Tectonics and Seismic Hazard in the Himalaya

B.N. Upreti Department of Geology Tribhuvan University, Nepal Tectonics (M. Mattauer,1989)

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I M.F.T. MFT (After Gansser, 1964) (After Hodges, 2000) S N Hig he r Him a la ya n Ind us-Tsangpo Zone Eu ra si a Si w a l i k Zo n e Le sse r Him a la ya n M S Gangetic MB C TD Suture Zone M T Zone T S Pla in FT

Indian Pla te

STDS: So u t h Tibetan Detachment System MCT: Ma in Centra l Thrust MBT: Main Boundary Thrust MFT: Main Frontal Thrust

Age of Structures: (Modified after N. Harris, 2002) MCT: formed at about 24 Ma before STD: Nearly contemporaneous with MCT MBT: Formed before 10 Ma MFT: Less than 2 Ma M FT

M FT

(After Upreti, 1999) (After Pandey et al., 1999) (DeCelles et al, 2001) (Pandey et al. 1999) (Mugnier, 1999) Bashyal, 1996)

Earthquakes in the Himalaya SEISMIC HAZARD OF PACIFIC REGION

Nepal

GSHAPUSGS website Some Historic Earthquakes in Nepal (source: UNDP/UNCHS, 1993, Pandey and Molnar, 1988, Bilham et al., 1995)

Year (AD) Deaths Damages 1255 One third of the population of A lot of damages to residential buildings was affected. Many deaths and temples 1260 Many people died, Famine after the A lot of damages to residential buildings earthquake and temples 1408 Many people died A lot of damages to temples, residential buildings, fissures developed in the ground

1681 Many people died A lot of damages to residential buildings 1767 No record of deaths No record of damage 1810 Some people died, many lives were lost A lot of damages to buildings and temples particularly in Bhaktapur 1823 No record of deaths Some damage to houses 1833 Estimated magnitude 7.7, 414 people died in Nearly 4040 houses destroyed in the vicinity of the Kathmandu valley Kathmandu, Bhaktapur, and Patan in the valley and adjoining Banepa and a total of 18,000 buildings damaged in the whole country. 1834 No good record available Many buildings collapsed 1837 No good record available No damage in Nepal recorded but greatly affected Patna and other parts of Bihar, India.

1869 No good record available No good record available

1897 No good record available No good record available

1917 No record deaths No record on damage

1934 Estimated Magnitude 8.3 (epicenter, eastern Over 200,000 buildings and temples etc damaged Nepal). 8519 people died out of which out of which nearly 81 thousand completely 4296 died in Kathmandu valley alone destroyed in the country. Max Intensity X. 55,000 building affected in Kathmandu (12,397 completely destroyed).

1936 No good record available No good record available

1954 No good record available No good record available

1966 24 people died 1,300 houses collapsed

1980 Magnitude 6.5 (epicenter far western Nepal). 12, 817 buildings completely destroyed, 2,500 103 people died houses collapsed

1988 Magnitude 6.5 (epicenter in SE Nepal). 721 66,382 buildings collapsed or seriously damaged. people died

19 great earthquakes in the last 7 centuries (Pandey et al., 1999) (Pandey et al. 1999) width great ruptures 70-90 km S contraction N uplift Tibet Himalaya India locking line locked sliding Indian plat e 20 mm/y 100 km

(Bilham et al. , 2001) Potential areas for next large earthquakes

(Modified after Pandey et al., 1999) Seismic gaps

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(Modified after Pandey et al., 1999) Historic Earthquakes

2005

Summary of current slip potential (Bilham et al., 2001) Collaborating Organizations and projects In Nepal 1. Labarotoire de Geophyique Applique (LGA), Paris University France 2. Department Analyse Survillance Environment (DASE), France 3. California Institute of Technology (CALTECH), USA 4. Oregon State University, USA New Projects 1. The Himalayan Nepal Tibet Seismic Experiment (HIMNT) 2. Hi-CLIMB Nepal-Bihar Earthquake 1934 X XI

X IX

VIII

IX IX

IX

VIII

1934 Earthquake Pandey and Molnar, 1988, Jr. NGS, v.5 Kirtipur

Harisidhi

(After Roy et al., 1939, redrawn) Damage in Bhaktapur, Kathmandu Valley (Rana, 1935) Lubhu town, Kathmandu valley after the 1934 earthquake (Rana, 1935) A road in Bhaktapur, Kathmandu Valley (Rana, 1935) Fissures in Tundikhel, Kathmandu (Rana, 1935) Deaths due to 1934 earthquake out of Valley Place Men Women Total Eastern Mountain 1792 2182 3974 region Western Mountain 29 36 65 region Terai 77 107 184 1898 2325 4223

Total Deaths by 1934 earthquake Kathmandu 1952 2344 4296 Valley

Rest of Nepal 1898 2325 4223

Total 3850 4669 8519 Impact of Future Earthquake in Kathmandu

A recent study (UNDP/BCPR, 2004) ranked Nepal as the eleventh most at risk country to earthquakes. Presently Kathmandu is one of the few cities in the world at a very high alert due to Earthquake disaster GEOMORPHOLOGY

Kathmandu

(After DMG, 2005) 85 20' N (After Sakai et al, 2001)

Shivapuri Lekh

Gokarna T fluvio-deltaic facies Kathmandu R Bhaktapur Patan D Thimi 27 40'

CB lacustrine facies DK The deepest drilling CK was at R: 284 m) CP talus deposits fandeposits basement rocks J isolated basement rocks L lacustrine facies (Kalimati Clay) Bagmati River fluvio-deltaic facies (Gokarna, Thimi & Patan Formation) Mahabharat Lekh faults 0 10km N

Sundarijal Itaiti Gokarna airport Harisiddhi Chapagaun 1500 1340~1386 m Manahara Khola G 1320~1340 m 1340 m 1400 T 1305~1310 m 1300~1310 m T P P 1300

Kathmandu Basin Group 1200 Patan Fm 1100 Thimi Fm LD 1000 Gokarna Fm Itaiti Fm RB 900

Kalimati Fm 800 Lukundol Fm (Basal Lignite Member) 700 Bagmati Fm (Tarebhir Fm) 0 5 km m

(After Sakai et al., 2001

Potential Impact due to scenario EQ in KV (KVERMP estimates for IX MMI)

Impact Extent Death >40,000 Injuries >95,000 Buildings destroyed/collapsed >60% Homeless population >700,000 Bridges impassable >50% Road length damaged >10% Water supply pipes damaged >95% Telephone exchange buildings most Telephone lines >60% Electric substations most Electric lines 40% (Bilham, 1995) Area affected by the July 29,1980 Bajhang earthquake (6.5 Richter scale) 1988, 21 Aug. (2045 BS) earthquake in Nepal

Kathmandu V V

VI VII Dikte l V VIII VIII Ilam Gaighat VI VI Dharan Epicentre VII V Biratnagar

(Dixit, 1991, Jr. NGS, V.7, 199) Active Faults in Nepal (After Nakata, et al, 1990) (Nakata et al, unpublished) (After Nakata, et al, 1990)

(After Upreti et al, 2000)

(After Upreti et al, 2000) (After Upreti et al, 2000) Bardibas along E-W highway Nakata et al., unpublished)

(After ICIMOD, 2006)