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Browsing by Author "Poulos Campbell, Alan John"

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An Updated Recurrence Model for Chilean Subduction Seismicity and Statistical Validation of Its Poisson Nature
(2019) Poulos Campbell, Alan John; Monsalve, Mauricio; Zamora, Natalia; Llera Martin, Juan Carlos de la
Earthquake recurrence models are the basis of seismic hazard analysis and seismic risk evaluation of physical infrastructure. They are based on statistical analysis of earthquake occurrence data available in a specific geographical region. This work proposes a new earthquake recurrence model for the interface and intraslab seismicity of the subduction margin along Chile. The model improves some of the shortcomings of previous available models in the region such as the lack of earthquake declustering or the use of magnitude scales inconsistent with modern ground‐motion prediction equations. Significant differences in seismic rates are found with some previous models. Indeed, the resulting frequencies from the Gutenberg–Richter relations are not only similar to some of the previous works, but also one order of magnitude higher and lower than two of the previously reported models. Because one of the strongest assumptions in earthquake occurrence models is that they follow a homogeneous Poisson process, this hypothesis is statistically tested herein, finding that the declustered catalog only partially complies with this assumption, showing for instance that the interevent times follow approximately an exponential distribution.
Correlations of spectral accelerations in the Chilean subduction zone
(2020) Candia, G.; Poulos Campbell, Alan John; Llera Martin, Juan Carlos de la; Crempien de la Carrera, Jorge Gustavo Federico; Macedo, J.
The correlation between spectral accelerations is key in the construction of conditional mean spectra, the computation of vector-valued seismic hazard, and the assessment of seismic risk of spatially distributed systems, among other applications. Spectral correlations are highly dependent on the earthquake database used, and thus, region-specific correlation models have been developed mainly for earthquakes in western United States, Europe, Middle East, and Japan. Correlation models based on global data sets for crustal and subduction zones have also become available, but there is no consensus about their applicability on a specific region. This study proposes a new correlation model for 5% damped spectral accelerations and peak ground velocity in the Chilean subduction zone. The correlations obtained were generally higher than those observed from shallow crustal earthquakes and subduction zones such as Japan and Taiwan. The study provides two illustrative applications of the correlation model: (1) computation of conditional spectra for a firm soil site located in Santiago, Chile and (2) computation of bivariate hazard for spectral accelerations at two structural periods.
Earthquake risk assessment of buildings accounting for human evacuation
(2017) Poulos Campbell, Alan John; Llera Martin, Juan Carlos de la; Mitrani-Reiser, Judith
A primary goal of earthquake engineering is to protect society from the possible negative consequences of future earthquakes. Conventionally, this goal has been achieved indirectly by reducing seismic damage of the built environment through better building codes, or more comprehensibly, by minimizing seismic risk. However, the effect that building damage has on occupants is not explicitly taken into account while designing infrastructure. Consequently, this paper introduces a conceptual framework and numerical algorithm to assess earthquake risk on building occupants during seismic events, considering the evacuation process of the structure. The framework combines probabilistic seismic hazard analysis, inelastic structural response analysis and damage assessment, and couples these results with the response of evacuating agents. The results are cast as probability distributions of variables that measure the overall performance of the system (e.g., evacuation times, number of injured people, and repair costs) for specific time windows. As a testbed, the framework was applied to the response of a reinforced concrete frame building that exemplifies the use of all steps of the methodology. The results suggest that this seismic risk evaluation framework of structural systems that combine the response of a physical model with human agents can be extended to a wide variety of other situations, including the assessment of mitigation actions in communities and people to improve their earthquake resilience. Copyright © 2016 John Wiley & Sons, Ltd.
Empirical site classification of seismological stations in Chile using horizontal-to-vertical spectral ratios determined from recordings of large subduction-zone earthquakes
(2019) Yang, Shuo; Mavroeidis, G. P.; Llera Martin, Juan Carlos de la; Poulos Campbell, Alan John; Aguirre Aparicio, Paula; Rahpeyma, Sahar; Sonnemann, Tim; Halldorsson, Benedikt
Despite the significant upgrade and expansion of the seismic monitoring network in Chile over the past several years, precise site characterization of a large number of seismological stations is still lacking, thus hindering a robust development of tools that could improve prediction of regional seismic hazard. To enhance our understanding of site effects in Chilean seismological data, this study classifies 136 stations using the horizontal-to-vertical spectral ratio (HVSR) method based on a database of 283 triaxial ground-motion records from 22 subduction interface earthquakes with moment magnitudes ranging from 6.8 to 8.8 that occurred between 1985 and 2015. This classification, which is based on the SESAME guidelines, divides recording stations into four types according to the shape of the station-average HVSR curve (single-peak, double-peak, broad/multiple-peak, and flat). Furthermore, the variability of the mean HVSRs with different source, path and site parameters is investigated. The derived HVSR results are also compared with those presented in previous HVSR studies for Chile. Finally, representative shear-wave velocity profiles along with parametric uncertainties are estimated for stations with a single-peak HVSR curve using a Bayesian statistical inversion framework.
Impact on chilean hospitals following the 2015 Illapel earthquake
(National Information Centre of Earthquake Engineering, 2017) Favier, Philomène; Rivera Jofré, Felipe Andrés; Poulos Campbell, Alan John; Vásquez P., Jorge; Llera Martin, Juan Carlos de la; Mitrani-Reiser, Judith
In a post-disaster environment, hospitals play a critical role in healthcare services continuities to the population while effectively coping with eventual losses of functionality. These losses come from physical damage to the facility, loss of utility lifelines, failure in supply chains, and reduction of personnel. However, data describing the detailed performance of hospitals during past earthquakes are scarce. Consequently, following the 2015 Mw 8.3 Illapel earthquake in central Chile, an exhaustive field campaign was carried out in the Coquimbo region to collect substantial perishable data to describe physical damage to hospitals and functionality losses. This study presents first the baseline information obtained in nine surveyed government hospitals, including size, location and type of infrastructure. Then, the seismic impact was analyzed and classified to show the main physical structural and non-structural damage, lifeline interruptions, losses in hospital units, and variations in flow of patients and staff. Transfers, discharges and evacuations of patients that occurred after the event were also reported. We found that the earthquake did not affect strongly the healthcare service despite the fact that most of the structural and non-structural damage was localized in the largest regional hospital. The archival nature of the data collected may deepen our understanding of the post-earthquake healthcare system performance, which is very useful in improving disaster preparation and overall resilience.
Modeling the Impact of Earthquake-Induced Debris on Tsunami Evacuation Times of Coastal Cities
(2019) Castro, SebastIán; Poulos Campbell, Alan John; Herrera Maldonado, Juan Carlos; Llera Martin, Juan Carlos de la
Tsunami alerts following severe earthquakes usually affect large geographical regions and require people to evacuate to higher safety zones. However, evacuation routes may be hindered by building debris and vehicles, thus leading to longer evacuation times and an increased risk of loss of life. Herein, we apply an agent-based model to study the evacuation situation of the coastal city of Iquique, north Chile, where most of the population is exposed to inundation from an incoming tsunami. The study evaluates different earthquake scenarios characterized by different ground motion intensities in terms of the evacuation process within a predefined inundation zone. Evacuating agents consider the microscale interactions with cars and other people using a collision avoidance algorithm. Results for the no ground shaking scenario are compared for validation with those of a real evacuation drill done in 2013 for the entire city. Finally, a parametric analysis is performed with ten different levels of ground motion intensity, showing that evacuation times for 95% of the population increase in 2.5 min on average when considering the effect of building debris.
Reconnaissance observations by CIGIDEN after the 2015 Illapel, Chile earthquake and tsunami
(National Information Centre of Earthquake Engineering, 2017) Rivera Jofré, Felipe Andrés; Jünemann Ureta, Rosita; Candia, Gabriel A.; Favier, Philomène; Fernández Soto, Claudio; Chacón de la Cruz, Matías Fernando Nicolás; Hube Ginestar, Matías Andrés; Chamorro Giné, Marcela Alondra; Aguirre Aparicio, Paula; Llera Martin, Juan Carlos de la; Poulos Campbell, Alan John; Illapel earthquake; Critical infrastructure
This paper describes the reconnaissance work conducted by researchers from the National Research Center for Integrated Natural Disaster Management (CIGIDEN) between September 23rd and October 2nd in the area affected by the Mw 8.3 Illapel megathrust earthquake, which struck offshore the coast of the Coquimbo Region in central Chile on September 16th, 2015. A first team focused on the seismic performance and effects of the tsunami on public hospitals and on reinforced concrete (RC) buildings. A second team focused on the road network infrastructure. Field work included: (i) a survey on the physical and functional damages of the public hospitals in the Region; (ii) a visual inspection and preliminary damage assessment of 20 RC buildings in the largest cities of the region and an aftershock instrumentation of the Coquimbo hospital; and (iii) the inspection of bridges, pedestrian bridges, and rockfall along overstepped cut slopes of the road network. The overall limited impact of this megathrust earthquake may be explained in part by the long-term efforts made by the country to prepare for such events. Learnings from the 2010 Maule earthquake were evidenced in the successful evacuation along the coast of the country, and the overall good performance of engineered masonry structures, and of RC buildings designed after 2010.
Risk and Resilience Assessment With Component Criticality Ranking of Electric Power Systems Subject to Earthquakes
(2020) Espinoza, Sebastián Andrés; Poulos Campbell, Alan John; Rudnick van de Wyngard, Hugh; De la Llera Martin, Juan Carlos; Panteli, M.; Mancarella, P.
Countries around the world suffer the dramatic impact of earthquakes and other natural hazards reflected in casualties, infrastructure damage, service interruptions, and recovery costs. Although disaster exposure consciousness of electric power systems has increased in recent years, mitigation and adaptation actions, such as reserve scheduling and infrastructure investments, are usually performed without quantitative tools to account for the underlying stochasticity of these events. This article first discusses why an integrated assessment, which incorporates sources of uncertainty (risk) and manages the time-dependency of the recovery process (resilience), should be used to assess the impact of seismic events on electric power systems. Thereafter, a probabilistic methodology that considers the hazard, vulnerability, operation, and recovery of the system is presented. As a case study, the probabilistic seismic resilience of the electric power system of Northern Chile is assessed using different risk measures, including expected annual loss, value at risk, and conditional value-at-risk. Finally, a novel criticality assessment based on these metrics is developed to demonstrate that, for certain networks such as the study case, retrofit of selective components can notably improve the resilience of the complete system to seismic events. For example, if one specific component from the 152 components of the study system is assumed invulnerable, expected annual interruption costs decrease by 8%.
Risk model of human evacuation under earthquake loads
(2014) Poulos Campbell, Alan John; Llera Martin, Juan Carlos de la; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
Esta investigación tiene dos objetivos principales: (i) desarrollar un modelo basado en agentes que simula procesos de evacuación en edificios para casos de emergencia, y (ii) evaluar el riesgo que los ocupantes de un edificio tienen a eventos sísmicos. La metodología usada integra el efecto físico del movimiento de los agentes con distintos comportamientos sociales que han sido observados durante evacuaciones reales. El modelo fue usado para reproducir lo ocurrido en simulacros de evacuación reales llevados a cabo en un colegio y un edificio de oficinas, resultando en errores promedio entre los tiempos de evacuación predichos y medidos de 5.9% y 5.7%, respectivamente. Estas pequeñas diferencias probablemente se deben en parte al conocimiento preciso de la verdadera distribución inicial de la gente en ambos simulacros. Sin embargo, prueban que los problemas de evacuación pueden ser representados mediante la modelación basada en agentes con una precisión razonable. El modelo es luego usado dentro de un marco probabilístico que también integra análisis probabilístico de amenaza sísmica, análisis estructural no lineal y la evaluación del daño de componentes no estructurales del edificio. Múltiples simulaciones de Monte Carlo son usadas para calcular distribuciones de variables de riego sísmico, tales como pérdidas económicas, tiempos de evacuación y número de gente herida. Finalmente, el marco probabilístico fue aplicado a un edificio de prueba con el objetivo de ejemplificar el uso de la metodología. Los resultados sugieren que esta habilidad de calcular el riesgo sísmico de un sistema que tienen tanto componentes físicas como sociales puede ser usada en variadas aplicaciones futuras, incluyendo en evaluar los efectos positivos de posibles medidas de mitigación que comunidades o personas pueden efectuar para mejorar su respuesta de evacuación.
Seismic resilience assessment and adaptation of the Northern Chilean power system
(IEEE, 2017) Espinoza Lara, Sebastián Andres; Poulos Campbell, Alan John; Rudnick Van de Wyngard, Hugh; Llera Martin, Juan Carlos de la; Panteli, Mathaios; Mancarella, Pierluigi; Sacaan, Rafael; Navarro, Alejandro; Moreno, Rodrigo
Even though the concept of resilience is becoming widely used in electric power systems, there is no consensus on how to systematically model or quantify it. This article begins by proposing a classification for different types of system risk analyses, associating them to the concept of power systems resilience. Thereafter, it describes and applies a resilience assessment and adaptation framework to the Northern Chilean electric power system in the context of its exposure to seismic events. This time-dependent analysis is evaluated throughout the disaster's impact and the network's operation and restoration timeframes with two indices: Energy not Supplied and Energy Index of Unreliability. Finally, the article compares a base case with three resilience adaptation strategies, namely, robust, redundant and responsive cases, in terms of their expected energy annual loss and the return period of different levels of network performance.
Seismic Risk Assessment of an Emergency Department of a Chilean Hospital Using a Patient-Oriented Performance Model
(2019) Favier, Philomène; Poulos Campbell, Alan John; Vásquez, J. A.; Aguirre Aparicio, Paula Andrea; Llera Martin, Juan Carlos de la
After an earthquake, hospital emergency departments need to provide continuous health care services to respond to the eventual sudden increase in injured people. The service performance of an emergency department is influenced by internal factors, such as physical damage and staff availability, and external factors, such as an increased patient arrival rate and disruptions in its supply chain. This research presents a quantification methodology for the performance of the emergency department. The novelty of the proposed approach lies in the explicit integration of the inelastic structural and nonstructural response of the building and damage with its loss of functionality, downtime, and emergency patient treatment rate. A discrete event simulation model is used to model the flow of patients within the different units of the emergency department. The seismic risk is expressed as return periods of exceeding different levels of patient waiting times. Results show that 1,000 and 30,000 accumulated waiting hours correspond to return periods of 100 and 1,000 years, respectively. It is concluded that this model may contribute to improving the risk management of critical emergency department infrastructure.
Seismic risk assessment of human evacuations in buildings
(National Information Centre of Earthquake Engineering, 2017) Poulos Campbell, Alan John; Castro Hernández, Sebastián Andrés; Llera Martin, Juan Carlos de la; Mitrani-Reiser, Judith
Major earthquakes may require people to evacuate immediately from buildings as recently observed in the 2015 Mw 8.3 Illapel earthquake in Chile. The building may suffer damage, thus affecting the evacuation process. Perhaps due to its apparent complexity, this interaction has not been taken into account when computing seismic risk variables that are intrinsically coupled, such as evacuation times and number of injured people. This limitation can be addressed by simulating the evacuation processes and the physical damage together using agent-based modelling. The evacuation of the building emerges from a set of rules that govern the interaction between agents and with their (damaged) physical surrounding. This research focuses first on modeling evacuations when no physical damage occurs, and uses real evacuation drills performed in a K-12 school and an office building as validation. The comparison was carried out under a low level of uncertainty in the initial conditions of the occupants, i.e., their initial positions and pre-evacuation times were relatively well known, resulting in prediction errors in total evacuation time of only 5.9% and 5.7% for the school and office building, respectively. The evacuation model is then extended to consider building damage and used in an integrated methodology to evaluate the seismic risk of building occupants. This assessment was divided into five steps: (i) seismic hazard, (ii) structural response, (iii) building damage, (iv) evacuation, and (v) risk assessment. First, probabilistic seismic hazard analysis was used to compute the frequency of different levels of local earthquake intensity, characterized herein by the spectral acceleration at the fundamental period of the structure. Ground motions accelerograms matching these intensities were then used in dynamic analyses of the inelastic structure to compute the building response. Story drifts and floor accelerations of the building were related to the damage of non-structural components (e.g., ceilings and partition walls) using appropriate fragility curves. The estimated damage state of the building was used to feed an agent-based evacuation model and assess the evacuation response of the building occupants in this new environment. The outputs of the model are probability distributions of different performance measures and losses, such as evacuation times and number of injured people. These results can better inform decision making processes to mitigate the consequences that future earthquakes will have on buildings and their inhabitants, as well as provide useful information in modeling other larger scale city evacuation scenarios.
Seismic risk assessment of spatially distributed electric power systems
(National Information Centre of Earthquake Engineering, 2017) Poulos Campbell, Alan John; Espinoza, Sebastián Andrés; Llera Martin, Juan Carlos de la; Rudnick van de Wyngard, Hugh
The adequate performance of critical infrastructure such as transportation, telecommunications, healthcare, and electric power systems are essential to the resilience of communities after major earthquakes. However, assessing the seismic risk of networks is more complex than for individual structures since the performance of systems depend on several spatially distributed intensity measures and the interdependence amongst the system’s components. A convenient and probabilistically consistent way of performing the assessment is by the use of a stochastically-generated earthquake catalogue. This paper computes the seismic risk of electric power systems and its methodology can be summarized in three steps: (i) sample hazard-consistent seismic scenarios; (ii) compute the overall performance of the system for each scenario; and (iii) estimate the seismic risk from the performances of all earthquake scenarios. The resulting risk is represented by the commonly used expected annual service loss of the system, but also by the complete probability distribution of accumulated deficit of electric service. The methodology is applied to the electric network in north Chile, and is used to estimate the Energy Not Supplied (ENS) and the Energy Index of Unreliability (EIU) due to seismic events. Finally, an evaluation of the effect that different sampling methods have on the expected values and uncertainty of results is presented.
The 2010 Chile Earthquake: a five-year reflection
(Australian Earthquake Engineering Society, 2015) Llera Martin, Juan Carlos de la; Mitrani-Reiser, Judith; Rivera Jofré, Felipe Andrés; Fortuño, C.; Jünemann Ureta, Rosita; Poulos Campbell, Alan John; Vásquez P., Jorge
At 3:34AM local time, on February 27th, 2010, a moment magnitude Mw 8.8 megathrust earthquake struck offshore the coast of Chile. The earthquake ruptured a 540 by 200 km mature seismic gap of the underlying subduction pacific plate interlocking mechanism. More than 75% of the 16 million Chileans spread over several large urban areas in the center-south of the country were affected by the earthquake, which caused 521 fatalities with 124 of them due to the tsunami, and an overall damage estimate of USD 30 billion. Because the earthquake struck the most densely populated area of the country, it represents a very unique opportunity to reflect on its ubiquitous impact over many different physical and social systems. The reflection contained in this article occurs five years later, once reconstruction and recovery are complete from this longitudinal wound of the country. Seismic codes have changed, research on the supposedly indestructible reinforced concrete shear walls has been done, new seismic protection technologies have been incorporated, and whole new seismic standards have been adopted by communities and people. The price it took was quite high, but we can confidently say that Chile is better prepared today for the next large earthquake.
Torsion control in structures isolated with the triple friction pendulum system
(2020) Olivares, Claudio; Llera Martin, Juan Carlos de la; Poulos Campbell, Alan John
A parametric study was carried out to investigate the torsional response of structures isolated with the Triple Friction Pendulum (TFP) system with building properties such as uncoupled torsional to lateral frequency ratio, , building slenderness, and mass and stiffness eccentricities. A simplified model of a parametric multistory structure and a small deformation model of the TFP, but with the ability to capture uplift, were used to perform parametric 3D non-linear dynamic analyses. The input ground motions were 20 Chilean records selected using a conditional mean spectrum. Response history results showed that uplift in the devices occurs in structures with large mass eccentricity, and in some extreme cases, normal force values in the TFPs may be as large as 6 times the nominal average gravitational load in each isolator. Torsional envelope response results also show that mass eccentric systems may undergo larger normalized edge amplification factors relative to stiffness eccentric systems, with values 2.5 and 1.8, respectively, and that torsional balance cannot be achieved naturally. Although rotations are small in magnitude due to seismic isolation, displacement values in resisting planes of the superstructure equidistant from the geometric center of the plan will be different. Moreover, structures with large present correlation values between response histories of torsion and translation measured at the geometric center of the plan near one, as well as values above zero for different and plan eccentricity, which implies no torsional control in the weak sense. It is concluded that parameter strongly influences the torsional amplification values computed herein.
Validation of an agent-based building evacuation model with a school drill
(2018) Poulos Campbell, Alan John; Tocornal, Felipe; Llera Martin, Juan Carlos de la; Mitrani-Reiser, Judith
An effective evacuation of buildings is critical to minimize casualties due to natural or anthropogenic hazards. Building evacuation models help in preparing for future events and shed light on possible shortcomings of current evacuation designs. However, such models are seldom compared or validated with real evacuations, which is a critical step in assessing their predictive capacities. This research focuses on the evacuation of a K-12 (kindergarten to 12th grade) school located within the tsunami inundation zone of Iquique, Chile. An agent-based evacuation model was developed to simulate the evacuation of approximately 1500 children and staff from the school during a global evacuation drill carried out for the entire city. The model simulates the motions of heterogeneous human agents, and the simulations were validated using video analysis of the real event. Resulting error estimations between predicted versus measured flow rates and evacuation times are 13.5% and 5.9%, respectively. The good agreement between the simulated and measured values can be attributed to the known distribution of students and staff at the start of the drill, and their known exposure to emergency preparedness protocols. However, the results presented herein show that this mathematical evacuation model can be used for logistical changes in the emergency planning.

Browsing by Author "Poulos Campbell, Alan John"

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