The Nepalese government placed the preliminary death toll in excess of 2, people, with 5, injured—but both figures are expected to grow. The earthquake is the largest to strike South Asia since , when a tremor in Pakistan-administered Kashmir killed over 80, Saturday's earthquake caused extensive damage in and around Kathmandu, Nepal's densely populated capital, and destroyed numerous historic structures.
The Dhararara Tower, a famous 19th century tower in Kathmandu popular with visitors, completely collapsed. Nepalese police have pulled 60 bodies from the wreckage.
This is what we feared for decades -- that a massive earthquake is coming and we would be helpless. Devastated to hear about Nepal. Media reports indicate that teams of hikers and guides remain missing on the mountain. Last April, an avalanche swept through Everest's Khumbu Icefall and killed 16 climbers in what was then the deadliest day in the mountain's history.
Most avalanches on Mount Everest occur at altitudes between 18, and 21, feet, disproportionately victimizing Nepalese Sherpas hired to guide adventure-seekers.
It looks like the worst devastation and most deaths in Nepal came from brick buildings, as usual, and tragically predictable--and predicted. But the country, plagued by poor infrastructure, is particularly vulnerable to earthquakes. Few Nepalese citizens live in retrofitted homes, and the government has struggled to prepare the population for such a disaster.
According to the Wall Street Journal, Saturday's earthquake was the fourth measuring over 6. In addition to the many dead in Nepal, the earthquake also claimed 34 lives in India, 12 in China, and 2 in Bangladesh. It is also interesting to note that the recent ground motion prediction model, such as Boore et al. Using the empirical model by Boore et al. Therefore, it is important to adopt advanced ground motion models that can account for major systematic components e. Scenario Shake Map Rapid earthquake impact reports [e.
In producing rapid earthquake impact assessment, scenario shake maps are the essential input. In these applications, shake maps are generated by using a suitable ground motion model together with observed instrumental data and seismic intensity information e. In seismic regions with limited monitoring capability of strong motion, shake maps are more dependent on the accuracy of an adopted ground motion model as well as on initial estimates of the seismic event e.
This is because there will not be many real-time observations to constrain the shake map predictions. Modern ground motion models adopt extended-source-based distance measures, such as Rrup and Rjb i. A simpler representation of an earthquake source is a point source model; in this case, hypocentral and epicentral distances, Rhypo and Repi, are often used.
When a slip distribution is available, another useful distance measure is the shortest distance to the asperity Rasp Goda and Atkinson, For large subduction events having large fault plane dimensions, the calculated distance measures can vary significantly, depending on how a fault plane model is defined and which distance measure is adopted.
For instance, for the Mw7. The influence of distance measures is particularly significant for large magnitude events. The above-mentioned problem has an important implication on shake map generation for a large earthquake. To demonstrate this for the Mw7. The results are shown in Figure 7. For all shake maps, VS30 information at individual sites is taken into account.
Strictly, Rhypo and Rasp should not be used in the Kanno06 model as the distance measures and the model development process are incompatible ; this is for illustration only. Figure 7 A shows the predicted PGAs at sites above the fault plane are large 0.
Figures 7 B,C show different patterns from Figure 7 A because the distance measures are essentially defined for point source but with different source locations i. Importantly, bias in estimated ground motions propagates into rapid earthquake impact assessment.
The key issue here is that the current ground motion model together with a finite-fault plane can result in biased predictions of overall earthquake impact which may affect subsequent decisions for emergency response actions.
From practical viewpoints, this issue needs to be resolved in the near future. Comparison of scenario shake maps for the Mw7. Earthquake Damage Survey This section presents main observations and findings from the earthquake damage survey in Nepal.
The building typology in Nepal is briefly reviewed, and then, field observations in Kathmandu, Melamchi, Trishuli, and Baluwa are discussed. The regional map of the visited locations is shown in Figure 3 , and the main survey locations in Kathmandu are indicated in Figure 4. The cases discussed in the following are selected to highlight main observations from the survey trip.
Numerous photos are available through the Google Earth file as supplementary material to this paper. Building Typology in Nepal Buildings in Nepal are vulnerable to seismic actions. The majority of houses and buildings are not seismically designed and constructed, lacking ductile behavior.
This subsection briefly summarizes general characteristics of building typology in Nepal. More complete information e. According to the National Population and Housing Census, the total number of individual households in Nepal is 5,,, while the population is 26,, In urban areas e. These types of buildings generally have flexible floors and roof, and are prevalent in rural areas. The masonry materials are of low strength and thus are seismically vulnerable.
The wooden buildings are popular near the forest areas in Nepal. The reinforced concrete RC building is a modern form of construction in Nepal, which began in late s.
The RC moment resisting frame assembly is comprised of cast-in-place concrete beams and columns with cast-in-place concrete slabs for floor and roof. Most of the conventional RC constructions are non-engineered i. Engineered RC buildings, which are relatively new, often adopt the Indian standard code with seismic provisions. Figure 8 A shows the collapse of the Basantapur Tower.
The complete destruction in the Durbar Square was in sharp contrast with undamaged buildings surrounding the Durbar Square Figure 8 B; several wall cracks can be found on these buildings; however, the majority of the masonry buildings are structurally stable. This indicates that the ground shaking experienced in this area note: this is relatively close to the KATNP station; see Figure 4 was sufficient to cause the collapses of the old historical buildings but was not to cause severe damage to the surrounding buildings.
This observation was confirmed by walking through the Indra Chowk area market squares near the Old Palace , where many old masonry buildings three to six stories were densely constructed. Nevertheless, there were several buildings that collapsed completely and some search and rescue activities were undertaken Figures 8 C,D. Damage in Kathmandu area 1 in Figure 4. C Collapse of four 5- or 6-story old masonry buildings. D Collapse of a 4-story masonry building.
There were numerous building collapses in the north—west section of the Ring Road along the Bishnumati River area 2 in Figure 4. According to the local geomorphological map, sites within about m from the river are alluvial Holocene soil deposits, whereas sites farther east are Pleistocene soil deposits. Therefore, site amplification effects due to different soil conditions may be expected in this area.
A walk-through survey was carried out to investigate the spatial distribution of collapsed and severely damaged buildings in this area. Out of 28 collapsed or severely damaged buildings, 19 buildings were in the alluvial deposit area Figure 9 A , whereas 9 buildings were in the Pleistocene deposit area but nearer to the boundary Figure 9 B.
This qualitatively confirms the effects of local site conditions on the building damage and collapse. Damage in Kathmandu areas 2—5 in Figure 4.
A Collapsed building along the Bishnumati River alluvial soil deposit area; area 2 in Figure 4. B Collapsed building soft story collapse near the Bishnumati River boundary between alluvial and Pleistocene soil deposit areas; area 2 in Figure 4. C Horizon apartment buildings area 3 in Figure 4. D Settlement of the Araniko Highway area 4 in Figure 4. E Damage to the Araniko Highway area 4 in Figure 4. F Collapsed church in the Imadol area area 5 in Figure 4. In area 3, there was a story high-rise apartment complex Park View Horizon.
The walls of this building suffered from many major cracks along its height Figure 9 C. Currently, the apartments are unfit for living and residents have evacuated. The causes of the major damage of the Horizon apartments and similar high-rise buildings in Kathmandu may be attributed to the long-period ground motions Figure 5. In addition, local topological features may have contributed to extensive damage there the complex is on a hill. Along the Araniko Highway between Kathmandu and Bhaktapur area 4 in Figure 4 , a section of the highway about m in length built upon embankments was damaged due to the ground settlement.
The amount of settlements was about 0. The central section of the highway was constructed using reinforced soil retaining wall and gravity-type retaining wall 2—3 m high and m wide. The retaining walls were structurally intact and suffered from minor cracks and outward deformation only, whereas the natural slopes at both ends of the highway embankments experienced noticeable settlements Figure 9 E.
Several buildings along the highway were tilted due to the settlements. A pedestrian footbridge crossing the highway suffered from the differential settlement of foundation, resulting in a gap of 45 cm between the bridge girder and the stair steps. In area 5 Figure 4 , minor liquefaction, which was evidenced by sand boils and did not cause any structural damage, was observed in a small open land near a canal.
In the surveyed area, a church was collapsed due to the ground shaking Figure 9 F. According to local residents, the church building was standing after the Mw7. The extent of structural damage before the Mw6. There were several houses that settled and tilted in this area. However, the degree of destruction in this area was minor. Overall, earthquake damage in Kathmandu was not widespread but more localized. This may suggest that overall strong shaking experienced in Kathmandu was not extremely large.
The areas that suffered from major destruction tend to have some local characteristics, such as soft soil conditions and structural deficiencies.
Survey Results in Melamchi The survey was conducted along the road to Melamchi about 30 km north—east of Kathmandu; Figure 3. Melamchi and the surrounding areas were close to the locations of major aftershocks i. On the way to Melamchi, there were many small villages that suffered from earthquake damage. During interviews with local residents, they expressed serious concerns about incessant aftershocks and urgent need of repairs of the damaged houses before the arrival of rainy season.
Proceeding north toward Melamchi, the occurrence of earthquake damage becomes more frequent. Melamchi is a small town along the Indrawati River, and residents in the town have been involved with a major Melamchi Water Supply project 8 , which diverts the river and channels its water to Kathmandu through tunnels.
There were several factories along the road, which make water main pipes. Overall, the earthquake damage in Melamchi was severe, mostly affecting vulnerable masonry buildings, whereas the damage to RC buildings 4- to 5-story was limited. For instance, the main street of Melamchi was not completely destroyed Figure 10 A ; most buildings looked undamaged based on their appearances, although several buildings were collapsed.
On the other hand, buildings along a side street were devastated by the earthquakes Figures 10 B,C. The majority of the damaged buildings were made of brick and stone. Along the road, several sections of the slope suffered from shallow landsides Figure 10 D , their debris blocked the road at one time but was removed. There was a steel truss bridge with RC deck for vehicle crossing; the bridge was not damaged inspected from backside.
It has been reported that further damage occurred in Melamchi due to the 12 May Mw7. A further damage survey in Melamchi is required to investigate the effects of the aftershock with respect to the incurred damage prior to the aftershock although it is beyond the scope of this study.
Damage in Melamchi see Figure 3. A Main street in Melamchi. B Damaged stone masonry house. C Devastated street in Melamchi. D Shallow landslide along the main road. Survey Results in Trishuli The survey was conducted along the road to Trishuli about 30 km north—west of Kathmandu; Figure 3. One of the purposes of the trip was to investigate the earthquake damage near the Trishuli hydroelectric station. Trishuli was closer to the hypocenter of the Mw7.
Along the way to Trishuli, earthquake damage in Ranipauwa about 15 km north—west of Kathmandu appeared relatively minor. Proceeding further north—west, earthquake damage to houses and landslides along the mountain slopes were observed more frequently. The rock fall, as secondary hazard, can be dangerous; a bus was hit by fallen boulder and several people were killed Figure 11 A.
The building materials of these damaged buildings were of poor quality; for example, two different types of the fragile bricks were used in one of the damaged houses Figure 11 C. According to local residents, many buildings were collapsed due to the 25 April Mw6.
Damage in Trishuli see Figure 3. A Destroyed bus due to boulder fall. B Damaged brick masonry house in Battar. C Different types of bricks used in the damaged masonry house in Battar. D Ground fissures in the Trishuli dam reservoir. In Trishuli, there was an earth fill dam for hydroelectric power generation. The main body of the dam was the excavated and compacted soil. The height of the dam was 12 m upstream side and 20 m downstream side , and the crest width was about 4 m.In Bhaktapur, several monuments, including the Phasi Deva temple, the Chardham temple and the 17th century Vatsala Durga Temple were fully or partially destroyed. To gain valuable lessons from this tragic event, an earthquake damage investigation team was dispatched to Nepal from 1 May to 7 May It looks like the worst devastation and most deaths in Nepal came from brick buildings, as usual, and tragically predictable--and predicted. To demonstrate this for the Mw7.
As there are several major hydroelectric projects along the Trishuli River as well as in other major rivers in Nepal, ensuring dam safety against large earthquakes is important. Comparison of the observed PGA A and spectral accelerations [0.
But the earthquake—which according to the latest estimates is thought to have killed nearly 4, people—has left scores of Nepalis without adequate food or shelter. Last April, an avalanche swept through Everest's Khumbu Icefall and killed 16 climbers in what was then the deadliest day in the mountain's history. Modern ground motion models adopt extended-source-based distance measures, such as Rrup and Rjb i. The regional map of the visited locations is shown in Figure 3 , and the main survey locations in Kathmandu are indicated in Figure 4. The walls of this building suffered from many major cracks along its height Figure 9 C.
The amplitude—distance plots of PGA and spectral accelerations at 0. For the Kanno06 model, 16th and 84th percentile curves are also shown to indicate a typical range of predicted ground motion variability. For instance, the main street of Melamchi was not completely destroyed Figure 10 A ; most buildings looked undamaged based on their appearances, although several buildings were collapsed. The majority of the damaged buildings were made of brick and stone. It has been reported that further damage occurred in Melamchi due to the 12 May Mw7. Geological Survey USGS , are analyzed to gain scientific insights into ground motions that were experienced during the mainshock and major aftershocks.
Aftershocks In post-earthquake situations, one of the major concerns for evacuees and emergency response teams is the occurrence of major aftershocks, triggering secondary hazards.
Another useful source of information in assessing site amplification potential of near-surface soil deposits in Kathmandu is the USGS global VS30 server Wald and Allen, 4. An earthquake with a magnitude of 7. These hazard estimates are obtained for rock sites, therefore, when typical soil sites are considered e. The Gutenberg—Richter law describes the frequency—magnitude characteristics of an aftershock sequence, whereas the modified Omori law models a temporal decay of an aftershock occurrence rate.
A Destroyed bus due to boulder fall. The retaining walls were structurally intact and suffered from minor cracks and outward deformation only, whereas the natural slopes at both ends of the highway embankments experienced noticeable settlements Figure 9 E. The amount of settlements was about 0.