2015 Nepal Earthquake Event Recap Report
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Aon Benfield Analy tics | Impact Forecasting 2015 Nepal Earthquake Event Recap Report September 2015 Risk. Reinsurance. Human Resources. Aon Benfield Analy tics | Impact Forecasting Table of Contents Executive Summary 3 Introduction 4 Seismological Recap 5 Human Casualty 9 Property Effects 10 Commercial Effects 13 Utility Effects 15 Infrastructure Effects 15 Impact Forecasting Reconnaissance 16 Impact Forecasting: Real-Time Response 26 Financial Losses 29 Appendix A 34 Appendix B 35 Appendix C 37 Contact Information 38 2015 Nepal Earthquake Event Recap Report 2 Aon Benfield Analy tics | Impact Forecasting Executive Summary A major magnitude-7.8 earthquake struck central Nepal on April 25, 2015, leaving catastrophic impacts across the country. It was the largest earthquake to strike Nepal in over 80 years. That tremor, plus subsequent aftershocks, left more than 9,100 people dead and nearly 25,000 others injured. Extensive damage was recorded throughout Nepal, particularly in the capital city of Kathmandu. The main jolt was later followed by a major magnitude-7.3 aftershock on May 12, 2015. Ground shaking from the first earthquake lasted for two minutes according to local reports and was felt as far away as New Delhi in India, Lahore in Pakistan, Lhasa in Tibet, and Dhaka in Bangladesh. Minimally 379 aftershocks rattled Nepal and the surrounding region with magnitudes 4.0 or greater in the months after the event, including five which registered above magnitude-6.0. Extensive catastrophic damage to property was reported throughout central Nepal, including in Kathmandu and throughout the Kathmandu Valley. Hundreds of thousands of buildings collapsed across many parts of Nepal as a result of the earthquakes, and the combined total of houses destroyed stood at 605,254. A further 288,255 were partially destroyed. Tens of thousands of other structures, including schools, health facilities and public government buildings, were also impacted. Additional damage to thousands of structures was reported in parts of India, Tibet, and Bangladesh. Several important historical buildings collapsed or sustained severe damage in Kathmandu and in the surrounding area including monuments that comprised the United Nations Educational, Scientific, and Cultural Organization’s (UNESCO) cultural heritage site of the Kathmandu Valley. More than 30 monuments in the Kathmandu Valley collapsed, and an additional 120 incurred partial damage. Nationwide, more than 1,000 monasteries, temples, historic houses, and shrines were impacted. Nepal’s state utility provider, Nepal Electricity Authority (NEA) reported that 16 hydropower facilities – out of 23 that were operational – were significantly damaged (one of which was under construction at the time of the temblor). Collectively, the shutdowns resulted in a loss of 150 megawatts from Nepal’s power grid which represents approximately one-fifth of the country’s total power supply. The road and highway network across Nepal was heavily impacted, with more than 2,000 kilometers (1,242 miles) – or 13 percent of the network – damaged or destroyed. Worst affected were the districts of Sindhupalchowk, Dolakha, and Nuwakot. Impact Forecasting sent a team of seismological and engineering experts to survey the damage in Nepal. The main building typologies in Nepal are adobe structures, brick or stone masonry with mud mortar (BM/SM), brick or stone masonry with cement mortar (BC/SC), wooden structures (W), and reinforced concrete (RC) buildings. Impact Forecasting was able to determine how the differing building types and structures performed. This analysis was critical as we work to further improve the earthquake scenario model that we have developed for Nepal. The model is to be used as a tool for companies and clients to further analyze their earthquake hazard risks and exposures in the country. The overall economic cost of the Nepal earthquake(s) – including damage in Nepal, India, Tibet and Bangladesh – is estimated around USD8.0 billion. A World Bank assessment tentatively listed total economic damage solely in Nepal at USD5.1 billion and valued additional economic losses (including business interruption and specific sector losses) at nearly USD1.9 billion. This value is equivalent to more than one-third of Nepal’s entire Gross Domestic Product (GDP). Overall insured losses in Nepal, India, Tibet and Bangladesh were estimated around USD200 million. As of August 2015, the Nepal Insurance Board (IB) reported that 16,603 claims were filed to the 17 non-life insurance companies operating in the country with a total value of NPR18.43 billion (USD175 million). The agency expected total non-life claims to settle around NPR20 billion (USD190 million). 2015 Nepal Earthquake Event Recap Report 3 Aon Benfield Analy tics | Impact Forecasting Introduction A major magnitude-7.8 earthquake struck central Nepal on April 25, 2015, leaving catastrophic impacts across the country. It was the largest earthquake to strike Nepal in over 80 years. That tremor, plus subsequent aftershocks, left more than 9,100 people dead and nearly 25,000 others injured. Extensive damage was recorded throughout Nepal, particularly in the capital city of Kathmandu. The main jolt was later followed by a magnitude-7.3 aftershock on May 12, 2015. The combined death toll from both tremors stood at 8,891 and the number of injured was 22,302 in Nepal alone. A further 229 fatalities were registered in India, Epicenter of April 25, 2015 M7.8 event (Source: USGS) Bangladesh, China’s Tibet, and Mount Everest. The first earthquake struck at 11:56 AM local time (06:11 UTC) with an epicenter located 77 kilometers (48 miles) northwest of Kathmandu at a shallow depth of 15.0 kilometers (9.3 miles). The second earthquake struck at 12:50 PM local time (07:05 UTC) with a shallow epicenter located 18 kilometers (11 miles) southeast of Kodari, on the southwestern flanks of Mount Everest, also at a depth of 15.0 kilometers (9.3 miles). Ground shaking from the first earthquake lasted for two minutes according to local reports and was felt as far away as New Delhi in India, Lahore in Pakistan, Lhasa in Tibet, and Dhaka in Bangladesh. Minimally 379 aftershocks rattled Nepal and the surrounding region with magnitudes 4.0 or greater in the months after the event, including five which registered above magnitude-6.0. The European Space Agency’s satellite Sentinel-1A used imagery obtained before and after the earthquake to determine that the maximum land deformation occurred only 17 kilometers (11 miles) from Kathmandu which explained the catastrophic levels of damage experienced in that area. The earthquake’s slip – defined by the United States Geological Survey (USGS) as relative displacement of formerly adjacent points on opposite sides of a fault, measured on the fault surface – occurred over an area roughly 2,600 to 5,200 square kilometers (1,000 to 2,000 square miles) across a zone that included the cities of Kathmandu and Pokhara in one direction and nearly the entire Himalaya mountain width in the other. It is estimated that as much as 3.0 meters (10 feet) of northern India’s Bihar state slid beneath Nepal in a matter of seconds. Plot of M6.0+ earthquakes following main April 25 event in blue (Source: USGS) 2015 Nepal Earthquake Event Recap Report 4 Aon Benfield Analy tics | Impact Forecasting Seismological Recap The active collision of the Indian tectonic plate with its Eurasian counterpart is the driving force for tectonic activity in the Himalayan region. The subduction of the Indian plate beneath the Eurasian plate at a rate of 40-50 millimeters per year has produced an active fault system that extends from the Karakoram Ridge in the west to the Bengal Plain in the east. It comprises several major faults including the Himalayan Frontal Thrust (HFT), the Main Boundary Thrust (MBT), and the Main Central Thrust (MCT) (Figure 1). These active boundaries are located within Nepal and are the primary source of earthquakes in the country. Figure 1: Active faults in and around Nepal (Nakata and Kumahara 2002) Seismic Hazard The geographical location of Nepal naturally makes it one of the most seismically hazardous regions in the world. Nepal resides on the boundary of the Indian and Eurasian plates and numerous active faults have been identified in the Himalayan region. Several significant earthquakes (Mw > 7.5) have occurred in the past 500 years, including the Mw7.8 Kangara earthquake in 1905 and the Mw8.1 Nepal-Bihar earthquake in 1934 (Bilham and Ambraseys 2005). The complexity and uniqueness of the tectonic setting has attracted the attention of several researchers from across the globe. As a result, there is a wealth of knowledge available related to tectonic settings, seismic sources, and seismicity of the Himalayan region. However, the lack of observations of ground motion from earthquakes has been a major setback, especially for the quantification of seismic hazard. The global scientific community has yet to develop robust ground motion predictive models specific to this region. Despite that, hazard studies have progressed and Ram and Guoxin (2013) have developed a hazard map for Nepal for different return periods. Figure 2 shows peak ground acceleration (PGA) maps for 475 and 2,475 years return periods. The hazard maps show larger hazards in the far-western and eastern portions of Nepal, and lower hazards in southern Nepal. The estimated PGA values are in the range of 0.21-0.62 g, and 0.38-1.1 g for 475 and 2,475 years return periods respectively. 2015 Nepal Earthquake Event Recap Report 5 Aon Benfield Analy tics | Impact Forecasting 475 years return period hazard 2,475 years return period hazard Figure 2: Seismic hazard maps of Nepal showing the peak ground acceleration distribution at bedrock level (Ram and Guoxin 2013) 2015 Nepal Earthquake Sequence On April 25, 2015, a magnitude Mw 7.8 earthquake struck the Kathmandu region.