Ground Motion Values Research Articles

Probabilistic Seismic Hazard Assessment of the Southwestern Region of Saudi Arabia

In relation to its rapid infrastructure expansion, exemplified by projects like the Najran Valley Dam or the rehabilitation of agricultural terraces, Saudi Arabia stands out among the Arabian Gulf nations. To mitigate the earthquake-related risks effectively, it is imperative to conduct an exhaustive analysis of its natural hazards. The southwesternmost region of Saudi Arabia is the main subject area of this study for the probabilistic seismic hazard assessment (PSHA), which aims to identify the peak ground acceleration (PGA) and spectral acceleration (SA) values. The investigation encompasses a 10% and 5% probability of occurrence over a 50-year exposure time for both B/C and C NEHRP soils. In order to take into account the earthquake activity that takes place in the vicinity of the Red Sea Rift, which in fact may have an impact on the seismic hazard in this active tectonic region, different seismic source zones were especially designed for this evaluation. Various characteristics such as the uncertainties related to the b-value, the expected maximum magnitude, and different ground motion prediction equations (GMPEs) were integrated using a logic tree scheme. Additionally, regression relationships between the computed ground motion values were established, and a novel design response spectrum was developed and recommended for several cities. Regarding the key findings, it is significant to highlight that the seismic hazard decreases towards the northeast, when moving away from the Red Sea Rift, confirming anticipated trends where proximity to the rift corresponds to increased seismic hazard. Notably, cities such as Farasan Island, Jazan, Al Qunfundhah, Al Lith and Al Birk present the highest observed hazard values among all the cities analyzed. For these cities, the obtained maximum SA values for both 475 and 975 years under B/C site conditions are as follows: 0.268 g and 0.412 g, 0.121 g and 0.167 g, 0.099 g and 0.150 g, 0.083 g and 0.135 g, and 0.066 g and 0.118 g, respectively. These results emphasize the crucial necessity of adequately evaluating and thoroughly updating the seismic hazard inherent to these particular areas to enhance the risk reduction and disaster readiness initiatives.

Regional and Site-Specific Ground Motion Model for Probabilistic Seismic Hazard Analysis in Taiwan: A Case Study of I-Lan

In this study, a probabilistic seismic hazard analysis (PSHA) using a traditional approach with a simple logic tree that handles a single-site sigma is developed to present a site-specific ground motion hazard. The analysis relies on the accelerometer data collected from the I-Lan Plain, a deep sedimentary basin in Northeastern Taiwan where hundreds of earthquake sequences (with [Formula: see text] = 4.0–7.6) were recorded by the Taiwan Strong Motion Instrument Program (TSMIP) network between 1992 and 2016. The performance of PSHA on soil and hard sites is evaluated from two representative instrumented sites (ILA048 and ILA025), using residual measures available from a ground motion model (GMM) developed by Phung et al. [ 2023 ] (referred to as Ph23), from which the uncertainties in site terms ([Formula: see text] and single-site sigma ([Formula: see text] are estimated. We address key conceptual issues in the current PSHA approach and introduce a new region- and site-specific PSHA approach in which (1) site-to-site variability ([Formula: see text] is estimated as a random variance in a mixed effects GMM regression and (2) the GMM site-specific single-site sigma ([Formula: see text] is replaced with a generic site-corrected aleatory variability ([Formula: see text]). Comparison of the region- and site-specific hazard curves from our method against the traditional method estimates at two well-recorded sites in the I-Lan region shows an approximate 50% difference in prediction ground motion values considering for 2% and 10% probability of exceedance in 50 years.

Comprehensive seismic loss model of Tehran, Iran in the case of Mosha fault seismic scenario using stochastic finite-fault method

This paper presents the results of a study caried out to assess probable seismic loss, in term of damage to the residential buildings and the number of fatalities, in the case of Mosha Fault seismic scenario in Tehran, Iran. Accordingly, seismic risk components (including seismic hazard, exposure model and fragility curves) are evaluated. The stochastic finite-fault method with dynamic corner frequency is applied for quantifying ground motion values. The results shows that PGA on the soil surface could range between 0.1 g to 0.45 g. Then, a reliable model of building exposure by analyzing census data from Tehran is compiled. This model included 19 different classes of buildings and is used to evaluate the potential damage to buildings from seismic scenario. The results indicate that the median of damage ratio from 100,000 iterations for the whole of the city is about 6% ± 1.54%. The study found that the central and eastern parts of Tehran are the most vulnerable areas, with an estimated 15,952 residents at risk of losing their lives in this scenario. This is equivalent to 0.2 percent of total population of Tehran. The finding from this study can be used by local authorities to provide appropriate emergency-response and preparedness plans in the case of Mosha Fault seismic scenario.

An updated strong-motion database of Türkiye (SMD-TR)

We updated the earthquake strong-motion database of Türkiye (SMD-TR) that is initially compiled by Akkar et al. The updated data set consists of of 9244 earthquakes of magnitudes 3.0 ≤ M ≤ 7.8 that occurred between 1976 and 2023. It includes 95,890 three-component waveforms recorded at 1022 stations (55,375 records that are processed from 6710 events and 974 stations). The database is disseminated under research-oriented website DesignSafe ( https://doi.org/10.17603/ds2-f21x-s189 ) and is compiled to provide ground-motion flatfile, which will be updated periodically until 2025. The released version includes events occurred in Türkiye until 28 February 2023, and hence, it comprises of the mainshocks and a great portion of aftershocks from the February 6th, 2023, Kahramanmaraş earthquakes. The database includes event metadata compiled from national and international seismological agencies as well as the literature. We classified events according to their tectonic environments (i.e. active crustal and subduction) and identified the aftershocks. The station information provided by AFAD1 was used to compute the major site parameters, including time-based average of shear-wave velocity of uppermost 30 m (VS30) and depth-to-rock horizon at which the shear-wave velocity (VS) attains 1 km/s (Z1). We also computed the finite-fault distance metrics and flagged the stations located on the hanging-wall side of the rupture, as well as identified pulse-like records. We developed an automatic processing algorithm to determine the waveform quality, apply appropriate filtercut-offs to remove low- and high-frequency noise, and compute ground-motion parameters. The automatic processing was applied to small-magnitude (M < 5.5) events, whereas manual processing scheme is preferred for waveforms recorded from larger events (M ≥ 5.5). The peak ground-motion values, spectral ordinates, and ground-motion duration are provided along with the key data processing parameters in the flatfile.

New Methodology for Unbiased Ground-Motion Intensity Conversion Equations

ABSTRACT Ground-motion intensity conversion equations (GMICEs) allow for conversions between ground-motion amplitude and shaking intensity. The current methods used to develop GMICEs model the dependence of the intensity on the peak ground-motion (PGM) parameter. For some models, there is a second step that models the magnitude and distance dependence of the residuals from the initial regression. We show that this approach for developing GMICEs works well for estimating the intensity from median ground motions, but for ground-motion values away from the medians, the intensities estimated by the GMICE can have large bias, with overprediction for positive PGM residuals and underprediction for negative PGM residuals. The bias is due to an implicit assumption in the current approach that there is a direct causal relation between intensity and the ground-motion parameter and that the residuals of the intensity and ground-motion parameter are fully correlated. We present two alternative methodologies for developing GMICEs that do not suffer from this bias. The first method includes the magnitude and distance scaling of the GMICE in the initial regression for the scaling with the PGM. The second method excludes the magnitude and distance terms but includes the number of standard deviations of the PGM (ϵ) as an additional parameter in the GMICE. Using a synthetic data set of intensity and peak ground acceleration values, we show that the GMICE developed using the proposed method leads to more accurate estimates of the intensity than current methods. We also discuss implications of using GMICEs based on the proposed methods for the evaluation of probabilistic hazard maps and as input to ShakeAlert estimates.

Probabilistic seismic hazard assessment for Western Mexico

An updated probabilistic seismic hazard analysis in terms of peak ground acceleration and spectral acceleration values, for B, B/C, and C NEHRP site classes, for a 5% and 10% probability of exceedance in 50 years, has been conducted for Western Mexico. To achieve this assessment, a unified and updated declustered earthquake catalog (1787–2019), as well as an updated focal mechanism database (1963–2016), was compiled, prepared, and processed specifically for this work. Two alternative source models (area sources and a spatially smoothed seismicity model) were considered in the assessment, within a logic tree scheme. A characteristic earthquake model has been also implemented for some of the defined sources. The designed logic tree has additionally included other parameters: the possible uncertainty related to the Gutenberg-Richter b-value way of estimation, the maximum expected magnitude value, as well as two-alternative GMPEs selected for the subduction seismic sources. The obtained ground-motion results have been presented as seismic hazard isoacceleration maps, as well as uniform hazard spectra and hazard curves for 15 selected cities, for the three considered site conditions. A comparison between the obtained hazard values and the current seismic design regulations, as well as previous studies, has been also performed, and a new design response spectrum has been proposed. Finally, some regression fitting relationships between the obtained ground-motion values have been achieved. Concerning the most significant results, it is worth noting that the southwestern coast (in the perimeter of the Middle America Trench of the Mexican Subduction Zone) presents the highest hazard values. For instance, the cities of Apatzingán, Autlán, Colima, Lázaro Cárdenas, and Manzanillo exhibit the largest observed PGA values among all the studied cities. Our approach and results are supported by the fact that the recent September 19, 2022, Mw 7.6 earthquake has been located in this highest seismic hazard area.

The 2022 Seismic Hazard Model for Costa Rica

AB4STRACTCosta Rica is located at the boundary of four tectonic plates where the regularity of destructive earthquakes highlights the necessity of seismic hazard estimations. This study contains the most recent Probabilistic Seismic Hazard Assessment (PSHA) for Costa Rica, calculated with the largest and the most updated earthquake database from both—the Earthquake Engineering Laboratory and the National Seismological Network of the University of Costa Rica. For the PSHA, we updated the seismicity parameters for the upper plate, subduction interplate, and intraslab tectonic domains, characterized the upper-plate zones by percentages of fault types, and used weighted ground-motion models for each of the tectonic domains. The resulted maps of peak ground acceleration (PGA) at return periods of 475 yr (PGA-475) and 2475 yr, as well as the spectral accelerations, show geographic trends that allow for the division of the country in four seismic hazard levels: (1) extremely high for the Nicoya, Osa, and Burica peninsulas, situated directly above the subduction interplate, where the PGA-475 could be 0.55–1.20g; (2) very high for most of the Guanacaste Province, where the PGA-475 may be 0.55–0.70g; (3) high for most of the country (∼41%) with PGA-475 values of 0.40–0.55g, including Central Costa Rica and the capital city of San Jose; and (4) moderate for the Talamanca Cordillera and Northern Costa Rica, with PGA-475 up to 0.40g. These ground-motion values are 0.1–0.6g higher than the previous PSHA for the Pacific peninsulas, Guanacaste, and the southeastern Caribbean. Further, hazard curves, uniform hazard spectra, and a hazard disaggregation indicate that the seismic hazard is lower but more complex in San Jose than in Liberia—the largest city in Guanacaste.

Developing a new fatality model for Iran's earthquakes using fuzzy regression analysis

This paper presents the results of a study carried out to develop an empirical fatality model based on data of fatal and non-fatal earthquakes occurred in Iran since 1962. Two reliable databases (RAISE-DAT and REXPO-DAT) which incorporate the number of deaths and the affected population in the past earthquakes of Iran were compiled to make correlation between fatality rate and shaking related parameters. The uncertainties of these parameters (i.e., the number of fatalities in the past earthquakes and the ground motion values provided by the ShakeMap) were considered in the analysis, using the fuzzy regression and Monte Carlo simulation tools. In addition, the appropriateness of three distinct parameters including PGA, PGV and MMI were examined to be employed in the fatality model. The results show that PGA represents the best estimation of fatality (especially for strong earthquakes), while the other parameters (PGV and MMI) underestimate the fatality rate. As a case study, the model was applied in the Ahar-Varzaghan (6.5 Mw) 2012, Iran earthquake. The result shows a good agreement between the actual number of deaths and the estimated fatality. The proposed model can provide an initial assessment of death toll after destructive earthquakes. This is important for organizing rescue and relief activities during golden hours' after an earthquake. Accordingly, the model is used for rapid loss assessment system of Iran's earthquakes, called RAISE. The model can also be used for simulation potential impacts of earthquakes; therefore, it can be employed for seismic risk mitigation planning in Iran.

Efficient non-ergodic ground-motion prediction for large datasets

An efficient numerical method for non-ergodic ground-motion inference and prediction is proposed that alleviates the large computational and memory requirements associated with the traditional approach based on Gaussian Processes described in Landwehr et al. (Bull Seismol Soc Am, https://doi.org/10.1785/0120160118, 2016). The method uses the latest developments in Gaussian Processes and Machine Learning from Wilson and Nickisch (in: International Conference on Machine Learning, pp 1775–1784, 2015) (SKI) and Gardner et al. (in: International Conference on Artificial Intelligence and Statistics, pp. 1407–1416, 2018) (SKIP) and uses sparse approximations combined with efficient matrix decompositions to accurately approximate the large covariance matrices involved in the calculations. This efficient method can be used for both inference of hyperparameters of the non-ergodic ground-motion models and for forward predictions of non-ergodic median ground-motion. The application to predictions are presented. For large datasets of 100,000 to 1,000,000 ground motion values, the proposed method increases the computation speed by factors of 100 to 1000, reducing run times from days to minutes. In addition, the memory requirements are reduced from hundreds of GB to a few GB only, which makes the development of non-ergodic ground-motion models practical using traditional desktop computers.

Ground motion simulations in Quito (Ecuador) due to major earthquakes from the subduction zone

SUMMARY In 1906, an earthquake with a magnitude estimated between Mw 8.4 and 8.8 occurred in the subduction zone along the coast of Ecuador and Colombia. This earthquake caused extensive damage on the coast but had a rather small impact on the capital city of Quito, situated 180 km away. At that time, the city of Quito extended over a small area with a few thousand inhabitants, while today it stretches over 40 km and has a population of over 3 million, with most of the city built without paraseismic regulations. The aim of this study is to obtain new insights on the impact that large earthquakes from the subduction zone would have on the city today. This question is crucial since we know that the city of Quito is prone to site effects and that the southern part of the city amplifies seismic waves at low frequencies, around 0.3–0.4 Hz. In April 2016, an Mw 7.8 earthquake occurred on the subduction interface in the Pedernales area. This event was the first large earthquake in the city of Quito to be well recorded by 13 stations of the permanent accelerometric network (RENAC). In this study, we take advantage of this data set (main shock and large aftershock recordings) to (1) test an empirical Green's function blind simulation approach where the input stress drop is taken from a global catalogue of source time functions, (2) compare the synthetic accelerograms and ground motion values we obtain for an Mw 7.8 earthquake with the actual recordings of the Pedernales earthquake and then (3) simulate larger earthquakes of Mw 8.2 and 8.5 from the subduction zone. For Mw 7.8 simulations, our approach allows a good reproduction of the ground motions in the whole frequency bands and properly takes into account site effects. For Mw 8.2 and 8.5 simulations, we obtain for the stations in the southern part of the basin, larger values at low frequencies than the predicted motion given by ground motion models. These values, although high, should be supported by new or recent buildings if they are constructed respecting the building code that applies in Quito. Therefore, for this type of strong but distant earthquake, the seismic standards appear to be well suited and it is imperative to ensure that they are well considered in the design of the new buildings to be constructed, especially in the southern part of the expanding city.

Seismic behavior of LRB and FPS type isolators considering torsional effects

This study aims to investigate seismic behavior of lead-core rubber elastomeric bearing (LRB) and curved surface friction pendulum slider (FPS) base isolated models considering torsional irregularity for typical reinforced concrete buildings. Nonlinear behavior of structural members was considered in analysis models. Total of 1408 different nonlinear time history analyses of 3-dimensional 3, 5, 7 and 9-story models were performed considering 11 spectrum compatible ground motion record pairs. The results indicate that when the rigidity center of base isolator system is not coincided with mass center of superstructure, highest torsional irregularity coefficients were calculated. Lead-core rubber elastomeric bearing type isolators are more sensitive to torsional effects compared to curved surface friction pendulum slider type isolators. Torsional irregularity coefficient values of lead-core rubber elastomeric bearing models with 20% eccentricity are 47% higher than models without eccentricity in terms of averages. The obtained results indicate that significant scatter exists in displacement values of individual ground motion records for all models. Using limited number of ground motion records may lead to inaccurate predictions of seismic demands.

Site Amplification at Permanent Stations in Northeastern Italy

ABSTRACTThe application of earthquake recordings to the estimation of an event’s magnitude and the construction of rapid-response ground-motion maps requires an adequate classification of the recording stations in terms of their site response. For permanent stations, this information can be obtained from a sufficiently large database of past recordings.In this work, we analyze more than 7300 three-component recordings collected between 1996 and 2017 by 67 permanent stations in northeastern Italy to assess their site amplification. The signals come from 368 earthquakes with a magnitude range of M 3.2–5.8 and a distance range of 10–300 km. We evaluate the frequency-dependent amplification function with respect to a reference station with a flat seismic noise horizontal-to-vertical spectral ratio. The evaluation relies on the decomposition of the S-wave amplitude spectra in terms of source, propagation, and site response. We solve the decomposition with a nonparametric, single-step generalized inversion in the frequency band 0.5–20 Hz. In addition, we compute the amplification factors for peak ground acceleration and velocity with respect to a well-established ground-motion prediction equation. The results highlight that only 11 stations show a relatively flat unitary response with respect to the reference site, whereas the frequency-averaged amplification function at 23 out of 67 stations exhibits a value larger than 2. We classified the sites according to their surface geology and geomorphological scenario and found that amplification affects not only stations installed on the alluvial soil but also several stations installed on what are assumed to be rock sites. Sites in caves and mines exhibit deamplification, whereas the stations with sensors in boreholes exhibit the typical interference pattern. A good correlation between the amplification factors and the frequency-averaged amplification functions suggests the possibility of predicting time-domain peak ground-motion values from amplification functions estimated by generalized inversion.

Earthquakes and dams: Remote and direct monitoring of UK earthquakes affecting dam infrastructure

Although earthquake hazard in the UK is low, there is a long history of earthquakes that have been widely felt or in some cases caused damage. Although these events are relatively rare, earthquake hazard assessment is still required for structures, such as dams, where the consequence of failure may be very high. Since 1990 the UK has experienced more than 13 earthquakes of greater than magnitude 4. The largest recorded onshore earthquake was a 5.4 local magnitude (ML) (Lleyn Peninsula, 1984) and the largest offshore was the 6.1 ML (Dogger bank, 1931). Smaller earthquakes can also produce levels of ground motion more typically associated with larger earthquakes; for instance, if they are unusually shallow or otherwise close to a structure of interest. In this talk two different, but potentially complimentary, methods of monitoring reservoir infrastructure for the affects of earthquakes are considered: remote monitoring of a region with a rapid alert system combined with the use of ground motion prediction equations to assess the likely ground motions at facilities of interest and direct emplacement of seismic sensors in or around reservoir structures to provide absolute values of ground motion during an earthquake.

A backbone probabilistic seismic hazard analysis for the North Tehran Fault scenario

In this study, a comprehensive probabilistic seismic hazard analysis (PSHA) using both time-independent and time-dependent approaches is carried out for the North Tehran fault (NTF) scenario. We applied a novel backbone approach to consider the epistemic uncertainty associated with the ground motion estimates. For this purpose, a backbone ground motion model (GMM) is selected using the data-driven deviance information criterion (DIC) method, and the logic tree branches are populated with the backbone GMMs that are added/subtracted from a scale factor. The results show that the estimated ground motions follow the spatial pattern of the NTF and decrease in the far-field, but this spatial pattern is also influenced by the amplification from site effects, in the southern alluvium part where the sites are classified as the category D of NEHRP. Furthermore, the effect of the multi-segment rupture is investigated using a cascading model. The results show that the ground motion values are increased by 20–40% and 10–20% for the 10%-in-50 years and 2%-in-50 years, respectively, particularly at near-fault distances. The results of this study are generally compatible with the previous seismic hazard studies for the Tehran region. Therefore, the novel backbone approach used in this study provides a more reliable seismic hazard estimates for the Tehran metropolis.

Fault System-Based Probabilistic Seismic Hazard Assessment of a Moderate Seismicity Region: The Eastern Betics Shear Zone (SE Spain)

Including faults as seismogenic sources in probabilistic seismic hazard assessments (PSHA) has turned into a common practice as knowledge of active faults is improving. Moreover, the occurrence of earthquakes in multi-fault ruptures has evidenced the need to understand faults as interacting systems rather than independent sources. We present a PSHA for the Southeastern Spain obtained by including the faults of a moderate seismicity region, the Eastern Betics Shear Zone (EBSZ) in SE Spain, as the main seismogenic sources in two separate source models, one considering background seismicity. In contrast with previous studies in Spain, earthquake occurrence of the EBSZ system is modeled considering different hypotheses of multi-fault ruptures at the whole fault system scale and weighted in a logic tree. We compare the hazard levels with those from an area source PSHA and a previous fault-based approach. The results show a clear control of the EBSZ faults in the seismic hazard for all return periods, increasing drastically the hazard levels in the regions close to the fault traces and influencing up to 20 km farther with respect to the area source PSHA. The seismic hazard is dependent on the fault slip rates as peak ground accelerations and territorial extension of the fault influence appear higher around the Alhama de Murcia and Carboneras faults, while lower slip rate faults (Palomares Fault) show minor contribution to the hazard. For the return period of 475 years and near-fault locations, our models are more consistent with the ground motion values reached in the 2011 Mw 5.2 Lorca event than the building code or national seismic hazard map, which suggest that our fault system-based model performs more accurate estimations for this return period. Fault data, mainly slip rates, and its uncertainties have a clear impact on the seismic hazard and, for some faults, the lack of detailed paleoseismic studies can compromise the reliability of the hazard estimations. This, together with epistemic uncertainties concerning the background seismicity, are key discussion points in the present study, having an impact on further research and aiming to serve as a case example for other low-to-moderate seismicity regions worldwide.

Ground Motion to Intensity Conversion Equations for Iran

New empirical relations between macroseismic intensity and ground motion parameters including peak ground acceleration and velocity are developed using strong ground motion data and Modified Mercalli Intensity (MMI) information from earthquakes within Iran plateau. The strong motion data consists of 116 three-component waveforms of 23 earthquakes with Mw 5.1–7.3 occurred from 1977 to 2017. The intensity values for each ground motion record were assigned considering the location of accelerograph stations on the isoseismal maps. Simple predictive equations are obtained by fitting a linear model to the mean peak ground motion values applying least squares regression. However, visual inspection of residuals shows magnitude and distance dependency for this set of equations. Improved relationships between ground motion and intensity are derived by comprising magnitude and distance terms as predictive variables. The refined ground motion to intensity conversion equations show smaller variability than simple linear equations in predicting MMI values. Both proposed models are compared with similar relationships in Iran and other regions of the world. The observed discrepancies in relationships may reflect the differences in input data, especially the macroseismic intensity assignments as well as regional variability. The proposed relations can be used for rapid hazard assessments and loss estimation in Iran and surrounding regions.

Prediction of rotational ground motion for mining-induced seismicity – Case study from Upper Silesian Coal Basin, Poland

For decades, coal mining in the Upper Silesian Coal Basin (USCB) in Poland has been inducing annually more than 150 seismic events with local magnitude M > 2. Two sets of sensors were installed in the USCB in Poland to measure angular velocities and translational accelerations from seismic events induced by underground coal mining. In the period from December 2015 to November 2016, 503 seismic events were recorded with local magnitude M between 1.1 and 3.5. Analysis of measurement data for induced seismicity confirmed a strong linear correlation between peak ground acceleration of shear S-waves, PGA and peak ground motion of angular velocity, PRV. The observed correlation can be a result of previously observed coupling between the angular instantaneous velocity vector and the respective displacement vector at the ground surface. Three types of empirical equations for induced seismicity in Upper Silesia in Poland were developed to predict the peak rotational ground motion of the vertical (torsion), horizontal (rocking), and instantaneous 3D-xyz components. The prediction values of horizontal peak angular velocity ground motion indicate that for strong mining-induced seismic events in the USCB with a magnitude of M = 3.5, we can expect that the mean values of PRVH will reach 7.5 mrad/s in the epicentral area (r = 500 m) and with magnitude M = 4 respectively will reach 19.7 mrad/s. Such values of ground rotation may substantially contribute to the overall seismic response of civil infrastructure, particularly for tall buildings. The study of angular velocity ground motion is important not only from the cognitive point of view, but also from practical significance for assessing the seismic impact on very high buildings, chimneys and stability of slopes.

Quantifying Uncertainties in Ground Motion-Macroseismic Intensity Conversion Equations. A Probabilistic Relationship for Western China

ABSTRACT We analyze the global and local uncertainties of ground motion-macroseismic intensity conversion equations and derive new probabilistic relationships between the macroseismic intensity and peak ground motion parameters (peak ground acceleration and peak ground velocity) for western China based on the assumption that the peak values of ground motion are randomly distributed for each MMI level, bounded by a normal distribution. For this purpose, a strong ground motion database consisting of 37 moderate- to large-magnitude earthquakes that occurred in western China between 1994 and 2017 is employed along with the corresponding modified Mercalli intensity (MMI) information inferred from isoseismal maps and earthquake damage reports. The mean value and standard deviation parameters in the probabilistic formulas are obtained from the result of the analysis of the local uncertainties of the data compiled for Western China. We propose a method for the rapid assessment of computer-generated intensity maps using the new probabilistic formulas. Our method composed of two steps. (1) According to a Bayesian formula, the possibility, expectation and standard deviation of the seismic intensity are calculated by the ground motion parameters recorded at a site station. (2) Furthermore, expectation and standard deviation maps of the seismic intensity throughout an area are obtained through spatial interpolation. Finally, an application is illustrated to validate this new methodology by presenting rapidly estimated (computed) intensity maps of the 8 December 2016 Hutubi (Ms 6.2) earthquake in western China.

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.

Numerical Study of Potential Indonesian Rubber for Elastomeric Base Isolators in Highly-Seismic Zones

Indonesia is located in high seismic zones. Therefore, earthquake dissipated devices such as elastomeric base isolator is needed to minimize building’s damages when an earthquake occurs. In this study, a numerical two-stage analysis was carried out to evaluate the behaviour of elastomeric base isolators. First, elastomeric base isolators were modelled in the finite element software to obtain vertical and horizontal stiffness and damping values based on local rubber of mechanical properties that is obtained from the previous tests. Second, the values of vertical and horizontal stiffness and damping values were analysed in a case study of a ten-stories hospital building located in Padang, West Sumatra, Indonesia using nonlinear time history analysis of seven different ground motion values. The studied results showed that the structure with base isolators using a local rubber base material can reduce damage caused by the earthquake with an indication of an increase in time period, decreased base shear, and also a decrease in displacement of the structure. Therefore, the use of local rubber for elastomeric base isolators is promising a good future for the advancement of the construction industry in Indonesia.