ORI GIN AL PA PER

Probabilistic seismic hazard map of NW Himalayaand its adjoining area, India

A. K. Mahajan Æ V. C. Thakur Æ Mukat Lal Sharma Æ Mukesh Chauhan

Received: 5 March 2008 / Accepted: 20 July 2009 / Published online: 27 August 2009� Springer Science+Business Media B.V. 2009

Abstract The seismically active Northwest (NW) Himalaya falls within Seismic Zone IV

and V of the hazard zonation map of India. The region has suffered several moderate

(*25), large-to-great earthquakes (*4) since Assam earthquake of 1897. In view of the

major advancement made in understanding the seismicity and seismotectonics of this

region during the last two decades, an updated probabilistic seismic hazard map of NW

Himalaya and its adjoining areas covering 28–34�N and 74–82�E is prepared. The

northwest Himalaya and its adjoining area is divided into nineteen different seismogenic

source zones; and two different region-specific attenuation relationships have been used for

seismic hazard assessment. The peak ground acceleration (PGA) estimated for 10%

probability of exceedance in 50 and 10 years at locations defined in the grid of

0.25 9 0.25�. The computed seismic hazard map reveals longitudinal variation in hazard

level along the NW Himalayan arc. The high hazard potential zones are centred around

Kashmir region (0.70 g/0.35 g), Kangra region (0.50 g/0.020 g), Kaurik-Spitti region

(0.45 g/0.20 g), Garhwal region (0.50 g/0.20 g) and Darchula region (0.50 g/0.20 g) with

intervening low hazard area of the order of 0.25 g/0.02 g for 10% probability in 50 and

10 years in each region respectively.

Keywords Seismic Hazard � Probabilistic � 1905 Kangra earthquake �Seismotectonics � Northwest Himalaya

1 Introduction

The Himalaya is a result of continent–continent collision between the Indian and the

Eurasian plates. Since collision during *55 Ma, India has been under-thrusting Asia

(Tibet) at a rate of 45–50 mm/year (Besse and Courtillot 1988; Dewey et al. 1989). The

A. K. Mahajan (&) � V. C. Thakur � M. ChauhanWadia Institute of Himalayan Geology, 33, GMS Road, Dehradun, Indiae-mail: mahajan@wihg.res.in

M. L. SharmaIndian Institute of Technology Roorkee, Rookree, India

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Nat Hazards (2010) 53:443–457DOI 10.1007/s11069-009-9439-3

GPS measurements indicates that India is moving northeast at a convergence rate of

55 mm/year, of which 18–22 mm/year is accommodated within the Himalaya (Bilham

et al. 1997), and the remaining convergence is taken up farther north in Tibet and Asia

(Avouac and Tapponier 1993; Peltzer and Saucier 1996). The ongoing northward con-

vergence of India produces active deformation in the Himalaya, Tibet and adjoining areas,

keeping the entire region seismically active.

The Himalayan mountain arc and the adjoining Shillong plateau and western Assam

experienced four great earthquakes of magnitude Mw C 8.0 within the last 110 years. The

four great earthquakes are 1897 Western Assam, 1905 Kangra, 1934 Bihar–Nepal and

1950 Eastern Assam (Arunachal) (Fig. 1). Of these, the 1897 earthquake is reported to

have suffered peak ground acceleration exceeding 1 g, because the pebbles embedded in

the matrix were plucked up from the ground, and the 1905 earthquake caused the maxi-

mum loss of lives of *18,000 people. Arya (1990) forecasted if the 1905 Kangra earth-

quake reoccurs with same magnitude and in the same region during present time, there

would be a loss of 80,000 lives even if the earthquake strikes during daytime. This forecast

has been to an extent verified by causality figure (86,000) of the 2005 Muzaffarabad

earthquake of magnitude Mw = 7.6. The four times increase in number of fatalities of the

2005 event when compared to the 1905 earthquake is mainly due to several times increase

in population and ‘‘haphazard’’ construction of the dwellings and infrastructures without

any consideration to seismic hazard. In addition to the great earthquakes, Himalaya has

suffered several large earthquakes with magnitude 7.0 \ M \ 8.0. These earthquakes are

Fig. 1 Location map of Himalayan arc and the study area (after Thakur 2008)

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1505 Central Himalaya, 1555 Kashmir, 1720 Kumaon, 1751 Satluj, 1803 Garhwal–

Mathura, 1833 Nepal and the 2005 Kashmir (Thakur 2006). Recently, the 1905 Kangra

earthquake magnitude has been revised to Mw = 7.8 (Ambraseys and Bilham 2000;

Ambraseys and Douglas 2004). Among several moderate earthquakes of magnitude

6.0 \ M \ 7.0, the documented events are 1555 Kashmir, 1974 Pattan, 1988 Bihar–Nepal,

1991 Uttarkashi and 1999 Chamoli earthquakes. These earthquakes also inflicted moderate

damage to life and property (Pennington 1979; Kumar and Mahajan 1993; Iyengar and

Sharma 1999; Mahajan and Virdi 2001).

The issue of seismic hazard was addressed in India as early as 1956 when a seismic

zoning map of India showing three zones were produced by India Meteorology

Department (Tandon 1956). These frameworks were based on the maximum expected

intensity shaking in terms of MM intensity. Since then, many versions of the seismic

zoning map of India has been published by the Bureau of Indian Standard (BIS), the

official agency for publishing such maps from time to time, the latest being the seismic

zoning map of India showing four zones (I–IV)(BIS code 1893 2002). Following the

probabilistic hazard computation approach, Khattri et al. (1984) probabilistic seismic

hazard (PSH) model calculated PGA for the Himalayan region of the order of 0.7 g for

10% probability of exceedance in 50 years. Under the GSHAP (Global Seismic Hazard

Assessment Programme), Bhatia et al. (1999) calculated the PSH using the Joyner and

Boore’s (1981) attenuation relation for Indian region and produced PGA of the order

0.35–0.4 g for 10% probability of exceedance in 50 years. Kumar (2006) has estimated

the conditional probabilities for the whole Indian region by dividing it into 24 seismo-

genic source regions and found that the conditional probabilities of occurrence of

magnitude more than 6.0 were relatively more than the estimates using classical methods

of probabilistic seismic hazard. The distribution used in this study were Weibul, normal,

Gaussian and Poissonian. The conditional probabilities were estimated for last occur-

rence of magnitude 6.0 in the region.

Since the publication of GSHAP map about a decade ago, our understanding has

considerably enhanced in seismicity, regional tectonics and neo-active tectonics of the

Himalayan region. The seismicity monitoring networks have increased their coverage with

improved resolution in epicentral locations and focal depths. The GPS measurements

across the Himalaya have shown varying rates of convergence and slip, indicating locked

segments of the Indian plate in Himalaya. The palaeo-seismic investigations in Northwest

Himalaya and Nepal have shown surface ruptures indicative of very large palaeo-earth-

quakes on the Himalayan Frontal Thrust (Lave et al. 2005; Kumar et al. 2006). Neotec-

tonics and active fault studies have added another dimension in understanding the active

tectonics vis-a-vis seismicity. Many lessons have been learnt from the 2005 Kashmir

earthquake with new information, which were not reported in earlier Himalayan earth-

quakes. Keeping all these new developments in the subject as background, we attempt to

construct the probabilistic seismic hazard map of NW Himalaya, India, focusing the region

extending 74.5–82�E, i.e., between Kishtwar (Chenab river) in the west to Kali river

(India–Nepal border) in the east. The present map has been prepared based on seismic

hazard calculation method followed under the GSHAP programme. The ground shaking

probabilities at various levels in the regions have been calculated using an integration of

the potential earthquake shaking from all the possible seismogenic source locations and

magnitudes.

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2 Seismotectonic aspect

Following the collision, northward converging India against Asia deformed the northern

part of the Indian continent. The shortening of the Indian crust was accommodated through

imbrications along the principal thrusts in Himalaya, namely the Main Central Thrust

(MCT), the Main Boundary Thrust (MBT) and the Himalayan Frontal Thrust (HFT). These

thrusts propagated southward from the collision zone, showing progressive younger ages

and shallower depths. During collision, the Indus Tsangpo Suture Zone (ITSZ) acts as the

plate boundary between the Indian and Asian plates. Subsequently the boundary between

the Indian plate and the growing Himalaya shifted southward along the sole thrust

(decollement), referred to Main Himalayan Thrust (MHT) (Zhao et al. 1993; Nelson et al.

1996). The MHT, evolved in a thrust system on crustal scale as the MHT–MCT, the MHT–

MBT and the MHT–HFT (Bollinger et al. 2004). The MHT is imaged as decollement

underneath the Tethys Himalaya, Indus Tsanpgo Suture Zone and southern Tibet in seismic

reflection profiles of the INDEPTH project (Zhao et al. 1993; Nelson et al. 1996). The

existence of decollement underneath the entire breadth of Himalaya has been further

confirmed through receiver function analysis in Nepal Himalaya and southern Tibet

(Schulte-Palkum et al. 2005).

The instrumental seismicity is mainly distributed underneath the topographical front of

Higher Himalaya at a depth of 10–20 km, covering the northern part of Lesser Himalaya

and the MCT Zone. This *900 km long seismicity zone extends from Nepal (Pandey et al.

1995), through Kumaon-Garhwal (Khattri et al. 1989), Kangra (Chaterjee and Bhattach-

arya 1992; Kumar and Mahajan 2001) to Indus Kohistan seismic zone in Pakistan (Seeber

and Armbruster 1981). The 1905 Kangra and 2005 Kashmir earthquakes with magnitudes

Mw = 7.8 and 7.6, respectively, and the moderate earthquakes like 1945 Chamba

Earthquake (mb = 6.5), 1986 Dharamsala earthquake (mb = 5.7), Kinnaur Earthquake

(mb = 6.5), 1991 Uttarkashi (mb = 6.4) and 1999 Chamoli (mb = 6.8) occur in this zone.

The instrumental seismicity zone is also interpreted as the region where the elastic strain is

accumulating to generate an earthquake. The GPS measurements in Nepal and 1905

Kangra earthquake meizoseismal region indicate 100 km wide segment from the southern

extent of the seismicity zone to the Himalayan front is locked, showing negligible amount

of convergence/slip (Bilham et al. 1997; Banerjee and Burgman 2002; Bettinelli et al.

2006). The large and great earthquakes are generated as a result of rupturing of this locked

segment along the decollement (Bilham et al. 2001).

The 1905 Kangra earthquake (Mw = 7.8) was interpreted to have occurred as a result of

slip over the detachment (decollement) propagating southward towards the foreland

(Seeber and Armbruster 1981). No surface rupture was reported during 1905 Kangra

earthquake, implying that the fault was blind. The epicentre of 1934 Bihar–Nepal earth-

quake was located east of Kathmandu, but the damage and maximum intensity extended

from Kathmandu valley to the Himalayan front including the liquefaction zone of Bihar

Ganga Plain (Dunn et al. 1939; Bilham et al. 1997). Two surface rupture earthquakes have

been documented along the HFT in Nepal Sub-Himalaya and NW Sub-Himalaya based on

palaeo-seismological studies. The earthquakes have been dated as 1100 AD in Nepal and

1450 AD in Indian part, having lateral extent of the rupture [240 km with 17–26 m co-

seismic slip and 9–13 m vertical separation (Lave et al. 2005; Kumar et al. 2006). These

earthquakes may be mega-thrust type events with their epicentres lying in the locked

segment of the lesser Himalaya, but their rupture extending south right up to the Hima-

layan front. Two types of scenario emerge from the review of seismotectonic history of the

Himalaya. The probability exists in the first scenario for the occurrence of large distributed

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earthquake similar to that of 2005 Kashmir or 1905 Kangra earthquake. The second sce-

nario, a mega-thrust type earthquake as documented in the palaeo-seismological trenches;

the former having a recurrence interval B500 years and the latter with recurrence interval

C1,000 years (Feldl and Bilham 2006; Kumar et al. 2006). Although we are not able to

tightly constraint the timing and magnitude of great/major earthquakes in the Himalayan

region, these data are nevertheless useful in evaluating the probabilistic estimates of

seismic hazard.

3 PSH methodology

The earthquake catalogue and database makes the first essential input for the delineation of

seismic source zones and their characterisation. Preparation of homogeneous catalogue for

NW Himalaya is an important task. As recognised under GSHAP programme, we have

compiled a uniform earthquake catalogue data from historical to recent times using three

temporal categories (1) Since 1964, the modern instrumentation-based data are available,

(2) 1900–1963, encompasses the era of early instrumental data and (3) pre-1900 include

pre-instrumental data based primarily on historical and macroseismic information.

Several catalogues of historical and instrumental seismicity of the studied region have

been analysed and collated to delineate and characterise the seismogenic source zones. The

earthquake catalogue for our study has been prepared by extracting data from different

sources, such as International Seismological Centre (ISC), United States Geological Sur-

vey (USGS), India Meteorological Department (IMD) and several individual workers

(Bapat et al. 1983; Chandra 1992; Iyenger and Sharma 1999).

The seismic hazard assessment reported earlier was based on seismic catalogues, which

were highly uncertain and incomplete. It is pre-requisite for complete earthquake catalogue

to have a uniform magnitude scale for denoting the size of past earthquakes, so that a

reliable parameterisation of the magnitude distributions homogeneous and complete with

respect to time and size is used in hazard analysis. The homogeneous surface wave

magnitude, Ms, based on working file from ISC catalogue for the whole study area was

developed. The mb and Ms empirical relation for magnitude \5.0 was derived using

different magnitude scale for the same earthquake. The exponential curve obtained (Fig. 2)

shows considerably good correlation up to magnitude \5.5 mb. The earthquakes with

magnitude\5.5 have been converted to Ms, and the rest of the earthquakes with magnitude

[5.5 given in the catalogue have been used for analysis.

Ms ¼ 3:196485þ exp �3:674908ð Þ þ 0:7880748ð Þ �mb ð1Þ

The aftershocks and foreshocks data were not considered (deleted) while preparation of

earthquake catalogue. The filtering of data was done by analysing the spatial and temporal

distribution of the events based on modified Omori’s relationship (Utsu 2002). Analysis for

completeness, i.e., determining the period over which the data of a given magnitude

interval are complete (Mahajan and Ghosh 2007), is generally done by using the procedure

described and applied by Stepp (1972). However, the historical data were taken into

consideration while assigning maximum magnitude for each source zone. The cut-off

magnitude has been found using the Goodness-of-fit test (GFT) method given by Wiemer

and Wyss (2000). The goodness-of-fit for the Gutenberg Richter relationship has been

estimated, and the lowest error level has been found to be at magnitude 3.5, which is

treated as cut-off magnitude for the present study.

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A seismicity map thus plotted on the tectonic map of NW Himalaya (Fig. 3) shows

maximum concentration of seismic activity in a narrow zone of *50 km width between

the MBT and the MCT. The isolated concentration of seismic activity has been noticed

around Kashmir Basin (KB), Chamba-Kangra, Garhwal and Dharchula regions with

intervening zones of low seismic activity (Fig. 3). The longitudinal variation in seismic

activity along the Himalayan region may be due to different rates of convergence and

segmental behaviour of the Himalayan arc or existence of different tectonic blocks in NW

Fig. 2 Relation between Ms and mb for Northwest Himalayan arc and its adjoining areas

Fig. 3 Seismotectonic map of Northwest Himalayan arc and its adjoining area

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Himalaya. It has also been noticed that at places the activity has been concentrated along

the NE-SW trending tectonic features.

3.1 Delineation of source zones

The Himalayan orogenic belt is essentially a compressional tectonic arc as indicated by the

MCT, MBT and HFT thrust systems. The current ongoing northeast convergence also

produces compressional regime in Himalaya. The strike-slip motion observed in some

major faults like MBT and MCT represent reactivation of existing faults. The transverse

and tear faults are actually transfer faults, which may represent oblique ramps expressing

transfer of motions on the thrust faults (Valdiya 1973; Thakur 1992; Narula et al. 2000).

The fault plane solutions of the Himalayan earthquakes predominantly indicate thrust

mechanism (Ni and Barazangi 1984; Chandra 1992). However, some normal faults (Singh

et al. 1977; Khattri et al. 1978) and strike-slip mechanism (Das Gupta et al. 1982; Gaur

et al. 1985; Khattri et al. 1989; Kumar and Mahajan 1991, 2001; Srivastava and Mitra

1994; Power et al. 1998; Kayal 2007) have also been reported for the same region. The

normal fault and strike-slip mechanism are not typical of the Himalayan earthquakes. They

represent accommodation and distribution of strain in a heterogeneous and complex

geotectonic framework of the Himalaya undergoing regional northeast compression.

The source zone delineation is based on seismicity record, knowledge gained through

past earthquakes, GPS measurements, palaeo-seismic evidence and structural tectonic

framework in the Himalaya. The instrumental seismicity belt, *50 km wide, extending

from Nepal to Kashmir and IKSZ represent a zone of strain accumulation. The moderate

earthquakes like 1991 Uttarkashi and 1999 Chamoli and the large earthquakes like 1905

Kangra and 2005 Kashmir have occurred within this seismicity zone.

The 2005 Kashmir earthquake has provided important information on the Himalayan

earthquakes. It was for the first time the surface rupture was recorded in any Himalayan

earthquake. The 70 km long surface rupture showing 3–7 m vertical offsets has been

mapped (Kaneeda et al. 2008). The surface rupture corresponds to already mapped active

Balakote Bagh Fault (BBF) (Hussain and Yeats 2006). The causative fault determined on

the basis of seismic data, strikes 3318 and dip N308E with focal depth at 20 km. The

earthquake originated over the wedge decollement reactivating the BBF (Bendick et al.

2007). The BBF cuts across the Hazara syntaxis structure and the MBT suggesting its

origin independent of the MBT. Similarly, the 1905 Kangra earthquake rupture,

100 km 9 50 km dimension, was generated as a result of reactivation of the Jawalamukhi

Thrust (Wallace et al. 2005). The 1934 Bihar–Nepal earthquake rupture propagated

southward from the Lesser Himalaya to the Himalayan range front and the Bihar plain

along the decollement (MHT). The large surface ruptured earthquakes documented along

the HFT on the Himalayan front in Nepal and Northwest Himalaya (Lave et al. 2005;

Kumar et al. 2006) were not generated in situ on the Himalayan front, as we do not find

historical records of such large earthquakes during *1100 AD and 1450 AD affecting the

Ganga plain adjoining the Himalayan front. The large and great earthquakes are originated

as a result of rupture of the locked segment between the southern extents of instrumental

seismicity zone and the Himalayan range front. The rupture propagates southward as

observed in 2005 Kashmir and 1934 Bihar–Nepal earthquakes. It may remain blind, but in

certain situation where the earthquake is large and the overburden over the decollement is

less as observed in the Himalayan front zone, the rupture may appear on the surface as

documented along the HFT (Thakur 2008).

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The delineation of seismic source zones are primarily guided by the occurrence of large

earthquakes, planar distribution of all earthquakes above certain level of magnitude, shape

of isoseismals, intensity distribution, neotectonic activity and regional tectonic frame work.

Based on these factors, sixteen rectangular source zones and three line source zones have

been delineated in the map (Fig. 4). The recurrence relation is computed for each source

model based on parameters that characterise the seismicity of the region. This information

is used as input to the algorithm for computation of seismic hazard viz. minimum and

maximum magnitude for the specified time period and parameters ‘a’ and ‘b’ in the

earthquake frequency magnitude relationship using maximum likelihood method Log

N = a - bM for the same time period (Table 1). The third element used for seismic

hazard assessment involves designation of the strong ground motion (ground acceleration

estimation). The equation specifies ground acceleration as a function of earthquake mag-

nitude and hypocentral/epicentral distance.

3.2 Attenuation relation

The strong ground motion parameters of 1986 Dharamsala (5.7 mb), 1991 Uttarkashi

(6.4 mb) are used to test different equations for having realistic estimates of representative

strong motion in northwest Himalaya by Kumar et al. (1997). Using the worldwide dataset,

the attenuation relations of Abrahamson and Litcheister (1989) and Hasegawa et al. (1981)

are found to be capable of predicting the Uttarkashi acceleration data and that of Peng et al.

(1985) for predicting the Dharamsala earthquake dataset (Fig. 5). The Kangra (Himachal)

and Uttarkashi (Garhwal) regions of Himalaya are characterised by different attenuation

properties, which may be a reflection of ground geology (lithology) present in the

Fig. 4 Seismogenic source zones in Northwest Himalayan arc and its adjoining area

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respective regions (Kumar et al. 1997). The Kangra region shows a higher attenuation rate

because thick Neogene Siwalik sediments cover the upper few kilometre of the crust. The

Siwaliks also contain gravel and boulder beds, which promote scattering and attenuation of

waves. The Uttarkashi region comprising Proterozoic meta-sedimentary rocks in the Lesser

Himalaya shows lower scattering and attenuation of waves when compared to the Kangra

region. The present investigation has taken into account such geological factors in

assigning the region-specific attenuation relations for each source zone.

3.3 Seismic hazard computation

We apply standard method of PSHA in this study (Cornell 1968; Mc Guire 1993) for

computing the peak ground acceleration (PGA) for 10% probability of exceedance in 50

and 10 years at locations defined in the grid of 0.25 9 0.25�. Nineteen source zones

(sixteen rectangular and three line sources) identified in study area have different geo-

tectonic environments and lithological variations. So, two different attenuation relation-

ships have been used for computing the seismic hazard of the region. To compute the

seismic hazard of NW Himalayan arc and its adjoining areas, seismic parameters for each

source like a-value, b-value, attenuation relation, depth, minimum and maximum

Table 1 Showing seismic parameters (‘a’ and ‘b’) of each source zone

S. No Name and no. ofthe source zone

Magnitude Depth Area of rectangularsource zonein sq km

a b Log N =a - bM

Min Max ‘a’ ‘b’

1 NW J & K Zone-1 3.5 7.6 30 17039.97 1.3575 0.7679 0.58 0.33

2 West Jammu Zone-2 3.5 7.3 25 19127.87 6.2190 1.6262 2.70 0.70

3 Kangra-Chamba Zone-3 3.5 7.8 20 12875.16 3.4472 1.1063 1.49 0.48

4 West Panjab Zone-4 3.5 6.5 20 20608.97 7.8708 2.5376 3.41 1.10

5 Panjab re-entrant Zone-5 3.5 7.5 20 35231.79 2.896 1.1485 1.25 0.49

6 Garhwal Zone-8 3.5 7.5 20 25992.34 6.1523 1.5833 2.67 0.68

7 Kumaon (Almora)Zone-9

3.5 7.5 20 23462.09 5.0313 1.4230 2.18 0.61

8 East Kumaon Zone-10 3.5 7.5 33 12248.42 6.6395 1.6484 2.88 0.71

9 West Nepal Zone-11 3.5 7.5 36 32954.38 6.1428 1.8652 2.66 0.80

10 East Nepal Zone-12 3.5 5.5 30 25828.84 8.5470 2.4244 3.71 1.05

11 West STFS Zone-13 3.5 7.5 37 46020.19 4.2992 1.2727 1.86 0.55

12 Tibet Zone-14 3.5 6.3 64 52579.80 2.8124 1.1440 1.22 0.49

13 ITSZ Zone-15 3.5 6.0 31 48357.19 6.5398 1.8300 2.83 0.79

14 Ladhakh Zone-16 3.5 6.3 83 31693.01 2.8124 1.1440 1.22 0.49

15 Nawalkot Zone-18 3.5 5.5 32 12359.68 4.9188 1.7658 2.13 0.76

16 China Zone-19 3.5 7.0 34 108049.67 5.0187 1.4483 2.17 0.62

Line source

1 Kinnaur Zone-6 3.5 7.5 30 5.4135 1.4521 2.35 0.63

2 DHR Zone-7 3.5 5.5 20 6.1888 1.9366 2.68 0.84

3 Takholang Fault Zone-17 3.5 5.5 40 3.4132 1.4749 1.48 0.64

ITSZ Indo Tsangpo suture zone, STFS South Tibetan fault system, DHR Delhi Haridwar ridge

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magnitude, boundary and area of source zone and type of fault have been written in ASCII

format to be used by Haz. 81 (Dojcinvoski and Mihailov 2001) and SEISRISK-III (Bender

and Perkins 1987) softwares. PGA value over the grid is contoured to obtain a seismic

Hazard Map (Fig. 6). A contour interval of 0.1 g is chosen, presuming that the paucity of

historical earthquake data would not permit resolution better than 0.1 g.

4 Results

The prepared map is an improved and updated version of the Global Seismic Hazard Map

(GSHAP) for the Himalayan arc. According to the GSHAP hazard map, the hazard level

depicted is of the order of 0.25 g for majority of the plate boundary and Tibetan plateau

region (Bhatia et al. 1999). The GSHAP map shows nearly uniform hazard all along the

Himalayan arc in longitudinal direction with maximum PGA value of the order 0.35–0.4 g.

The present analysis indicates isolated zones of high hazard of the order of 0.7–0.5 g for

10% probability in 50 years and 0.35–0.2 g for 10% probability in 10 years with

Fig. 5 Attenuation curves formagnitude 5 and 6 according tothe empirical relation given byKumar et al. (1997) aftercorrelation of strong motion dataof 1991 Uttarkashi earthquake(mb = 6.4) and 1986Dharamsala earthquake(mb = 5.7) with the attenuationcurves given by Hasegawa et al.(1981) (a) and Peng et al. (1985)(b), respectively

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Fig. 6 Seismic Hazard map of Northwest Himalayan arc and its adjoining areas showing peak groundaccelerations with 10% probability in 50 years (Fig. 6a) and 10 years (Fig. 6b)

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intervening low hazard zones as depicted by the epicentral map (Fig. 2) of the region.

Earlier the low level hazard zones were referred as the seismic gap regions (Khattri et al.

1989). The Himalayan foothill zone shows a hazard level of the order of 0.15–0.25 g and

0.02 for 10% probability in 50 and 10 years respectively (Fig. 6a, b).

5 Discussion and conclusion

Our seismic hazard map shows longitudinal variations in hazard level. This variation is

very well correlated with the seismicity map, theory of segmental behaviour of Himalayan

arc (Validya 1973; Kaila and Narian 1979), existence of different tectonic blocks in

Northwest Himalaya by Narula et al. (2000) and GPS data showing variation in rate of

northward movements of different blocks i.e., Kangra, Garhwal and Dharchula region

along with locking of strains. This variation in hazard level in the present map is due to the

considerations of several factors such as use of region-specific attenuation relationship,

depth of source and division of Himalayan arc in to different source zones (rectangular and

line sources) or tectonic blocks depending upon local tectonics and seismicity pattern. Five

major zones of high seismic hazard with intervening low order hazard have been recog-

nised; they are Kashmir, Chamba-Kangra, Garhwal, Kumaon and Upper Sutlej valley

having higher PGA values with intervening areas showing lower PGA values. The

recurrence period for large Himalayan earthquake Mw [ 7.0 with total slip 5–7 m and slip

rate 15 mm/year in NW Himalaya provides a value of 350–450 years. The Kashmir region

had an earthquake magnitude Mw = 7.4 (Ambraseys and Jackson 2003) in 1555. The PGA

value of 0.75 g assigned for the Kashmir region (Fig. 6a) appears to be justified, since the

region has approached the threshold recurrence period, and the segment between the

rupture zones of 1555 Kashmir and 1905 Kangra has not been ruptured for more than

500 years. The Chamba–Kangra segment, ruptured during 1905 earthquake Mw = 7.8,

shows PGA value of 0.50 g, as all the accumulated elastic strain has not been released by

the magnitude Mw = 7.8 earthquake (Bilham and Wallace 2005). The Garhwal and Ku-

maon segment with maximum PGA value 0.4–0.5 lies in the central seismic gap (Khatri

and Tyagi 1983). The region has also been identified where the threshold elastic strain has

been accumulated to trigger a very large earthquake (Bilham and Wallace 2005). Northeast

of Shimla in Upper Sutlej valley, which was struck by 1975 Kinnaur earthquake (6.5 mb)

shows PGA value of the order of 0.60 g. The causative normal fault for this earthquake

corresponds with the NE trending normal faults in northern Tethys Himalaya–southern

Tibet. The low PGA value 0.10 g along the Himalayan frontal range contradicts the

recently reported surface rupture earthquake, dated 1450 AD, on the HFT in Garhwal–

Kumaon. According to our interpretation, this earthquake did not originate on the Hima-

layan front as there is no historical record for such an event. It appears the earthquake

rupture propagated southward from its epicentre in the Lesser Himalaya along the

detachment and was registered as surface rupture on the range front. A similar phenom-

enon is observed in 1934 Bihar–Nepal and 2005 Kashmir earthquakes, where the observed

surface rupture appeared to have migrated several tens of kilometre from the epicentre. A

large number of dams for hydroelectric power are being constructed in the Himalaya, and it

is presumed that the updated earthquake hazard map of NW Himalaya with PGA values

will be useful to civil engineers for constructing safer infrastructures and to policy planners

for hazard prevention and mitigation.

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Acknowledgments The present work has been carried out under the DST sponsored project no. DST/23(322)/SU/2001, and authors duly acknowledge the grant received under this project to complete the task.The authors are also thankful to Dr H. K. Gupta, Dr H. N. Srivastava and other committee members whohave provided guidance while carrying out this work. The authors are also thankful to Prof. B. R. AroraDirector, Wadia Institute of Himalayan Geology, Dehradun for fruitful discussion and suggestions inimproving this manuscript. The Director, WIHG, is thanked for according permission to publish thismanuscript.

References

Abrahamson NA, Litcheister JJ (1989) Attenuation of vertical peak acceleration. Bull Seismol Soc Am79:549–580

Ambraseys N, Bilham R (2000) A note on the Kangra Ms = 7.8 earthquake of 4 April, 1905. Curr Sci79(1):45–50

Ambraseys N, Douglas J (2004) Magnitude calibration of north Indian earthquakes. Geoph J Intern159(1):165–206

Ambraseys N, Jackson D (2003) A note on early earthquakes in northern India and southern Tibet. Curr Sci84:570–582

Arya AS (1990) Damage scenario of a hypothetical 8.0 magnitude earthquake in Kangra region of HimachalPradesh. Bull Ind Soc, Earthquake Tech Paper 297 27(3):121–132

Avouac J, Tapponnier P (1993) Kinematic model of active deformation in central Asia. Geophys Res Lett20:895–898

Banerjee P, Burgmann R (2002) Convergence across the northwest Himalaya from GPS measurements.Goephy Res Lett 29(13):1–4

Bapat A, Kulakarni RC, Guha SK (1983) Catalogue of earthquakes of India and neighborhood fromhistorical period to 1979. Indian Society of Earthquake Technology. pp 211

Bender B, Perkins DM (1987) SEISRISK-III—A computer program for seismic hazard estimation. U.S.Geological Survey, Bulletin 1972

Bendick R, Bilham R, Khan MA, Khas SF (2007) Slip on an active wedge thrust from geodetic observationsof 8 October 2005 Kashmir earthquake. Geology 35:267–270

Besse J, Courtillot V (1988) Palaeogeographic maps of the continents bordering the Indian Ocean since theearly Jurassic. J Geophys Res B 93:1791–1808

Bettinelli P, Avouac JP, Flouzat M, Jouanne F, Bollinger L, Willis P, Chitrakar GR (2006) Plate motion ofIndia and interseismic strain in the Nepal Himalaya from GPS and Doris measurements. J Geod80:567–589

Bhatia SC, Kumar RM, Gupta HK (1999) A probabilistic seismic hazard map of India and adjoining regions.Ann Geofis 42(6):1153–1164

Bilham R, Wallace K (2005) Future Mw [ 8 earthquakes in the Himalaya: implications from the 26 Dec.2004 Mw = 9.0 earthquake on India’s eastern plate margin. Geol Surv India Spec Publ 85:1–14

Bilham R, Larson L, Jeffrey F (1997) GPS measurements of present day convergence across the NepalHimalaya. Nature 386:61–64

Bilham R, Gaur VK, Molnar P (2001) Himalayan seismic hazard. Science 293:1442–1444BIS Code 1893. (2002) Earthquake hazard zoning map of India. www.bis.org.inBollinger L, Avouac JP, Cartin R, Pandey MR (2004). Stress building in the Himalaya. J Geophys Res 109

BIP 405:1–8Chandra U (1992) Seismotectonics of Himalaya, in seismology in India. Curr Sci Ind Acad Sci Banglore

62:40–71Chaterjee SN, Bhattacharya SN (1992) In: Gupta GD (ed), Microearthquake survey and seismicity of NW

Himalaya. Himalayan seismicity. Geol Soc Ind 23:23–44Cornell CA (1968) Engineering seismic risk analysis. Bull Seismol Soc Am 58:1583–1606Das Gupta A, Srivastava HN, Basu Malik S (1982) Source mechanism of earthquakes in Kanga-Chamba

regions of Himachal Pradesh, India. Bull Ind Soc Earthquake Tech 19:102–116Dewey JF, Cande S, Pitman WC (1989) Tectonic evolution of the India/Eurasia collision zone. Eclogae

Geol Helv 82:717–734Dojcinvoski D, Mihailov V (2001) Seismic hazard assessment, A computer program. Course material of

twentieth international twelve week course of a seismic design and construction, IZIIOZ, Skopje,pp 1–15

Nat Hazards (2010) 53:443–457 455

123

Dunn JA, Auden JB, Ghosh AMN, Roy SC (1939) The Bihar-Nepal earthquake of 1934. Mem Geol SurvInd 73:391 Reprinted (1981)

Feldl N, Bilham R (2006) Great Himalayan earthquakes and the Tibetan plateau. Nature 444(7116):165–170Gaur VK, Chander R, Sarkar I, Khattri KN, Sinhwal H (1985) Seismicity and state of stress from inves-

tigations of local earthquakes in the Kumaon Himalaya. Tectonophysics 118:243–251Hasegawa HS, Basham PW, Berry MJ (1981) Attenuation relations for strong seismic ground motion in

Canada. Bull Seismol Soc Am 71:1943–1962Hussain A, Yeats RS (2006) The Balakot Bagh Fault that triggered the Ocotber 8, 2005 earthquake and other

active faults in the Himalayan foreland region, Pakistan. Extended abstract, International Conferenceon 8 October 2005 earthquake in Pakistan: its implications and hazard mitigation. Geol Surv Paki-stan:125–126. www.gol.gov.pk/internationalconference.pdf

Iyenger RN, Sharma D (1999) Some earthquake of Himalayan region from historical sources. J Him Geol2(1):81–86

Joyner WB, Boore DM (1981) Peal ground and velocity from strong–motion records including records fromthe 1979 Imperial Valley, California earthquake. Bull Seismol Soc Am 71:2011–2038

Kaila KL, Narian H (1979) Evolution of the Himalaya based on seismotectonics and deep seismicsoundings. Proceedings of Himalayan Geol. Sem., New Delhi, Sect. IIB. Geol Surv Ind Misc Pub 41:1–41

Kaneeda H, Nakata T, Tsutsumi H, Kondo H, Sugito N, Awata Y, Akhtar S, Majid A, Khata W, Awan A,Yeats RS, Hussain A, Ashraf M, Wesnousky SG, Keusar B (2008) Surface rupture of the 2005Kashmir-Pakistan earthquake and its active tectonic implications. Bull Seism Soc Am 98:521–557

Kayal JR (2007) Recent large earthquakes in India: seismotectonic perspectives. IAGR Memoir no 10:189–199

Khattri KN, Tyagi AK (1983) Seismicity pattern in the Himalayan plate boundary and identification of areasof high seismic potential. Tectonophysics 96:281–297

Khattri KN, Rai K, Jain AK, Sinvhal H, Gaur VK, Mithal RS (1978) The Kinnaur earthquake, HimachalPradesh, India of 19 January, 1975. Tectonophysics 49:1–21

Khattri KN, Rogers AM, Perkins DM, Algermissen ST (1984) A seismic hazard map of India and adjacentareas. Tectonophysics 108:93–134

Khattri KN, Chander R, Gaur VK, Sarkar I, Kumar S (1989) New seismological results on the tectonics ofthe Garhwal Himalaya. Proc India Acad Sci (Earth Planet Sci) 98(1):91–109

Kumar R (2006) Earthquake occurrence in India and its use in seismic hazard estimation using probabilisticmethods. PhD Thesis, Garhwal University, India, pp 406

Kumar S, Mahajan AK (1991) Dharamsala Seismotectonic zone-Neotectonic and state of stress in the area. JHim Geol 2(1):53–57

Kumar S, Mahajan AK (1993) The Uttarkashi earthquake of 20th Ocotber, 1991: field observations. TerraNova 6(2):95–99

Kumar S, Mahajan AK (2001) Seismotectonics of the Kangra region, Northwest Himalaya. Tectonophysics331:359–371

Kumar D, Teotia SS, Khattri KN (1997) The representability of attenuation characteristics of strong groundmotion observed in 1986 Dharamsala and 1991 Uttarkashi earthquake by available empirical relation.Curr Sci 73(6):543–547

Kumar S, Wesnousky SG, Rockwell TK, Briggs RW, Thakur VC, Jayangondaperumal R (2006) Palae-oseismic evidence of great surface-rupture earthquakes along the Indian Himalaya. J Geophys Res III:330:4–3309

Lave J, Yule D, Sapkota S, Basant K, Madden C, Attal M, Pandey R (2005) Evidence for a great medievalearthquake (1100 A.D.) in the Central Himalayas, Nepal. Science 307:1302–1305

Mahajan AK, Ghosh GK (2007) Statistical analysis of completeness of earthquake data of NorthwestHimalayan region and its implication for seismicity evaluation. (Varma OP, Mahajan AK, Gupta V(eds) Natural hazard: proceeding of the National Conference on ‘‘Natural hazards (earthquakes andlandslides): challenges, perspectives and societal dimensions with focus on the state of Uttaranchal’’,Dehradun, December 26-28, 2003:45–56

Mahajan AK, Virdi NS (2001) Macroseismic field generated by the 29th March Chamoli earthquake, 1999and its seismotectonics. J Asian Earth Sci 19(4):507–512

Mc Guire RK (1993) In: Giardini D, Basham P (eds), Computation of seismic hazard, global seismic hazardassessment program. Ann Geofis 34(3–4):181–200

Narula PL, Shankar R, Chopra S (2000) Rupture mechanism of Chamoli earthquake on 29th March 1999and its implications for seismotectonics of Garhwal Himalaya. J Geol Soc Ind 55:493–503

Nelson KD, Zhao W, Brown LD, Kuo J, Che J, Liu X, Klemperer SL, Makovsky Y, Meissner R, Mechie J,Kind R, Wenzel F, Ni J, Nabelek J, Leshou C, Tan H, Wei W, Jones AG, Booker J, Unsworth M, Kidd

456 Nat Hazards (2010) 53:443–457

123

WSF, Hauck M, Alsdorf D, Ross A, Cogan M, Wu C, Sandvol E, Edward M (1996) Partially moltenmiddle crust beneath southern Tibet: synthesis of project-INDEPTH results. Science 276:1684–1686

Ni J, Barazangi M (1984) Seismotectonics of the Himalayan collision zone: geometry of the under thrustingIndian plate beneath the Himalaya. J Geophy Res 89:1147–1163

Pandey MR, Tandulkar RP, Avouac JP (1995) Interseismic strain accumulation on the Himalyan crustalramp (Nepal). Geophys Res Lett 22:751–754

Peltzer G, Saucier F (1996) Present day kinematics of Asia derived from geological fault rates. J Geopy Res101:27943–27956

Peng KZ, Wu FT, Song L (1985) Attenuation characteristics of peak horizontal acceleration in northeast andsouthwest china. Earthquake Eng Struct Dynam 13:337–350

Pennington WD (1979) A summary of field and seismic observations of the Pattan earthquake: 28December, 1974. In: Farah A, Delong KA (eds) Geodynmics of Pakistan, Geological Survey ofPakistan, Quetta, pp 143–147

Power PM, Lillie RJ, Yeats RS (1998) Structure and shortening of the Knagra and Dehradun re-entrants,sub-Himalaya, India. GSA Bulletin 110(8):1010–1027

Schulte-Pelkum V, Monslave G, Sheehan A, Pandey MR, Bilham R, Wu F (2005) Imaging the Indiansubcontinent beneath the Himalaya. Nature 435:1222–1225

Seeber L, Armbruster J (1981). Great detachment earthquakes along the Himalayan Arc and long termforecasting In: Simpson DW, Richards PG (eds), Earthquake prediction-an international review.Maurice-Ewing Series 4, American Geophysical Union, Washington DC, pp 259–277

Singh S, Jain AK, Singh VN, Srivastavam LS (1977) Damage during Kinnaur earthquake of January 19,1975 in Himachal Pradesh, India, Pre-Print of sixth world conference on Earthquake Engineering 1:1–6

Srivastava P, Mitra G (1994) Thrust geometries and deep structures of the outer and lesser Himalaya.Kumaon and Garhwal (India): implications for evolution of the Himalayan fold-and-thrust belt.Tectonics 13:89–109

Stepp JC (1972) Analysis of the completeness of the earthquake sample with Puget Sound area. In: HardingST (ed) Contribution to seismic hazard zoning. NOAA Tech. Report ERL 267-ESL 30, BoulderColorado

Tandon AN (1956) Zones of India liable to earthquake damage. Ind J Meteorol Geophys 10:137–146Thakur VC (1992) Geology of the Western Himalaya. Pergamanon press, London, p 362Thakur VC (2006) Reassessment of earthquake hazard in the Himalaya and implications from the 2004

Sumatra-Andaman earthquake. Curr Sci 90(8):1070–1072Thakur VC (2008) Active tectonics of the Himalaya. Mem Geol Soc India 66:227–258Utsu T (2002) Statistical features of seismicity, international handbook of earthquake engineering and

engineering seismology. 81A:719–732Valdiya KS (1973) Tectonic framework of India: a review and interpretation of recent structural and tectonic

studies. Geophys Res Bull 11:79–114Wallace K, Bilham R, Blum F, Gaur VK, Gahlaut V (2005) Surface deformation in the region of the 1905

Kangra Mw = 7.8 earthquake in the period 1846–2001. Geophys Res Lett 32(15):L15307. doi:10.1029/2005GL022906

Wiemer S, Wyss M (2000) Minimum magnitude of complete reporting in earthquake catalogs: examplesfrom Alaska, the Western United States, and Japan. Bull Seism Soc Am 90:859–869

Zhao WJ, Nelson KD, Che J, Quo J, Lu D, Wu C, Liu X, Brown LD, Hauck ML, Kuo JT, Klemperer S,Makovsky Y (1993) Deep seismic reflection evidence for continental underthrusting beneath southernTibet. Nature 366:557–559

Nat Hazards (2010) 53:443–457 457

123