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Developing an effective emergency collaborative distribution system is critical to improve on-time response performance, especially considering secondary disasters. To address the challenge, this paper investigates a bi-objective robust optimisation model on relief collaborative distribution among three echelons of authorities, the province, the municipality, and the county, which aims to minimise the total travel time and the total humanitarian logistics cost simultaneously. The optimal location of relief supply facilities and the relief distribution schemes will be determined by the optimisation model, which considers uncertain demand and travel time. Moreover, two robust optimisation methods are utilised to deduce the robust counterparts of the proposed model. An epsilon-constraint-based approach is used to solve the bi-objective optimisation model. A real-world case study based on an earthquake and aftershocks with different magnitudes in Yunnan Province is provided. The results show that incorporating secondary disaster scenarios contributes to reducing the total travel time and cost. For making full use of emergency resources and preventing situations from worsening, the centralised decision scheme is more effective than the decentralised one. The uncertainty of demand of primary disaster relief has a higher impact on the optimal solution than that of travel time. [ABSTRACT FROM AUTHOR]

This research aims to establish a new methodology for defining building functionality and resilience under successive damage-retrofit processes during recovery. Resilience is the ability of systems to rebound after severe disasters. It mainly depends on the performance of the building under the different mainshock and aftershock scenarios, the recovery process, and recovery time. Considering different scenarios of mainshock and aftershock (time of occurrence, intensity, etc.) and the parameters that affect the recovery process, calculating seismic resilience has many uncertainties. The methodology is proposed using the performance-based earthquake engineering approach (PBEE) and probabilistic methods to consider the uncertainties. The main objective of the proposed methodology is to provide a practical approach to evaluating the impact of aftershocks on the performance of damaged buildings that are partially restored after a mainshock occurrence. A probabilistic recovery model is proposed to compute the recovery path. Two case studies are performed to illustrate the applicability of the methodology. Reinforced concrete buildings with 3 and 6 stories are considered, while their functionality and seismic resilience are calculated under an assumed mainshock-aftershock scenario. The findings of this work may be used to estimate the resilience of damaged buildings to have resilient communities and buildings. [ABSTRACT FROM AUTHOR]

In this paper, I explore how the racial structure of an immigrant-receiving Latin American society informs the strategies that are available to its members when they are confronted with the arrival of perceived racial outsiders. Using survey data, I explore how Dominicans responded to the rapid influx of displaced Haitians in the aftermath of the 2010 earthquake in Haiti, and find that when surveyed after the earthquake, Dominicans were more likely to self-identify with the popular and nationalist identity category of indio. I argue that this signaled a heightening of anti-Haitian sentiment in a moment of perceived increased racial threat to the Dominican racial order, and that this shift was facilitated by Latin American racial dynamics that allow for movement between enumerated racial categories in societies structured around the logic of mestizaje. [ABSTRACT FROM AUTHOR]

This document is a collection of articles that explore the relationship between spatial thinking, geography, reading, and math. It discusses the use of spatial analogies, which involve comparing spatial relationships between different locations to make predictions or explanations. The articles emphasize the importance of teaching spatial thinking skills through hands-on activities and provide examples of activities that can be used in the classroom. They also highlight the complexity of spatial reasoning and the need for teachers to be aware of different modes of spatial reasoning in reading and math instruction. The overall goal is to provide insights from research in neuroscience, linguistics, and developmental psychology to help teachers design better geography lessons for students. [Extracted from the article]

A seismic sequence has struck the Yangbi county, west part of Yunnan Province in southwest China since May 18, 2021. This region experienced the strongest ground shakings on the night of 21 May with the successive occurrence of four earthquakes with MS ≥5.0 in a short time and more small earthquakes. Large numbers of strong-motion recordings obtained in the four earthquakes with MS ≥5.0 (i.e. the MS 5.6 foreshock, the MS 6.4 mainshock, the MS 5.0 and MS 5.2 aftershocks) were analyzed in detail to characterize the source effects, distance decay, etc. The velocity pulse-like waveform at near-source station 53YBX and the significant asymmetry of distance decay along the SSE-NNW direction (i.e. much slower toward the SSE) in the MS 6.4 mainshock seem to hint the occurrence of the asymmetrical source rupture. The source rupture directivity for the four events were investigated by fitting the azimuth-dependent residuals of the PGAs. The MS 6.4 mainshock is characterized by the significantly asymmetrical bilateral rupture propagation, predominantly in the SSE direction with a rupture velocity of about 2.24 km/s. The PGA and PSAs from the four earthquakes were further compared with the predicted medians of the ASK14 and CY14 prediction models for global shallow crustal earthquakes. The negative inter-events residuals reflect the weaker source contributions of the Yangbi events to ground motions. The source contributions to short-period ground motions approximately show the dependence on earthquake type, that is, MS 5.6 foreshock > MS 6.4 mainshock > MS 5.2 aftershock, consistent with the dependence of stress drop on earthquake type. We further noted that the inter-events values for the MS 5.0 aftershock are far below those for the MS 5.2 aftershock. This may be attributed to the differences in the spatial and temporal distance to the mainshock, that is, weak source contributions from the close aftershocks to the mainshock. The values of adjustment coefficient Δc3 are almost positive, indicating the weaker anelastic attenuations in the study region. Finally, we also found that the distance scaling of significant duration can be well described by both empirical models (AS16 model for predicting significant duration and the BT14 model for empirically illustrating the ground-motion path duration). [ABSTRACT FROM AUTHOR]

Shake table tests were conducted on a three-story steel braced frame with pretensioned basalt fiber reinforced polymer (BFRP) under the mainshock and aftershock sequences. The BFRPs were firstly tested to evaluate their dynamic behaviors. Then the self-centering braced frame was excited to a series of scaled earthquakes whose PGAs range from 0.2 g to 1.2 g. Through the pinned connections in the tested frame, the self-centering braces (SCBs) with pretensioned BFRPs were the standalone components to dissipate the seismic energy. The results revealed that the BFRPs with slight performance degradation were suitable to provide the restoring force for SCBs even under the strongest earthquake intensity. SCBs with pretensioned BFRPs were efficient in preventing damage and reducing the residual drift ratios. Although the aftershock slightly amplified the accelerations of the tested frame, the self-centering braced frame with pretensioned BFRPs presented similar drift ratios under the aftershock and separate mainshock with the same PGA. Therefore, the self-centering steel braced frame with pretensioned BFRPs has favorable resilient seismic behaviors and could quickly restore its functions after a strong mainshock-aftershock sequence. [ABSTRACT FROM AUTHOR]

More and more earthquake cases demonstrate that sandy deposits may be more prone to becoming liquefied again in aftershock events. This phenomenon has also been authenticated by some laboratory element tests and shaking table tests. However, most of the existing studies on reliquefaction only put particular emphasis on the completely reconsolidated soil. Due to the possible short time interval between the main shock and its aftershock events, the generated pore pressure in soil deposits may not have completely dissipated when the aftershock occurred; the reliquefaction is more likely to occur under incomplete consolidation conditions. To investigate the reliquefaction behaviors and the related microscopic mechanisms for the incompletely and completely reconsolidated soil, a series of numerical cyclic triaxial tests are performed in this study via the 3D Discrete Element Method (DEM). Results demonstrated that the reliquefaction resistance of soil is significantly affected by the residual strain and the reconsolidation degree. From the microscopic point of view, the fabric anisotropy and the tightness of inter-particle contacts are the main factors affecting the reliquefaction resistance. [ABSTRACT FROM AUTHOR]

Aftershock probabilistic seismic hazard analysis (APSHA) is essentially useful for various earthquake engineering problems. In this paper, a series of aftershock seismic hazard analyses were conducted in western Zagros region in Iran using different approaches. The results were obtained in terms of exceedance probabilities of peak ground accelerations within different time intervals following the mainshock. The results were generally compatible with the recorded data; however, the accuracy depended on the causative fault geometry and spatial distribution of aftershocks. The accuracy decreased in shorter time intervals after the mainshock and also in longer time spans especially when strong aftershocks occurred. [ABSTRACT FROM AUTHOR]

Shallow crustal earthquakes (SCE) occur in different seismotectonic regions of the Iranian plateau. In this study, 10 ground motion prediction equations (GMPEs) developed based on local, regional, and global data from SCE are considered as candidates to test their explanatory power against Iranian strong motion data. To show the applicability of candidate GMPEs in the plateau as a united region and its different seismotectonic sub-regions, a dataset including 3045 records from 678 seismic events (both mainshocks and aftershocks) is used for statistical analyses. Moreover, using 1662 records from 245 mainshocks, we tried to find more appropriate GMPEs against mainshock ground motions through statistical tests. This work also concentrates on differences in ground motions from mainshock and aftershock earthquakes using the Iranian database. The statistical analyses including LH (Likelihood), LLH (Log-Likelihood) and EDR (Euclidean distance-based ranking) are also performed on GMPEs modified by a local anelastic term. According to the LH and LLH analyses results, local and regional models have better performances for PGA and spectral accelerations (SA) at different periods ranging from 0.05 to 3 sec. However, according to the EDR test, it can be said that some global GMPEs also show acceptable performance for predicting the Iranian ground motions. Also, the adjustment factors added to the GMPEs can considerably improve their explanatory performance. [ABSTRACT FROM AUTHOR]

Bridges subjected to mainshock–aftershock sequences experience significant damage as a result of repeated shaking. Therefore, neglecting the effects of multiple earthquakes may lead to a considerable underestimation of bridges seismic vulnerability. The uncertainties in modeling bridge structural systems as well as the representation of seismic loads significantly affect the bridge vulnerability, especially for horizontally curved bridges, where complex loading conditions exist. In this study, fragility curves for horizontally curved bridges are developed for both mainshock only and mainshock–aftershock sequence cases. The seismic response of a typical four-span horizontally curved reinforcement concrete box-girder bridge is evaluated using the cloud analysis method and the effects of uncertainties on the probability of failure of the bridge components are examined and quantified using the Latin hypercube sampling technique. The results from this investigation indicate that considering the mainshock only could significantly underestimate the damage level even by around 50% and that incorporating uncertainties could change the bridge capacity by more than 45% of its estimated value. [ABSTRACT FROM AUTHOR]

Ageing structures located in moderate to high seismicity regions are exposed to multiple natural stressors during their lifetime. Large earthquake events coupled with environmental aggressive agents increase the progressive failure probability of these structures. The accumulated damage during the main earthquake event might be exacerbated by its following aftershocks. This might result in catastrophic failure of these structures, and consequently, result in several socio-economic losses. Taking such progressive deterioration mechanism into consideration, the current study presents a framework to assess the vulnerability of ageing Reinforced Concrete (RC) frames subject to real Mainshock-Aftershock (MS-AS) ground motion sequences. Employing an advanced fibre-based finite element modelling technique, the nonlinear static and dynamic behaviour of a case-study RC frame with various ages is simulated under 48 real MS-AS record pairs. Quantifying corrosion-variant damage states, the age-specific fragility curves are developed for the considered structure under both single MS events and MS-AS sequences. It was found that the severely corroded RC frames are most likely to collapse before the second event comes up. Moreover, results show that the PGA ratio of AS to MS plays a critical role in seismic vulnerability assessment of highly corrosion-damaged RC frames. [ABSTRACT FROM AUTHOR]

The dynamic responses of an instrumented twenty-story steel-moment frame office building were identified with the data from mainshock (M 7.1) occurred on November 30, 2018 and its six aftershocks ranging from M4.2 to 5.7 in the Alaska-Aleutian subduction zone. The deconvolution-based seismic interferometry was used to identify the traveling waves and intrinsic-damping ratio in the building. The median shear-wave velocity is 179 m/s for the east-west (EW), 201 m/s for the north-south (NS), and 174 m/s for the torsional responses. The building's average intrinsic-damping ratio is estimated to be 4.4% and 3.7% for the EW and NS directions, respectively. [ABSTRACT FROM AUTHOR]

The M 6.5 earthquake that occurred in the Monte Cristo Range near Mina, Nevada on 15 May 2020 was exceptionally well-recorded with both seismic and geodetic instrumentation. The arid nature of the region also facilitated detailed ground mapping of the surface rupture. Here we integrate several independent data sets to illustrate the educational and research opportunities afforded by these rich data sets. We construct a series of models for slip at depth that are consistent with the satellite-derived geodetic data, the distribution of aftershocks, and the mapped surface rupture. We also show that the modelled depth of maximum slip is in good agreement with heat flow and laboratory data on quartz rheology defining the depth of the brittle-ductile transition. The Monte Cristo Range earthquake also suggests new approaches to seismic hazard assessment may be required for earthquakes in rapidly evolving tectonic regions such as the Walker Lane and Eastern California shear zone. [ABSTRACT FROM AUTHOR]

Reinforced concrete intake towers are considered as main hydraulic structures constructed in dams' reservoirs, connected to the dam or as a separate structure. If an intake tower is damaged, the powerhouse or downstream of the dam may experience serious problems. In this research, the influence of mainshock-aftershock seismic sequences is studied on real intake tower. The intake tower of Encino dam is modeled by using the finite element method. The dynamic time history analyses are conducted with the real as-recorded earthquakes and the nonlinear behavior of concrete and steel bars is considered. The tower is modeled with reservoir and foundation, and their interactions are considered. The earthquake records are applied to the tower in three cases: (i) one horizontal component, (ii) two horizontal components, and (iii) two horizontal components with vertical component. The main dynamic responses of the tower including relative deflections and nonlinear material responses are presented. The obtained results are discussed, and the influence of the main shock-aftershock sequences are thoroughly examined. [ABSTRACT FROM AUTHOR]

The Canonical Correlation Analysis (CCA) estimates the correlation between two vector variables by maximizing the correlation of linear combinations of their respective components. Here, the CCA is used to find correlation patterns in the last five successive, per pairs, earthquakes ( M ≥ 4.0) preceding 271 main shocks ( M ≥ 5.5) that occurred in the Greek territory during 1964–2018. The vector variables have two components, the earthquake magnitude and interevent time. The statistical significance of CCA is determined by the standard parametric test along with two proposed randomization tests, one using random shuffling of each paired dataset and one using randomly selected pairs of successive earthquakes. Simulations were designed on synthetic data from vector variables having the statistical characteristics of the real observations. The results on uncorrelated variables showed the correct size for the two randomization tests but larger type I error for the parametric significance test for small sample size. For correlated variables, the test power was equally high for both test types. The application of CCA and the significance tests to the Greek seismicity evidence the significant correlation among the last five successive preshocks, proving to be a promising tool in an a posteriori short-term earthquake forecasting. [ABSTRACT FROM AUTHOR]

The effect of mainshock-aftershock (MS-AS) sequences on seismic performance of ordinary reinforced concrete (RC) moment frames (ORCFs) is studied by considering various levels of mainshock damage represented by maximum inter-story drift (MID) parameter. Incremental dynamic analysis (IDA) is performed to extract collapse capacity of structures under aftershock records after imposing the intended mainshock damage. The study results indicate that a smooth reduction in aftershock collapse capacity occurs due to increase in mainshock damage level. Regression equations are also provided to aid in predicting the aftershock collapse capacity in presence of various mainshock damage levels. [ABSTRACT FROM AUTHOR]

In the Western China, soft rocks, in particular, phyllites are very widespread. With the increase of soft rock tunnels in recent years, the secondary lining cracking of newly-built tunnels have frequently occurred. In this work, a case study on the Dujiashan Tunnel in the Western China was conducted in order to get insight into the damage mechanisms of such soft rock tunnels in the strong earthquake zone. Furthermore, for the engineering background, the cracking characteristics, on-site monitoring data, influencing factors and damage causes for the the second lining of Dujiashan Tunnel were also investigated. It was demonstrated that with the concentration of the bending moment and shear stress, the reduction in axial pressure appeared on the lining structure at the cavities due to local collapses. Moreover, the aftershocks of the Wenchuan earthquakes could further weaken the strength characteristics. It was revealed that the secondary lining measures were useful for the reinforcement of the Dujiashan Tunnel, and the treatment measures could achieve mainly the backfilling collapse cavities, leading to reinforcing the surrounding rocks, preventing the cracking behavior, strengthening lining, and smoothing drainage. It is therefore suggested that for the newly-built soft-rock tunnels, especially those located in strong earthquake zones, the use of the secondary lining should be at the appropriate time and backfilling the cavities due to local collapses timely, and all the factors are important for the protection and reinforcements of the surrounding rocks to ensure the safety of the tunnel structure. [ABSTRACT FROM AUTHOR]

Seismic performance of postmainshock buildings considering seismic mainshock-aftershock sequences are studied. The case studies correspond to three SAC steel MRF buildings of three, nine and twenty stories. The 2-D models are able to capture important properties of deterioration of strength and stiffness. Endurance time method is used to predict the response of structures in different hazard levels. Results are compared with those from of nonlinear incremental dynamic analysis. Maximum dynamic seismic responses of structures are captured during synthetic mainshock-aftershock seismic sequences which are produced by endurance time method. Interactional-conceptual curves for different seismic performance levels and residual collapse capacity of post-mainshock damaged buildings are presented. The collapse fragility curves of case studies are extracted. The results show that the residual seismic response of building caused by the mainshock and the direction of applied aftershocks are highly significant factors in evaluation of postmainshock buildings. It is found that in a seismic sequence which has two earthquakes with different intensities, occurrence of the stronger shake before the less intensive one, imposes higher seismic risk to the building. [ABSTRACT FROM AUTHOR]

The current study aims at seismic analysis of damaged concrete gravity dams subjected to aftershocks loading of earthquake. Dams' sliding behaviour is also discussed to shed light on the issue. For the purpose of the study, a cracked concrete gravity dam was modelled, and zero thickness contact elements were used to model the contact between the main body and the separated damaged parts of the dam. The augmented Lagrangian method, considering frictional sliding and opening of contact joints, was used in non-linear analyses. Fluid-structure-interaction, considering fluid compressibility and absorptive boundary of reservoir, was also taken into account. The damage model of 'Konya' and 'Manjil' dams comprised our case study. Non-linear dynamic analyses were done based on both models. Stiffness and damping coefficients effect on the seismic response of dam were examined. Dam, foundation and reservoir interaction effects were also included. The results were compared to the results obtained from other methods, which showed adequate similarities. The differences between damages caused by aftershocks are discussed, and it is pinpointed that the stability of dam during aftershocks is not compromised. It is demonstrated that top block slides during each aftershock and finally incurs some permanent sliding which may destroy the dam. [ABSTRACT FROM AUTHOR]

A destructive earthquake of moment magnitude Mw 7.8 struck central Nepal on April 25, 2015, followed by hundreds of aftershocks. A preliminary report of the Department of Archaeology (DOA), Nepal, suggested that as many as 745 monuments in 20 districts were affected. The heritage structures are crucial sectors for development, mainly through tourism and employment generation. However, over three years following the Gorkha Nepal earthquake, many collapsed heritage structures were not reconstructed. This paper explores the progress of heritage reconstruction in Kathmandu Valley along with the reasons behind the slow reconstruction process. Ethnographic fieldwork was carried out in the seven UNESCO listed heritage sites and other heritage areas over six months from November 2019 to April 2020. The research shows that the delay in heritage reconstruction was primarily due to the lack of a well-defined policy for heritage reconstruction; conflict on construction materials to be used for reconstruction; procurement modality for reconstruction; limited governance capacity; lack of workforce for traditional artwork; and the lack of a framework to support community-driven rebuilding initiatives. Some recommendations are made to accelerate the reconstruction of heritage structures in Kathmandu Valley. [ABSTRACT FROM AUTHOR]

This manuscript quantifies the effects of aftershocks with pulse characteristics on the cumulative damage of structures. The revised randomization method is developed to generate the artificial mainshock-aftershock (MSAS) ground motions showing pulse characteristics. The efficiency of period normalization is discussed from the point of view of dispersion, and the effects of the aftershocks are quantitatively studied. It is found that strong aftershock can contaminate the efficiency of period normalization, and the effects of strong aftershocks in the near-fault region on cumulative damage can exceed 20% and reach 40%. The equations are proposed for the prediction of damage induced by pulse-like MSAS sequences. [ABSTRACT FROM AUTHOR]

This research attempts to propose a new simulating model capable of generating synthetic stochastic earthquake scenario including both seismological, and acceleration signal properties. The Iranian plateau is selected as a mainland for developing the model due to the existence of high-quality earthquake databases. This model is composed of two sub-models. The first one generates random seismic event scenarios including mainshocks and aftershocks. The second one procreates 3-dimensional synthetic stochastic accelerograms for each of the previously simulated events. This scenario-based predictive model offers a powerful tool to the risk modelers interested in lifetime seismic risk assessment through more realistic earthquake scenarios. [ABSTRACT FROM AUTHOR]

One of the efficient methods for seismic design of structures is Performance-based Plastic Design (PBPD) in which by choosing the desired yield mechanism and the target drift at the beginning of the design, unlike that in conventional design methods, there is no need for a time-consuming process of trial and error to achieve the desired performance. On the other hand, recent earthquakes have shown that aftershocks can increase the damage to a building after the main earthquake and thereby threaten the safety of the inhabitants. However, the seismic hazard of aftershocks is still not explicitly included in the current design codes. In this study, attempts have been made to develop the PBPD method for considering the effects of aftershocks. For this purpose, by performing an incremental dynamic analysis (IDA), the ductility factor μ and the ductility reduction factor Rμ of six PBPD frames (2-, 4-, 6-, 8-, 10-, and 12-story) were calculated under mainshock and mainshock-aftershock sequences. Then, the energy modification factor γ, which is related to the two parameters μ and Rμ, was calculated for both the mainshock and the mainshock-aftershock sequences. An equation is presented in order to calculate the ratio of the energy modification factor of the mainshock-aftershock sequence to the mainshock energy modification factor ( γ m s + a s γ m s ) according to the design period, and the factor obtained is multiplied by the energy modification factor γ so that the effect of aftershock can be considered for the frame design, and by using this modification, the performance of the frame under the mainshock-aftershock sequence can be improved. The results of the time-history analysis performed on the modified PBPD frames show better performance by the frames designed on the basis of modified PBPD than the frames designed on the basis of the original PBPD method under MS-AS sequences in terms of inter-story drift and rotation of plastic hinges. [ABSTRACT FROM AUTHOR]

This paper discusses a computationally efficient methodology for probabilistic fragility and resilience analysis of bridges explicitly incorporating the effects of aftershock seismic events, based on nonlinear time history analysis, stochastic simulation and kriging surrogate modeling. Aftershock fragilities dependent on mainshock-induced damage states are developed and used in conjunction with restoration models for estimating bridge functionality and resilience. The input parameter space for the surrogate models consists of uncertain hazard and structural parameters and deterministic structural/geometrical bridge parameters, leading to probabilistic estimates of bridge performance metrics (i.e., fragility, functionality, resilience). Kriging surrogate modeling is used for estimating these metrics, facilitating efficient adoption of these complex structural and probability models. Relative importance of the predictive parameters is quantified by extending and integrating a probabilistic sensitivity analysis into the proposed framework. An illustrative example of the proposed framework is demonstrated through fragility and resilience assessment of a typical bridge in California subjected to mainshock and aftershock. [ABSTRACT FROM AUTHOR]

Due to the potential of strong aftershocks to cause further damage to mainshock-damaged structures, accurate evaluation of the structural performance during a real seismic sequence is essential. Because of the deficiency of such real data, the necessity for developing artificial aftershock accelerograms consistent with the real mainshock accelerogram is indisputable. This article presents a new method for generating aftershock spectrum, using an artificial neural network. In this procedure, a multilayer perceptron neural network is used to create a network, whose input is response acceleration spectrum of the mainshock and the output is response acceleration spectrum of the aftershock corresponds to the mainshock with equal hazard level. To train this network, 126 seismic sequences recorded on soil type C are used. Results show good agreement between the response acceleration spectrum derived from the artificial neural network and the real aftershock spectrum. In the next step, a simple approximate logarithmic equation is proposed to calculate the aftershock strong-motion duration in terms of the mainshock strong-motion duration, and the ratio of mainshock-aftershock intensity. Finally, with the presence of the response acceleration spectrum and the aftershock strong-motion duration, accelerograms consistent with this aftershock artificial spectrum is extracted using the wavelet method. [ABSTRACT FROM AUTHOR]

Seismicity in the intraplate southwest of Western Australia is poorly understood, despite evidence for potentially damaging earthquakes of magnitude > M6. Identifying stress-focusing geological structures near significant earthquake sequences assists in understanding why these earthquakes occur in seemingly random locations across a region of more than 250 000 km2. On 16 September 2018, an ML5.7 earthquake occurred near Lake Muir in the southwest of Western Australia and was followed by an ML5.4 aftershock. The main earthquake formed a mainly north-trending fault scarp ∼5 km in length and with a maximum vertical displacement of ∼40 cm. The main event was followed by a series of aftershocks, one of which had a magnitude of ML5.4. Using high-resolution aeromagnetic data, we analyse bedrock geology in a wide area surrounding the new scarp and map a series of major ∼ east–west-trending faults segmenting eight distinct geological domains, as well as a network of less prominent northwest-trending faults, one of which aligns with the southern segment of the scarp. Surface faulting, surface deformation and earthquake focal mechanism studies suggest movements on north- and northeast-trending structures. The main shock, the aftershocks, surface faulting and changes in InSAR-derived surface elevation all occur in a region bounded to the south by a prominent northwest-trending fault and to the north by a west-northwest-trending domain-bounding structure. Thus, we interpret the north-trending thrust fault associated with the main Lake Muir event as due to local stress concentration of the regional east–west stress field at the intersection of these structures. Further, we propose that a particularly large west-northwest-trending structure may be broadly focusing stress in the Lake Muir area. These findings encourage similar studies to be undertaken in other areas of Australia's southwest to further the current understanding of seismic release in the region. A large ML5.7 earthquake occurred in southwest Western Australia in September 2018, damaging infrastructure and forming a 40 cm-high thrust fault scarp. An aeromagnetic interpretation of the Lake Muir region revealed that the new scarp aligned with pre-existing faults that were reactivated. Local and regional structures likely acted as regional stress focusers in the Lake Muir area. Identifying regional stress-focusing structures is important for the purpose of understanding seismic risk in intraplate areas such as Western Australia. [ABSTRACT FROM AUTHOR]

Studies from past earthquakes have shown that aftershocks can increase the vulnerability of structures damaged under mainshocks. However, the main challenge is to take these threats into account during the process of design and retrofit. Using the accelerograms that are compatible with the mainshock and the corresponding aftershocks can lead to a proper evaluation of seismic performance of a structure during the mainshock and aftershock, based on time history analyses. Therefore, it is necessary to simulate the aftershock motions consistent with the predicted mainshock spectrum. This study first investigates the relationship between the frequency content of an aftershock and its corresponding mainshock. It then discusses the development of a method for the generation of artificial aftershocks based on the acceleration response spectrum obtained from the artificial neural networks. To evaluate the effectiveness of the proposed method for the generation of artificial seismic sequences, a large number of time-history analyses have been conducted using both the current (the conventional back-to-back approach) and the proposed methods for three different structures including a column (representing the pier of a bridge), a reinforced concrete (RC) building, and an RC bridge. In these analyses, a wide range of different elements and materials have been employed and different responses, including maximum drift, residual drift, inter-story drift, floor acceleration, column curvature, and base shear, have also been studied. The results revealed that the proposed method produces the appropriate estimation of structural responses, and has a considerably higher efficiency compared to the conventional BTB approach that often introduces considerably large errors in the estimation of responses. [ABSTRACT FROM AUTHOR]

A Bayesian approach has been applied to estimate the distribution of magnitudes, interevent distances and times of earthquakes occurred in 2017 in central Italy by using a small amount of random samples drawn from the distribution of the same seismic parameters for the earthquakes occurred in 2014-2016. We applied the method to the whole and aftershock-depleted seismicity by using the exponential and the normal model to fit the distributions of the seismic parameters. Our findings indicate that the exponential model fits the distributions of the seismic parameters much better than the normal model. Furthermore, in the whole seismicity case, the method requires at least 2100 to 2300 random samples to estimate the distributions of the seismic parameters of earthquakes occurred in 2017 with an estimation error less than 0.01; while in the aftershock-depleted case, a minimum number of random samples varying between 360 and 1470 occurred in 2014-2017 is required to estimate the distributions of the seismic parameters of earthquakes occurred in 2017 with an estimation error less than 0.01. [ABSTRACT FROM AUTHOR]

This study investigated the collapse capacity of inelastic single-degree-of-freedom (SDOF) systems subjected to mainshock-aftershock earthquake sequences. A hysteretic model incorporating strength and stiffness deterioration was used to describe the inelastic behaviors of SDOF systems under seismic excitations. An ATC63 far-field record set was adopted as seed mainshock records to synthesize earthquake sequences. An extended IDA method was employed to calculate the collapse capacity of inelastic SDOF systems subjected to mainshock-aftershock earthquake sequences by scaling the earthquake sequence as a whole. An extensive parametric study was conducted for examining the effects of hysteretic model parameters and artificial earthquake sequences synthesized by different methods and with near-field and far-field mainshock earthquakes on system collapse capacity. Through comparing the collapse capacity for mainshock-aftershock earthquake sequences and that for mainshock earthquakes only, it is found that aftershocks can yield a significant reduction on the median collapse capacity for all systems and lead to an important increase on the dispersion of collapse capacity for the systems at most periods. Based on the parametric study results, empirical expressions were proposed to predict the aftershock-induced reduction and increase on the median and dispersion of collapse capacity, respectively. [ABSTRACT FROM AUTHOR]

Vulnerable areas of the world, including many developing countries, are increasingly exposed to natural disasters. New technologies, such as geospatial technologies, could help them manage the risks of extreme events and cope with disaster aftershock. However, new technologies are often disseminated slowly among the relevant stakeholders. Assuming that knowledge exchange through stakeholder networks can effectively enhance the uptake of innovation, this research applied a social network approach focussing on the structural patterns of communication and collaboration networks regarding landslide-related disasters in Nepal and floods in Kenya. Using methods of formal social network analysis, we reveal centrally positioned stakeholders and discuss their actual and potential roles in outscaling innovations between the different sectors and upscaling them to different levels within the disaster management communities under study. In doing so, this case study demonstrates the potential of social network analysis for improving the dissemination of innovations for disaster risk management. [ABSTRACT FROM AUTHOR]

Earthquake disaster management involves determining locations in which to construct shelters and how to allocate the affected population to them. A multi-objective, hierarchical mathematical model, allied with an interleaved modified particle swarm optimization algorithm and genetic algorithm (MPSO–GA), have been developed to solve the earthquake shelter location-allocation problem. From a set of candidate shelter locations, the model first determines which of these should act as emergency shelters and then which should be used as long-term shelters, while simultaneously optimizing the allocation of a population to them. Damage caused to evacuation routes is considered in addition to the number of evacuees and shelter capacity. In terms of the model's emergency and long-term shelter stages, the objectives are to minimize (i) total weighted evacuation time, and (ii) total shelter area used. An interleaved MPSO–GA applied to the model yielded better results than achieved using MPSO or GA in isolation. For a case study with an earthquake affecting the area of Jinzhan within Beijing's Chaoyang district in China, results generated present government with a range of solution options. Thus, based on government preferences, choices can be made regarding the locations in which to construct shelters and how to allocate the population to them. [ABSTRACT FROM AUTHOR]

We present perturbations in very low frequency (VLF) signals received at Ionospheric & Earthquake Research Centre (IERC) (Lat. 22.50 ° N, Long. 87.48 ° E) during and prior to two earthquakes, one on 11 March 2011 at 11:16:24 LT (M = 9) in Honshu, Japan and another on 12 May 2015 at 12:35:19 LT (M = 7.3) in Kodari, Nepal. The VLF signal transmitted from JJI (22.2 kHz) in Japan (Lat. 32.05 ° N, Long. 131.51 ° E) showed strong shift in VLF-sunrise terminator times towards night-time few days prior to both the earthquakes. These two earthquakes took place near the transmitter JJI and receiver IERC respectively. We simulated the VLF sunrise terminator time shifts using the long wavelength propagation capability (LWPC) code. To effectively represent the D-region ionospheric variabilities, we assumed a mean dynamic perturbation over the path and presented them with a set of effective Wait's parameters (βeff, h eff ′ ). We have successfully reproduced the temporal trend of the normalized VLF signal amplitude at VLF sunrise terminators for a few days around both the earthquakes. We used Wait's exponential model for estimating the altitude profile of D-region electron density ( N e (h) ) at VLF sunrise terminator times around both the earthquakes and quantified the changes of those N e (h) profiles. [ABSTRACT FROM AUTHOR]

Multiple parameters (brightness temperature, soil moisture, surface latent heat flux, surface air temperature and carbon monoxide) before and after the 2015 Nepal M7.8 Gorkha main earthquake and M7.3 Dolakha aftershock were analysed using satellite observation data. The thermal anomalies from optical and microwave data appear about two months prior to the 2015 Gorkha earthquake. Some of the parameters show anomalous changes at different altitudes about 20 days prior to the main earthquake event and 10 days prior to the strong aftershock. Our results show that pre-earthquake anomalous signals propagate from the in situ to the top of atmosphere, and the anomalies in the atmosphere often observed prior to an impending earthquake. The changes on the land surface and corresponding changes in meteorological and atmospheric parameters show existence of strong coupling during the seismogenic period, although the transfer mechanism of seismic/electromagnetic is still has to be investigated and understood. [ABSTRACT FROM AUTHOR]

Existing masonry buildings show significant vulnerability to seismic sequences. This topic has so far received limited attention, concentrated on simplified simulations of the global response, governed by in-plane wall behaviour, or on a very detailed representation of monumental buildings. This paper looks at the out-of-plane response of an ordinary-building wall restrained by an elastoplastic tie-rod under Italian seismic sequence conditions. A recently proposed model is extended to account for a flexible interface defined by its compressive strength and stiffness. Response to 30 series of four events belonging to six seismic sequences shows limited damage accumulation in most cases, with most hysteretic energy dissipated in a single plastic cycle. In these cases, we find a strong correlation between the maximum rotation and intensity measures such as peak ground acceleration, peak ground velocity and acceleration spectrum intensity. This suggests that current hazard studies are adequate and that design can be based on the features of the maximum event expected. However, exceptions are noticed for the 2016 Central Italy Earthquakes, in which the considered sequence is made of multiple mainshocks inducing significant damage accumulation, but can still be resolved by a practitioner resorting to equivalent static procedures by reducing the commonly assumed behaviour factor. [ABSTRACT FROM AUTHOR]

This paper reports the structural failures and collapse of heritage structures in Kathmandu Valley, Nepal, during the 2015 Nepal earthquake, and presents preliminary findings regarding the causes of failures and collapses. Field reconnaissance was carried out immediately after the main shock (Mw 7.8) on April 25 and the strongest aftershock (Mw 7.3) on May 12. It was observed that the performance of heritage structures was influenced by the combination of several factors, including structural and architecture type, configuration and structural deficiency, local site effects and ground-motion characteristics, age and maintenance level, material quality, etc. It was observed that dome structures performed very well, followed by pagoda (tiered temple), and shikhara structures were found as the most vulnerable structures. Moreover, it was observed that structures that had been seismically retrofitted and well maintained appeared to perform well. Some recommendations are made to improve the seismic performance of the heritage structures in Kathmandu Valley. [ABSTRACT FROM AUTHOR]

The Ludian earthquake (MW 6.2) and Nepal earthquake (MW 7.8) are parameterized and then simulated using a new improved version of the stochastic point source method based on a proposed equivalent distance (REQL) measure. The improved method considers uniform slip distribution along the fault and is validated by comparing the simulated Fourier response spectrum. Simulated ShakeMaps of Ludian and Nepal earthquakes in terms of PGA also indicate that the results of the improved method are in good agreement with finite-fault method with high efficiency. [ABSTRACT FROM AUTHOR]

After a damaging earthquake, assessment of the residual seismic capacity is required for large parts of the building stock. Increased vulnerability of structures together with the threat of immediate aftershocks call for rapid and objective decision making. Structural identification has the potential to reduce parameter-value uncertainties of physics-based models through interpreting measurement data. Significant amounts of uncertainty are associated with the non-linear behaviour of structures during extreme events such as earthquakes. Therefore, a structural identification methodology that accommodates multiple sources of systematic modelling uncertainties is used. Error-domain model falsification (EDMF) enables structural identification through combining damage grades observed by visual inspection with fundamental frequencies that are derived from ambient vibrations. Parametric uncertainties of a hysteretic model are reduced with the two information sources in order to extrapolate the vulnerability of the building regarding future earthquakes. The applicability of the methodology is shown using measurements made on a mixed reinforced-concrete unreinforced-masonry building tested on a shaking table. Based on nonlinear time-history analyses involving single-degree-of-freedom models, EDMF leads to more precise, yet robust, vulnerability predictions of earthquake-damaged buildings when compared with prediction ranges that are obtained without data interpretation. [ABSTRACT FROM AUTHOR]

This paper discusses the application of the Pacific Asia Travel Association's (PATA) risk and recovery strategy for Nepal following the April/May 2015 earthquake and aftershocks. The impact of the earthquake on tourism to Nepal, the establishment and evolution of PATA's Nepal Rapid Recovery Taskforce and strategic approaches to tourism recovery contained within the report and its outcomes are discussed. The methodology involved participant observation with three key players in the recovery process, email interviews of key informants, analysis of secondary data sources and reviews of management information systems. Collaborative theory was at the core of PATA's recovery process and provided a lens through which to understand the intent, direction and actions undertaken. The application of Nepal's recovery strategy is examined through volunteer tourism, which played a central role in Nepal's tourism recovery and accessible tourism as an innovative approach to introducing a new market sector in Nepal. Volunteer and accessible tourism enterprises provided opportunities for these organisations to create their own narratives and to include them in the broader media and marketing approach towards stimulating tourism recovery to Nepal between 2015 and 2017. [ABSTRACT FROM AUTHOR]

In 2008, Marsan and Lengliné presented a nonparametric way to estimate the triggering function of a Hawkes process. Their method requires an iterative and computationally intensive procedure which ultimately produces only approximate maximum likelihood estimates (MLEs) whose asymptotic properties are poorly understood. Here, we note a mathematical curiosity that allows one to compute, directly and extremely rapidly, exact MLEs of the nonparametric triggering function. The method here requires that the number q of intervals on which the nonparametric estimate is sought equals the number n of observed points. The resulting estimates have very high variance but may be smoothed to form more stable estimates. The performance and computational efficiency of the proposed method is verified in two disparate, highly challenging simulation scenarios: first to estimate the triggering functions, with simulation-based 95% confidence bands, for earthquakes and their aftershocks in Loma Prieta, California, and second, to characterise triggering in confirmed cases of plague in the United States over the last century. In both cases, the proposed estimator can be used to describe the rate of contagion of the processes in detail, and the computational efficiency of the estimator facilitates the construction of simulation-based confidence intervals. [ABSTRACT FROM AUTHOR]

The main purpose of this study is to develop an estimation procedure of seismic design level setting for reinforced concrete (RC) piers considering aftershock-induced seismic hazards. This work develops an assessment method of the seismic hazards induced by aftershocks and takes an example of the Chi-Chi Earthquake in Taiwan. The number of aftershocks is assumed to follow the modified Gutenberg-Richter law with lower and upper bounds when analysing the cumulative density function of the magnitude of the aftershock within a specified post-mainshock period for the earthquake. Additionally, this work considers the spatial uncertainty in the hypocentres of aftershocks to assess the aftershock-induced seismic hazards. Fragility curves and residual factors of damaged RC piers are used in the transition probability matrix of Markov Chain model for considering the cumulative damage induced by aftershocks by incorporating uncertainty into aftershock events, as well as into structural capacity and residual factors corresponding to a specified damage state, the exceedance probabilities for various damage states can be estimated using Markov Chain model and Monte Carlo Simulation. Finally, in the case study, the proposed procedure is used to determine the important factor in the preliminary seismic design of typical RC piers for the Chi-Chi Earthquake in Taiwan. [ABSTRACT FROM AUTHOR]

The damaging effects of aftershocks are overlooked by current building codes and not properly accounted for in commercial seismic loss assessment software. In this paper, an evaluation of the seismic fragility relationships for reinforced concrete (RC) frame systems prone to mainshock-aftershocks sequences is conducted. Fiber-based finite element models for different types of RC frames are established and subjected to a suite of ground motions obtained from the Tohoku sequence. Fragility relationships are derived with and without consideration to multiple earthquake effects. The results from this study confirm that multiple earthquakes have significant effects on the vulnerability relationships of RC frames. [ABSTRACT FROM AUTHOR]

Recent research has shown that for the larger earthquakes recorded (M ≥ 5.2) within the global centroid moment tensor (gCMT) there is a positive correlation between the magnitudes of earthquakes and the magnitudes of their aftershocks [13]. Through a modification of model independent stochastic de-clustering [12] and a more localized catalog provided by the Southern California Earthquake Data Center (SCEDC), the methodologies of Nichols and Schoenberg can be extended to catalogs complete with a much lower minimum magnitude of completeness (M ≥ 2.2). Results indicate that the positive correlation observed between larger earthquakes in the gCMT catalog and their aftershocks is also evident in the relationship between the magnitudes of earthquakes in the SCEDC data and their aftershocks. However, with the lower minimum magnitude of completeness found in the SCEDC catalog and with short periods of extreme earthquake activity evident within the data, the statistical power of the stochastic de-clustering algorithms to distinguish between mainshocks and aftershocks is diminished. [ABSTRACT FROM AUTHOR]

In this study, rate and state Coulomb stress transfer model is adopted to forecast the seismicity rate of earthquakes (MW ≥5) in the north-west Himalaya region within the testing period 2011–2013. Coulomb stress changes (ΔCFF), considered to be the most critical parameter in the model, exhibit stress increase in the whole study region, excluding the Chaman fault of the Kirthar range where significant stress shadow has been observed. The estimated background seismicity rate varies in the range 0.0–0.7 in the region, which is preoccupied by low aftershock duration of <50 years. Furthermore, a lowb-value that varies between 0.54 and 0.83 is observed in Kirthar ranges, Karakoram fault and Pamir-Hindukush region. However, areas like Hazara syntaxis of the northern Pakistan and northern Pamir of the Eurasian plate exhibit higherb-values in the range 1.23–1.74. Considering constant constitutive properties of the faults (i.e.Aσ = 0.05 MPa), our forecast model for variable ΔCFF and heterogeneousb-value successfully captures the observed seismicity rate of earthquakes. Results have been verified using statisticalS-test. However, the model fails to capture the observed seismicity rate during the period when reconstructed for averageb-value to be 0.86 and no change in ΔCFF (ΔCFF = 0). [ABSTRACT FROM AUTHOR]

The 7.8 Mw Gorkha earthquake struck the east of Lamjung in Nepal, followed by a sequence of powerful aftershocks. Chinese Team Six including the authors inspected the seismic damage to civil structures along 10 paths in densely populated areas with a seismic intensity of VII to IX, 40 days after the main shock. The damage was categorized according to structure types and described in detail. Several conclusions are made: powerful aftershocks can significantly affect the failure patterns; geological conditions, structure types, and height have great influence on the level of damage; and the local risky retrofitting technique needs improvement badly. [ABSTRACT FROM AUTHOR]

We conducted single-site and array observations of microtremors in order to revise the shallow subsurface structure of the Furukawa district, Miyagi, Japan, where severe residential damage was reported during the Great Eastern Japan Earthquake of 2011, off the Pacific coast of Tohoku. The phase velocities of Rayleigh waves are estimated from array observations at three sites, and S-wave velocity models are established. The spatial distribution of predominant periods is estimated for the surface layer, on the basis of the spectral ratio of horizontal and vertical components (H/V) of microtremors obtained from single-site observations. We then compared ground motion records from a dense seismometer network with results of microtremor observations, and revised a model of the shallow (~100 m) subsurface structure in the Furukawa district. The model implies that slower near-surface S-wave velocity and deeper basement are to be found in the southern and eastern areas. It was found that the damage in residential structures was concentrated in an area where the average value for the transfer functions in the frequency range of 2 to 4 Hz was large. [ABSTRACT FROM AUTHOR]

The article presents a special study on the May 31, 1970 earthquake that hit Nevados Huascaran in Peru. According to the U.S. Geological Survey (USGS), the earthquake buried the towns of Yungay and Ranrahirca and killed more than 20,000 inhabitants. USGS geologist George Eriksen said that the destruction was wrought by the avalanche of ice and rock debris triggered by the earthquake shock. However, Eriksen indicated that the destruction and death due to collapse of buildings was greater than that of the debris avalanche, with an estimated number of 30,000 people killed as a result of collapse of buildings.

The aim of this paper was to investigate the dynamic response of a concrete structure subjected to a mainshock–aftershock seismic sequence. In the dynamic analysis, three components of the registered mainshock and aftershock were taken into account. The peak ground accelerations of about 0.5 g were assumed for both shocks. A one-storey shed was modelled with the ABAQUS software to represent a large concrete structure under the repeated earthquakes. For proper characterization of concrete structure behaviour under the sequence of shocks, a concrete damage plasticity model was assumed as a constitutive model of concrete. The obtained results indicate that aftershocks can have considerable effect on dynamic behaviour of concrete structures in terms of enlarging zones affected by irreversible strains or additional damage evolution. The analysis revealed that aftershocks, which are usually not as strong as mainshocks, may result even in total loss of concrete material strength while performing in mainshock–aftershock seismic sequences. [ABSTRACT FROM PUBLISHER]

There is ample evidence that in applications of self-exciting point-process models, the intensity of background events is often far from constant. If a constant background is imposed that assumption can reduce significantly the quality of statistical analysis, in problems as diverse as modeling the after-shocks of earthquakes and the study of ultra-high frequency financial data. Parametric models can be used to alleviate this problem, but they run the risk of distorting inference by misspecifying the nature of the background intensity function. On the other hand, a purely nonparametric approach to analysis leads to problems of identifiability; when a nonparametric approach is taken, not every aspect of the model can be identified from data recorded along a single observed sample path. In this article, we suggest overcoming this difficulty by using an approach based on the principle of parsimony, or Occam’s razor. In particular, we suggest taking the point-process intensity to be either a constant or to have maximum differential entropy, in cases where there is not sufficient empirical evidence to suggest that the background intensity function is more complex than those models. This approach is seldom, if ever, used for nonparametric function estimation in other settings, not least because in those cases more data are typically available. However, our “ontological parsimony” argument is appropriate in the context of self-exciting point-process models. Supplementary materials are available online. [ABSTRACT FROM AUTHOR]

In ‘Quake City: From Ruination to Representation’, Sharon Mazer looks at the shoehorning of experience into a prescribed social frame in not-quite-post-earthquake Christchurch, New Zealand. Quake City – Christchurch's Earthquake Attraction was built by the Canterbury Museum. Safely set into a repurposed shipping container on the Re:Start Mall, Quake City advertises itself as a ‘unique multi-sensory attraction aimed at informing, engaging and educating New Zealanders and international tourists about the Canterbury earthquakes.’ As such, Quake City is this essay's paradigm for the way the forces of nature are forced into line by the machinery of the state. When the earth shakes, time, body and consciousness are suspended, lifted from the everyday and then dropped back into whatever's left,however it's been left. From solid to liquid, from standing to fallen, from edifice to rubble, from order to . . . well, we don't quite know yet what. Earthquakes, aftershocks, earthquakes again: the physical ruptures the metaphysical, at once absolute and transcendent, abject and sublime. As the visceral sensations began to recede, we were told, repeatedly, that we must ‘tell our stories’. Not in the way we did while riding the adrenaline rush of those first few days, sharing with strangers at supermarkets or over strangely convivial ad hoc meals made from the detritus of warming fridges over barbeques and gas stoves, debating relative virtues of improvised toilets. Our stories now have been sifted from the fragments of memory, ground into the generic, locked into hegemonic templates, eroded into clichés of terror, loss, recovery and, of course, the triumph of the human spirit. They are being produced for purification, to re-repress what was released by ruination. [ABSTRACT FROM PUBLISHER]

The deformation of the North Aegean Sea is mainly controlled by the westernmost segments of North Anatolian Fault System. On 8 January 2013, a moderate earthquake (Mw = 5.7) occurred in the North Aegean Sea. A series of aftershocks were occurred within four months following the mainshock, which have magnitudes varying from Ml = 0.9 to 5.0. We have obtained a total of 23 earthquake moment tensor solutions that belong to the 2013 earthquake sequence. The source of this earthquake sequence is a N75°E trending pure dextral strike-slip fault. The temporal and spatial distribution of the earthquakes indicate that the rupture unilaterally propagates from SW to NE. The stress tensor analysis shows that the direction of the regional compressive stress is WNW–ESE. The 1968 Aghios earthquake (Ms = 7.3) and the 2013 North Aegean Sea earthquake sequences indicate that the regional stress has been transferred from SW to NE in this region. The 1672 Bozcaada earthquake (M = 7.0) had been occurred to the north-east of the 2013 earthquake sequence. The elapsed time (342 year) and the regional stress transfer point out that the 1672 earthquake segment is probably a seismic gap and it is a potential earthquake hazard for this region. [ABSTRACT FROM AUTHOR]