Análisis de efectos sísmicos ortogonales horizontales en terreno blando

En este artículo se estudia el problema que representa la combinación de los efectos sísmicos en las estructuras causados por la acción simultánea de los dos componentes ortogonales horizontales del movimiento del suelo. Mediante el uso de la teoría de vibraciones aleatorias se desarrollan algunas expresiones analíticas que permiten combinar los efectos sísmicos causados por la acción de ambos componentes ortogonales horizontales del movimiento del suelo con el propósito de estimar la máxima respuesta elástica, bi-direccional de la estructura. La principal hipótesis que se hace en el desarrollo de estas expresiones, se refiere a la representación del espectro de amplitudes de Fourier de ambos componentes del movimiento del suelo mediante funciones tipo delta de Dirac. Por medio del análisis elástico bi-direccional, paso a paso de distintos modelos estructurales, se verifica la precisión del planteamiento de combinación propuesto. El procedimiento desarrollado es aplicable exclusivamente al caso de suelo blando y considera explícitamente el ángulo de incidencia del temblor y el tipo de respuesta que se analiza (ortogonal o colineal)

Las concepciones del profesor y su relación con la enseñanza del concepto ecuación lineal

El estudio de las ecuaciones en la enseñanza del álgebra en bachillerato desempeña un papel importante en el aprendizaje de los estudiantes, no sólo por estar relacionado con temas de otras asignaturas, sino porque permite modelar problemas reales. Sin embargo, el tratamiento escolar de éstas, propicia dificultades en su aprendizaje, e ideas incompletas de ecuación. Conviene entonces indagar sobre las razones de que los profesores de matemáticas aborden la enseñanza de la ecuación de una forma y no de otra. En particular uno de nuestros objetivos, fue caracterizar las concepciones sobre el concepto ecuación lineal, para lo cual establecimos cuatro categorías de concepciones: operacional, estructural, funcional y geométrico. Los resultados obtenidos al momento indican que la ecuación lineal es concebida como un objeto matemático definido por medio de reglas, propiedades y procedimientos propios del álgebra y no como herramienta para la resolución de problemas

Seismic Damage Estimation in Buried Pipelines Due to Future Earthquakes – The Case of the Mexico City Water System

Since the mid-70s, there have been advances in the development of models to better understand how earthquakes affect buried pipelines. These natural events can cause damage due to two phenomena: seismic wave propagation and permanent ground deformation. The combined effect of both phenomena in pipeline damage estimation is a subject still complex to address, especially if the objective is to estimate damage due to future earthquakes. In this chapter, the damage assessment methods only consider the impact of seismic wave propagation. The effects of permanent ground deformation phenomena, like ground subsidence, landslides, and ground rupture, are omitted. The exceptional damage caused by the 1985 Michoacan earthquake in Mexico City has encouraged researchers to develop sophisticated tools to estimate ground motion in the Valley of Mexico from Pacific coastal earthquakes, including the important site effects largely observed in the city. These tools have helped to better understand how earthquakes affect buildings and other structures like pipeline systems. The most remarkably case of pipeline damage caused by the 1985 seismic event is the extensive damage suffered by the Mexico City Water System (MCWS) that left almost 3.5 million people without water, and caused water service disruptions over a period of two months. The 1985 MCWS damage scenario has been extensively analyzed for developing models to better understand how seismic wave propagation affects buried pipelines; some of those models are employed in the future damage prediction methods described in this manuscript. Fragility functions are typically the tools most used to assess seismic damage in buried pipelines. These functions relate pipeline damage with seismic intensity. Pipeline damage is generally expressed as a linear pipe repair density. Seismic intensity is usually quantified through a seismic parameter. There are many seismic parameters used as arguments of fragility functions; the most important of these are described in Section 2. Section 3 describes the most important fragility functions proposed until now, including the two employed in the seismic damage estimation for the MCWS presented in Section 4. Finally, Section 5 contains a summary of the most important conclusions of this work

Estimation of Probabilistic Seismic Losses and the Public Economic Resilience—An Approach for a Macroeconomic Impact Evaluation

The Disaster Deficit Index (DDI) measures country risk from a macroeconomic and financial perspective, according to possible catastrophic events. The DDI captures the relationship between the demand for contingent resources to cover the maximum probable losses and the public sector’s economic resilience; that is, the availability of internal and external funds for restoring affected inventories. For calculating potential losses, the model follows the insurance industry in establishing a probable loss, based on the critical impacts during a given period of exposure, and for the economic resilience the model computes the country’s financial ability to cope with the situation taking into account: the insurance and reinsurance payments; the reserve funds for disasters; the funds that may be received as aid and donations; the possible value of new taxes; the margin for budgetary reallocations; the feasible value of external credit; and the internal credit the country may obtain. Access to these resources has limitations and costs that must be taken into account as feasible values according to the macroeconomic and financial conditions of the country. This article presents the model of DDI and proposes it as a simple way of measuring a country’s fiscal exposure and potential deficit—or contingency liabilities—in case of extreme disasters to guide the governmental decisionmaking from economic, financial, and disaster risk reduction perspectives

Probabilistic earthquake risk assessment using CAPRA: application to the city of Barcelona, Spain

The risk evaluation model CAPRA (Comprehensive Approach to Probabilistic Risk Assessment) is a techno-scientific methodology and information platform, composed of tools for evaluating and communicating risk at various territorial levels. The model allows evaluating losses on exposed elements using probabilistic metrics, such as the loss exceedance curve, the expected annual loss and the probable maximum loss, useful for multi-hazard risk analyses. In this article, the process of probabilistic seismic risk analysis is described, explaining the main features of the CAPRA modules of hazard, vulnerability and risk estimation applied to the city of Barcelona, Spain. In addition, according to the physical risk results and the information on the socioeconomic indicators of the city, this article presents the holistic evaluation of seismic risk, which is a valuable result to facilitate the integrated risk management by the different stakeholders involved in risk reduction decision making

Latin American and Caribbean earthquakes in the GEM’s Earthquake Consequences Database (GEMECD)

Among the activities developed under the framework of the Global Earthquake Model, the development of a global consequences database was included. This was defined with the objective of serving as public repository of damages and losses, occurred on different types of elements because of a selected list of earthquakes with epicentres at varying locations around the globe, but also to be used as a benchmark for the development of vulnerability models that capture specific characteristics of the building typologies in each country. The online earthquakes consequences’ database has information on 71 events where 16 of them occurred in the Latin America and the Caribbean Region. A complete and comprehensive review and data gathering process were developed for these selected earthquakes accounting for different aspects and dimensions that were considered of interest, besides the physical damage, such as casualties, socio-economic implications, damages and disruptions in critical facilities and infrastructures, together with the occurrence of secondary events triggered by the ground shaking such as landslides and tsunamis. When possible, the damage and casualties were geo-located using a standardized approach and included in the database. The contributions of the Latin America and Caribbean Region to the database were at the same time a challenge and an opportunity to collect, review, put together and standardize, up to a certain point, damage data of previous earthquakes additionally of being a step forward in the field of open data

Disaster risk from a macroeconomic perspective: a metric for fiscal vulnerability evaluation

The Disaster Deficit Index (DDI) measures macroeconomic and financial risk in a country according to possible catastrophic scenario events. Extreme disasters can generate financial deficit due to sudden and elevated need of resources to restore affected inventories. The DDI captures the relationship between the economic loss that a country could experience when a catastrophic event occurs and the availability of funds to address the situation. The proposed model utilises the procedures of the insurance industry in establishing probable losses, based on critical impacts during a given period of exposure; for economic resilience, the model allows one to calculate the country’s financial ability to cope with a critical impact. There are limitations and costs associated with access to resources that one must consider as feasible values according to the country’s macroeconomic and financial conditions. This paper presents the DDI model and the results of its application to 19 countries of the Americas and aims to guide governmental decision-making in disaster risk reduction

Earthquake Loss Assessment for Integrated Disaster Risk Management

Understanding probable losses and reconstruction costs due to earthquakes creates powerful incentives for countries to develop planning options and tools to cope with risk, including allocating the sustained budgetary resources necessary to reduce those potential damages and safeguard development. A specific catastrophic risk model has been developed to evaluate, building by building, the probabilistic losses and pure premiums of different portfolios, taking into account the seismic microzonation of cities. This model has been used to evaluate the fiscal contingency liabilities of the government and to build an optimal structure for risk transfer and retention, considering contingent credits, reserve funds, insurance/reinsurance, and cat bonds. Lastly, the model allows the evaluation of an exceedance probability curve of benefit-cost ratio, providing an innovative and ground-breaking tool for decision makers to analyze the net benefits of the risk mitigation strategies, such as earthquake retrofitting and seismic code enforcement. This article describes the model and the derived abovementioned tools, using the results of loss scenarios and the strategies implemented in some earthquake prone urban centers

Evaluación probabilista de la amenaza sísmica a nivel mundial

En el marco del Global Assessment Report on Disaster Risk Reduction 2013, preparado por la Oficina de las Naciones Unidas para la Reducción del Riesgo de Desastres (UNISDR), se llevó a cabo, por primera vez, un estudio probabilista de peligro sísmico a nivel global, usando los mismos métodos para todo el Globo. A partir de sus resultados fue posible obtener un conjunto estocástico de escenarios para diferentes intensidades sísmicas (aceleraciones espectrales, 5% del amortiguamiento crítico), que a su vez fueron usados en un estudio de riesgo sísmico completamente probabilista. Primero, el Globo se dividió en un conjunto de áreas sismogenéticas, a cada una de las cuales se asignó una magnitud máxima y un régimen tectónico predominante. Se supuso que la sismicidad de cada región quedaba correctamente definida utilizando una relación magnitud-frecuencia del tipo Gutenberg-Richter, cuyos valores a y b fueron obtenidos usando un procedimiento de sismicidad suavizada basada en el catálogo sísmico NEIC-USGS. Este catálogo fue previamente sometido a un proceso de remoción de réplicas y verificación de completez para varios valores de magnitud umbral. A partir del régimen tectónico predominante asignado a cada región, se le asignó una relación de atenuación. Los cálculos probabilistas de peligro sísmico se llevaron a cabo con el programa CRISIS2014, el cual generó curvas convencionales de peligro sísmico para diferentes intensidades, y mapas de aceleraciones asociadas a varios periodos de retorno; adicionalmente, CRISIS generó un conjunto de escenarios estocásticos compatibles con la plataforma CAPRA. Estos escenarios fueron usados para llevar a cabo un análisis probabilista grueso de riesgo sísmico para todo el mundo.Peer ReviewedPostprint (published version