Probabilistic Seismic Hazard Analysis of Kathmandu City (original) (raw)

Probabilistic Seismic hazard Analysis of Kathmandu City, Nepal

2014

ABSTRACT-Kathmandu is classified as a highly earthquake prone city of Nepal. The center of Kathmandu City is located in the vicinity of ten independent seismic source zones which in reality are active faults. This creates uncertainties in the size, location and the rate of recurrence of earthquakes. Probabilistic seismic hazard analysis provides a framework in which these uncertainties can be identified, quantified and combined in a rational manner to provide a more complete picture of the seismic hazard. This study presents a PSHA of the center of Kathmandu city using the attenuation relationship given by Cornell et al (1979) in order to determine various levels of earthquake-caused ground motion that will be exceeded in a given future time period.

Probabilistic Seismic Hazard Analysis of Nepal

2017

Probabilistic seismic hazard assessment of Nepal has been updated. Nepal has been divided into four area sources based upon density of historical earthquakes. At each sources, earthquake data has been collected from various sources. All data has been converted to moment magnitude, aftershocks and repeated events have been removed, and completeness analysis has been performed. Magnitude-frequency relationship has been developed. Entire area of Nepal has been divided into 1.2*0.6 degrees grid size. Earthquake densities are calculated based upon historical earthquakes using kernel estimation method which accounts the significance of both numbers of earthquakes and size. Considering various attenuation laws developed for subduction zone, peak ground acceleration and spectral acceleration for return period 475 years are calculated at 64 sites.

Probabilistic seismic hazard assessment for Nepal

Risk Analysis VII, 2010

Written history of great earthquakes in excess of magnitude M8 and recently identified 92 small faults around underlying big three fault systems parallel to the Himalayas show a high seismicity in Nepal. However, since faults are so closed that it is difficult to judge which earthquake belongs to which fault and even some of the faults do not hold earthquakes, the usual method of assigning the earthquakes to the nearest fault developing magnitude-frequency relationship is not applicable. Thus, an attempt has been made here to address the problem considering area sources with different densities at each location based upon historical earthquakes and faults which is real evidence of the seismicity of the region. Separate earthquake densities are calculated based upon historical earthquakes and maximum magnitudes of faults using the kernel estimation method which accounts the significance of both the number of earthquakes and size. Since there is no specific attenuation laws developed for the Himalayan region, five attenuation laws developed for seduction zone are selected and used, giving equal weight to all to minimize the uncertainties. Then, the probabilistic spectra for various return periods are calculated, compared with previous estimates and various aspects discussed.

Estimation of Seismic Hazard for Kathmandu, Nepal and Adjacent Regions

An earthquake Mw7.8 occurred on 25 April 2015 in a seismically dominant area of Nepal. No major earthquakes (>Mw7.0) were recorded in the past two decades, though Nepal is one of the active seismic regions in the world. The combined effect of the main event and the aftershocks, which are temporally distributed over 40 days, has led to a huge devastation, killing thousands of people in the epi-central area. A complete seismic catalog and influencing parameters such as type of fault, epi-central/hypo-central distance, type of soil are required for a region to assess seismic hazard scenario. The seismic hazard can be represented in terms of Peak Ground Acceleration (PGA), which is the most widely used parameter in strong motion studies. The main objective of this paper is to understand the characteristics of ground motion of the 2015 Nepal earthquake. Since the available ground motion records are limited, an attempt has been made to generate ground motion records using a modified se...

Seismic hazard assessment of eastern Nepal using 1934 and 1988 earthquakes

Journal of Nepal Geological Society, 2011

The Himalayan arc is widely considered as one of the hot spots in terms of earthquake disaster. Nepal, which is centrally located in the Himalayan region, has witnessed many medium to large earthquakes in the past, e.g., 1934 Bihar-Nepal earthquake, 19 88 Udayapur earthquake. Because of lack of income resources in rural area, considerable number of population has already migrated to the major urban areas of the country and the trend is still continued. With such population pressure and also economic constrains, major part of population is residing in weak and non-engineered structures of the unplanned urban areas. Consequently, it has put large population at high risk of earthquake disaster. It is, therefore, necessary to assess the seismic hazard so that proper mitigation measures may be adopted for the safeguard of the population, property and infrastructures under risk. In this contribution, preliminary Probabilistic Seismic Hazard Analysis (PSHA) for eastern Nepal is carried out...

Probabilistic Seismic Hazard Analysis Of Dehradun City , Uttrakhand

Dehradun is very old city and also rapidly growing urban area located in valley at foothills of Garhwal Himalayas. Dehradun city and adjoining region in western Himalayas is a is a very active seismic region of Himalayan belt , stretching from Pamir -Hindukush to Arkans in Burma.According to seismic zoning map of India , Dehradun city lies in Zone 4 and expected MSK intensity 8 .Dehradun city is located in the vicinity of twenty four independent seismic source zones which in reality are active faults. This creates uncertainties in size , location and the rate of recurrence of earthquakes. Probabilistic seismic hazard analysis provides a framework in which these uncertainties can be identified , quantified and combined in a rational manner to provide a more complete picture of the seismic hazard . This study presents a PSHA of the Dehradun city using the attenuation relationship given by Cornell et al (1979) in order to determinate various levels of earthquake-caused ground motion that will be exceeded in a given future time period.

Updating Probabilistic Seismic Intensity at Kathmandu after 2015 Gorkha Earthquake

Journal of Civil Engineering and Architecture, 2018

Subduction of Indian plate beneath the Eurasian plate has formed three thrust faults along Himalayas. Due to continuous shortening, many earthquakes have occurred in the past causing massive deaths and destructions showing that earthquakes are the greatest threat. Seismic hazard of the central Himalayan region has been examined based upon kernel density function method. Faults are so nearer that it is difficult to judge which earthquake belongs to which fault and even some parts of the faults do not hold earthquakes, and usual method of assigning the earthquakes to the nearest fault developing magnitude-frequency relationship is not applicable. Thus, seismic hazard is estimated considering area sources with different densities at each location based upon historical earthquakes using kernel density functions which account both earthquake sizes and numbers. Fault is considered as one earthquake with its highest magnitude at centre when calculating density but does not aid in earthquake data base for recurrence relationship. Since there are no specific attenuation laws developed for the Himalayan region, five attenuation laws developed for other subduction zones are selected and used giving equal weight to all to minimize the uncertainties. Then, probabilistic spectra for various natural periods at Kathmandu are calculated and plotted.

Probabilistic seismic hazard assessment of NW and central Himalayas and the adjoining region

Journal of Earth System Science, 2015

The Himalayan region has undergone significant development and to ensure safe and secure progress in such a seismically vulnerable region there is a need for hazard assessment. For seismic hazard assessment, it is important to assess the quality, consistency, and homogeneity of the seismicity data collected from different sources. In the present study, an improved magnitude conversion technique has been used to convert different magnitude scales to moment magnitude scale. The study area and its adjoining region have been divided into 22 seismogenic zones based upon the geology, tectonics, and seismicity including source mechanism relevant to the region. Region specific attenuation equations have been used for seismic hazard assessment. Standard procedure for PSHA has been adopted for this study and peak ground motion is estimated for 10% and 2% probability of exceedance in 50 years at the bed rock level. For the 10% and 2% probability of exceedance in 50 years, the PGA values vary from 0.06 to 0.36 g and 0.11 to 0.65 g, respectively considering varying b-value. Higher PGA values are observed in the southeast part region situated around Kaurik Fault System (KFS) and western parts of Nepal. Management Authority (NDMA 2011), Government of India, presented various probabilistic seismic

An Assessment of Earthquake Risk in Thecho of Kathmandu Valley Nepal: Scenario and Reality

2018

Natural disaster cannot be stopped but its effect can be minimized or avoided by adopting technology and necessary human adjustment. Earthquake is a natural event which occurs without early warning signs. Computer based earthquake scenarios are used worldwide to describe and estimate the damage from potential earthquakes. The current study is an attempt to explore potential risk with respect to physical infrastructure and assess modeled and actual physical damage and human loss caused by different earthquake scenario and actual 2015 earthquake event in Thecho of Kathmandu valley. The earthquake scenario is based on two nearest fault lines. Risk Assessment Tools for the Diagnosis of Urban Seismic Risk (RADIUS) method has been applied for estimation of potential building damage and casualties..The research has adopted integrated approach using secondary and primary data sources such as field observation, key informant survey and building survey through purposive random sampling.The st...

Re-Evaluation of Seismic Hazard in Tasikmalaya City Using Probabilistic Approach

International Journal of GEOMATE, 2019

Tasikmalaya is one of the earthquake-prone cities in Indonesia as a result of collision of the Indo-Australian and the Eurasian plate. Earthquake mitigation efforts are needed to reduce the impact of future earthquakes. One of the mitigation efforts that can be proposed is a re-evaluation of the seismic hazard of the city. The main objective of this study was to re-evaluate seismic hazard expressed in Peak Ground Acceleration (PGA) and spectral acceleration at bedrock level based on a probabilistic approach, particularly in Tasikmalaya City. We first processed the earthquake data then adopted the new 22 seismogenic structures as the earthquake sources. Furthermore, we determined the characterization of each earthquake sources, selected, and adjusted the ground motion attenuation, and logic tree processed to manage the uncertainty of earthquake recurrence, magnitude distribution, and ground motion attenuation. Using Probabilistic Seismic Hazard Analysis (PSHA), PGA and spectral acceleration at bedrock level corresponding to 2% exceedance of 50 years' probability were calculated. The seismic hazards were quantified in terms of PGA and spectral acceleration at two fundamental periods of 0.2 and 1.0 s. The results showed that the subduction interface zones in southern Java and background seismicity significantly contributed to the seismic hazard in Tasikmalaya City. If compared with the 2010 Indonesian earthquake hazard maps, the results have relatively higher values in the three hazard maps which might due to the different characterization of earthquake sources, earthquake catalogs, and the GMPE to be used.