Ground Acceleration Values Research Articles

Regional spectral characteristics, quality factor and site responses in western-central Sichuan, China (II): Application to stochastic ground motion simulation

The stochastic finite-fault approach was used to model the 2022 Luding earthquake with a magnitude of Mw 6.6 in China at 16 selected near-field stations. To investigate the impact of the site effect on the synthetic results, two models were taken into account: One model was obtained from the generalized inversion technique, and the other model was obtained from the horizontal-to-vertical spectral ratio method. The high-frequency attenuation parameter was estimated to be 0.040 s and the value of 4.0 MPa for the stress parameter was adopted. Comparisons of the recorded and simulated Fourier amplitude spectrum, pseudospectral acceleration, peak ground acceleration, and peak ground velocity were performed to investigate the capability of the selected input parameters. In addition, the model bias, simulated peak ground acceleration and peak ground velocity were calculated by the local site amplification estimated by the two methods. The results show that the site effects estimated by the generalized inversion technique can well simulate the high-frequency response spectra and Fourier amplitude spectrum and can provide peak ground acceleration and peak ground velocity values consistent with the recorded values, while the local site amplification roughly calculated by the horizontal-to-vertical ratio method underestimates the main ground motion characteristics. Furthermore, strong-motion records with the same magnitude but different hypocentral distance ranges in the generalized inversion technique are used to estimate near-surface site effects, which shows that the distance range has a small impact on the estimation of local site amplification. Model parameters that performed well in this study provide confidence in understanding and quantifying seismic hazards in the Luding area from earthquake scenarios with different magnitudes.

Assessment of Landslide Susceptibility Microzonation using Microtremor Measurements Along Mountain Road in North Bengkulu–Lebong, Bengkulu Province

Based on the geological condition, the research location on the North Bengkulu - Lebong crossing is on the Sumatra fault zone that extends from south to north, which causes this area to have a morphological shape and topography of hills and hills extreme slopes. This research results in landslide-prone micro zonation based on GSS and PGA values obtained from Horizontal-to-Vertical Spectral Ratio (HVSR) method measurements. The research was conducted by measuring 25 research sites. The results of Peak Ground Acceleration (PGA) values processing at the research site, between 0.14 gal - 0.53 gal. Locations with the potential for landslides, shown in blue (0.14-0.29 gal), are located in several spots of the research site. The distribution of Ground Shear Strain (GSS) at the study site is evenly distributed at a value of 10-4, which indicates that the study site is prone to cracking and ground movement. In the distribution of GSS values, it is suspected that the location in the dark red color (10-3) has the highest potential to experience repeated landslides. Based on the results of the calculation of PGA and GSS values on the North Bengkulu - Lebong crossing, the points of landslide-prone locations can be known so that disaster mitigation can be carried out at these locations to reduce the risk that will occur.

Comparative Analysis of the 2023 Pazarcık and Elbistan Earthquakes in Diyarbakır

Türkiye is prone to earthquakes due to its location on various tectonic plates, which can lead to a loss of lives and property. Recently, on 6 February 2023, two major earthquakes hit Pazarcık and Elbistan in Türkiye, causing widespread destruction on the East Anatolian Fault (EAF) zone. Even Diyarbakır, a distant province from the epicentre, was severely affected, highlighting the need to evaluate Turkish earthquake codes. As part of this evaluation, a structural analysis was conducted on earthquake-damaged and collapsed buildings in Diyarbakır. The study analysed three buildings with different levels of damage and six collapsed buildings as case studies. The seismic parameters of the earthquakes were compared to the values in the two recent earthquake hazard maps used in Türkiye’s codes, as well as the Eurocode 8 damage limit values obtained from pushover analysis. The results revealed significant differences between the current seismic values of earthquakes and the current peak ground acceleration (PGA) values specified in the Turkish Earthquake Design Regulations. Additionally, the selected buildings showed inadequate structural behaviours, with significant differences between the expected and actual seismic performances with respect to the PGA values as one of the most important earthquake characteristics.

Force distribution on polymeric geostrip reinforcements in MSE walls under seismic excitation

In this experimental study, the values and distributions of dynamic tensile force along the polymeric geostrip reinforcements were investigated under stepped increasing sinusoidal excitations with a series of shaking table tests on 1500 mm high or 1/3 scale physical mechanically stabilized earth wall (MSE) model. The effects of the peak ground acceleration ([Formula: see text]), slope angle of the cohesionless backfill material ([Formula: see text]), and stiffness of the polymeric geostrip reinforcement were assessed on both the potential failure surface geometry in the backfill soil and dynamic tensile forces along the lengths of polymeric geostrips. Three potential failure surfaces from the results of shaking table tests in the backfill cohesionless soil were detected as for states of quasi-elastic, plastic, and failure. However, neither the current design codes for MSE walls nor the theoretical recommendations truly reflect potential failure surface geometry in the backfill soil. Additionally, the values and distribution geometry of maximum incremental dynamic tensile forces ([Formula: see text]) on the reinforcements along the height of MSE wall recommended by design codes are not compatible with test results; however, the normalized location of total maximum incremental dynamic tensile force ([Formula: see text]) acclaimed by design codes is consistent with the test results. The traditional pseudo-static limit equilibrium methods result in over conservative horizontal dynamic earth pressure coefficient ([Formula: see text]) values generally as compared with the test results. The slope angle of the backfill material and stiffness of reinforcement have a negligible effect on the potential failure surface geometry; however, incremental dynamic tensile forces, total maximum incremental tensile forces, and horizontal dynamic earth pressure coefficient values increase with an increase in the stiffness of reinforcement and inclination angle of the backfill and peak ground acceleration value.

Decision-making method for high-speed rail early warning system in complex earthquake situations

Abstract To address the shortcomings in decision-making methods for ground motion threshold warning models in high-speed rail earthquake early warning systems (HSREEWs), we propose a dual judgement method and corresponding early warning process for earthquake early warning decisions based on joint peak ground acceleration (PGA) and complex earthquake environmental risk evaluation (ERE) values. First, we analyse the characteristics of four complex earthquake environments based on the characteristics of high-speed rail (HSR) operating environments. Second, we establish an earthquake environmental risk evaluation index system and propose an adversarial interpretive structure modelling method-based complex earthquake situation evaluation model (AISM-based ESEM). The AISM method firstly evaluates the proximity by the TOPSIS (technique for order preference by similarity to an ideal solution) method, then effectively rank targets with fuzzy attributes through opposite hierarchical extraction rules without sacrificing system functionality. Since PGA can reflect the current size of earthquake energy, combining PGA thresholds with ESEM-derived values of ERE can effectively determine the risk status of each train and make decisions on the most appropriate alarm form and control measures for that status. Finally, case analysis results under the background of Wenchuan Earthquake show that the new early warning decision-making method accurately assesses environmental risks in affected areas and provides corresponding warning levels as a supplement to existing HSREEWs warning models.

Analysis of peak ground acceleration based on microtremor data in Rejang Lebong, Bengkulu

Rejang Lebong is a regency in the province of Bengkulu, located in the Bukit Barisan mountainous region. The area is dominated by fault earthquakes due to its proximity to the Musi and Ketaun faults. This article presents the results of a study on earthquake hazard analysis through microtremor measurement using the HVSR method to determine the value of Peak Ground Acceleration (PGA). Measurements were taken at 10 points for 60 minutes with a 2 km interval. The HVSR method was used to obtain the dominant period value. The determination of PGA value was based on historical fault earthquakes in RejangLebong in 1943 with a magnitude of Mw 7.4. The largest PGA value obtained was 627.34 gal, which was in the western part of the study area. This is significantly correlated with the earthquake hazard in 1943, which caused the highest damage in the Tes village located in the western part of the study area. This research is useful for pre-disaster earthquake mitigation plans through risk management to reduce the impact of earthquake hazards.

Seismic Load Design of Rukoh Dam Suppletion Tunnel in Pidie Regency, Aceh, Indonesia, Based on Deterministic and Probabilistic Seismic Hazard Analyses

The Rukoh Dam suppletion tunnel construction site in Pidie Regency, Aceh province, is located 5.6 kilometers from the Seulimeum-South segment of the active Sumatran fault. The active fault features a strike-slip fault mechanism with a slip rate of 7.0 millimeters per year and a maximum earthquake-recorded magnitude of 6.9 Mw. Considering that the construction site is located less than 10 kilometers from the active fault, which may cause earthquakes with a magnitude of at least 6 Mw, the SNI 1729:2019, which describes the procedures for planning earthquake resistance for buildings and non-building structures, requires the seismic load to be designed based on the site-specific responses analysis. Determination of the seismic load using a deterministic seismic hazard analysis was the objective of this study. The seismic load based on the probabilistic seismic hazard analysis by Pusat Studi Gempa Nasional (PusGen) in 2017 is also compared. The 2017 Indonesian Earthquake Source and Hazard Map were used to find out about the fault mechanism, slip rate, deterministic magnitude, orientation, and coordinates of traces. The deterministic seismic hazard analysis was conducted using EZ-FRISK 8.07 software and attenuation equations with shallow crustal earthquake sources for fault and shallow background earthquake sources, i.e., the Boore-Atkinson NGA 2014, the Campbell-Bozorgnia NGA 2014, and the Chiou-Youngs NGA 2014 equations. The deterministic analysis based on those attenuation equations predicted the active fault to result in a peak ground acceleration (PGA) value of 0.66 g at the construction site of the Rukoh Dam suppletion tunnel. In comparison, the probabilistic hazard analysis conducted by Pusat Studi Gempa Nasional (PusGen) in 2017 indicated a peak ground acceleration (PGA) of 0.537 g. Therefore, the seismic load is recommended for the structural designs of the embankment dam and the other infrastructures, particularly the suppletion tunnel.

Ground motion characteristics of the 2015 central Nepal (Gorkha-Dolakha) Earthquake and 2023 SE Turkey Earthquake doublets

The Alpine-Himalayan orogenic belt, the well-identified seismically active region in the world, has been evidenced by the occurrence of recent two devastating earthquake doublets in 2015 in central Nepal (MW 7.8 and MW 7.3) and in 2023 in southeastern Turkey(MW 7.8 and MW 7.5). In this study, seismic ground motion characteristics of two damaging earthquakes namely the 2015 central Nepal earthquake doublet that occurred in the central Himalaya and the 2023 southeastern Turkey earthquake doublet that occurred in the eastern Mediterranean has been investigated. The observed strong-motion recordings indicate that the peak ground acceleration (PGA) values are about 152.61–154.96 cm/s2 of the 2015 central Nepal earthquake doublet at KATNP station and about 451.834–842.924 cm/s2 of the 2023 southeastern Turkey earthquake doublet at station 3137. The seismic ground motion of both the 2015 central Nepal and the 2023 SE Turkey earthquakes doublet shows that the 2015 central Nepal doublet produced much lower peak ground acceleration than the 2023 southeastern Turkey earthquake doublet.

Site effect influence on the seismic vulnerability of unreinforced masonry buildings in low to moderate seismic urban areas in Algeria

PurposeThis paper aims to develop preliminary damage scenarios for unreinforced masonry buildings located in low to moderate seismic hazard areas in Algeria, taking into account the specific site effects.Design/methodology/approachThree soil types were considered in this analysis according to the definition of the Algerian seismic code (RPA99/2003). Peak ground acceleration values were assigned to each soil type issued from a probabilistic seismic hazard analysis (PSHA). To highlight the effect of soil conditions on the seismic vulnerability analysis of masonry buildings, a site vulnerability increment is carried out, and the macroseismic Risk-UE method has been adopted and applied by developing two main seismic scenarios according to both return periods of the PSHA, 100 and 475 years, respectively.FindingsBased on the preliminary results of rock site condition, it can be outlined that the significant damage obtained for different earthquake scenarios discovered a substantial worldwide seismic risk to the building stock of the study area. Once the site effect is integrated into the analysis, more high values of vulnerability indexes and expected damages are obtained. Moreover, it can be concluded that soft soil (S3) is a little bit more influential than stiff soil (S2) on the final vulnerability index compared to (S1). However, the difference between the soil effect S2 and S3 on the vulnerability index can be neglected.Research limitations/implicationsResearchers are encouraged to test the mechanical approaches for more detailed outcomes of a specific building analysis.Practical implicationsThis research proves to the Algerian decision-makers that due to the site effects and the vulnerability of the masonry buildings, an urgent intervention program is required even for existing buildings located in low to moderate seismic hazard areas.Originality/valueSeveral seismic vulnerability types of research have been conducted in Algeria for the unreinforced masonry buildings in moderate to high seismic areas in which generally the soil effect is neglected. In this context, this research paper proves that due to the site effects and the vulnerability of the masonry buildings, special attention is required even for existing buildings located in low to moderate seismic hazard areas. With this conclusion, the requirement of taking into account the soli effect in the high seismic areas is even more pronounced and should be conducted.

Predicting Models for Local Sedimentary Basin Effect Using a Convolutional Neural Network

Although the numerical models can estimate the significant influence of local site conditions on the seismic propagation characteristics near the surface in many studies, they cannot feasibly predict the seismic ground motion amplification in regular engineering practice or earthquake hazard assessment due to the high computational cost and their complex implementation. In this paper, the scattering problem of trapezoidal sedimentary basins, one of the representatives of local complex sites with a relatively small model size, and simplified by practice in this type of study, was selected as the basin model. A series of standard basin models were built to quantify the relationship between the site condition parameters and the site amplification parameters (the peak ground acceleration and the hazard location). In addition, the factors that influence seismic ground motion amplification, such as the basin shape ratio, the soil depth, the basin edge dip angle, the ratio of shear wave velocity between the bedrock and the soil layer, the damping coefficient, and the fundamental frequency, were selected to investigate the sensitivity. A convolutional neural network (CNN) algorithm based on deep learning replacing traditional recursive algorithms was explored to establish a prediction model of basin amplification characteristics. By the Bayesian optimization method, the structural parameters of the CNN predicting model were selected to improve the accuracy of the prediction model. The results show that the optimized CNN models could predict the amplification characteristics of the basin better than the un-optimized CNN models. Three prediction models were established with the site condition parameters as the input parameters and their output parameters were the maximum amplification value of the peak ground acceleration (PGA), the hazard location, and their combination for each basin. To analyze the CNN’s prediction ability, each CNN model used about 80% of the data from the seismic model repose results for training and the remaining data (20%) for testing. By comparing the CNN prediction results with the FE simulation results, the accuracy and rationality of each prediction model were studied. The results show that, compared to a single numerical model, the CNN prediction results of the site amplification features could be quickly obtained by inputting the relevant parameters. Compared to recursive class models, the established CNN prediction model can directly establish the relationships among multiple input and multiple output parameters. A comparison of the three kinds of CNN models shows that the prediction accuracy of the joint parameter model was slightly lower than that of the two single-output models.

Cost Estimation of Structural Work for Residential Building with Seismic Design Consideration

The Sumatra-Andaman earthquakes had triggered local earthquakes in Malaysia by reactivation of ancient inactive faults. Previously on 5thJune 2015, Ranau, a region located in Sabah, Malaysia, had experienced a moderate earthquake of Mw6.1. The structural failures occurred because all existing buildings only designed for gravity load without any seismic provision. Recent research work exhibits the seismic designs’ impact on the cost of material and its parameters thatimpact the cost. There are two types reinforced concrete residential buildings called Type 1 and Type 2 for two storey and four storeywhich had been used as models. This research applied four seismicity levels to the reference peak ground acceleration value, αgR= 0.07g, 0.10g, 0.13g & 0.16g, and two soil types: Soil Types B and D. The result shows that for twostorey reinforced concreteresidential buildings on soil types B and D, seismic design increases structural work costs, which is around 0.62% to 1.31% and 0.61% to 2.16%, respectively,for Type 1 modelcompared to non-seismic design. Besides,model Type 2, the increment is around 0.24% to 1.22% and 0.20% to 1.71%, respectively.Otherwise, for reinforced concreteresidential building with four storeyon soil types B and D,the result shows that seismic design tends to have a higher structural work’s costaround 0.41% to 2.48% and 0.98% to 11.23%, respectively, for Type 1 model. Besides, for model Type 2 the increment is around 1.80% to 2.05% and 2.34% to 8.53%, respectively, compared to non-seismicdesign.

Fuzzy Inference System (FIS) Model for the Seismic Parameters of Code-Based Earthquake Response Spectra

The response spectra defined in seismic design codes include crisp classifications of seismic parameters, which directly affect the spectra’s shape and greatly alter seismic design loads. The optimum design phase seismic forces have an important role in the efficiency of the construction costs and structural safety. Various parameters are used to calculate the seismic design forces, especially presented in the codes with earthquake design spectra. This study presents a rule-based fuzzy inference model with fuzzy sets to determine these parameters using fuzzy inference system (FIS) modelling, which is the most appropriate approach among the different alternatives because both the input and output variables have numerical and linguistic uncertainties in the earthquake problem. Using the seismic zone factor of the region and shear wave velocity of the soil profile as inputs, the model generates the seismic coefficients and peak ground acceleration values of the response spectra specified in the Uniform Building Code (UBC, 1997). The response spectra in this code can be easily generated with these seismic coefficients after their fuzzification. Response spectra of twenty-five different sample cases with and without the FIS model are generated, which provide comparisons for the model superiority assessment. Significant differences are observed between the crisp logic and the FIS model-generated spectra. It is suggested that the FIS model can be modified and applied to various parameters to generate response spectra in different seismic design codes.

Investigation of RC Buildings after 6 February 2023, Kahramanmaraş, Türkiye Earthquakes

Two major earthquakes struck Pazarcık and Elbistan, towns in Kahramanmaraş, Türkiye, on 6 February 2023, approximately 9 h apart. The first earthquake, recorded at 04:17 local time, had a Mw = 7.7, with a focal depth of 8.6 km. At 13:24 local time, a second earthquake occurred with Mw = 7.6 at a focal depth of 7 km, approximately 90 km north of the first one. A total of 11 provinces were severely affected by these earthquakes. As of 15 April 2023, they caused close to 51,000 deaths and almost 215,000 completely destroyed/severely damaged buildings. At some locations, the largest horizontal peak ground acceleration (PGA) values of the first and second earthquakes exceeded the code-generated PGAs by almost 3 and 1.75 times, respectively. A technical team visited these areas within 15 h of the first earthquake. The purpose of this article is to present their observations, findings, and the characteristics of the two earthquakes, with comprehensive site survey results supported by photographs. This study concludes that most of the collapsed and severely/moderately damaged buildings in the region were built between 1975 and 2000, when site inspections were rare or non-existent. In addition to the high PGAs recorded in these earthquakes, it was verified that the design and construction of these buildings did not fully comply with the earthquake codes valid at the time. The collapsed buildings and their damage patterns confirm inadequate development length, violation of bending stirrup ends at 135°, deficiencies in construction materials and reinforcement configuration, noncompliance with confinement zones, violation of the strong beam-stronger column analogy, and issues related to building inspection. Based on the extent of the damage, it is strongly recommended that the structural performance inspection of all other buildings located near major fault lines, specifically those constructed between 1975 and 2000, should be completed. Since these earthquakes generated much higher PGAs, which is believed to be one of the main reasons for the extensive damage, a re-evaluation of all other PGAs along major fault lines is also recommended.

Penghitungan Peak Ground Acceleration (PGA) di Desa Kuta Menggunakan Persamaan Empiris pada Gempabumi 19 Agustus 1977 (Mw = 8.3)

The August 19, 1977 earthquake was one of the major earthquakes that ever occurred in the Nusa Tenggara area with an impact on the island of Lombok, one of which was in Kuta Village. The purpose of this research is to determine the empirical equation that is suitable for use in Kuta Village to calculate the Peak Ground Acceleration (PGA) value in the form of a distribution map. The PGA value can provide an overview of the damage to buildings caused by the earthquake. The PGA calculation uses several empirical equations of Donovan, M.C.Guirre, Esteva, and Oliviera. Earthquake data was obtained through data released from the USGS and the destructive earthquake catalog. The PGA value obtained with the Donovan empirical equation is a PGA value that is close to the value from the results of the BMKG Shakemap scenario with the MMI III scale. This earthquake did not cause damage to the Kuta Village area but damage was caused by the tsunami after the earthquake occurred. Keywords: Sumba Earthquake, Kuta Village, Maximum Ground Acceleration, Empirical Equation.

A Logic-Tree Approach for Probabilistic Seismic Hazard Assessment in the Administrative Region of Attica (Greece)

Probabilistic Seismic Hazard Assessment (PSHA) was carried out for the administrative region of Attica (Greece). Peak Ground Acceleration (PGA) and Peak Ground Velocity (PGV) values were calculated for return periods of 475 and 950 years for five sub-areas covering the entire region. PGA hazard curves and Uniform Hazard Spectra (UHS) in terms of spectral acceleration (Sa) values were generated for Athens, Methana, and the capitals of each island of Attica (Salamina, Aegina, Poros, Hydra, Spetses, Kythira, and Antikythira). Area sources were adopted from the Euro-Mediterranean Seismic Hazard Model 2013 (ESHM13) and its update, ESHM20, taking into account both crustal and slab tectonic environments. Ground Motion Prediction Equations (GMPEs) proposed for the Greek territory were ranked for PGA and PGV. Each GMPE was reconstructed as a weighted model, accounting for normal and non-normal focal mechanisms for each area source. PGA, PGV, and Sa values were computed using a logic tree, integrating the seismotectonic models as major branches and sub-logic trees, comprised of multiple ranked GMPEs for each area source, as minor branches. The results showed higher seismic hazard values in sub-areas near the Gulf of Corinth and the slab interface, which could indicate a need to revise the active building code in Attica.

Penghitungan Peak Ground Acceleration (PGA) di Desa Kuta Menggunakan Persamaan Empiris pada Gempa Bumi 19 Agustus 1977 (Mw = 8.3)

The August 19, 1977 earthquake was one of the major earthquakes that ever occurred in the Nusa Tenggara region with an impact on the island of Lombok, one of which was in Kuta Village. The purpose of this research is to determine the empirical equation that is suitable for use in Kuta Village to calculate the Peak Ground Acceleration (PGA) value in the form of a distribution map. The PGA value can provide an overview of the damage to buildings caused by the earthquake. The PGA calculation uses several empirical equations of Donovan, M.C.Guirre, Esteva and Oliviera. Earthquake data obtained through data released from the USGS and the destructive earthquake catalog. The PGA value obtained with the Donovan empirical equation is a PGA value that is close to the value from the results of the BMKG Shakemap scenario with the MMI III scale. This earthquake did not cause damage to the Kuta Village area but damage was caused by the tsunami after the earthquake occurred.

Comparative Study of Intze Type of Water Tank for Different Bracing Pattern under Wind and Seismic Load

Abstract Overhead water tank is a water storage facility supported by a tower and constructed at an elevation to provide useful storage and pressure for a water distribution system. Safety as well as working of such structures is considered as very crucial during earthquakes, since they put up for necessities like drinking water, firefighting during fire accidents, etc. Such structures should stay in operating condition even after several earthquakes. This RC overhead water tanks involves huge water mass supported on the top of tank supporting system known as staging. This investigation is basically to discover the seismic behavior of RC overhead water tanks. In this study, a FEM based model is used for finding out the nonlinear seismic performance of RC overhead water tanks with several staging variations. The staging that is different bracing patterns considered in this study in lateral and vertical direction, which relatively increases the strength and stiffness of tank in supporting system. Staad models are prepared and analyze for different seismic zones as well as for cyclonic regions and observed the parameters such as base shear, base moment and lateral displacement. The commercial software STAAD.Pro is used for structural analysis. Since the seismic response of water tank structure depends on its dynamic properties and frequency of ground motion. This seismic analysis of overhead water tank structure cannot be carried out on the basis of maximum value of ground acceleration because of nonavailability of ground acceleration data at every location. Hence for seismic analysis of overhead water tank, earthquake response spectrum analysis is widely used. While using this method, smooth design spectra is used to determine the value of displacement and forces in members at every mode of vibration. Octagonal, Radial, Cross, Alternate tie , Diagonal and X- type bracings are used to analyze the structure under all the seismic zones viz. II, III, IV & V. Also observed the behavior of tank for cyclonic region where wind load is increased by 30%. Analysed the overhead water tanks of same capacity for different bottom dome deviation angles and concluded.

Ground motion hazard of the China–Pakistan Economic Corridor (CPEC) routes in Pakistan

Pakistan has seen a burst of infrastructure development recently due to the increased connection between Asia and East Europe. The China–Pakistan Economic Corridor is a project between China and Pakistan aimed to improve the regional infrastructure that would ultimately enhance the connection between Asia and Eastern Europe. However, the active tectonics of Pakistan could put this infrastructure at risk if it is not built to the highest hazard prevention standard. This study reports the ground motion hazard by using the probabilistic seismic hazard assessment approach and the areal seismic source model. The seismic hazard maps of the China–Pakistan Economic Corridor in Pakistan are derived using the Cornell–McGuire (1968–1976) approach, which takes into account all earthquakes (25AD-2020) that occurred in Pakistan and nearby regions, the newest ground motion prediction equations, and an updated seismotectonic source model of Pakistan. The final ground motion intensities are attained as peak ground acceleration and 5% damped spectral acceleration at T = 0.2 s and 1.0 s for 475- and 2475-year return periods (estimated for bedrock site conditions). The results are displayed as color-coded maps that represent the amplitude deviation of ground motion. From the spatial evaluation of the maps, a peak ground acceleration value of 0.40–0.52 g for the 475-year return period and a spectral acceleration (0.2 s) value of 1.66–2.13 g for 2475-year return period are mostly observed on the northern and western routes. The central and eastern routes are mostly characterized by a peak ground acceleration value of 0.22–0.24 g for the 475-year return period and a spectral acceleration (0.2 s) value of 0.95–1.13 g due to diffused seismicity and lower number of faults in this region. The ground motion intensity values obtained in this study can be utilized for the seismic design of all kinds of infrastructure and bridges along the CPEC routes in accordance with the Building Code of Pakistan, the International Building codes, and the load and resistance factor design codes published by American Association of the State Highway and Transportation Officials.

Probabilistic and deterministic-based approach for liquefaction potential assessment of layered soil

In the present study, deterministic and probabilistic approaches have been used for the assessment of liquefaction potential of ground during an earthquake. The deterministic approach was used to analyze and assess the liquefaction of loose saturated river bed deposit with emphasis on two benchmark locations. A wide range of earthquake data in the form of peak ground acceleration (PGA) values of 0.18 g, 0.37 g, 0.6 g and 0.75 g was used as input motions. The dynamic properties of soil were evaluated using standard penetration test (SPT) data obtained from the bore logs. The shear stress induced within soil deposit due to the seismic excitation was calculated in the form of cyclic stress ratio (CSR) and cyclic resistance ratio (CRR) in order to calculate the factor of safety (FOS) against liquefaction. In addition, liquefaction potential index (LPI) and probability of liquefaction (PL) were also calculated using input motion. It was observed, based on the probability analysis and liquefaction indices, that the shallow layer soil profile is safe against liquefaction, whereas deep layer soil profile is unsafe.

Updated probabilistic seismic hazard assessment of Pakistan

A probabilistic seismic hazard analysis of Pakistan is carried out to produce seismic hazard maps showing peak ground acceleration for the 2% and 10% of probability of exceedance in 50 years and spectral acceleration for the 5% and 2% probabilities of exceedance in 50 years. The main objective of this work is to define seismic hazard definition for Pakistan based on the classical approach using updated seismic hazards analysis inputs. A composite earthquake catalogue consisting of 32,700 events was compiled and used in the analysis with a magnitude range of Mw 4.0–8.3. The computations were made at a rectangular grid of 5 km in the OpenQuake engine. Ground motion parameter values have been obtained for flat rock reference seismic site conditions having a shear wave velocity of 760 m/s. Through the logic tree, epistemic uncertainties inherent in ground motion prediction equations and the maximum magnitude potential of seismic sources were estimated. Ground motion prediction equations were assigned equal weights in the logic tree while different weights were assigned to the maximum magnitude potential models. Results of the study were expressed as ground motion contour maps and median uniform hazard spectra for important cities in Pakistan. The results showed that peak ground acceleration values in Pakistan range from 0.16 to 0.54 g for the 10% of probability of exceedance, 0.23–0.72 g for the 5% probability of exceedance and 0.32–1.02 g for the 2% of probability of exceedance in 50 years. Spectral acceleration values at 0.2 s range from 0.67 to 2.19 g for the 2% chance of exceedance in 50 years, respectively, whereas spectral acceleration at 1.0 s ranges from 0.09 to 0.52 g for the 2% chance of exceedance in 50 years. The centre of Pakistan and the southern and the northern region are exposed to high hazard compared to the central-eastern part of the country. Quetta, Chitral, Peshawar, Islamabad Ziarat and Gwadar are exposed to seismic hazard in the PGA range of 0.32–0.45 g. Comparison of the results of this study with those of similar studies suggests that the seismic estimates proposed are reliable. The study provides a demonstration that the classical seismic hazard approach applied here is rational and applicable in Pakistan.