Earthquake Phenomena Research Articles

Distribution Related to All Samples and Extreme Events in the ETAS Cluster

Abstract The probabilistic approach of statistical seismology plays a fundamental role in analyzing the evolution of an earthquake sequence at different scales to deliver reliable forecasts of complex earthquake phenomena. This study contributes to the field by extending previous results relative to the extreme events probability. We derive the explicit formulation of the probability of extreme events in any seismic cluster generated by the epidemic-type aftershock sequence model, as a function of time, space, and magnitude. The results give insights into understanding the distinguishing features between mainshocks and foreshocks, thus helping to shed light on earthquake prediction.

Steps of Creation of Seismic Isolation Strategies for Sustainable Development of Construction Industry in Armenia

Earthquake engineering is one of the rather complicated fields of human activities. There is too much uncertainty in this discipline, from the earthquake phenomenon to the properties of building structures that have to withstand it. Despite notable achievements in this field, we have to admit that the humankind is still far from solving the puzzles of the Nature that it opens to us little by little with each new earthquake.

Finding the Particularity of the Active Episode of SGR J1935+2154 during Which FRB 20200428 Occurred: Implication from Statistics of Fermi/GBM X-Ray Bursts

By using the Fermi/Gamma-ray Burst Monitor data of the X-ray bursts (XRBs) of SGR J1935+2154, we investigate the temporal clustering of the bursts and the cumulative distribution of the waiting time and fluence/flux. It is found that the bursts occurring in the episode hosting FRB 20200428 have obviously shorter waiting times than those in the other episodes. The general statistical properties of the XRBs further indicate they could belong to a self-organized critical system (e.g., starquakes), making them very similar to the earthquake phenomena. Then, according to a unified scaling law between the waiting time and energy of the earthquakes as well as their aftershocks, we implement an analogy analysis on the XRBs and find that the fast radio burst (FRB) episode owns more dependent burst events than the other episodes. It is indicated that the FRB emission could be produced by the interaction between different burst events, which could correspond to a collision between different seismic/Alfvén waves or different explosion outflows. Such a situation could appear when the magnetar enters into a global intensive activity period.

Identification of Ground Vulnerability Based on Kg, PGA, and GSS Assessment by Single Station Microtremor in Bendosari Hamlet, Kalasan Village, Yogyakarta

Bendosari Hamlet, Kalasan, Yogyakarta is a research area that is one of the areas affected by the earthquake that occurred on May 27, 2006. The earthquake with a magnitude of 6.4 caused quite severe damage to buildings around the research area. Based on the phenomenon of earthquakes that have occurred, there needs to be further study related to vulnerable areas in the event of another earthquake. Research data is primary data taken using a single statiun microtremor tool with an overall acquisition point of 50 measurement points. This study aims to find out the value of seismic vulnerability index (Kg), Peak Ground Acceleration (PGA), and Ground Shear Strain (GSS). Using the Horizontal to Vertical Spectral Ratio (HVSR) method, the dominant frequency result (f0) and amplification factor value (A0) from data that has been recorded through the microtremor tool. Based on research that has been done, the results are obtained in the f0rm of seismic vulnerability index values that are in the range of 0.49 - 30.18, the value of the acceleration of ground movement is in the range of 0.21 - 0.61 Gal, and the ground shear strain value is in the range of 4 x 10-6 to 38 x 10-5. Point K26 which is the original documentation of buildings affected by the earthquake, analyzed that the value of Vs of 858.112 m / s on the vs ground profile indicates that there is hard soil at a depth after 27.2 m. This shows that the thickness of subsurface sedimentary rocks at point K26 is quite thick. Keywords: Bendosari Hamlet; Mikrotremor; GSS; HVSR; PGA; Seismic Vulnerability

Regional-scale fault-to-structure earthquake simulations with the EQSIM framework: Workflow maturation and computational performance on GPU-accelerated exascale platforms

Continuous advancements in scientific and engineering understanding of earthquake phenomena, combined with the associated development of representative physics-based models, is providing a foundation for high-performance, fault-to-structure earthquake simulations. However, regional-scale applications of high-performance models have been challenged by the computational requirements at the resolutions required for engineering risk assessments. The EarthQuake SIMulation (EQSIM) framework, a software application development under the US Department of Energy (DOE) Exascale Computing Project, is focused on overcoming the existing computational barriers and enabling routine regional-scale simulations at resolutions relevant to a breadth of engineered systems. This multidisciplinary software development—drawing upon expertise in geophysics, engineering, applied math and computer science—is preparing the advanced computational workflow necessary to fully exploit the DOE’s exaflop computer platforms coming online in the 2023 to 2024 timeframe. Achievement of the computational performance required for high-resolution regional models containing upward of hundreds of billions to trillions of model grid points requires numerical efficiency in every phase of a regional simulation. This includes run time start-up and regional model generation, effective distribution of the computational workload across thousands of computer nodes, efficient coupling of regional geophysics and local engineering models, and application-tailored highly efficient transfer, storage, and interrogation of very large volumes of simulation data. This article summarizes the most recent advancements and refinements incorporated in the workflow design for the EQSIM integrated fault-to-structure framework, which are based on extensive numerical testing across multiple graphics processing unit (GPU)-accelerated platforms, and demonstrates the computational performance achieved on the world’s first exaflop computer platform through representative regional-scale earthquake simulations for the San Francisco Bay Area in California, USA.

Mathematical and Physical Characteristics of the Phase Spectrum of Earthquake Ground Motions

This study presents a rigorous investigation into the mathematical and physical properties inherent in the Fourier phase spectrum of earthquake ground motions. This exploration includes a detailed examination of the probability distribution of phase angles and differences, elucidated through two novel numerical experiments utilizing the reduction ad absurdum approach. Moreover, the study scrutinizes the physical attributes of earthquake ground motion’s phase spectrum, employing the circular frequency-dependent phase derivative as a key analytical factor. In a novel approach, the research delves into the relationship between circular frequency-dependent phase derivatives and Fourier amplitudes, shedding light on essential connections within earthquake phenomena, particularly addressing non-stationarity. Expanding the scope, the study comprehensively examines the influence of source, propagation path, and site on both the phase spectrum and accelerogram. Employing the control variate technique facilitates this analysis, providing valuable insights into the underlying physical mechanisms governing earthquake wave behavior. The findings highlight the temporal properties of the phase spectrum, attributing its complexity to the temporal heterogeneity in energy release during the fault rupture and dispersion of earthquake waves. This novel approach not only enhances the understanding of earthquake dynamics, but also underscores the significance of considering temporal variations in earthquake events.

Subduction plate interface shear stress associated with rapid subduction at deep slow earthquake depths: example from the Sanbagawa belt, southwestern Japan

Abstract. Maximum shear stress along an active deformation zone marking the subduction plate interface is important for understanding earthquake phenomena and is an important input parameter in subduction zone thermomechanical modeling. However, such maximum shear stress is difficult to measure directly at depths more than a few kilometers and is generally estimated by simulation using a range of input parameters with large associated uncertainties. In addition, estimated values generally represent maximum shear stress conditions over short observation timescales, which may not be directly applicable to long-timescale subduction zone modeling. Rocks originally located deep in subduction zones can record information about deformation processes, including maximum shear stress conditions, occurring in regions that cannot be directly accessed. The estimated maximum shear stress is likely to be representative of maximum shear stress experienced over geological timescales and be suitable to use in subduction zone modeling over timescales of millions to tens of millions of years. In this study, we estimated maximum shear stress along a subduction plate interface by using samples from the Sanbagawa metamorphic belt of southwestern (SW) Japan, in which slivers of mantle-wedge-derived serpentinite are widely distributed and in direct contact with metasedimentary rocks derived from the subducted oceanic plate. These areas can be related to the zone of active deformation along the subduction plate interface. To obtain estimates of maximum shear stress at the subduction interface, we focused on the microstructure of quartz-rich metamorphic rocks – quartz is the main component of the rocks we collected and its deformation stress is assumed to be roughly representative of the stress experienced by the surrounding rock and plate interface deformation zone. Maximum shear stress was calculated by applying deformation temperatures estimated by the crystallographic orientation of quartz (the quartz c-axis fabric opening-angle thermometer) and the apparent grain size of dynamically recrystallized quartz in a thin section to an appropriate piezometer. Combined with information on sample deformation depth, estimated from the P–T (pressure–temperature) path and deformation temperatures, it is suggested that there was nearly constant maximum shear stress of 15–41 MPa in the depth range of about 15–30 km, assuming plane stress conditions even when uncertainties related to the measurement direction of thin section and piezometer differences are included. The Sanbagawa belt formed in a warm subduction zone. Deep slow earthquakes are commonly observed in modern-day warm subduction zones such as SW Japan, which has a similar thermal structure to the Sanbagawa belt. In addition, deep slow earthquakes are commonly observed to be concentrated in a domain under the shallow part of the mantle wedge. Samples showed the depth conditions near the mantle wedge, suggesting that these samples were formed in a region with features similar to the deep slow earthquake domain. Estimated maximum shear stress may not only be useful for long-timescale subduction zone modeling but also represent the initial conditions from which slow earthquakes in the same domain nucleated.

Spring water anomalies before two consecutive earthquakes (Mw 7.7 and Mw 7.6) in Kahramanmaraş (Türkiye) on 6 February 2023

Abstract. Understanding earthquake phenomena is always challenging. The search for reliable precursors of earthquakes is important but requires systematic and long-time monitoring employing multi-disciplinary techniques. In search of possible precursors, we obtained commercially bottled spring waters dated before and after the earthquakes of 6 February 2023. Hydrogeochemical precursors have been detected in commercially bottled natural spring waters (Ayran Spring and Bahçepınar Spring), which are at a distance of about 100 and 175 km from the epicenters of the Mw 7.7 and Mw 7.6 Kahramanmaraş (Türkiye) earthquakes of 6 February 2023, respectively. The available water samples cover the period from March 2022 to March 2023. The pre-earthquake anomaly is characterized by an increase in electrical conductivity and major ions (Ca2+, Mg2+, K+, Na+, Cl−, and SO42-) compared to the background for Ayran Spring water samples. The pre-earthquake anomaly lasted for at least 6 months. The anomaly in major ions sharply declined and the ion content approached the background values about 2 weeks after the earthquakes. Although only 6.5 km away from the Ayran Spring, the bottled water samples of the Bahçepınar Spring did not show any anomalies in electrical conductivity; therefore, the samples were not analyzed for ion content. Bahçepınar water is collected from shallow boreholes dug into alluvial deposits, which we believe are decoupled from the basement rocks, and this may be the reason for the lack of abnormal water chemistry prior to the earthquakes. This attests to the fact that sampling locations are very important in the detection of possible earthquake precursors. Results of the Ayran spring water samples indicate that spring water chemical anomalies of discrete samples may provide valuable information on pre-earthquake crustal deformation. Monitoring of spring waters, along with other monitoring techniques in a multidisciplinary network, and for a sufficiently long time, could potentially enable obtaining reliable proxy indicators of pre-earthquake crustal deformation.

Earthquake Phenomenon in The Quran

Deprem dünyanın varoluşundan bu yana farklı coğrafyalarda görülen bir olgudur. İnsanlara ve ekonomiye yönelik yıkıcı etkisi sebebiyle daha çok verdiği zararlar dile getirilse de yerkürenin dönüşümü için faydalı ve zorunlu bir tabiat olayıdır. Son birkaç yıl içerisinde ülkemizde meydana gelen depremlerin sayısının artması depreme ilişkin bilimsel çalışmaların hız kazanmasına neden olmuştur. Deprem çok boyutlu bir olgu olduğundan birçok bilimin inceleme alanına girmektedir. Deprem Kur’an’da da ele alınan bir olgudur. Kur’an’ın temel amacı insanların hidayeti olduğundan deprem de bu Kur’an’da bu kapsamda ele alınmaktadır. Bu amaç sebebiyle Kur’an’da Dünya’nın hareketli yapısı hakkında verilen bilgiler dışında depremin bilimsel bir olgu olarak ele alınmadığı görülmektedir. Kur’an’da depremden çoğunlukla önceki kavimlerin helak aracı olarak bahsedilmesi gerek Kur’an araştırmalarında gerekse dini söylemlerde depremin bir ceza unsuru olarak algılanmasına neden olmuştur. Arapların gerek ilahi kitaplardaki bilgiler gerekse tarih bilgileri sebebiyle eski kavimler hakkında bilgi sahibi olmaları Kur’an’da depreme neden bu kadar çok yer verildiği hakkında ipucu vermektedir. Kur’an’ın ilk muhatapları gerek tarihi bilgi gerekse cezalandırma açısından ele alınsın ilk muhatapların hakkında bilgi sahibi oldukları ve kendi başlarına gelmesinden endişe ettikleri bir olgu ile korkutulmaktadır. Kur’an’da depremden mecazi ve hakiki anlamlarda bahsedilmektedir. Kur’an’da depremden insanın bedensel ve psikolojik açıdan sarsılması açısından mecazi olarak bahsedilmektedir. Hakiki anlamda ise Kur’an’da deprem ve işin vahametini göstermek, cezalandırma aracı, tehdit unsuru ve kıyametin bir unsuru olarak da bahsedilmektedir. Kur’an’da depreme çoğunlukla kıyamet anlatılarında değinilmesi depremin inkarcılar için bir tehdit, inananlar için ise Allah’ın kudretinin ve ona karşı sorumluluğun hatırlatıldığı bir uyarı olarak görüldüğünü göstermektedir. Nitel araştırma yönteminin doküman analizi modeli ile hazırlanan bu çalışmada Kur’an’ın depreme ilişkin verdiği bilgiler incelenerek alana bir katkı sunulması amaçlanmaktadır.

An Analytical Approach to the Traces of Settlement of the City of Sakarya from Antiquity to the Present

According to the known history of the world, the first communities generally chose natural cave environments on the edges of sea, lake and stream for settlement and spread towards the interior of the land over time. These communities have learned to move to higher elevations in order to be protected from phenomena such as water rises and ground movements in the natural flow of the earth. It is an ironic situation that these natural phenomena that shape the earth are called disasters today. In this context, the aim of the study is to question Sakarya River, which was formed as a result of an earthquake action, and along this river, the settlement decisions of the cultures that established living spaces within the borders of the city of Sakarya by mapping them chronologically from the Paleolithic period to the present day with an analytical approach. Within the scope of the study, the effect of the earthquake phenomenon in the city, from the ancient times to the present, while the settlement decisions are taken, will be discussed and the effect of this information on the current settlement decisions of the city will be questioned. Types of analysis specific to the method developed within the scope of the study are; systematic literature review, epigraphic documents, aerial and archive photographs, maps. While reading the traces of settlement in the historical process, the study makes the structural constructs created by the cultures visible through the icons created within the scope of the study.

Dynamic effects on the lattice boom crane due to the wind, moving load and earthquake events

The present research concerns the evaluation of the dynamic effect on lattice boom cranes. The dynamic actions involved in this research are: wind, moving load and earthquake, assumed as time-varying actions. The research starts with the design of a large crane by adopting classical standards for these structures (UNI EN 13001 series). The elaborations were performed by analytical methods followed by solid model building and finite element analysis (Solidworks® and Ansys® software). The next step was to define the aforementioned loads acting on these structures. The wind action model was compared with the static approach. Payload displacement induces high-intensity actions on the crane structure; to better understand these effects, several load curves were simulated. The last action considered is the earthquake phenomenon, which is not usually adopted to design this type of structure.

Potential Usage of Mosques in Earthquake Management in Contemporary Cities: The Case of Diyarbakır

Earthquake phenomenon is a natural disaster that must be managed meticulously because it has devastating effects on large masses. Earthquake management aims to meet the needs of affected communities in many areas such as emergency response, search and rescue, shelter, nutrition, health services, psychosocial support through effective use and coordination of resourcesThis study examines the potential usagee of mosques in earthquake management by considering their urban, spatial, and structural characteristics, as well as their religious and social contexts. The research was conducted in the sample of Diyarbakır, which was directly affected by two major earthquakes on February 6, 2023; the epicenter of which was Gaziantep (7.7) and Kahramanmaraş (7.6). Data on the urban area and 23 mosques in the region were collected through Geographic Information Systems (GIS) and fieldwork. The study concludes that mosques have significant potential for usagee in earthquake management due to their unique features and strategic locations.

Numerical Analysis on Effects of Soil Improvement on Pile Forces on Existing High-Rise Building

Nowadays, seismic codes are regularly updated with new knowledge and a better understanding of the earthquake phenomenon. With these updates, existing buildings require a reevaluation of their stability and a process of reinforcement and/or retrofitting. This study investigated the effects of two types of ground improvement which use cement-mixing soil surrounding the foundation structure to reduce and redistribute forces acting on piles. This is especially important when the reevaluation of high-rise buildings leads to increased forces in the piles. Typically, buildings are designed while assuming fixed base boundary conditions at the foundation level, without considering soil–pile–structure interaction (SPSI). SPSI significantly influences the response of high-rise buildings supported by soft soil. Increasing the lateral resistance of the surrounding soil can reduce the influence of SPSI. In this study, a detailed dynamic numerical analysis was used to investigate the dynamic response of an SPSI system of a high-rise building under seismic load. A dynamic analysis was conducted on a modified layout of a real building, using real-time earthquake motion. The finite element program DIANA FEA was used to perform nonlinear 3D FEM numerical simulations, taking into account the essential SPSI phenomena, gap-slip between the piles and the soil, and free-field boundary conditions. A comparison of the data suggests that the bending moment and shear forces in the piles are reduced in magnitude and evenly distributed along the upper part of the pile, which reduces the stress concentration of the bending moment and shear forces at the contact between the piles and the pile cap.

Application of Mobile-Based Augmented Reality Technology Concepts in Interactive Learning Systems for Liquefaction Phenomena for the Deaf

One of the natural disasters currently happening in Indonesia is an earthquake. An earthquake is a condition where the earth shakes due to volcanic activity and collisions due to the movement of the earth's plates. Earthquake activity causes many problems. One of them is liquefaction. Liquefaction is an event that indicates a loss of soil shear strength due to an increase in pore water pressure. This occurs because the earthquake load occurs so quickly and briefly. Liquefaction is an illustration of the effect of an earthquake so that the soil layer loses its strength. The public rarely knows the phenomenon of earthquakes and liquefaction. Not many people know how the process of the movement of the earth is the forerunner of earthquakes, especially people with hearing impairments. They could only feel an earthquake. Therefore, there is a need for education that can be conveyed to the public. Educational techniques in the virtual form will be a special attraction for people, especially people who are deaf or hard of hearing. Augmented Reality (AR) technology is a technology where virtual objects and real objects are combined. The AR is used to create virtual and interactive learning media. This study produced an application as a learning media that utilizes AR technology with the Marker Based Tracking method. The technology was developed using the MDLC (Multimedia Development Life Cycle) method for the learning media to be more interactive. The results of the tests concluded that the application could be used as an interactive learning medium to increase knowledge about earthquakes and the effects of liquefaction on the community.

The coulomb stress changes for correlation analysis of tectonic earthquake activity and volcanic of the 2001–2010 Merapi eruption based on focal mechanism data

The incident of increased seismic activity of the Merapi volcano was initiated by several tectonic earthquake phenomena. Analysis of the mechanism of tectonic earthquakes can be studied based on the combination of static stress on the rock. This paper describes the distribution of the Coulomb stress changes due to the interaction that occurs in tectonic earthquakes with volcanic activity. The data in the calculation of the Coulomb stress distribution are secondary in the form of tectonic seismicity data downloaded from the ISC (International Seismological Center), USGS (United States Geological Survey), and Global CMT (Global Centroid Moment Tensor) catalogs between 2001 and 2010. Calculation results and data analysis is the occurrence of an increase in Coulomb stress response in the Merapi Volcano area with a value range of 0.2–10 ​kPa at a depth of 2–4 ​km below the peak of Merapi Volcano. The Coulomb stress changes distribution is thought to indicate the accumulation of stress due to tectonic earthquakes that downward at the top of the volcano, thereby affecting the stability of the magma chamber and causing volcanic activity at the Merapi volcano.

The Evolution of Pore Pressure, Stress, and Physical Properties During Sediment Accretion at Subduction Zones

AbstractWe study stress, pressure, and rock properties in evolving accretionary wedges using analytical formulations and geomechanical models. The evolution of the stress state from that imposed by uniaxial burial seaward of the trench to Coulomb failure within the wedge generates overpressure and drives compaction above the décollement. Changes in both mean and shear stress generate overpressure and shear‐induced pressures play a particularly important role in the trench area. In the transition zone between uniaxial burial and Coulomb failure, shear‐induced overpressures increase more than overburden and are higher than footwall pressures. This rapid increase in overpressure reduces the effective normal stress and weakens the plate interface along a zone that onsets ahead of the trench and persists well into the subduction zone. It also drives dewatering at the trench, which enables compaction of the hanging‐wall sediments and a porosity offset at the décollement. Within the accretionary wedge, sediments are at Coulomb failure and the pore pressure response is proportional to changes in mean stress. Low permeability and high convergence rates promote overpressure generation in the wedge, which limits sediment strength. Our results may provide a hydromechanical explanation for a wide range of observed behaviors, including the development of protothrust zones, widespread occurrence of shallow slow earthquake phenomena, and the propagation of large shallow coseismic slip.

A cross-cultural study of students’ awareness of natural disasters: voices from KSA, Yemen and Egypt

In recent years, there has been a remarkable increase in the intensity and frequency of natural disasters.There is no doubt that a thorough knowledge of natural disasters and an adequate awareness of how to protect against their negative consequences will spare many individuals considerable losses. Accordingly, the present study aims to investigate students’ level of awareness of natural disasters within a cross-cultural perspective. Twelve schools in Saudi Arabia, Egypt and Yemen were selected (four schools from each country). The total research sample consisted of 180 sixth and ninth grade students randomly selected from the targeted schools, with 60 students from each country. Semi-structured interviews were implemented. The results indicate that the majority of students in these three countries have a false or complete lack of perception of the phenomena of earthquakes and volcanoes. Only 20.6% of students in these three countries had a completely correct perception of how earthquakes occur. An analysis of students’ drawings of this phenomenon revealed that, on average,only 13.3% were able to clarify the scientific reason for earthquakes; the highest percentage of correct answers came from the students of the Arab Republic of Egypt (15.0%), followed by Saudi students (13.3%) and then Yemeni students (11.7%). Furthermore, it was found that the religious understanding, culture and day-to-day experiences of thelearners in these countries influence their cognizance and analysis of natural events, and that they develop intricate understanding and theories based on their beliefs and experiences.

An Analysis of Primary School Students' Earthquake Awareness

Although earthquake phenomena concerns all levels of society, explaining this phenomena to primary school students well is highly important in terms of creating a society prepared for disasters. In addition, relevant studies show that the group who is affected by earthquakes worst is primary school students. It is observed that earthquakes affect some children in this age groupa not only physically but also emotionally and pschologically more. In the aftermath of an earthquake some children experience bedwetting at night, sleep disorder, behavioral problems, obesity, suicidality and decline in literacy skill levels. Plus, when it is considered that the fastest and the most permanent learning occurs in primary school ages, giving earthquake education and awareness appropriate to these children's ages will enable the society to be more prepared for other possible earthquakes in the future. In the light of this information, this study aims to discuss how earthquake education is given to primary school students, what kind of actions are taken and how students perceive them.

A weakening-healing law to simulate stick-slip behavior of rock joint and the associated seismicity

The variation of frictional strength of asperities is one of the fundamental mechanisms that govern earthquake cycles. The rate - and - state friction (RSF) law has been widely employed to explain earthquake phenomena. In RSF, the frictional strength of fault depends upon the current slipping velocity and the conditions on the slipping surface (i.e., the state), which depends partly on the prior sliding history. In this study, we proposed a simplified weakening-healing law to describe the slip behavior of individual asperity. In the weakening-healing law, the friction strength linearly decreases to the residual value with shear displacement when slip occurs, and immediately recovers to its original value once slip terminates. In the numerical model, a power-law distribution is used to introduce asperity heterogeneity (e.g., size, frictional strength, and stiffness) on a rock joint. A displacement-based moment tensor method is used to calculate the seismic moment during fault slipping. The simulated b-value (magnitude-frequency distribution) and its evolution during stick-slip phases are compared with published experiments. Slip nucleation, growth, coalescence, and the associated spatial-temporal behavior of the simulated seismicity are delineated. Although this preliminary study focuses on simplified conditions (small-scale smooth rock joint sheared under constant normal pressure and shear rate), our method successfully duplicates laboratory observed stick-slip behavior, b-value evolution, slip nucleation process, etc., providing a promising way to mimic more realistic natural earthquake phenomena.

Effect of Declustering Algorithm in Probabilistic Seismic Hazard Analysis for Kathmandu Valley

An earthquake is a random event with uncertainty on time of occurrence, size of events, and location of rupture. So earthquake phenomenon is a model based on Poisson’s distribution. Thus, all the dependent event like foreshock and aftershock has to be removed before performing any Probabilistic Seismic Hazard Analysis (PSHA). Among the number of methodologies proposed for declustering methods, the process proposed by Gardener and Knopoff (1974) and Reasenberg (1985) was mostly used due to the availability of source code and reliability of declustering work. In this study, an attempt has been made to compare the effect of the declustering process at hazard level for the scenario of Kathmandu Valley. Probabilistic seismic hazard analysis of Kathmandu valley is performed using RCRISIS software with different seismicity parameters calculated for without declustering, declustering using Gardener and Knopoff (1974), and declustering using Reasenberg (1985). Calculated PGA value at bedrock level for 760 years return period for three declustering models compared with the measured square root of the sum of square (SRSS) PGA by 2015 Gorkha earthquake at Kathmandu valley at KTP station. Obtained results highlighted the suitability of the Gardener and Knopoff source code for the study area.