2475-year Return Period Research Articles

Seismic evaluation and retrofit of a typical reinforced concrete hospital building in Indonesia with DCFP isolation system

In this paper, a study on seismic evaluation and retrofit of a typical reinforced concrete (RC) hospital building in Indonesia is presented. Seismic evaluation is performed against basic structural performance objectives outlined in the current code for structural seismic evaluation. The target building is a typical 5-story RC building designed by the 1970s Indonesia seismic and building codes, which imposed lower seismic demand and were not as strict as the current codes in the requirements for strength and ductility. The first part of the paper describes a seismic evaluation procedure against specific target performance levels. Nonlinear time history analysis (NLTHA) is conducted and structural performances were evaluated against structural responses (base shear force and inter-story drift ratio) and acceptance of seismic performance level for local (element rotational limit) and global (roof drift ratio) performance criteria under 225, 975, and 2475-year return period earthquake scenarios. Results reveal that seismic performances of some structural elements are unsatisfactory and under the acceptable performance level, especially for 2475-year return period (BSE-2 N/MCER) earthquake scenario. Seismic retrofit is thus recommended and the use of double-concave friction pendulum (DCFP) base-isolation system as a retrofit strategy is explored. The seismic performance of DCFP-retrofitted building is examined by NLTHA, where effectiveness of DCFP base-isolation system in improving seismic performance is confirmed by comparing structural responses, local and global structural performance of the existing building and the DCFP-retrofitted building under 2475-year return period earthquake scenario. Results of NLTHA demonstrate that local structural performance level has improved from Collapse Prevention to Immediate Occupancy level, whereas the global structural performance has improved from Limited Safety level to Operational level.

A prolegomenon to Design Input Energy Spectra for the Himalayan region

Energy-based design is becoming progressively significant as a new age of earthquake-resistant design unfolds. Thitherto, very little is known about energy-based design in India despite the fact that the Himalayan region is one of the most seismically active regions in the world. Therefore, the current work provides a preliminary analysis of the elastic input energy and equivalent velocity (Vea) spectra for the active regions in the Himalayas. In this regard, the ground motions of Himalayan databases are blended with NGA WEST2 to estimate the Vea spectra, an inertia-independent representation of the input energy spectra. Incipiently, an Artificial Neural Network-based ground motion model (GMM) is developed for Vea spectra based on the predictor variables as magnitude, distance, hypocentral depth and site conditions. Consequently, a Probabilistic Seismic Hazard analysis is performed to obtain the uniform hazard energy spectra for a 2475-year return period. In addition, a Design Input Energy Spectra is proposed for the active regions in the Indian Himalayas. In addition, the relationship between the Vea and pseudo-spectral velocity (PSV) is analyzed to develop a Vea-informed GMM for PSV. Furthermore, the PSA estimated from the Vea-PSV model is compared with the design spectra recommended by the Indian Standard Code of Practice (IS1893-1:2016).

Seismic Hazard Microzonation Map for the Central Plain of Thailand

A study was conducted to investigate the seismic hazard microzonation of the central plain of Thailand, which is situated in an area with a thick quaternary basin. Unconsolidated sediments can lead to amplification of earthquake ground shaking at fundamental frequency and can cause a significant increase in damage to buildings. The research yielded significant results, including the development of a fundamental frequency map through the analysis of HVSR for 149 microtremor measurement sites. Subsequently, a Vs30 map was derived utilizing HVSR inversion techniques, and a soil classification map was constructed based on the NEHRP classification. The upper central plain along the Yom River and the Nan River had a low fundamental frequency of 0.3-0.5 Hz and low Vs30, which can be classified as soil type Class E. In the southern areas of Ayutthaya, Pathum Thani, and central Bangkok, an extremely low Vs30 of less than 100 m/s was observed, indicating soil class F or special soft soil. A comprehensive investigation was conducted on probabilistic seismic hazard analysis by considering the Vs30 sites condition for PGA, SA0.2s, and SA1.0s with a 2475-year return period. The northern region of the upper central plain and the western side of the central basin exhibit relatively high seismic hazards. Furthermore, the site effect significantly amplifies ground motion at the 1.0 second period, surpassing the earthquake-resistant design standard for buildings in Thailand by more than 5 times, particularly in the central region of the lower central plain.

Design energy spectra for Peninsular India: A preliminary step towards energy-based design in India

Force-based and displacement-based approaches in seismic codes have been widely used in structural design practices for decades. These methods use either the peak forces or the maximum deformations to quantify the destructive potential of a structure subjected to ground motion and does not account for either the duration of ground motion or the loading history on the structure. Hence, several studies proposed many energy-based parameters, of which, the equivalent velocity (VEA) considered as a stable measure and an effective tool in energy-based seismic design. As a preliminary step towards energy-based design in India, we propose design energy spectra for the Peninsular India (PI) in this study as it can provide an improved means of framework in the earthquake resistant design. In order to quantify the probability of exceedance in probabilistic seismic hazard analysis (PSHA), a ground motion model (GMM) for VEA is derived for the PI region using an Artificial Neural Network (ANN) technique. Since the ground motion data is limited in the PI shield, records from a similar tectonic region, such as the Central and Eastern America (CENA) database, are used for deriving the GMM. In the GMM, magnitude (Mw), rupture distance (Rrup), average shear wave velocity of the soil in the top 30 m (Vs30), and focal mechanism, are used as predictor variables; and the target variable constitutes the logarithm of VEA at 24 spectral periods. Consequently, uniform hazard energy response spectra (UHERS) for a 2475-year return period are obtained. In addition, acceleration spectra corresponding to the resulting UHERS are compared with that of the Indian Standard (IS) code recommended design spectra to observe for any underestimations. Finally, a tripartite Design Energy Spectra (DES) is proposed for the entire PI shield, for ease of access.

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.

Beam-Truss Models to Simulate the Axial-Flexural-Torsional Performance of RC U-Shaped Wall Buildings

Reinforced concrete (RC) core walls are commonly used to provide buildings with lateral and torsional resistance against the actions of wind and earthquakes. In low-to-moderate seismic regions, it is not unusual to find a single peripheral core wall that alone should resist these actions, where the torsional (rotational) twist cannot be neglected. It has previously been difficult to have confidence in simulating the axial-flexure-torsion behavior of these RC core walls, primarily due to: (i) some types of modelling approaches being unable to appropriately account for the shear-flexural action, as well as torsional response; and (ii) the scarcity of experimental data, particularly for walls under torsional loads, which would be required to validate such models. In this research, beam-truss models (BTMs), which correspond to an interesting compromise between detailed modelling and practical applications, were used to simulate the in-plane and diagonal flexural response of RC U-shaped walls. Furthermore, the global torque-rotation results from a recent experimental wall test provided the evidence to further validate this powerful modelling technique. A case study building, comprising an RC U-shaped core wall structure with varying eccentricity values, was evaluated for an earthquake event with a 2475-year return period in the city of Melbourne, Australia, using the capacity spectrum method. Nonlinear static pushover analyses showed that, depending on the magnitude of torsion, the in-plane flexural strength and displacement capacity can be significantly reduced. The results from this research emphasize the importance of including torsional actions in the design and assessment of reinforced concrete buildings.

Seismic hazard analysis on Solok Regency, West Sumatra to support local government development program

Solok Regency is an administrative area located in West Sumatra that is currently carrying out disaster mitigation programs. Mostly, major infrastructure such as the Solok Local Government Buildings Complex, school facilities, hospital buildings, and many dense residential buildings are scattered over this area. One notable event happened on September 30, 2009, which forced the local government to take serious prevention steps to reduce casualties and damages in the future. Furthermore, there is a need to develop a comprehensive study to analyze the seismic hazards by determining the value of Peak Ground Acceleration (PGA) at the bedrock. The analysis was carried out using the Probability Seismic Hazard Analysis (PSHA) by calculating several seismic sources towards Solok regency by a radius of 500 kilometers from the Arosuka area for a 2475-year return period. The result showed a PGA value of 1.052g on Arosuka, Solok regency, while the Openquake platform shows the range of PGA values varies from 0.576g – 1.368g. The PGA values were then visualized into a seismic hazard map using a geographic information system (GIS). In addition, these scientific results are used as basic information to estimate the seismic vulnerability to support the disaster risk reduction program in West Sumatra.

Force based Design Approach for Seismic Evaluation of Padma Multipurpose Bridge Pier at Different Performance Levels

The Padma Multipurpose Bridge (PMB) is one of the biggest megaprojects of Bangladesh connecting one third of the country with the capital city, Dhaka. The infrastructure is expected to produce considerable uplift on the nation’s transport system, the national and regional economy, employment, household income, and ultimately, poverty reduction. From construction and river management points of view, it is the most difficult and engineering innovation-intenstive project in the world. Hence the Padma Multipurpose Bridge (PMB) required analytical, computational and experimental studies. In this work, a 3D Finite Element (FE) model of the actual PMB containing a single (6x150m) 900m modules has been developed in MIDAS Civil, a commercial computer program for bridges. P-y soil spring model following API guideline has been developed to conform flexible support system of the bridge pier. Following BNBC 2020, the bridge's performance has been evaluated for the 475-year, 975 years, and 2475-year return periods for Service Level, Design Basis and the Maximum Credible Earthquake (MCE), respectively. The forced based design shows that the bridge pier reached only 28% and 36% of its axial and shear capacity respectively for an earthquake return period of 2475 years. On the other hand, the pier has reached a maximum of 41% of its total shear capacity for the same seismic level.

Seismic collapse risk of RC-timber hybrid building with different energy dissipation connections considering NBCC 2020 hazard

The 2020 National Building Code of Canada (NBCC) seismic hazard model (SHM) marks a comprehensive update over its predecessor (NBCC 2015). For different regions in Canada, this will have an impact on the design of new buildings and performance assessment of existing ones. In the present study, a recently developed hybrid building system with reinforced concrete (RC) moment-resisting frames and cross-laminated timber (CLT) infills is assessed for its seismic performance against the latest SHM. The six-story RC-CLT hybrid system, designed using the direct displacement-based method, is located in Vancouver, Canada. Along with very high seismicity, southwestern British Columbia is characterized by complex seismotectonics, consisting of subduction, shallow crustal, and in-slab faulting mechanisms. A hazard-consistent set of 40 ground motion pairs is selected from the PEER and KiK-net databases, and used to estimate the building’s seismic performance. The effects of using steel slit dampers (associated with large hysteresis loops) and flag-shaped energy dissipators (associated with the recentering capability) are investigated. The results indicate that the hybrid system has good seismic performance with a probability of collapse of 2–3% at the 2475-year return period shaking intensity. The hybrid building with steel slit dampers exhibits a collapse margin ratio of 2.8, which increases to 3.5–3.6 when flag-shaped dissipators are used. The flag-shaped dissipators are found to significantly reduce the residual drift of the hybrid building. Additionally, the seismic performance of the hybrid building equipped with flag-shaped dissipators is found to improve marginally when the recentering ratio is increased.

Neural Network-Based Subduction Ground Motion Model and Its Application to New Zealand and the Andaman and Nicobar Islands

ABSTRACT A deep learning model is developed for the Next Generation Attenuation – Subduction database for predicting spectral accelerations and peak amplitude measures. The developed model satisfies the statistical criteria necessary for prediction. Standard deviations lie in 0.2864–0.3809, 0–0.2696, and 0.4514–0.7892, range for inter-event, -region, and intra-events, respectively. Transfer learning is applied to the New Zealand region. Probabilistic seismic hazard analysis is performed for the Andaman-Nicobar region and obtained a peak ground acceleration of 0.6–0.7 g and 0.4–0.5 g at the Andaman and the Nicobar Islands, respectively, for a 2475-year return period.

Estimation of inter-story drifts at onset of damage statesfor RC high-rise buildings

In this paper, a detailed probabilistic seismic damage analysis of RC high-rise buildings was performed and as a result, the damage states (DSs) and appropriate performance levels (PLs) were defined in a quantitative manner. DSs were quantified using inter-story drift, where the drifts were determined at the onset of each DS. The analysis was performed on three RC high-rise buildings: 20-story, 30-story and 40-story with core wall structural system. Probabilistic seismic damage analysis was performed for 60 earthquake records, recorded on rock and stiff soil, and scaled to two intensity levels associated with probability of exceedance, 10 % in 50 years - 475-year return period (10%/50) and probability of exceedance, 2 % in 50 years - 2475-year return period (2%/50). In addition to these analyses for estimation the damage index, nonlinear static pushover analyses (NSPAs) were performed using different modal combination patterns. Large deviations among the pushover curves for individual considered modal combination patterns were observed. In order to adequately select the parameters for calculating damage index, an analysis of drifts and shear forces for individual modal combination patterns was performed. The functional dependencies between inter-story drifts and damage index were derived using the regression analysis. Based on the derived dependencies, the values of inter-story drifts at the onset of considered DSs for high-rise buildings were proposed.

Probabilistic seismic vulnerability and loss assessment of a seismic resistance bridge system with post-tensioning precast segmental ultra-high performance concrete bridge columns

Precast segmental ultra-high performance concrete (UHPC) columns with post-tensioned (PT) tendons can effectively protect the compression toe from damage and enhance energy dissipation (ED) capacity of column compared to conventional segmental concrete columns. Extensive experiments and numerical studies have been carried out to explore the cyclic response of segmental UHPC columns in the existing literature; however, the effect of such novel columns on the seismic safety of bridge structures has not been thoroughly understood. This study aims to numerically assess the seismic fragility and seismic life-cycle loss of bridge structures supported by the precast segmental UHPC columns. For comparison, the seismic performance of the same bridge with monolithic reinforced concrete (RC) piers are also evaluated. Here, three-dimensional (3D) numerical models are generated to simulate these two bridge types. A performance-based earthquake engineering (PBEE) framework is used to evaluate and compare their seismic performance. The segmental UHPC column model is validated with the previous experimental studies. The validated model is combined into the whole bridge. Numerical results showed that the precast segmental UHPC bridge experiences similar peak acceleration and larger peak displacement in comparison to the monolithic RC bridge. The segmental UHPC bridge pier experiencing lower residual deformation can effectively reduce the damage probability and life-cycle loss of a bridge compared to the conventional monolithic RC pier. Under the design event (2475-year return period) and maximum considered event (5000-year return period), the expected losses of the segmental bridge in the lifetime were approximate 92% and 84% of that of the monolithic bridge, respectively. The segmental UHPC bridge has a noticeable economic benefit when such a bridge is constructed in regions of high seismicity.

Probabilistic seismic hazard assessments for Northern Southeast Asia (Indochina): Smooth seismicity approach

We present an evaluation of the 2018 Northern Southeast Asia Seismic Hazard Model (NSAHM18) based on a combination of smoothed seismicity, subduction zone, and fault models. The smoothed seismicity is used to model observed distributed seismicity from largely unknown sources in the current study area. In addition, due to a short instrumental earthquake catalog, slip rate and characteristic earthquake magnitudes are incorporated through the fault model. To achieve this objective, the compiled earthquake catalogs and updated active fault databases in this region were reexamined with consistent use of these input parameters. To take into account epistemic uncertainty, logic tree analysis has been implemented incorporating basic quantities such as ground-motion models (GMMs) for three different tectonic regions (shallow active, subduction interface, and subduction intraslab), maximum magnitude, and earthquake magnitude frequency relationships. The seismic hazard results are presented in peak ground acceleration maps at 475- and 2475-year return periods.

Updating a probabilistic seismic hazard model for Sultanate of Oman

Earthquake Monitoring Center (EMC) at Sultan Qaboos University (SQU) initiated evaluating the seismic hazard in the Sultanate of Oman in 2009. EMC has produced the first probabilistic and deterministic seismic hazard maps for Oman in 2012 and 2013, respectively. In the current study, the probabilistic seismic hazard assessment (PSHA) is revisited to provide an updated assessment of the seismic actions on the Sultanate. The present study has several advantages over its predecessor: using an updated homogeneous earthquake catalogue, recently developed seismic source model; inclusion of epistemic uncertainties for the source models, recurrence parameters, maximum magnitude, and more recent and applicable ground-motion prediction equations (GMPEs). Epistemic uncertainties were treated using a combination of the best available databases within a properly weighted logic tree framework. Seismic hazard maps in terms of horizontal peak ground acceleration (PGA) and 5% damped spectral accelerations (SA) at the bedrock conditions (VS = 760 m/s) for 475- and 2475-year return periods were generated using the classical Cornell-McGuire approach. Additionally, uniform hazard spectra (UHS) for the important population centers are provided. The results show higher values at the northern parts of the country compared to the hazard values obtained in the previous study.

Probabilistic seismic hazard assessment for some parts of the Indo-Gangetic plains, India

Indo-Gangetic plains are seismically most vulnerable due to the proximity of adjacent great Himalayan earthquakes and thick alluvium deposits of the Ganga River system. As the urbanization on this plain is increasing, there is a need to quantify seismic hazard in the Indo-Gangetic plains (IGPs). IGP also includes major cities with high population density. A probabilistic seismic hazard analysis (PSHA) plays an essential role in ensuring the safety of buildings, bridges and nuclear power stations. A seismic hazard analysis (SHA) was performed deterministically for most of the atomic power stations in India. An attempt has been made to perform PSHA of the part of Indo-Gangetic plains around Narora nuclear power plant (NNPP), accounting for a wide variety of uncertainties associated with SHA. Geological and tectonic features, as well as seismicity distribution around NNPP, are studied in detail, and four source zones are identified according to the geology, seismotectonics and diffuse seismicity. Mmax values for all the source zones based on 300-km distance around NNPP are 7.61 ± 0.54 for Himalaya zone (Zone 1), 6.12 ± 0.54 for Indo-Gangetic Peninsular India (IGPI) East zone (Zone 2), 6.29 ± 0.54 for IGPI Central zone (Zone 3) and 6.38 ± 0.64 for IGPI West zone (Zone 4). The b-value and return period of earthquakes in these zones are also estimated using Kijko–Sellevoll–Bayes model. The hazard curve for peak ground acceleration (PGA) and pseudo-spectral acceleration (PSA) at 0.2 s for the study region is obtained. Hazard map shows a PGA value of 0.0294 g for 100-year return period, 0.0616 g for 475-year return period design-based earthquakes, 0.1033 g for 2475-year return period maximum considered earthquakes, 0.1508 g for 10K-year return period and 0.2598 g for 100K-year return period level at PGA considering all source zones. Similarly, the hazard curve and maps for PSA at 0.2 s are also plotted. According to seismic zonation map of India, most of the study area lies in Zone 4, and the PGA values reported in seismic zonation map and Global Seismic Hazard Analysis Program for the study area range from 0.3 to 0.4 g. The obtained PGA values denote the maximum expected PGA at bedrock level in the study area.

Probabilistic Seismic Hazard Assessment of Pakistan Territory Using an Areal Source Model

A seismic hazard map for the national seismic design code of Pakistan (i.e., Building Code of Pakistan) is derived using probabilistic seismic hazard assessment (PSHA) approach. In order to update the seismic code, an updated seismic zoning map is required that should be based on usage of the recent seismic hazard elements. PSHA of Pakistan is an essential and important milestone. For this purpose, the standard Cornell–McGuire (1968–1976) approach is employed, and the computations are made over a rectangular grid of 0.1°. The main features of this study include usage of a recently compiled earthquake catalogue, recent ground motion prediction equations and an updated seismic source model. The resulting ground motions are obtained as peak ground acceleration (PGA) and 5% damped spectral acceleration (SA) at T = 0.2 s and T = 1.0 s for 475-, 975- and 2475-year return periods (RPs) (evaluated for the flat rock site conditions). Results of the study show that seismic hazard in Pakistan is highest in its central and northern parts. In the central part near Quetta, severe seismic hazard (PGA 0.40 g) is observed. Among the important cities in Pakistan, Balakot city is likely to experience a PGA value of 0.36 g, while Islamabad, Peshawar and Chitral are likely to experience 0.33 g. The cities of Gilgit, Karachi and Gwadar experience ground motion values of 0.34, 0.26 and 0.29 g, respectively, for the 475-year return period (RP). It has also been observed that ground motion values show variation in the distribution and magnitude in contrast to the hazard map of national design code. The hazard map presented in this study is the improved seismic hazard zoning map of Pakistan that would be helpful in developing pre-disaster mitigation strategies and risk assessment studies in Pakistan. It is concluded that the seismic zoning map of the national seismic design code of Pakistan underestimates the ground motion values, and it should be updated or replaced.

Seismic vulnerability and loss assessment of an isolated simply-supported highway bridge retrofitted with optimized superelastic shape memory alloy cable restrainers

Restrainers, being of relatively low cost and easy to install, are often used to prevent unseating of bridge spans. The potential of using superelastic shape memory alloy (SMA) restrainers in preventing such failure has been discussed in the literature; however, the impact of such smart restrainers with optimized configurations in reducing the failure probability of bridge components and system as well as the long-term economic losses given different earthquake scenarios has not been investigated yet. This study presents a probabilistic seismic fragility and long-term performance assessment on isolated multi-span simply-supported bridges retrofitted with optimized SMA restrainers. First, SMA restrainers are designed following the displacement-based approach and their configuration is optimized. Then, seismic fragility assessment is conducted for the bridge retrofitted with optimized SMA restrainers and compared with those of the original bridge and the bridges with elastic restrainers (steel and CFRP). Finally, long-term seismic loss (both direct and indirect) are evaluated to assess the performance of the retrofitted bridges in a life-cycle context. Results showed that among three considered restrainers, SMA restrainers make the bridge less fragile and help the system lower long-term seismic loss. The design event (DE, 2475-year return period) specified in Canadian Highway Bridge Design Code (CHBDC, CSA S6-14 2014) may underestimate the long-term seismic losses of the highway bridges. Under DE, the damage probability of the bridge retrofitted with optimized SMA restrainers experiencing collapse damage is only 0.7%. Under the same situation, its expected long-term loss is approximate 17.6% of that with respect to the unretrofitted bridge.

Evaluation of seismic hazard in low to moderate seismic regions, Sri Lanka—a case study

An assessment of seismic hazard based on the probabilistic approach was undertaken for a low seismic island region, Sri Lanka. Potential source zones in both local and regional contexts were identified in a comprehensive manner based on active tectonic structures and past evidence of seismic activities in the region. This source zonation, because of “dormant to mild seismic nature” of the region, led to characterize most of the regionally dominant seismic sources simply into large area zones. Recurrence rates of seismicity in each of the identified source zones were obtained for pre-estimated periods of completeness, unless otherwise data of a source zone were clearly incomplete due to lack of earthquake records, in which case recurrence parameters were found based on a subjective evaluation concerning the need of conservative recurrence rates for the area. Computed hazard values in terms of expected ground motions (peak ground acceleration (PGA) and spectral accelerations (SAs) at 0.1, 0.5, and 1.0 s natural periods) at rock sites in Sri Lanka for 10% (475-year return period), 5% (975-year return period), 2% (2475-year return period), and 0.5% (9975-year return period) probabilities of exceedance in 50 years’ time were depicted in separate raster maps. Hazard values showed that the area around the capital Colombo possesses maximum expected PGA (in rock sites) which is about 0.11g for a 475-year return period. Most of the other areas indicated relatively low values.

Earthquake risk assessment for the building inventory of Muscat, Sultanate of Oman

Earthquake risk can be quantified in terms of the estimated numbers of human casualties and of damaged buildings as well as the monetary losses. The information required for the assessment of earthquake risk in a given region includes the expected level of ground shaking intensity (i.e., the seismic hazard), inventory data for building stock at risk, identification of predominant building typologies and of their vulnerability characteristics, and spatial distribution of number of inhabitants. This study presents an indicative assessment of earthquake risk associated with the building stock in Muscat, the capital city of the Sultanate of Oman. For this purpose, building inventory and demographic data for the city are compiled in GIS environment. The buildings are classified to identify their damageability/vulnerability characteristics, and predominant building typologies are determined. For the estimation of casualties, Muscat population data are further analyzed to calculate number of occupants in the exposed building stock. Spectral acceleration–displacement based damage estimation methodology is implemented for risk calculations. Site-specific ground motions in terms spectral accelerations obtained from the probabilistic seismic hazard assessment for 475- and 2475-year return periods are considered for the representation of earthquake demand in damage analyses. Assessment of damage to buildings and estimation of casualties are obtained using analytical fragility relationships and building damage related casualty–vulnerability models, respectively. Earthquake risk maps illustrating the spatial distribution of number of damaged buildings at different damage states are presented for the considered levels of seismic hazard.

Probabilistic seismic hazard for Himalayan region using kernel estimation method (zone-free method)

In view of active seismic status of the Himalayan belt and continued developmental activities in mountainous states, it is imperative to update knowledge of seismic hazard incorporating latest knowledge on earthquake occurrence and attenuation process. The present research work delivers new-generation probabilistic seismic hazard information for northwest and central Himalayan region. We adopted a noble approach following a zone-free method, first time, for the Himalayan region to estimate the ground motion at bedrock level, the results of which are compared with the contemporary zoning method for the same area. Employing new-generation ground motion prediction equations, peak ground acceleration and spectral acceleration have been estimated in the region for return periods of 475, 975 and 2475 years (10, 5 and 2% exceedance in 50 years, respectively). The zone-free method predicted maximum ground motions in two areas Kashmir valley and eastern part of the Uttarakhand and the westernmost part of the Nepal. The ground motion ranges from 0.04 to 0.60 g for 2475-year return period.