scholarly journals Liquefaction hazard assessment and ground failure probability analysis in the Kathmandu Valley of Nepal

2022 ◽  
Vol 9 (1) ◽  
Author(s):  
Mandip Subedi ◽  
Indra Prasad Acharya
Keyword(s):  
Soil Liquefaction ◽  
Kathmandu Valley ◽  
Borehole Data ◽  
Gorkha Earthquake ◽  
Engineering Structures ◽  
Liquefaction Potential ◽  
Ground Failure ◽  
2015 Gorkha Earthquake ◽  
Scenario Earthquakes ◽  
Liquefaction Hazard

AbstractDuring the 2015 Gorkha Earthquake (Mw7.8), extensive soil liquefaction was observed across the Kathmandu Valley. As a densely populated urban settlement, the assessment of liquefaction potential of the valley is crucial especially for ensuring the safety of engineering structures. In this study, we use borehole data including SPT-N values of 410 locations in the valley to assess the susceptibility, hazard, and risk of liquefaction of the valley soil considering three likely-to-recur scenario earthquakes. Some of the existing and frequently used analysis and computation methods are employed for the assessments, and the obtained results are presented in the form of liquefaction hazard maps indicating factor of safety, liquefaction potential index, and probability of ground failure (PG). The assessment results reveal that most of the areas have medium to very high liquefaction susceptibility, and that the central and southern parts of the valley are more susceptible to liquefaction and are at greater risk of liquefaction damage than the northern parts. The assessment outcomes are validated with the field manifestations during the 2015 Gorkha Earthquake. The target SPT-N values (Nimproved) at potentially liquefiable areas are determined using back analysis to ascertain no liquefaction during the aforesaid three scenario earthquakes.

scholarly journals Probabilistic Liquefaction Potential of Kathmandu Soil Based On Standard Penetration Tests

2021 ◽  
Author(s):  
Mandip Subedi ◽  
Indra Prasad Acharya
Keyword(s):  
Probabilistic Approach ◽  
Kathmandu Valley ◽  
Ground Acceleration ◽  
Liquefaction Potential ◽  
Earthquake Scenarios ◽  
Testing Procedures ◽  
Scenario Earthquakes ◽  
Liquefaction Hazard ◽  
First Order Second Moment ◽  
Penetration Tests

Abstract Despite being a liquefaction susceptible zone, Kathmandu Valley soil in Nepal has limited studies on liquefaction potential and most of them are based on the deterministic approach. Although this method is widely used, it ignores the uncertainties of seismic parameters such as peak ground acceleration, amax, and earthquake magnitude, Mw as well as the inherent variabilities of soil layers, in-situ testing procedures, and geotechnical properties. On the other hand, the probabilistic approach helps assess the liquefaction potential by considering all these uncertainties. In this study, we assess the liquefaction hazard in the Kathmandu Valley using the first-order second-moment (FOSM) method as a probabilistic approach for liquefaction hazard assessment. The assessment is done for three likely-to-recur scenario earthquakes utilizing the geotechnical data of 1510 boreholes. The soils are characterized geotechnically to further assess susceptibility criteria of liquefaction in the valley. The assessment reveals that the central part of the valley is more vulnerable to liquefaction than other parts and the liquefaction probability increases with increasing depth up to 9 m, after which has geared down the value. Moreover, a relationship between the probability of liquefaction (PL) and the factor of safety (FS) against liquefaction is established. The hazard maps prepared for different earthquake scenarios can be useful for future infrastructure planning in Kathmandu Valley.

scholarly journals The Influence of Surface Topography on the Weak Ground Shaking in Kathmandu Valley during the 2015 Gorkha Earthquake, Nepal

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 678
Author(s):  
Mark van der Meijde ◽  
Md Ashrafuzzaman ◽  
Norman Kerle ◽  
Saad Khan ◽  
Harald van der Werff
Keyword(s):  
Numerical Simulations ◽  
Surface Topography ◽  
Seismic Energy ◽  
Spectral Element ◽  
Kathmandu Valley ◽  
Ground Displacement ◽  
Gorkha Earthquake ◽  
Ground Shaking ◽  
Earthquake Scenarios ◽  
2015 Gorkha Earthquake

It remains elusive why there was only weak and limited ground shaking in Kathmandu valley during the 25 April 2015 Mw 7.8 Gorkha, Nepal, earthquake. Our spectral element numerical simulations show that, during this earthquake, surface topography restricted the propagation of seismic energy into the valley. The mountains diverted the incoming seismic wave mostly to the eastern and western margins of the valley. As a result, we find de-amplification of peak ground displacement in most of the valley interior. Modeling of alternative earthquake scenarios of the same magnitude occurring at different locations shows that these will affect the Kathmandu valley much more strongly, up to 2–3 times more, than the 2015 Gorkha earthquake did. This indicates that surface topography contributed to the reduced seismic shaking for this specific earthquake and lessened the earthquake impact within the valley.

Characterizing the Kathmandu Valley sediment response through strong motion recordings of the 2015 Gorkha earthquake sequence

2017 ◽  
Vol 714-715 ◽  
pp. 146-157 ◽  
Author(s):  
S. Rajaure ◽  
D. Asimaki ◽  
E.M. Thompson ◽  
S. Hough ◽  
S. Martin ◽  
...  
Keyword(s):  
Strong Motion ◽  
Earthquake Sequence ◽  
Kathmandu Valley ◽  
Gorkha Earthquake ◽  
2015 Gorkha Earthquake

scholarly journals Introduction and Application of a Simple Probabilistic Liquefaction Hazard Analysis Program: HAZ45PL Module

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Jui-Ching Chou ◽  
Pao-Shan Hsieh ◽  
Po-Shen Lin ◽  
Yin-Tung Yen ◽  
Yu-Hsi Lin
Keyword(s):  
Hazard Analysis ◽  
Probabilistic Approach ◽  
Soil Liquefaction ◽  
Shallow Foundation ◽  
Evaluation Procedure ◽  
Liquefaction Potential ◽  
Probability Map ◽  
Liquefaction Hazard ◽  
Potential Map ◽  
The Government

The 2016 Meinong Earthquake hit southern Taiwan and many shallow foundation structures were damaged due to soil liquefaction. In response, the government initiated an investigation project to construct liquefaction potential maps for metropolitans in Taiwan. These maps were used for the preliminary safety assessment of infrastructures or buildings. However, the constructed liquefaction potential map used the pseudo-probabilistic approach, which has inconsistent return period. To solve the inconsistency, the probabilistic liquefaction hazard analysis (PLHA) was introduced. However, due to its complicated calculation procedure, PLHA is not easy and convenient for engineers to use without a specialized program, such as in Taiwan. Therefore, PLHA is not a popular liquefaction evaluation procedure in practice. This study presents a simple PLHA program, HAZ45PL Module, customized for Taiwan. Sites in Tainan City and Yuanlin City are evaluated using the HAZ45PL Module to obtain the hazard curve and to construct the liquefaction probability map. The liquefaction probability map provides probabilities of different liquefaction potential levels for engineers or owners to assess the performance of an infrastructure or to design a mitigation plan.

scholarly journals The 2015 Gorkha Earthquake and response of the Kathmandu Valley sediments

2015 ◽  
Vol 49 (1) ◽  
pp. 1-5
Author(s):  
Sudhir Rajaure ◽  
Megh Raj Dhital ◽  
Lalu Prasad Paudel
Keyword(s):  
Source Zone ◽  
Great Earthquake ◽  
Kathmandu Valley ◽  
Main Central Thrust ◽  
Gorkha Earthquake ◽  
Ground Acceleration ◽  
Low Frequencies ◽  
High Frequencies ◽  
Nepal Earthquake ◽  
2015 Gorkha Earthquake

The Gorkha Earthquake occurred on the gently dipping part of the Main Himalayan Thrust (MHT), close to the Main Central Thrust (MCT). This earthquake possibly occurred in the source zone of the 1833 Nepal Earthquake (Mw 7.6), which occurred after 182 years. The region between the 1905 Kangra Earthquake and 1934 Bihar-Nepal Earthquake has not produced any great earthquake since the last 500 years and still remains a potential site for great earthquake(s) in future. The Kathmandu Valley witnessed moderate ground acceleration and comparatively large velocity as recorded at Kantipath during the Mw 7.8, Gorkha Earthquake. The analysis of the records show that high frequencies were damped and low frequencies were dominant over the sedimentary basin, which can be attributed to the response of the sediments underneath. Because of damping of high frequencies, the engineered, low storey buildings were less damaged and resisted the ground shaking comparatively well. However, on the other hand, the historical monument 'Dharahara' collapsed completely and the high rise apartment buildings suffered more because of the dominance of low frequencies.

scholarly journals LPI Based Earthquake Induced Soil Liquefaction Susceptibility Assessment at Probashi Palli Abasan Project Area, Tongi, Gazipur, Bangladesh

2018 ◽  
Vol 10 (2) ◽  
pp. 105-116
Author(s):  
A. H. Farazi ◽  
N. Ferdous ◽  
A. S. M. M. Kamal
Keyword(s):  
Threshold Value ◽  
Flood Plain ◽  
Standard Penetration Test ◽  
Soil Liquefaction ◽  
Cumulative Frequency ◽  
Liquefaction Potential ◽  
Project Area ◽  
Potential Index ◽  
Liquefaction Hazard ◽  
Simplified Procedure

This study aims at evaluation of seismic soil liquefaction hazard potential at Probashi Palli Abasan Project area of Tongi, Gazipur, exploiting standard penetration test (SPT) data of 15 boreholes, following Simplified Procedure. Liquefaction potential index (LPI) of each borehole was determined and then cumulative frequency distribution of clustered LPI values of each surface geology unit was determined assuming cumulative frequency at LPI = 5 as the threshold value for liquefaction initiation. By means of geotechnical investigation two surface geological units—Holocene flood plain deposits, and Pleistocene terrace deposits were identified in the study area. We predicted that 14% and 24% area of zones topped by Pleistocene terrace deposits and zones topped by Holocene flood plain deposits, respectively, would exhibit surface manifestation of liquefaction as a result of 7 magnitude earthquake. The engendered hazard map also depicts site specific liquefaction intensity through LPI values of respective boreholes, and color index, which was delineated by mapping with ArcGIS software. Very low to low, and low to high liquefaction potential, respectively, was found in the areas covered by Pleistocene terrace deposits and Holocene flood plain deposits. LPI values of both units are such that sand boils could be generated where LPI > 5.

scholarly journals The Performance of Slender Monuments during the 2015 Gorkha, Nepal, Earthquake

2017 ◽  
Vol 33 (1_suppl) ◽  
pp. 321-343 ◽  
Author(s):  
Anjali Mehrotra ◽  
Matthew DeJong
Keyword(s):  
Ground Motion ◽  
Low Frequency ◽  
Kathmandu Valley ◽  
Discrete Element Modeling ◽  
Frequency Content ◽  
Gorkha Earthquake ◽  
Long Period ◽  
2015 Gorkha Earthquake ◽  
Long Period Ground Motion ◽  
2015 Gorkha Nepal Earthquake

This paper studies damage to a few specific monuments in the Kathmandu Valley that were either partially or completely destroyed during the 2015 Gorkha earthquake. Three of these structures—namely, the Basantapur Column, the Dharahara Tower, and the Narayan Temple—were modeled both analytically using rocking dynamics and computationally using discrete element modeling (DEM). The results emphasize the importance of large low frequency content within the ground motion, demonstrating that the Dharahara Tower could have collapsed due to the primary long-period ground motion pulse alone. In addition, comparison of analytical and computational modeling to the observed response enables evaluation of structural behavior, including discussion of the importance of elastic amplification and column embedment on performance during the earthquake.

scholarly journals Identifying archaeological evidence of past earthquakes in a contemporary disaster scenario: case studies of damage, resilience and risk reduction from the 2015 Gorkha Earthquake and past seismic events within the Kathmandu Valley UNESCO World Heritage Property (Nepal)

2019 ◽  
Vol 24 (4) ◽  
pp. 729-751 ◽  
Author(s):  
Christopher Davis ◽  
Robin Coningham ◽  
Kosh Prasad Acharya ◽  
Ram Bahadur Kunwar ◽  
Paolo Forlin ◽  
...  
Keyword(s):  
Risk Reduction ◽  
World Heritage ◽  
Lessons Learned ◽  
Kathmandu Valley ◽  
Gorkha Earthquake ◽  
Unesco World Heritage ◽  
2015 Gorkha Earthquake ◽  
Reduction Strategies ◽  
The Face ◽  
Disaster Scenario

AbstractThe 2015 Gorkha Earthquake was a humanitarian disaster but also a cultural catastrophe that damaged and destroyed historic monuments across Nepal, including those within the Kathmandu Valley UNESCO World Heritage Property. In the rush to rebuild, traditionally constructed foundations are being removed and replaced with modern materials without assessments of whether these contributed to the collapse of a monument. Generally undertaken without scientific recording, these interventions have led to the irreversible destruction of earlier subsurface phases of cultural activity and the potential loss of evidence for successful traditional seismic adaptations and risk reduction strategies, with no research into whether modern materials, such as concrete and steel, would offer enhanced resilience. In response to this context, multidisciplinary post-disaster investigations were undertaken between 2015 and 2018, including archaeological excavation, geophysical survey, geoarchaeological analysis, linked to architectural and engineering studies, to begin to evaluate and assess the damage to, and seismic adaptations of, historic structures within Nepal’s Kathmandu Valley. Where possible, we draw on archaeoseismological approaches for the identification and classification of Earthquake Archaeological Effects (EAEs) at selected monuments damaged by the 2015 Gorkha Earthquake. Lessons learned from evidence of potential weaknesses, as well as historic ‘risk-sensitive tactics’ of hazard reduction within monuments, are now being incorporated into reconstruction and rehabilitation initiatives alongside the development of methods for the protection of heritage in the face of future earthquakes.

Site Characteristics of Kathmandu Valley from Array Microtremor Observations

2017 ◽  
Vol 33 (1_suppl) ◽  
pp. 85-93 ◽  
Author(s):  
Nakhorn Poovarodom ◽  
Deepak Chamlagain ◽  
Amorntep Jirasakjamroonsri ◽  
Pennung Warnitchai
Keyword(s):  
Main Shock ◽  
Site Response ◽  
Horizontal Component ◽  
Response Analysis ◽  
Kathmandu Valley ◽  
Gorkha Earthquake ◽  
Velocity Models ◽  
Site Characteristics ◽  
2015 Gorkha Earthquake ◽  
Good Agreement

Array microtremor observations were conducted in Kathmandu Valley close to six seismic stations. Sedimentary layers from surface to deep basement rock were modeled according to the derived velocity structures for site response analysis. The records in horizontal component from the 2015 Gorkha earthquake main shock at deep sedimentary sites were compared with the predictions from analysis using the records from a shallow sedimentary site as input motions. Generally, the comparisons are in good agreement where spectral amplification at long periods and suppression at short periods could be justified by the velocity models.

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