Earthquake Risk in the Himalayas: Special Reference to Kathmandu City Deepak Chamlagain PhD Department of Geology, Tribhuvan University, Kathmandu, Nepal
Science behind theHimalayan earthquakes• Active collision zone of the Eurasian and Indian plates• Belt segmented by many active Subduction followed by collision seismogenic faults• Continuous strain accumulation along Eurasi an Indian Plate the major active plate faults due to locking
Historical Earthquakes Pakistan(~75,000) Assam Bihar-Nepal (~1500) (10,653) Shillong Plateau (~1542)Estimated Rupture Area of major Himalayanearthquakes (M>7.5) India/Eurasia Plate MotionBilham (2004), Ambraseys and Bilham (2000), Kumar, (Bettinelli et al., J. Geodesy, 2006)et al. (2006) Lavé, et al. (2005)
Reasons for high earthquake risk in Kathmandu Valley• Active tectonic and fragile geological condition• Earthquake induced hazard (e.g. landslide, flood, fire, ground failures etc.)• Rampant urbanization• Lack of landuse regulation in place• Ineffective implementation of building regulations• Absence of licensing system to the technical persons for anti-seismic construction
Urban Earthquake Risk Assessment• The study on earthquake disaster mitigation in the Kathmandu valley, Nepal. JICA/MoHA (2002).• Earthquake Vulnerability Profile and Preparedness Plan (UNDP/ERRRP Municipalities programme)
Kathmandu Valley•Basin is located in midland andbounded by the Mahabharat Lekhin south and Shivapuri Lekh inNorth.•Inter-montane Basin with averageelevation of 1340m•Surrounded by mountains of Kathmandu2400-2800 m above sea level•Diameter of about 30 km in E-Wand 25 km in N-S•About 500m thick soft sediments After DMG
Flowchart for Earthquake Risk Assessment Source: JICA/MoHA, 2002
Fault and Lineaments in Kathmandu Valley Ground Model for Seismic Analysis Source: JICA/MoHA, 2002
Fault Model and Scenario Earthquake Fault Model Scenario Earthquake S. Earthquake Location Magnitude N. (Ms) 1 Mid Nepal 82°and 85° 8.0 Earthquake 2 North Bagmati North of 6.0 Earthquake Kathmandu 3 KV Local Local 5.7 Earthquake earthquake based on lineament 4 1934 Bihar NE of 8.4 Nepal Kathmandu EarthquakeSource: JICA/MoHA, 2002
Liquefaction Potential Distribution Heavily Damaged Building Number Distribution
Casualty Findings •The number of heavily damaged buildings would be 53,000, i.e., 21% of all buildings. •The death toll, 18,000, i.e., 1.3% of the total population in the Valley. •The seriously injured people: 53,000, i.e., 3.8% of the total population in the Valley. •Serious damage to road networks, hospital, sewerages etc.
On going preparedness/awareness programmes• Celebration of earthquake safety day• Formal/informal education on disaster management• Mock drilling on earthquake safety in schools• Mason training on earthquake resistant construction• Promotion of community based organizations
Gap areas• Investment on research, education, training, and human resource development• Enhancement of the earthquake technology• Mapping of the earthquake hazard both urban and rural areas and linking of these maps with the development plan and activities.• Establishment of Earthquake Risk Evaluation Centre (EREC)• Development of insurance policy for earthquake risk• Promotion of public awareness and preparedness programs intensively
Concluding Remarks• Owing to its tectonics and built environment risk of the earthquake is increasing day by day.• Haphazard urbanization, lack of landuse regulations, weak implementation of building codes, poverty etc. are the major reasons in fueling the earthquake risk in the Himalayas.• Seismic hazard mapping and corresponding vulnerability and risk assessment is most crucial and urgent for the major urban areas of Nepal.• Seismic microzonation and periodic risk and loss assessment is crucial in minimizing the effects of earthquake.• Regional collaboration both on technological and management aspects is necessary.