateach frequency are obtained by taking average overrespective values at all the stations (Table 1 and Fig. 6).

Using the relationQ=Q0 fn, whereQ0 isQ at 1 Hz and

“n” is the frequency relation parameter, the values of Q0

and n are estimated for each station (Table 2). It isobserved that the value of Q0 is very low for both P andS waves and the value of “n” is around 1 for both thecases. This indicates that the study region is seismicallyactive and highly heterogeneous. Taking the average Qp

andQs values for the entire Kinnaur region the power law

forms of Qp=(47±2)f(1.04±0.04) and Qs=(86±4)f

(0.96±0.03)

are obtained. The low Qp and Qs correspond to those ofthe seismically active areas in the world (Yoshimoto et al.1993).

We find that P waves attenuate more strongly than Swaves (Qs/Qp>1) for the entire frequency ranges(Table 1). For 1 Hz, the value is 1.83. For many otherregions Qs/Qp>1 is reported where in the upper crusthigh degree of lateral heterogeneity is present (Biancoet al. 1999; Sato and Fehler 1998). For the adjacentregion of Garwhal-Kumaon Himalayas, Singh et al.(2012) obtained Qs/Qp values greater than one andMukhopadhyay and Sharma (2010b) reported highdegree of lateral heterogeneity on the basis of tomo-graphic analysis. No tomographic study has been done

0

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0 5 10 15

Qp

f(Hz)

0

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400

600

800

1000

0 5 10 15

Qs

f(Hz)

Fig. 6 Plots of average Qp and Qs versus frequency for Kinnaur Himalaya. Vertical lines show error bars

Table 2 Values of Q0 for P and S and respective n values for different stations

Serial no. station Q0 (for P) ±ΔQ0 n ±n Q0 (for S) ±ΔQ0 n ±n

1 BNJR 38 1 1.19 0.04 67 11 1.18 0.02

2 HURL 56 4 0.9 0.02 78 8 0.91 0.01

3 KAZA 57 3 0.89 0.03 97 12 0.82 0.03

4 KHAB 44 7 1.05 0.04 103 23 0.84 0.03

5 LOSR 37 15 1.11 0.05 74 4 0.99 0.02

6 MUDH 44 6 1.04 0.03 88 13 0.95 0.02

7 PULG 57 3 1.01 0.02 101 10 0.94 0.01

8 RKCH 51 19 1.02 0.04 93 25 1.01 0.04

9 SPLO 36 6 1.19 0.02 68 10 1.05 0.03

10 SRHN 49 2 0.96 0.03 88 16 0.88 0.05

J Seismol (2014) 18:47–59 55

for Kinnaur Himalaya so far, as a consequence suchcomparison is not possible. Hough and Anderson(1988) opined that in a medium where scatterers arepresent Qs/Qp will be >1. Padhy (2009) suggested thatscattering from heterogeneities in the crust leads tohigh value of Qs/Qp. For Kinnaur Himalaya, this maybe the cause of high Qs/Qp value. As this area fallswithin tectonically highly active Himalayan ranges, itis expected that this region is highly heterogeneous.High value of Qs/Qp is also expected in regions par-tially saturated with fluids (de Lorenzo et al. 2013;Hauksson and Shearer 2006; Toksoz et al. 1979).

6 Comparison with global observations

Figure 7a and b shows the comparison between Qp andQs obtained in this study and those inferred in otherstudies. Seismically active regions show low Qp andQs values (Sharma et al. 2007; Yoshimoto et al. 1993;Singh et al. 2012), whereas stable regions show highvalues for these parameters (Kim et al. 2004; Kvammeand Havskov 1989). The values of Qp for KinnaurHimalaya lie within the range of values obtained forother seismically active areas and that ofQs for this areais the lowest among all the seismically active areas.

Figure 8 shows plot of Qs/Qp at 1 Hz for KinnaurHimalaya and those inferred from other studies. Thelarge scatter observed in this plot may reflect regionalvariation in attenuation characteristics (Lees andLindley 1994). According to theoretical considerations(Lay and Wallace 1995), Qp/Qs for the world should be9/4 or 2.25. However, worldwide reported values deviatesignificantly from this theoretical value. Yoshimoto et al.(1993) opined that the theoretical value ofQs/Qp accountsfor attenuation of seismic waves of frequency <0.1 Hz.They also found that Qs/Qp values are similar to Vp/Vsvalues for Kanto, Japan. For Garm region, Rautian andKhalturin (1978) also obtained similar results. For allstudies around the world, it is observed thatQs/Qp>1 forfrequencies>1 Hz (Yoshimoto et al. 1998; Castro andMunguia 1993; Chung and Sato 2001; Sharma et al.2007; Kinoshita 2008; Padhy 2009; Abdel-Fattah 2009;Singh et al. 2012). For the Kinnaur region, this valuevaries between 1.5 and 1.9 with varying frequency, i.e.,it is always >1. Therefore, the value of this parameter isin good agreement with the values obtained for otherregions of the world. Hough and Anderson (1988)opined that Qs/Qp≥1 for most types of scattering,

whereas Padhy (2009) states that high value of thisparameter is expected when scattering from shallowheterogeneities in the crust is involved. The value ofQs/Qp is around 4/9 for a medium where attenuation iscompletely due to intrinsic attenuation and no scatteringattenuation takes place (Lay and Wallace 1995). Hence,

0 5 10 15 20 25

0

400

800

1200

1600Kanto, JapanEast-IranBhuj, IndiaCairo, EgyptNE,IndiaKoyna, IndiaKumaon, IndiaThis studyQ

p

f(Hz)

a

0 5 10 15 20 25

0

1000

2000

3000

Kanto, JapanEast Central,IranBhuj, IndiaCairo, EgyptNE, IndiaKoyna, IndiaKumaun, IndiaThis study

Qs

f(Hz)

b

Fig. 7 Plot of a Qp versus frequency and b Qs versus frequencyfor different parts of the world superposed on that of presentstudy. Data for other region were taken from the following papers:Kanto, Japan (Yoshimoto et al. 1993); East-Central Iran (Ma’hoodet al. 2009); Bhuj, India (Padhy 2009); Cairo, Egypt (Abdel-Fattah2009); Northeast India (Padhy 2009); Koyna, India (Sharma et al.2007); Kumaon Himalaya (Singh et al. 2012)

56 J Seismol (2014) 18:47–59

a value greater than one indicates presence of scattering.The higher the value of Qs/Qp, the higher is the scatter-ing, hence the more the heterogeneity.

As P wave attenuation is stronger than S waveattenuation, this indicates that the crust in this area ishighly heterogeneous. It is observed that Qs is verylow; it is lowest among all the areas for which thisvalue was compared. This would mean that seismicwaves, especially the more damaging S waves, wouldattenuate fastest in this region compared to all the areasfor which this value was compared.

7 Conclusion

This work is an attempt to understand the attenuationcharacteristics in the Kinnaur Himalaya region. Thestudy indicates that the estimated Qp and Qs in theKinnaur Himalaya are strongly frequency dependent.The low values of Qp and Qs correspond to seismicallyactive areas. This is expected, as the study area is partof the Himalayan ranges where there is ongoing con-vergence between India and Eurasia. High degree of

heterogeneity in the crust of Kinnaur Himalaya is in-dicated by stronger P wave attenuation than S waveattenuation. Qs/Qp≥1 for the entire frequency rangestudied for this area. It also indicates that the regionis partially saturated with fluids. Our results are com-parable to other tectonically active regions character-ized by high degree of heterogeneity reported globally.S wave attenuation is strongest in this area compared toall the other areas whose data were used for compara-tive studies.

Acknowledgment The authors thank the Director, Wadia In-stitute of Himalayan Geology, for his kind permission to publishthis work.

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