Search

The 2015 Mw 7.8 Gorkha, Nepal, earthquake occurred in the central Himalayan collisional orogenic belt, which demonstrated complex fault kinematics and significant surface deformation. The coseismic deformation has been well documented by previous studies using Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data. However, due to some limitations of spatially sparse GPS stations and InSAR only-one-dimensional observation in the line-of-sight (LOS) direction, the complete distribution and detailed spatial variation of the three-dimensional surface deformation field are still not fully understood. In this study, we reconstructed the three-dimensional coseismic deformation fields using multi-view InSAR observations and investigated the refined surface deformation characteristics during this event. We firstly obtained four ascending and descending InSAR coseismic deformation maps from both Sentinel-1A/B and ALOS-2 data. Secondly, we obtained the synthetic north-south deformation field from our best-fitting slip distribution inversions. Finally, we calculated three-dimensional deformation fields, which were consistent with coseismic GPS displacements but with higher resolution. We found that the surface deformation is dominated by horizontal southward motion and vertical uplift and subsidence, with minor east-west deformation. In the north-south direction, the whole deformation area reaches at least 150 × 150 km with a maximum displacement of ~1.5 m. In the vertical direction, two areas, including uplift in the south and subsidence in the north, are mapped with a peak displacement of 1.5 and −1.0 m, respectively. East-west deformation presented a four-quadrant distribution with a maximum displacement of ~0.6 m. Complex thrusting movement occurred on the seismogenic fault; overall, there was southward push motion and wave-shaped fold motion.

Earthquakes are unpredictable and potentially destructive natural disasters that take a long time to recover from. Monitoring post-earthquake human activity (HA) is of great significance to recovery and reconstruction work. There is a strong correlation between night-time light (NTL) and HA, which aid in the study of spatiotemporal changes in post-earthquake human activities. However, seasonal and noise impact from National Polar-Orbiting Partnership Satellite Visible Infrared Imaging Radiometer Suite (NPP/VIIRS) data greatly limits their application. To tackle these issues, random noise and seasonal fluctuation of NPP/VIIRS from January 2014 to December 2018 is removed by adopting the seasonal-trend decomposition procedure based on loess (STL). Based on the theory of post-earthquake recovery model, a post-earthquake night-time light piecewise (PNLP) pattern is explored by employing the National Polar-Orbiting Partnership Satellite Visible Infrared Imaging Radiometer Suite (NPP/VIIRS) monthly data. PNLP indicators, including pre-earthquake development rate (kp), recovery rate (kr1), reconstruction rate (kr2), development rate (kd), relative reconstruction rate (krp) and loss (S), are defined to describe the PNLP pattern. Furthermore, the 2015 Nepal earthquake is chosen as a case study and the spatiotemporal changes in different areas are analyzed. The results reveal that: (1) STL is an effective algorithm for obtaining HA trend from the time series of denoising NTL; (2) the PNLP pattern, divided into four phases, namely the emergency phase (EP), recovery phase (RP-1), reconstruction phase (RP-2), and development phase (DP), aptly describes the variation in post-earthquake HA; (3) PNLP indicators are capable of evaluating the recovery differences across regions. The main socio-economic factors affecting the PNLP pattern and PNLP indicators are energy source for lighting, type of building, agricultural economy, and human poverty index. Based on the NPP/VIIRS data, the PNLP pattern can reflect the periodical changes of HA after earthquakes and provide an effective means for the analysis and evaluation of post-earthquake recovery and reconstruction.

Abstract There is still no consensus on seismo-ionospheric anomalies and coupling mechanism. One of important reasons is that multi- excitation factors of ionospheric disturbances interfere with the judgment of their source. In this paper, a Linear Model between TEC and F10.7 (LMTF) was built to detect seismo-ionospheric TEC anomalies before and after Nepal earthquake 2015. Firstly, LMTF and Kalman filter (KFM) were utilized to predict TEC and compare with the TEC from Global Ionosphere Map (GIM) for evaluating their prediction accuracies. The statistical results show that the mean square error (MSE), average absolute relative error (Δ ¯) and the correlation coefficient (Corr) between the TEC from GIM and the prediction TEC are ±0.88 TECU, 1.55 and 0.94 and all approximately equal to those of KMF, when their time moving windows are all set to 30 days. Further considering the period of the solar, the time moving window could be set to 27 days. Then, Sliding Quartile Method (SQM), KFM and LMTF were utilized to detect TEC anomalies above epicenter, International GNSS stations in affected area and the globe during the period of 15 days before and 10 days after Nepal earthquake by comparison. The comparative results demonstrate that LMTF is more effective to detect the TEC anomaly caused by Nepal earthquake in temporal and spatial scale. Moreover, the characteristics of the TEC anomalies caused by Nepal earthquake using LMTF are in agreement with the results of previous studies on Wenchuan and Nepal earthquake cases. At last, the coupling mechanism was discussed based on the characteristics of seismo-ionospheric TEC anomalies. It is supposed that the mechanism of seismo-ionospheric TEC anomalies can be explained by the combination action of internal gravity waves (IGWs) generated by the solar terminator and the electric field in seismogenic zone formed by the electric field effect of geochemical process and the piezo-electric potential effect of rock. [ABSTRACT FROM AUTHOR]

Shelters are additional arrangements in a complex urban system to accommodate displaced populations following any major hazards. Standard shelters are designed to provide basic services to support a normal life by ensuring the security, privacy, and dignity of the affected community. In a complex urban system, rather than staying as an isolated entity, shelter facilities act as an integrated part of urban dynamics influenced by other elements and leaving challenges for future management. This research found three major domains—urban settlements, urban slums, and peri-urban areas from where population surge directed to the temporary shelter in Ratna Park/Tundikhel. It is also observed that drivers of population surge are unique for different domains based on disaster consequences and socio-economic conditions of the communities. Quality of basic survives and their accessibility influenced in evacuation decision making by the disaster-displaced population. Based on the observations and findings, this article proposed two conceptual models/frameworks: (1) comprehensive shelter surge model, and (2) system dynamic model for temporary shelter operation and management in the urban environment. [ABSTRACT FROM AUTHOR]

The 2015 Gorkha (Nepal) earthquake caused tremendous damage to the cultural heritage buildings in the Kathmandu Valley. After the event, extensive field investigations were conducted to assess the seismic damages to the cultural heritage buildings in the Kathmandu, Patan, and Bhaktapur Durbar Squares. Major damages included failure of structural and non-structural components, tilting and collapse. Masonry-timber structures and masonry structures, the two structural types for the investigated heritage buildings, are analyzed separately in terms of the damage patterns. Damage classification criteria are proposed for the two structural types. Based on the criteria, a total of 68 structures investigated (52 masonry-timber and 16 masonry structures) are classified into four damage grades. The results show that only 30.8% of the masonry-timber structures and 18.8% of the masonry structures exhibited negligible to slight damage; the rest suffered more severe damage or even collapse. The seismic performance of the masonry-timber structures was slightly better than that of the masonry structures. Seismic retrofit strategies are recommended for the preservation of Nepalese cultural heritage buildings. [ABSTRACT FROM AUTHOR]

The devastating earthquake that struck Nepal in 25 April (Mw7.8) and 12 May (Mw7.3) 2015 have triggered numerous landslides and reactivated existing landslides extending over large areas. These two shocks mostly affected the northwest and northeast region of Kathmandu which accelerated large region along with southward up thrusting in the region. To detect the event of the landslides in time and space satellite images have been analysed using space remote sensing techniques like pseudo colour transformation technique and was employed to pre and post-earthquake images of the event to bring out only landslide affected areas from the image by masking the remaining part, where field based survey of the landslides provided information on real nature of it, slope and rock type. Surprisingly the observed mass movements are mostly belong to debris flow and rock fall types beginning from the top part of the ridge slope with south-westerly faces i.e. sun facing. Further, satellite images of different dates could be gathered which facilitated analysis on development of landslide with time. This study also revealed that the NE-SW trending geological faults have controlled the landslide occurrence especially in Ramche area and along the Bagmati river valley near Shital-chowk village on Kathmandu-Hetauda road. [ABSTRACT FROM AUTHOR]

The 2015 earthquake caused widespread damage in Nepal causing monetary loss of billions of dollars. Majority the households in Nepal are engaged in informal sector and relies heavily on local market and tourism. In Nepal, livelihood and households are not only linked through livelihood, built space, goods and services, but also through culture and traditions. As a result, understanding their linkage is important for effective recovery to further facilitate strengthening of community resilience. This article focuses on household and livelihood recovery within the first two years of the earthquake in traditional settlements Bungamati. Participatory mapping followed by narrative analysis of the interviews is used for understanding the linkages. Narrative analysis of the field interviews conducted with the shop owners generated six types household assets. Further, these assets were linked with the various coping strategies in the post disaster situation. The findings suggest three main type of coping strategies for livelihood recovery namely; Intensifying use of capitals, dependency on social capital and mitigate consumption and expenditure. [ABSTRACT FROM AUTHOR]

An Mw7.8 earthquake occurred in Nepal on April 25 , 2015. The epicenter is (28.147°N, 84. 708°E). It occurred aks a result of fault thrusting on the main thrust interface between the subducting India plate and the overriding Eurasia plate to the north. The movement and locking of the main Himalaya thrust (MHT)fault and its seismic potential need us to do some further study. We collected 6 sets of GFS horizontal velocity field covering Indian platen Qinghai-Tibet plateau and adjacent areas， and transformed them to an approximately unified reference frame. Fhen we used the negative disloca-lion model of DEF'NODE to invert the spatial fault locking and fault slip deficit in the MHT, and analyzed the far-near field movement of the fault combining with the GFS velocity profiles. Fhe results show that the locking depth of the MHT is about 18-24 km, and the locking width of the fault plane reaches 102-136 km. The locking depth is deeper and the locking width of the plane is wider in the fault between two major historical earthquakes rupture area and the fault of no historical earthquakes. The Mw7.8 Nepal Earthquake is located in the area between two major historical earthquakes rupture area where the fault is relatively deeply and lightly locked. The total slip deficit and vertical compressional slip deficit of the MHT gradually reduce from east to west. The vertical com-pressional slip deficit of the easternmost segment of the fault is about 28.0 mm/a, which gradually reduces in the tightly locked area, and decreases to about 6.4 mm/a at the westernmost segment. The dextral strike-slip of parallel slip deficit changes from 0.4-7.0 mm/a from east to wevSt in Nepal. The three profile model fitting results of the MHT are consistent with the slip deficit of corresponding fault plane, and it is very like the profile results acrOvSS the middle segment of the Longmenshan fault before the 2008 Wenchuan earthquake, which reflects that the MHT is tightly locked. We estimated that the Mw7.8 earthquake recurrence is about 230 years according to the peak slip and the vertical compressional slip deficit at the epicenter. Because only the 1905 India Kangra 8.0 earthquake，the 1934 Nepal Bihar 8.1 earthquake and this Nepal Mw7.8 earthquake happened for recent 500 years, it is pOvSsible that M8 earthquake happens on this fault evSpecially on the border of Nepal and India and possibly unruptured Bhutan. [ABSTRACT FROM AUTHOR]

Ionospheric anomalies possibly associated with large earthquakes, particularly coseismic ionospheric disturbances, have been detected by global positioning system (GPS). A large Nepal earthquake with magnitude Mw 7.8 occurred on April 25, 2015. In this paper, we investigate the multi-dimensional distribution of near-field coseismic ionospheric disturbances (CIDs) using total electron content (TEC) and computerized ionospheric tomography (CIT) from regional GPS observational data. The results show significant ionospheric TEC disturbances and interesting multi-dimensional structures around the main shock. Regarding the TEC changes, coseismic ionospheric disturbances occur approximately 10–20 min after the earthquake northeast and northwest of epicentre. The maximum ridge-to-trough amplitude of CIDs is up to approximately 0.90 TECU/min. Propagation velocities of the TEC disturbances are 1.27 ± 0.06 km/s and 1.91 ± 0.38 km/s. It is believed that the ionospheric disturbances are triggered by acoustic and Rayleigh waves. Tomographic results show that the three-dimensional distribution of ionospheric disturbances obviously increases at an altitude of 300 km above the surrounding epicentre, predominantly in the entire region between 200 km and 400 km. Significant ionospheric disturbances appear at 06:30 UT from tomographic images. This study reveals characteristics of an ionospheric anomaly caused by the Nepal earthquake. [ABSTRACT FROM AUTHOR]

The 2015 Nepal Mw7. 9 earthquake occurred in the central segment of the Himalayan colli­sion zone, where the rigid Indian plate thrusts beneath the Tibetan Plateau. The published focal mechanism solution shows this earthquake was dominated by thrust slip but minor right-lateral strike slip, so a significant vertical deformation appears on the surface caused by this event. Accurate coseis- inic vertical displacements in this region provide us a scarce chance to understand the long term uplift of the Himalaya and southern Tibet. By processing the resurvey ‘in-situ’ GPS data . we obtained a coseisrnic GPS horizontal displacement field at high precision. In combination with the coseisrnic GPS displacements and the L-band InSAR line of sight (LOS) observations, we extract the coseisrnic verti­cal deformation field due to the Nepal earthquake with a mean uncertainty of 1^2 cm and spatial reso­lution of 1 kin× 1 km. The result shows that the Kathmandu was uplifted '"'O. 95 m after the main shock. In particular, the Mount Everest and Shishapangma subsided'-'2-3 cm and ~-20 cm. respec­tively. The two-dimensional elastic half-space dislocation model suggests that the mean rupture width of the Nepal earthquake was^^O km and the average coseisrnic slip reached 4 rn. Our results indicate that the slip deficit of this event was equivalent to a moment magnitude of Mw 7.89 assuming a rup­ture length of 120 km and rigidity of 30 GPa. which is consistent with seismological estimation. The 2015 Nepal earthquake broke the trend of long term uplift in the central segment of higher Himalaya during an interseismic period. Whether this segment will continue to subside or uplift after the event can be discriminated by continuous post-seismic geodetic measurements. [ABSTRACT FROM AUTHOR]

The 25 April 2015 Mw 7.8 Gorkha, Nepal earthquake occurred at the bottom edge of the locked portion of the Main Himalayan Thrust, where the Indian plate underthrusts the Himalayan wedge. The earthquake was followed by a number of large aftershocks, but not preceded by any foreshocks within ~ 3 weeks according to the NEIC or ISC catalog. However, due to the limited station coverage of the local seismic network, a large portion of events may not be reported in routine catalogs. Here, we employ the matched filter technique to recover the undocumented earthquakes for the period beginning 80 days before through 30 days after the 2015 Gorkha earthquake. We detect twice as many aftershocks as those listed in the ISC catalog. We observe an along-strike aftershock expansion after the mainshock and before the largest Mw 7.3 aftershock that occurred on 12 May 2015. Repeating earthquakes are found to the ESE of the mainshock rupture area, suggesting that the expansion may be partially driven by afterslip. In addition, we observe a significant increase in seismicity rate ~ 3–4 days prior to the mainshock, initiating ~ 6 h after a M 5.2 earthquake, located ~ 240 km to the NW of the mainshock. The increase of seismic activities occurs in a wide region around the Gorkha principal slip zone, indicating the effect of delayed dynamic triggering may contribute to the large-scale unloading process prior to the 2015 Gorkha mainshock. [ABSTRACT FROM AUTHOR]

Due to the continuous movement of underthrusting Indian plate beneath the Eurasian plate the strain energy accumulates, which is released substantially in the form of great earthquakes. It is yet to be released in the unruptured zone which lies between the two great earthquakes viz. 1934 Bihar-Nepal earthquake and 1905 Kangra earthquake. This zone has been termed as the Central Seismic Gap (CSG). The occurrence of previous great earthquakes and recent Nepal earthquakes, gives a clue to the probable location of future great earthquake. On the basis of analysis of seismicity in the locked portion and the stress drop analysis the CSG has been redefined and location of probable zone of future great earthquake has been demarcated. [ABSTRACT FROM AUTHOR]

This article highlights the importance of various (im)mobilities that were induced by the massive 7.8-magnitude earthquake that struck Nepal on 25 April 2015. It analyzes over 120 news articles published in the immediate aftermath of the earthquake, arranging these into a mobility-centric narrative that highlights the politics of movement in the disaster’s wake. Drawing on the theoretical and methodological “mobilities turn”, I introduce the concept of linked (im)mobilities to demonstrate the complex dialectics structuring (im)mobilities after the disaster. More specifically, Nepal’s post-earthquake (im)mobilities intersected with one another and with a variety of geographic and political factors to produce a mutually constitutive web of contingent movements. Attending to these not only underscores the centrality of (im)mobilities themselves. By raising questions of scale, inequality, bordering, and “islanding”, the approach advanced here widens our analytical frame. It offers a conceptual architecture capable of encompassing more factors (beyond mobility), thereby facilitating a broader understanding of the disaster event and its various outcomes. [ABSTRACT FROM AUTHOR]

The 2015 Nepal earthquake and its aftershocks not only caused huge damage with severe loss of life and property, also induced many geohazards with the major type of landslide which should bring continuous threats to the affected region. To gain a better understanding of the landslides induced by this earthquake, we proposed a pixel-based change detection method for postearthquake landslide mapping by using bitemporal Landsat-8 remote sensing data [May 29, 2014 (pre-earthquake) and June 1, 2015 (postearthquake)]. Two river valleys (Trishuli river valley and Sun Koshi river valley) that contain important economic arteries linking Nepal and China were selected as the study areas. Validation of the mapping results with postearthquake high-resolution images from Google Earth shows that the pixel-based landslide mapping method is able to identify landslides with relatively high accuracy, and it also approves the applicability of Landsat-8 satellite for landslide mapping with its multispectral information. The spatial distribution analysis indicates that both river valleys are substantially affected by landslides, and the situation is even more serious in the high mountain areas. Landslides are generally found in areas of high elevation and large surface slopes, with mean values above 1600 m and 30°, respectively. These findings suggest that these areas suffer greatly from these geohazards, and the threat will continue for the next few years. [ABSTRACT FROM PUBLISHER]

For decades, the distinction between statistical models and machine learning ones has been clear. The former are optimized to produce interpretable results, whereas the latter seeks to maximize the predictive performance of the task at hand. This is valid for any scientific field and for any method belonging to the two categories mentioned above. When attempting to predict natural hazards, this difference has lead researchers to make drastic decisions on which aspect to prioritize, a difficult choice to make. In fact, one would always seek the highest performance because at higher performances correspond better decisions for disaster risk reduction. However, scientists also wish to understand the results, as a way to rely on the tool they developed. Today, very recent development in deep learning have brought forward a new generation of interpretable artificial intelligence, where the prediction power typical of machine learning tools is equipped with a level of explanatory power typical of statistical approaches. In this work, we attempt to demonstrate the capabilities of this new generation of explainable artificial intelligence (XAI). To do so, we take the landslide susceptibility context as reference. Specifically, we build an XAI trained to model landslides occurred in response to the Gorkha earthquake (April 25, 2015), providing an educational overview of the model design and its querying opportunities. The results show high performance, with an AUC score of 0.89, while the interpretability can be extended to the probabilistic result assigned to single mapping units. • A new generation of interpretable machine learning models is tested and presented to predict landslide occurrences. • The landslide susceptibility model is tested with the explainable machine learning approach limiting the black box approach. • A web-GIS platform is developed to showcase the use of explainable artificial intelligence for geoscientific applications. [ABSTRACT FROM AUTHOR]

Following the strong earthquake on April 25, 2015 in Nepal, a team from the University of Porto, in collaboration with other international institutions, made a field study on some of the most affected areas in the capital region of Kathmandu. One of the tasks was the study of a high-rise settle of buildings that were damaged following the earthquake sequence. A survey damage assessment was performed to a 15-storey infilled reinforced concrete structure, which will be detailed in the manuscript. Moreover, ambient vibration tests were carried out to determine the natural frequencies and corresponding vibration modes of the structure. The main aim of this manuscript is to present a numerical study concerning the influence of the masonry infill walls in the structure seismic response. For this, three numerical models were built discriminating the situations with and without damage and nondamaged infill walls. Validation and calibration of the numerical model was ensured by comparing the numerical frequencies with those obtained from ambient vibration tests. In addition, linear elastic analyses were carried out, using real accelerograms from the Gorkha earthquake to assess and quantify the major differences between the models in terms of inter-storey drifts ratios, inter-storey shear forces and seismic loadings.

In this study we evaluate stress evolution and change in seismic hazard after the 2015 Gorkha earthquake sequence. We take a methodology usually used in areas with well-established seismic monitoring and apply it to an area with a sparse dataset and a limited time observation window. Our goal is to validate this approach as a rapid response tool for seismic forecasting after large earthquakes. We propose a long-term seismic forecasting model of the Main Himalayan Thrust using the historical earthquake catalogue and regional paleo-seismicity. Through application of the rate-and-state friction model, we evaluate short-term rate evolution after the Gorkha earthquake. The long elapsed time since the last megathrust event and the mainshock coseismic stress increase on the Main Himalayan Thrust suggest high seismic potential in the Lalitpur and Lamjung areas along the fault system. We also calculate the stress change on optimally oriented planes in the region and model the regional seismicity rate using a smoothing kernel method and seismicity since 1921. The location of the consequent earthquakes coincides with areas of high background seismicity rate and areas where stress was enhanced by the M w 7.8 mainshock and M w 7.3 aftershock. We model the change of seismic rate over time and project a fast decrease, due to the short aftershock duration assumption we use. [ABSTRACT FROM AUTHOR]

On 25 April 2015 an Mw 7.8 earthquake occurred in Nepal and caused about 9000 casualties. This earthquake ruptured part of the Main Himalaya Thrust fault, which is due to the convergence of the subducting Indian plate to the overriding Eurasian plate, and showed thrust mechanism with a very small fault dip angle (about 7–10°). We apply teleseismic multiple-array back projection analysis to study the rupture process of this earthquake and find 6 clear high frequency radiation sources (subevents). Our results illustrate a simple unilateral eastward rupture of ∼160 km with relative stable rupture speed of ∼2.8 km/s and a duration of 56 s. The entire rupture processes can be divided into 3 stages. The high frequency radiation appears to be mainly located at the edge of the large slip area, but the subevents have different characteristics in the western and eastern rupture areas. For this 2015 Nepal earthquake, the scales of asperities appear to be mainly controlled by depth, which dominates the overall patterns of slip and high frequency radiation. We finally propose a multiple-scale asperity model with stress and structural heterogeneities along the rupture direction to explain the distribution of high frequency subevents, co-seismic slip, and aftershocks. [ABSTRACT FROM AUTHOR]

Seismic damage surveys and analyses conducted on modes of failure of structures during past earthquakes observed that the asymmetrical buildings show the most vulnerable effect throughout the course of failures (Wegner et al., 2009). Thus, all asymmetrical buildings significantly fails during the shaking events and it is really needed to focus on the accurate analysis of the building, including all possible accuracy in the analysis. Apart from superstructure geometry, the soil behavior during earthquake shaking plays a pivotal role in the building collapse (Chopra, 2012). Fixed base analysis where the soil is considered to be infinitely rigid cannot simulate the actual scenario of wave propagation during earthquakes and wave transfer mechanism in the superstructure (Wolf, 1985). This can be well explained in the soil structure interaction analysis, where the ground movement and structural movement can be considered with the equal rigor. In the present study the object oriented program has been developed in C++ to model the SSI system using the finite element methodology. In this attempt the seismic soil structure interaction analysis has been carried out for T, L and C types piled raft supported buildings in the recent 25th April 2015 Nepal earthquake ( M = 7.8). The soil properties have been considered with the appropriate soil data from the Katmandu valley region. The effect of asymmetry of the building on the responses of the superstructure is compared with the author’s research work. It has been studied/observed that the shape or geometry of the superstructure governs the response of the superstructure subjected to the same earthquake load. [ABSTRACT FROM AUTHOR]

Nepal is one of the most earthquake-prone regions in the world as it lies at the boundary of the actively converging Indo-Australian plate and Eurasian Plate. Most of the infrastructures in Nepal were constructed by individuals based on their own needs and budget without consulting engineers, and several studies have shown that many of these structures are likely to be inadequate in resisting earthquake forces. Though an earthquake design code is present in Nepal, it is not mandatory in every part of the country and people do not follow it properly even where it is mandatory. This paper presents a summary of the reconnaissance survey of a major earthquake of magnitude 7.8 (on 25th of April 2015) with epicentre in Gorkha District in Nepal, followed by a series of aftershocks including magnitude of 7.3 on the 12th of May 2015. This has resulted in 8969 casualties to date and about 900,000 houses and temples were damaged (partially and completely) leaving thousands of people homeless. Problems associated with the current practices in Nepal are discussed in detail and some suggestions are made for improvements in design and construction. Some of the major problems highlighted in the paper include code compliance, quality control in construction, and lack of preparedness. [ABSTRACT FROM PUBLISHER]

In order to satisfy the requirement of high-rate high-precision applications, 1 Hz BeiDou Navigation Satellite System (BDS) satellite clock corrections are generated based on precise orbit products, and the quality of the generated clock products is assessed by comparing with those from the other analysis centers. The comparisons show that the root mean square (RMS) of clock errors of geostationary Earth orbits (GEO) is about 0.63 ns, whereas those of inclined geosynchronous orbits (IGSO) and medium Earth orbits (MEO) are about 0.2-0.3 ns and 0.1 ns, respectively. Then, the 1 Hz clock products are used for BDS precise point positioning (PPP) to retrieve seismic displacements of the 2015 Mw 7.8 Gorkha, Nepal, earthquake. The derived seismic displacements from BDS PPP are consistent with those from the Global Positioning System (GPS) PPP, with RMS of 0.29, 0.38, and 1.08 cm in east, north, and vertical components, respectively. In addition, the BDS PPP solutions with different clock intervals of 1 s, 5 s, 30 s, and 300 s are processed and compared with each other. The results demonstrate that PPP with 300 s clock intervals is the worst and that with 1 s clock interval is the best. For the scenario of 5 s clock intervals, the precision of PPP solutions is almost the same to 1 s results. Considering the time consumption of clock estimates, we suggest that 5 s clock interval is competent for high-rate BDS solutions. [ABSTRACT FROM AUTHOR]

This paper analyzes the activation of the National Disaster Response Framework (NDRF) following the 2015 Nepal/Gorkha earthquake. Among the important policy areas regulated by the NDRF is the mechanism for inter-organizational coordination and cooperation, including that with international organizations. Regarding this, inter-organizational network modeling is performed with the use of social network analysis to identify structural gaps and on-the-ground inter-organizational cooperation previously undetected by the Nepali framework and/or stand-by arrangement of humanitarian organizations. Furthermore, a brief analysis of humanitarian operations’ performance and findings from the ground are also presented in the paper. The research found that the coordination mechanisms and mandatory emergency response operational activities outlined in the NDRF were partially implemented during the six months after the earthquake. As the network model suggests, the NDRF failed to capture the potential of local non-governmental organizations and communities as potential responders, although in reality they also collaborate with international organizations to provide emergency relief and may serve as potential key actors in post-disaster recovery. [ABSTRACT FROM AUTHOR]

This paper summarizes findings from reconnaissance fieldwork conducted five weeks after the Nepal earthquake in 2015. Data were collected using an exploratory, qualitative, semi-inductive approach. Themes converged through classic disaster research theoretical ideas but were also evident through the unique convergence of globalization and development in Nepal. Findings from informal conversations, photographs, and observations of relief and recovery efforts revealed several key themes: the occurrence of organizational transitions in activities and tasks, psychosocial well-being of Nepalese individuals and communities, issues in qualifying the definition of an earthquake victim, and the importance of chronological and social time in recovery processes. Other findings gleaned from fieldwork included uncovering complexities of cultural and social systems such as caste structure in Nepal, issues related to humanitarian logistics, and the vulnerability of special populations such as new mothers and migrant Nepalese. The massive presence of international non-profit organizations created an interesting setting for relief and recovery, mostly described in the section on organization evolutions and transformation. Finally, we also encountered various perceptions about what it means to shift from "relief" to "recovery"- a notion which intersected with all of the four main themes from our findings. [ABSTRACT FROM AUTHOR]

Catastrophic natural disasters often require rapid community mobilization to meet local needs. . This study uses social capital to explore how indigenous Newar communities in Kathmandu responded to the 2015 Nepal earthquake. Data from thirty-three semi-structured interviews with local Newar inhabitants, and secondary sources, form the basis of analysis. Newari prosocial behaviors learned through living in communal neighborhoods, experiences of working for community welfare through cultural Guthi systems, spiritual strength drawn from ancestors and their proud heritage, and the community's high level of equanimity facilitated disaster responses in a positive way. The study provides insights on how social capital among ethnic groups like the Newar influence community responses to natural disasters. [ABSTRACT FROM AUTHOR]

This study is an attempt to underline the lack of preparedness and the nature of immediate further measures to be taken for facing a moderate earthquake in Indian subcontinents. Surprisingly, moderate to severe damage was noticed in structures located in hundreds of kilometres away from epicentre during last Gorkha earthquake. In this context, the present study makes an effort to validate a proposed modified rapid visual screening schemes for low cost houses frequently available in India. This may be used extensively for quick vulnerability assessment of a locality. Examples of retrofitting measures for typical buildings presented in this study may be useful for upgrading the valuable structures. Thus this study may be helpful for quick vulnerability assessment and adopting retrofitting measures for identified structures for earthquake prone developing countries. [ABSTRACT FROM AUTHOR]

After M 7.8 Nepal earthquake occurred, the rearrangement of stresses in the crust commonly leads to subsequent damaging earthquakes. We present the calculations of the coseismic stress changes that resulted from the 25th April event using models of regional faults designed according to south Tibet-Nepal structure, and show that some indicative significant stress increases. We calculate static stress changes caused by the displacement of a fault on which dislocations happen and an earthquake occurs. A M 7.3 earthquake broke on 12 May at a distance of ~ 130 km SEE of the M 7.8 earthquake, whose focus roughly located on high Coulomb stress change (CSC) site. Aftershocks (first 15 days after the mainshock) are associated with stress increase zone caused by the main rupture. We set receiver faults with specified strikes, dips, and rakes, on which the stresses imparted by the source fault are resolved. Four group normal faults to the north of the Nepal earthquake seismogenic fault were set as receiver faults and variant results followed. We provide a discussion on Coulomb stress transfer for the seismogenic fault, which is useful to identify potential future rupture zones. [ABSTRACT FROM AUTHOR]

We present InSAR observations of the co-seismic deformation caused by the Mw 7.8 Gorkha, Nepal earthquake. Analysis of Sentinel-1 data revealed about 100 x 100 sq. km surface deformation with ~1 m upliftment near Kathmandu, and ~0.8 m subsidence towards north along the line of sight of the satellite. The maximum deformation is observed about 40 km east--southeast of the epicentre, suggesting eastward propagation of the rupture. Elastic dislocation modelling revealed that the overall rupture occurred on a 170 km long, 60 km wide fault along the strike (286°) and dipping north (dip = 15°) with large amount of slip (4.5 m) confined to the centre (95 x 22 sq. km) and less slip (0.25 m) on the surrounding part of the fault plane. The corresponding moment magnitude is M w 7.75. The area, depth and dip of the modelled fault plane are fairly consistent and overlap with the location of mid-crustal ramp in the Main Himalayan Thrust. We infer that the earthquake was possibly caused by the release of inter-seismic strain energy accumulated in the environs of mid-crustal ramp due to plate boundary forces. [ABSTRACT FROM AUTHOR]

Coseismic deformation fields caused by the moment magnitude (Mw)7.8 mainshock and Mw7.3 aftershock of the 2015 Gorkha-Nepal earthquake are obtained by analyzing Sentinel-1A/IW ascending and descending interferometry data. Results show that the deformation field associated with the Mw7.8 mainshock roughly resembles a prolate ellipse, extending from the epicenter about 20° east by south. The main region of deformation is about 160 km by 110 km, comprising a large southern area of uplift, and a small northern area of subsidence. Assuming that rupture occurred in a homogeneous elastic half-space, the coseismic fault slip models of the mainshock and aftershock are inverted based on a shallow dip fault constrained by the three data sets, Sentinel-1A/IW descending data, ascending data, and ALOS-2 descending data, separately or in combination. Mainshock slip distributions generated from all three data sets are similar, and inversion constrained by all three in combination reveal a comprehensive fault slip model. Indeed, coseismic slip is mainly distributed within a narrow 40 km zone to the north of the Main Frontal Trust (MFT), and at 6–15 km subsurface depth. In addition, the maximum slip in this event was about 5.1 m, the Mw7.8 mainshock ruptured the deep part of the seismogenic zone, while the region between the southern boundary of the rupture area and the MFT remained locked. Therefore, a considerable earthquake risk remains to the south of Kathmandu. The inverted coseismic slip of the Mw7.3 aftershock was concentrated in a small area, close to, and southeast of the epicenter, with maximum displacement of about 3 m. Finally, because there is no overlap between the two slip areas of the mainshock and aftershock, the gap between them, about 15 km in length, has additional potential to generate future earthquakes. [ABSTRACT FROM AUTHOR]

An earthquake with a magnitude of 7.8 ( M ) occurred at 11:56 NST (local time) on 25 April 2015, in the central part of Nepal (Gorkha).We organized a damage survey team and dispatched it to the affected area for several periods following the earthquake (May 26 to June 3: first trip, June 17 to 24: second trip, August 16 to 21: third trip and October 27 to November 2: forth trip) to investigate the damage and collect data. We found traditional construction methods are stronger than imagined. Many traditional earthquake-resistance technologies exist in Nepal. The first and second surveys were to collect timely statistical information on the damage to brick and stone masonry buildings and to confirm the availability of data and their sources for subsequent surveys. We also carried out a first-hand building damage survey in selected areas. The investigation of the strong-motion data set from the USGS Center for Engineering Strong Motion Data includes information from stations in Nepal that continued to function throughout the main shock and the several subsequent strong aftershocks of the 2015 earthquake. The third and fourth surveys were to collect the every building damage survey in selected areas. The motivation behind the survey was to obtain ground truth data for the calibration and improvement of a wide-area damage estimation system that uses satellite data; the system is currently under development by National Research Institute for Earth Science and Disaster Prevention (NEID) and the Japan Aerospace Exploration Agency (JAXA). A survey of the degree of damage was conducted for every house in Sankhu and Khokana by the European Macroseismic Scale (EMS) -98. This report outlines the findings of this investigation team into various aspects of the earthquake disaster in the Kathmandu Valley. The motivation behind the survey was to obtain ground truth data for the calibration and improvement of a wide-area damage estimation system that uses satellite data. Field surveys confirmed that the severely damaged urban area was well detected by the decrease derived from the ALOS-2 satellite SAR data. The higher classification accuracy for non-damaged area helps to detect the damaged urban area using this technique, immediately after a disaster. [ABSTRACT FROM AUTHOR]

FORMOSAT-2, Taiwan's first remote sensing satellite, was successfully launched in May of 2004 into the Sun-synchronous orbit at 891 kilometers of altitude. With the daily revisit feature, the 2-m panchromatic, 8-m multi-spectral resolution images captured have been used for researches and operations in various societal benefit areas. This paper details the orchestration of various tasks conducted in different institutions in Taiwan in the efforts responding to international disasters. The institutes involved including its space agency-National Space Organization (NSPO), Center for Satellite Remote Sensing Research of National Central University, GIS Center of Feng-Chia University, and the National Center for High-performance Computing. Since each institution has its own mandate, the coordinated tasks ranged from receiving emergency observation requests, scheduling and tasking of satellite operation, downlink to ground stations, images processing including data injection, ortho-rectification, to delivery of image products. With the lessons learned from working with international partners, the FORMOSAT Image Processing System has been extensively automated and streamlined with a goal to shorten the time between request and delivery in an efficient manner. The integrated team has developed an Application Interface to its system platform that provides functions of search in archive catalogue, request of data services, mission planning, inquiry of services status, and image download. This automated system enables timely image acquisition and substantially increases the value of data product. Example outcome of these efforts in recent response to support Sentinel Asia in Nepal Earthquake is demonstrated herein. [ABSTRACT FROM AUTHOR]

On April 23, 2015, the VEI4 (volcanic explosive index) Calbuco volcano abruptly erupted in Chile and the Mw7.9 Nepal earthquake occurred on April 25. In order to investigate the similarities and differences between total electron content (TEC) anomalies preceding these two types of geophysical activities, the TEC time series over preparation zones before the volcanic eruption and earthquake extracted from global ionosphere map were analyzed. We used sunspot numbers (SSN), B z , Dst, and Kp indices to represent the solar-terrestrial environment and eliminate the effects of solar and geomagnetic activities on ionosphere by the sliding interquartile range method with the 27-day window. The results indicate that TEC-negative and -positive anomalies appeared in the 14th and 6th day before the eruption, respectively. The anomalies lasted about 4–6 h with a magnitude of 15–20 TECU. The TEC anomalies were also observed on the 14th and 6th day before the Nepal earthquake with a duration of 6–8 h, and the absolute magnitude of TEC anomalies was within 12–20 TECU. These findings indicate that the magnitude of TEC anomalies preceding volcanic eruption was larger, and the duration of TEC anomalies before the earthquake was longer, which may be associated with their particular physical mechanisms. The TEC anomalies before the Nepal earthquake in the Eastern hemisphere occurred in the afternoon local time, but those before the eruption were observed in the night local time. Peak regions of TEC anomalies did not coincide with the epicenters of geophysical activities, and the TEC anomalies also appeared in the magnetic conjugated region. Both the TEC anomalies in the preparation zone and conjugated region were distributed near the boundaries of equatorial anomaly zone and moved along the boundaries. In the moving process, sometimes the extent or magnitude of TEC anomalies in the conjugated region was larger than that in the preparation zone. Many more GPS stations and receivers should be distributed along the boundaries of equatorial anomaly zone, which will be significant in predicting volcanic eruptions and earthquakes in the low-mid-latitudes. [ABSTRACT FROM AUTHOR]

The spatial pattern and rate of strain accumulation on a fault during the pre- and inter-seismic phases are very important for interpreting the mechanism of earthquakes and evaluating seismic potentials. Here we use global positioning system (GPS) data and the block-dislocation model to invert for the locking degree and slip rate deficit of the Main Himalayan Thrust (MHT) fault in the southern margin of Tibet before the 2015 M w 7.9 Nepal earthquake. Results show that the locking depth and slip rate deficit increase from the west to the east. Along the western segment of the MHT fault (80°E–84°E), the locking depth is estimated to be 12–17 km with a slip rate deficit of 0–5 mm/a; along the central Nepal segment (84°E–87°E), the locking depth is 16–21 km with a slip rate deficit of 6–10 mm/a, whilst along the eastern segment (87°E–90°E), the locking depth increases to 23–26 km with a slip rate deficit of 8–13 mm/a. The 2015 Nepal earthquake initiated at the boundary between the western and central segments, an area with as where the slip rate deficit varies dramatically from 0 to 9 mm/a within 50 km resulting in high energy gradients. High strain concentration along the central and eastern segments leads to unilateral propagation of the rupture to the east. Given the paucity of large seismic events over the previous decades and the current high slip rate deficit, seismic hazard on the eastern Nepal segment remains high. [ABSTRACT FROM AUTHOR]

Earthquakes are one of the most disastrous natural disasters and can cause large-scale loss of life and property. Earthquakes can even destroy the whole cities. Earthquakes have secondary hazards including aftershock, landslide, liquefaction, tsunami and avalanche. And sometimes the earthquake-induced secondary effects are more dangerous than the quake itself. On April 25, 2015, a 7.8-magnitude earthquake struck Nepal. More than 8800 people were killed and 23,000 were injured. About 299,588 country's homes were destroyed and 269,107 were damaged. The earthquake is destructive for the Nepal's economy and social structure. This paper mainly introduces this catastrophe, geological features, secondary hazards and some of the related emergency responses. [ABSTRACT FROM AUTHOR]

Nepal is one of the most earthquake-prone areas in the world. This country is located in the Himalayan tectonic belt and the subduction and collision border of the Indian Ocean and Eurasian Plates. Given its special geological feature, quakes are extremely frequent in this area. An 8.1-magnitude tremor hit Nepal on April 25, 2015, which is the fifth magnitude 8 earthquake that occurred on land in this century. This earthquake caused numerous casualties and severe destruction. From a Chinese perspective, this article provides a brief introduction into the catastrophe, the emergency response that follows, and several related reflections. [ABSTRACT FROM AUTHOR]

This paper discusses comparison of recent observed ground motion parameters of Gorkha Nepal earthquake of April 25, 2015 ( M 7.8) with the predicted ground motion parameters using existing attenuation relation of the Himalayan region. The earthquake took about 8000 lives and destroyed thousands of buildings of poor quality, and the earthquake was felt by millions of people living in Nepal, China, India, Bangladesh, and Bhutan. The knowledge of ground parameters is very important in developing seismic code of seismic-prone regions like Himalaya for better design of buildings. The ground parameters recorded in recent earthquake event and aftershocks are compared with attenuation relations for the Himalayan region, and the predicted ground motion parameters show good correlation with the observed ground parameters. The results discussed in this paper will be of great use to civil engineers in updating existing building codes in the Himalayan and surrounding regions and also for the evaluation of seismic hazards. The results clearly show that the attenuation relation developed for the Himalayan region should only be used, and other attenuation relations based on other regions fail to provide good estimate of observed ground motion parameters. [ABSTRACT FROM AUTHOR]

The extensive damage to buildings caused by the Nepal M 8.1 earthquake has attracted much attention by the international community. After the preliminary scientific investigations on the different affected areas in Nepal, the construction and damage characteristics of five different types of buildings commonly existing in Nepal were discussed and the reasons of their disaster performance were analyzed. Types of buildings investigated include reinforced concrete (RC) frame structures, rubble structures, brick-wood structures, raw soil structures, and brick-wood structures of historic buildings. In addition, the weak links of the seismic design were pointed out, which was very important for the post-earthquake reconstruction and recovery, and gave a preliminary explanations for the damage experienced. [ABSTRACT FROM AUTHOR]

Housing reconstruction is a major and critical task to be carried out in the aftermath of a disaster in developing countries. The agencies responsible for managing and implementing these programmes tend to promote the success of these interventions. Following the Bourdieusian framework, and undertaking qualitative research in the four most-affected districts in Nepal, we go beyond the narratives of a successful reconstruction programme to show how reconstruction is a complex and contested socio-political field. Despite many concerns raised, most of the participants felt the post-earthquake housing to be rāmro (nice or beautiful); however, this paradox was not dealt with sufficiently in previous studies. To understand the contradictions, our paper engages with Bourdieu's theory of habitus and symbolic capital. Our findings show that the post-earthquake reconstruction produced houses unfit for purpose. They essentially replaced vernacular design and traditional construction technologies with concrete houses that are spatially insufficient, climatically unsuitable, and practically inconvenient for everyday rural life. Moreover, our paper shows that disaster-stricken locations are not only sites for rebuilding and reconstruction, but they are also social arenas for struggles, competition, and profit maximisation. Therefore, the article builds on debates on disaster profiteering through a Bourdieusian lens. Our paper ends by recognising the limitations of the current work and by discussing the scope for future research. [ABSTRACT FROM AUTHOR]

We use ALOS-2 and Sentinel-1 data spanning 2015–2020 to obtain the post-seismic deformation of the 2015 Mw 7.8 Nepal earthquake. ALOS-2 observations reveal that the post-seismic deformation was mainly distributed in four areas. A large-scale uplift deformation occurred in the northern subsidence area of the co-seismic deformation field, with a maximum uplift of ~80 mm within 4.5 yr after the mainshock. While in the southern coseismic uplift area, the direction of the post-seismic deformation is generally opposite to the co-seismic deformation. Additionally, two notable deformation areas are located in the region around 29° N, and near the MFT, respectively. Sentinel-1 observations reveal post-seismic uplift deformation on the north side of the co-seismic deformation field with an average rate of ~20 mm/yr in line-of-stght. The kinematic afterslip constrained by InSAR data shows that the frictional slip is distributed in both updip and downdip areas. The maximum cumulative afterslip is 0.35 m in downdip areas, and 0.2 m in the updip areas, constrained by the ALOS measurements. The stress-driven afterslip model shows that the afterslip is distributed in the downdip area with a maximum slip of 0.3 m during the first year after the earthquake. Within the 4.5 yr after the mainshock, the estimated moment released by afterslip is ~1.5174 × 1020 Nm,about 21.2% of that released by the main earthquake. [ABSTRACT FROM AUTHOR]