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The eruption of the Tajogaite volcano in 2021, in the Cumbre Vieja rift zone (La Palma, Canary Islands), is the most recent but also the most damaging and longest-lasting eruption on the island since historical records began. We analyzed geophysical parameters (seismicity, surface deformation, thermal anomalies, and volcanic activity) with the aim of reconstructing the temporal development of the magma plumbing system. The seismic sequence (> 9000 events, mbLg ≤ 5.0) can be grouped into nine distinct phases, which correspond to well-separated spatial clusters and distinct earthquake regimes. A strong premonitory thermal anomaly was calculated on July 2021 in the South of La Palma. The source of the magma was within the upper mantle (40–20 km depth). A second magma budget (< 15 km depth) indicated a short-term stagnation of alkaline magma within the lower crust, near the Moho. The outline of these earthquakes delineates the magma pathway. Just before and immediately after the eruption (phases 2 and 3), the high-frequency seismicity in the mantle disappeared completely, reappearing ten days after the eruption started. The pattern of deformation began before the eruption with a breakpoint around September 11, after which, deformation accelerated sharply, followed by stabilization in phase 3 and a decrease in the following phases. The level of deformation suggested that a shallow magma intrusion was established. Based on the historical eruptive pattern, it is possible to infer two possible hazard-forecast scenarios: (a) the volcano could enter a prolonged phase of tranquility for more than one century or, (b) a new eruption could occur between ca. 2045 and 2065, with a slightly shorter duration than this recent one. Therefore, if the more pessimistic scenario is assumed, appropriate territorial planning is required.

Los terremotos son fenómenos naturales e inevitables, causantes de grandes pérdidas humanas y económicas. Este texto presenta en forma concisa los fundamentos del diseño de estructuras sismorresistentes, disciplina cada vez más relevante en los estudios técnicos relacionados con la construcción. Tras un análisis de la naturaleza de la acción sísmica, se discute el comportamiento de las estructuras sometidas a terremotos, abarcando desde sistemas simples hasta edificios completos. La comprensión de esta respuesta permite exponer de manera fundada los principios básicos del diseño sismorresistente, enfatizando sus aspectos cualitativos mediante ejemplos construidos por los propios autores. Se introducen asimismo algunos conceptos más avanzados, como los sistemas de aislamiento y disipación de energía. Finalmente se discuten los principios de la peligrosidad, que forma la base del actual tratamiento normativo de la acción sísmica.

We present a procedure for assessing the urban exposure and seismic vulnerability that integrates LiDAR data with aerial images from the Spanish National Plan of Aerial Orthophotography (PNOA). It comprises three phases: first, we segment the satellite image to divide the study area into different urban patterns. Second, we extract building footprints and attributes that represent the type of building of each urban pattern. Finally, we assign the seismic vulnerability to each building using different machine-learning techniques: Decision trees, SVM, logistic regression and Bayesian networks. We apply the procedure to 826 buildings in the city of Lorca (SE Spain), where we count on a vulnerability database that we use as ground truth for the validation of results. The outcomes show that the machine learning techniques have similar performance, yielding vulnerability classification results with an accuracy of 77%–80% (F1-Score). The procedure is scalable and can be replicated in different areas. This is particularly relevant in Spain, where more than seven hundred towns have to develop seismic risk studies in the years to come, according to the General Direction of Civil Protection and Emergencies. It is especially interesting as a complement to conventional data gathering approaches for disaster risk applications in cities where field surveys need to be restricted to certain areas, dates or budget.

Identification and classification of the different structures and infrastructures that make up a city (conventional buildings, power stations, nuclear power stations, routes of communication, etc.) are of great importance at the time of characterize their vulnerability and carry out estimates of seismic risk. Different types have different physical damage to some seismic movement, hence the importance of correctly assign a class of vulnerability. For this reason, it is necessary to know, updated form, the distribution and composition of structures and infrastructure of a city. Behaviour that presented these elements to a seismic phenomenon is linked, among others, building material and its geometric shape. Today, cadastral information updated about the infrastructure of a city does not have the data necessary and useful to carry out a calculation of seismic risk. For decades, the way of being able to have such information, has been through the development of campaigns of field for the elaboration of databases. This practice entails long time of work and the need for qualified personnel for the identification of the constructive typologies of the different structures. Nowadays, there are different geospatial techniques that allow data acquisition on a massive scale in a short time. In particular, by means of laser measurements, it is possible to have clouds of millions of points with geometric and radiometric information in a matter of seconds. This article presents a line of research whose main objective is to innovate in the vulnerability mapping and seismic risk estimation methods using geospatial techniques: static and dynamic laser. The end is contributing to knowledge and more accurate risk results, on which will be supported after the emergency plans that facilitate post event actions.

This paper presents a methodological approach to seismic hazard assessment based on a hybrid source model composed of faults as independent entities and zones containing residual seismicity. The seismic potential of both types of sources is derived from different data: for the zones, the recurrence model is estimated from the seismic catalogue. For fault sources, it is inferred from slip rates derived from palaeoseismicity and GNSS (Global Navigation Satellite System) measurements. Distributing the seismic potential associated with each source is a key question when considering hybrid zone and fault models, and this is normally resolved using one of two possible alternatives: (1) considering a characteristic earthquake model for the fault and assigning the remaining magnitudes to the zone, or (2) establishing a cut-off magnitude, Mc, above which the seisms are assigned to the fault and below which they are considered to have occurred in the zone. This paper presents an approach to distributing seismic potential between zones and faults without restricting the magnitudes for each type of source, precluding the need to establish cut-off Mc values beforehand. This is the essential difference between our approach and other approaches that have been applied previously. The proposed approach is applied in southern Spain, a region of low-to-moderate seismicity where faults move slowly. The results obtained are contrasted with the results of a seismic hazard method based exclusively on the zone model. Using the hybrid approach, acceleration values show a concentration of expected accelerations around fault traces, which is not appreciated in the classic approach using only zones.

During the last years, several crustal seismic sources have been proposed in El Salvador; however, the actual destructive potential of these proposals has not been revealed yet. Here we present several seismic scenarios related with the main crustal faults in the country. We have characterized the corresponding hazard scenarios in a deterministic way, estimating the peak ground accelerations (PGA) including local site effects. In addition, we present a list of 29 sources that can be considered potentially dangerous with their main features when they are available and four seismic scenarios that we consider to be more probable. We have resorted to the February 13th 2001 Mw 6.6 destructive earthquake, the only earthquake occurred in a known crustal source in El Salvador and recorded by the strong motion network, in order to test the methodological approach and the reliability of the PGA results predicted by two available Ground Motion Prediction Equations (GMPEs) including the site effect. The consistence between the values given by the models and the ones recorded during the event provides reliability to our results. This approach allowed us to conclude that faults within the volcanic arc can produce accelerations up to 1 g in the most conservator case (Mw = 7.0), while accelerations up to 0.6 g are usual results related with specific faults within the Salvadoran Volcanic Arc. Besides, the reported damage distribution of the 8th June 1917 earthquakes and its similarity with one of the proposed scenarios allowed us to infer the possible source of this event, the Guaycume Fault.

Central America is one of the most active seismic zones in the World, due to the interaction of five tectonic plates (North America, Caribbean, Coco, Nazca and South America), and its internal deformation, which generates almost one destructive earthquakes (5.4 ≤ Mw ≤ 8.1) every year. A new seismological zonation for Central America is proposed based on seismotectonic framework, a geological context (tectonic and geological maps), geophysical and geodetic evidence (gravimetric maps, magnetometric, GPS observations), and previous works. As a main source of data a depurated earthquake catalog was collected covering the period from 1522 to 2015. This catalog was homogenized to a moment magnitude scale (Mw). After a careful analysis of all the integrated geological and seismological information, the seismogenic zones were established into seismic areas defined by similar patterns of faulting, seismicity, and rupture mechanism. The tectonic environment has required considering seismic zones in two particular seismological regimes: a) crustal faulting (including local faults, major fracture zones of plate boundary limits, and thrust fault of deformed belts) and b) subduction, taking into account the change in the subduction angle along the trench, and the type and location of the rupture. The seismicity in the subduction zone is divided into interplate and intraplate inslab seismicity. The regional seismic zonation proposed for the whole of Central America, include local seismic zonations, avoiding discontinuities at the national boundaries, because of a consensus between the 7 countries, based on the cooperative work of specialists on Central American seismotectonics and related topics.

Induced seismicity associated with energy production is becoming an increasingly important issue worldwide for the hazard it poses to the exposed population and structures. We analyze one of the rare cases of induced seismicity associated with the underwater gas storage operations observed in the Castor platform, located in the Valencia gulf, east Spain, near a complex and important geological structure. In September 2013, some gas injection operations started at Castor, producing a series of seismic events around the reservoir area. The larger magnitude events (up to 4.2) took place some days after the end of the injection, with EMS intensities in coastal towns up to degree III. In this work, the seismic sequence is analyzed with the aim of detecting changes in statistical parameters describing the earthquake occurrence before and after the injection and identifying possible proxies to be used for monitoring the sequence evolution. Moreover, we explore the potential predictability of these statistical parameters which can be used to control the field operations in injection/storage fluid reservoirs. We firstly perform a retrospective approach and next a perspective analysis. We use different techniques for estimating the value of the expected maximum magnitude that can occur due to antropogenic activities in Castor.

This study is in the frame of the cooperative line that several Spanish Universities and other foreign partners started with the Haitian government in 2010. According to our studies (Benito et al. in An evaluation of seismic hazard in La Hispaniola, after the 2010 Haiti earthquake, 33rd General Assembly of the European Seismological Commission, Moscow, Russia, 2012) and recent scientific literature, the earthquake hazard in Haiti remains high (Calais et al. in Nat Geosci 3:794–799, 2010). In view of this, we wonder whether the country is currently ready to face another earthquake. In this sense, we estimated several damage scenarios in Port-au-Prince and Cap-Haitien associated to realistic possible major earthquakes. Our findings show that almost 50 % of the building stock of both cities would result uninhabitable due to structural damage. Around 80 % of the buildings in both cities have reinforced concrete structure with concrete block infill; however, the presence of masonry buildings becomes significant (between 25 and 45 % of the reinforced concrete buildings) in rural areas and informal settlements on the outskirts, where the estimated damage is higher. The influence of the soil effect on the damage spatial distribution is evident in both cities. We have found that the percentage of uninhabitable buildings in soft soil areas may be double the percentage obtained in nearby districts located in hard soil. These results reveal that a new seismic catastrophe of similar or even greater consequences than the 2010 Haiti earthquake might happen if the earthquake resilience is not improved in the country. Nowadays, the design of prevention actions and mitigation policies is the best instrument the society has to face seismic risk. In this sense, the results of this research might contribute to define measures oriented to earthquake risk reduction in Haiti, which should be a real priority for national and international institutions.

This study is in the frame of the cooperative line that several Spanish Universities and other foreign partners started with the Haitian government in 2010. According to our studies (Benito et al. in An evaluation of seismic hazard in La Hispaniola, after the 2010 Haiti earthquake, 33rd General Assembly of the European Seismological Commission, Moscow, Russia, 2012) and recent scientific literature, the earthquake hazard in Haiti remains high (Calais et al. in Nat Geosci 3:794–799, 2010). In view of this, we wonder whether the country is currently ready to face another earthquake. In this sense, we estimated several damage scenarios in Port-au-Prince and Cap-Haitien associated to realistic possible major earthquakes. Our findings show that almost 50 % of the building stock of both cities would result uninhabitable due to structural damage. Around 80 % of the buildings in both cities have reinforced concrete structure with concrete block infill; however, the presence of masonry buildings becomes significant (between 25 and 45 % of the reinforced concrete buildings) in rural areas and informal settlements on the outskirts, where the estimated damage is higher. The influence of the soil effect on the damage spatial distribution is evident in both cities. We have found that the percentage of uninhabitable buildings in soft soil areas may be double the percentage obtained in nearby districts located in hard soil. These results reveal that a new seismic catastrophe of similar or even greater consequences than the 2010 Haiti earthquake might happen if the earthquake resilience is not improved in the country. Nowadays, the design of prevention actions and mitigation policies is the best instrument the society has to face seismic risk. In this sense, the results of this research might contribute to define measures oriented to earthquake risk reduction in Haiti, which should be a real priority for national and international institutions.

This study evaluates the potential of object-based image analysis in combination with supervised machine learning to identify urban structure type patterns from Landsat Thematic Mapper (TM) images. The main aim is to assess the influence of several critical choices commonly made during the training stage of a learning machine on the classification performance and to give recommendations for classifier-dependent intelligent training. Particular emphasis is given to assess the influence of size and class distribution of the training data, the approach of training data sampling (user-guided or random) and the type of training samples (squares or segments) on the classification performance of a Support Vector Machine (SVM). Different feature selection algorithms are compared and segmentation and classifier parameters are dynamically tuned for the specific image scene, classification task, and training data. The performance of the classifier is measured against a set of reference data sets from manual image interpretation and furthermore compared on the basis of landscape metrics to a very high resolution reference classification derived from light detection and ranging (lidar) measurements. The study highlights the importance of a careful design of the training stage and dynamically tuned classifier parameters, especially when dealing with noisy data and small training data sets. For the given experimental set-up, the study concludes that given optimized feature space and classifier parameters, training an SVM with segment-shaped samples that were sampled in a guided manner and are balanced between the classes provided the best classification results. If square-shaped samples are used, a random sampling provided better results than a guided selection. Equally balanced sample distributions outperformed unbalanced training sets.

This work provides a comprehensive explanation of the uncertainty assessment conducted during the development of Spain's new seismic hazard maps. It offers detailed insights into how uncertainties are addressed across various phases of the probabilistic seismic hazard assessment study. Particular attention is devoted to characterizing the uncertainty associated with earthquake size parameters found within the catalog. This includes an exploration of how these uncertainties propagate through subsequent phases of the analysis, such as catalog homogenization, completeness evaluation, and declustering. Both aleatory (inherent randomness) and epistemic (due to incomplete knowledge) uncertainties are meticulously examined and assessed. Monte Carlo simulations are employed to address aleatory uncertainties, while a logic tree approach is utilized for handling epistemic uncertainties. The study evaluates the final impact of uncertainty on hazard estimates using coefficient of variation maps. These maps visually depict areas where variability in hazard estimates is more pronounced or reduced, providing valuable insights into the reliability of the developed hazard maps. Ultimately, the hazard maps produced in this study serve as a foundational resource for the future revision of the Spanish seismic code. By thoroughly addressing and evaluating uncertainties, this work contributes to enhancing the accuracy and robustness of seismic hazard assessments, thus supporting improved seismic risk management practices.

In the recent seismic hazard assessment study of Spain, a crucial step in preparing and standardizing the seismic catalog involves establishing relationships among various scales used to measure earthquake size. The aim is to convert all earthquake size data from the original catalog into a single magnitude scale, specifically the moment magnitude (Mw). This ensures uniform and comparable size measurements across the dataset. To achieve this, new relationships between Mw and other magnitude scales used in the catalog are developed through regression analysis. This analysis is conducted across different epochs, allowing for a comprehensive understanding of seismicity trends over time. The reduced major axis regression scheme is employed for its symmetric treatment of variables involved in the fits, ensuring robustness in the derived relationships. The study presents the newly derived relationships for Spain, including Mw as a function of mbLg, Mw as a function of mb, and Mw as a function of Imax. The applicability limits and accuracy of these relationships are thoroughly discussed to provide insights into their reliability and utility in seismic analysis. Importantly, beyond their immediate application in seismic hazard assessment, these results could have broader practical implications in regional seismicity analysis, offering valuable tools for earthquake research and risk management initiatives.

(This is an excerpt from the content) On May 11 2011 at 1705 hours, a small 4.5 Mw. magnitude earthquake struck the town of Lorca in south-eastern Spain. Other than alarmed citizens, only minor damage to buildings occurred due to this quake. Unfortunately at 1847 hours, a second shock registering a magnitude of 5.1 Mw. and very shallow (just around 2 km under the city) produced the largest seismic catastrophe registered in Spain in the last 120 years. This second shock is commonly referred to as “Lorca’s earthquake” and the following papers describe the context, circumstances and consequences of the event. Spain is a country of moderate seismic hazard in a global context. Before the Lorca earthquake, the most destructive earthquake in modern times was the so-called “Andalusian earthquake” (25th December 1884) that resulted in 750 fatalities and more than 1,500 injuries, reaching X in Mercalli’s intensity scale. Despite the lack of catastrophic events in the last 120 years, Spain has always had a scientific interest in seismic ...

El 12 de agosto de 2014, se registró un sismo de magnitud 5.1, a una profundidad focal de 4 km., en el segmento de falla Bellavista Catequilla, el mismo que fue registrado en 8 estaciones localizadas en la ciudad de Quito. Estas se encuentran ubicadas a distancias epicentrales entre 12 y 19 km. En este artículo se comparan las aceleraciones máximas obtenidas en campo libre, con las que se obtienen al emplear las ecuaciones de movimientos fuertes de Campbell y Borzognia (2013) y el de Zhao et al. (2006). Para ello previamente se determina un plano de ruptura del sismo, utilizando las ecuaciones propuestas por Leonard (2010) y la geometría de las fallas ciegas propuestas por Alvarado (2014). ABSTRACT: On August 12 th 2014, a magnitude 5.1 earthquake occurred at a depth of 4 km, in the Bellavista Catequilla fault segment. This event was recorded by 8 strong-motion stations located between 12 and 19 km from the epicenter, in the city of Quito. In this article, the maximum ground accelerations recorded in free field are compared with the accelerations estimated using the models by Campbell y Borzognia (2013) and Zh ao et al. (2006). To this end, the earthquake rupture plane is determined using the equations proposed by Leonard (2010) and the geometry of the blind fault system of Quito proposed by Alvarado (2014).

After the 2010 Haiti earthquake, that hits the city of Port-au-Prince, capital city of Haiti, a multidisciplinary working group of specialists (seismologist, geologists, engineers and architects) from different Spanish Universities and also from Haiti, joined effort under the SISMO-HAITI project (financed by the Universidad Politecnica de Madrid), with an objective: Evaluation of seismic hazard and risk in Haiti and its application to the seismic design, urban planning, emergency and resource management. In this paper, as a first step for a structural damage estimation of future earthquakes in the country, a calibration of damage functions has been carried out by means of a two-stage procedure. After compiling a database with observed damage in the city after the earthquake, the exposure model (building stock) has been classified and through an iteratively two-step calibration process, a specific set of damage functions for the country has been proposed. Additionally, Next Generation Attenuation Models (NGA) and Vs30 models have been analysed to choose the most appropriate for the seismic risk estimation in the city. Finally in a next paper, these functions will be used to estimate a seismic risk scenario for a future earthquake.

After the 2010 Haiti earthquake, that hits the city of Port-au-Prince, capital city of Haiti, a multidisciplinary working group of specialists (seismologist, geologists, engineers and architects) from different Spanish Universities and also from Haiti, joined effort under the SISMO-HAITI project (financed by the Universidad Politecnica de Madrid), with an objective: Evaluation of seismic hazard and risk in Haiti and its application to the seismic design, urban planning, emergency and resource management. In this paper, as a first step for a structural damage estimation of future earthquakes in the country, a calibration of damage functions has been carried out by means of a two-stage procedure. After compiling a database with observed damage in the city after the earthquake, the exposure model (building stock) has been classified and through an iteratively two-step calibration process, a specific set of damage functions for the country has been proposed. Additionally, Next Generation Attenuation Models (NGA) and Vs30 models have been analysed to choose the most appropriate for the seismic risk estimation in the city. Finally in a next paper, these functions will be used to estimate a seismic risk scenario for a future earthquake.

This work outlines the development and utilization of a Geographic Information System (GIS) for studying urban seismic risk in the city of Almería, located in southern Spain. The GIS serves as a crucial tool in decision-making processes throughout the project's execution. Following the completion and approval of regional emergency plans for seismic risk in Spain, municipalities identified the need to develop specific local seismic risk plans. Consequently, the focus shifts towards conducting urban seismic risk analyses at an appropriate scale, termed Urban Seismic Risk Evaluation (Risk-UR). This evaluation integrates various factors influencing seismic risk, including seismic hazard, geotechnical soil characteristics, vulnerability of regional structures, repair costs of damaged buildings, and exposed population. By consolidating and analyzing these variables within a GIS, seismic risk estimation becomes more effective. The GIS proves invaluable due to its capability for data interoperability, streamlining the handling of extensive information and numerous processes involved in calculations. This expedites analysis, interpretation, and presentation of results across different project phases. The study's outcome encompasses a comprehensive array of variables, offering insights into urban seismic risk. These include the distribution of building and dwelling damage across different typologies, average damage levels, the count of uninhabitable buildings under expected seismic motion, casualties at various times of the day, and the financial implications of reconstruction and repair. These results aim to facilitate interpretation and decision-making in emergency management, catering to non-specialist users such as Civil Defence technicians and managers.

This paper presents a novel approach to characterizing ground motion hazards at the Itoiz dam site in Northern Spain. Our methodology offers various approximation levels to estimate expected ground motion, tailored to the site and dam's unique attributes. Employing Probabilistic Seismic Hazard Assessment (PSHA) with a logic tree, we account for diverse seismic source zones and ground-motion attenuation relationships. Our analysis focuses on peak ground acceleration and spectral accelerations aligned with the dam's fundamental vibration periods. Considering both empty and full reservoir conditions, hazard calculations encompass two significant return periods: 975 years, linked to the project earthquake, and 4,975 years, denoting an extreme event. Additionally, soil conditions are factored into the analysis. Our methodology encompasses diverse approaches to ground motion characterization. Initially, we derive uniform hazard response spectra for the two return periods. Subsequently, disaggregation analysis identifies the primary earthquakes influencing the dam. We then characterize ground motion at the dam site through specific response spectra for target motions corresponding to expected values for the respective return periods. Finally, we generate synthetic acceleration time histories for earthquakes matching the controlling parameters, utilizing the discrete wave-number method. Given the short distances between controlling earthquakes and the dam site, we consider finite sources in our computations. We conclude by emphasizing the significance of considering directivity effects as a crucial variable in such studies for accurately assessing ground motion characteristics.

Este trabajo presenta un análisis de diferentes aspectos relacionados con el sismo principal del 11 de Mayo de 2011, con epicentro en las proximidades de Lorca, que abarcan desde el movimiento fuerte registrado hasta el daño observado en diferentes tipologías constructivas, contrastando todo ello con los resultados de estudios previos de peligrosidad y riesgo sísmico en la provincia de Murcia. La cuestión esencial que se plantea en el análisis es si tanto el movimiento como el daño entraban dentro de lo esperado o pueden considerarse anómalos en el marco del riesgo sísmico del sureste de España. A este respecto se hacen una serie de reflexiones y se extraen lecciones aprendidas del terremoto, que llevan a proponer recomendaciones de cara a la revisión de la Norma Sismorresistente Española, así como a definir medidas para la reducción del riesgo sísmico en la región. Abstract: An analysis of the different aspects related to the May 11th, 2011 Lorca earthquake is presented,covering recorded ground motions, damage observed in different building typologies, and contrasting these observations with previous results on seismic hazard and seismic risk obtained in the province of Murcia. The essential question addressed in the analysis is whether observed ground motions and physical damage can be considered as expected or as anomalous in the frame of seismic risk in southeastern Spain. In this respect, a number of reflections are carried out and several learned lessons from the earthquake are extracted, which leads to the proposal of different recommendations for the future revision of the Spanish earthquake-resistant provisions, as well as for defining risk reduction measurements in the region.

El terremoto de Lorca del 11 de mayo de 2011, de magnitud Mw=5,2, causó un enorme impacto en la ciudad y una gran alarma social, provocando 9 víctimas mortales, centenares de heridos y cuantiosos daños materiales. Este trabajo recoge las opiniones de varios expertos que tuvieron un papel destacado en la gestión y análisis del suceso, y la de 627 lorquinos a través de una encuesta llevada a cabo por estudiantes del I.E.S. Ramón Arcas de Lorca. Aunque cada uno de los expertos y los ciudadanos inciden en aspectos diferentes, el análisis de sus opiniones nos permite concluir, como principal lección aprendida, que terremotos futuros como el de Lorca pueden producir muchos menos daños si se trabaja conjuntamente en mejorar: (1) la investigación sísmica, (2) la calidad de las construcciones, (3) la gestión de las catástrofes naturales y (4) la formación de la ciudadanía. Esta aproximación multidisciplinar al terremoto de Lorca puede resultar interesante para los estudiantes, y puede aportar ideas a los docentes para el análisis de futuros terremotos., The Mw 5,2 earthquake of 11 May 2011 in Lorca caused a great impact and social alarm, producing 9 fatalities, injuring hundreds and leaving widespread damage. This paper collects opinions by several experts on earthquakes and seismic risk management, and the opinions of 627 citizens from on an opinion poll conducted by students of the Ramon Arcas high school in Lorca. Although experts and citizens focus their attention on different items, anaylizing their opinions allows us to conclude that prevention or mitigation of the effects of future earthquakes needs combined efforts aimed at improving: (1) earthquake research, (2) earthquake-proof design of buildings, (3) seismic risk management and (4) self-protection measures and education of the population. This multidisciplinary approach of the Lorca earthquake is interesting for students and teachers when it comes to analyzing future earthquakes.

El SIG-RISNA es un sistema de información geográfica desarrollado en el marco de un proyecto de evaluación del riesgo sísmico en la Comunidad Foral de Navarra, Proyecto RISNA. El objetivo general del mismo es hacer una evaluación, de carácter científicotécnica, que sirva de base para desarrollar el Plan Especial de Emergencia de la región y para la identificación de municipios de especial riesgo de cara a su posterior estudio local. Para esta evaluación, se combinan diferentes factores influyentes en el riesgo sísmico, tales como la peligrosidad sísmica, las características geotécnicas del suelo y la vulnerabilidad de estructuras de la región. Todas estas variables se integran en la estimación del riesgo por medio un SIG, que constituye una herramienta de trabajo de gran utilidad, ya que facilita la interoperabilidad de los datos haciendo más manejable el gran volumen de información requerida y los numerosos procesos que intervienen en el cálculo. En este artículo de describirán las características y el esqueleto del SIG-RISNA, incluyendo los datos de partida necesarios y los procesos y análisis realizados para la consecución del mismo. El resultado de este estudio comprende un gran conjunto de variables que dan una visión global del riesgo sísmico en la región, como son la distribución de daños para diferentes tipologías, el daño medio y el número de edificaciones que quedarían inhabitables ante el movimiento esperado, entre otros. Estos resultados están destinados a la interpretación y toma de decisiones, de personal no especializado (técnicos y gestores de Protección Civil), hacia la gestión de la emergencia. Por este motivo, una transmisión comprensible de los resultados de forma que puedan ser correctamente interpretados se considera un apartado de especial importancia dentro del estudio. En este contexto se desarrolló el visualizador Web VISORRISNA, una aplicación Web que contiene todos los resultados del estudio expuestos por medio de un conjunto de capas de

Hazard-consistent ground-motion characterisations of three representative sites located in the Region of Murcia (southeast Spain) are presented. This is the area where the last three damaging events in Spain occurred and there is a significant amount of data for comparing them with seismic hazard estimates and earthquake-resistant provisions. Results of a probabilistic seismic hazard analysis are used to derive uniform hazard spectra (UHS) for the 475-year return period, on rock and soil conditions. Hazard deaggregation shows that the largest hazard contributions are due to small, local events for short-period target motions and to moderate, more distant events for long-period target motions. For each target motion and site considered, the associated specific response spectra (SRS) are obtained. It is shown that the combination of two SRS, for short- and long-period ground motions respectively, provides a good approximation to the UHS at each site. The UHS are compared to design response spectra contained in current Spanish and European seismic codes for the 475-year return period. For the three sites analysed, only the Eurocode 8 (EC8) type 2 spectrum captures the basic shape of the UHS (and not the EC8 type 1, as could be expected a priori). An alternative response spectrum, anchored at short- and long-period accelerations, is tested, providing a close match to the UHS spectra at the three sites. Results underline the important contribution of the frequent, low-to-moderate earthquakes that characterize the seismicity of this area to seismic hazard (at the 475-year return period).

This work has evaluated the probability of earthquake-triggered landslide occurrence in the whole of El Salvador, with a Geographic Information System (GIS) and a logistic regression model. Slope gradient, elevation, aspect, mean annual precipitation, lithology, land use, and terrain roughness are the predictor variables used to determine the dependent variable of occurrence or nonoccurrence of landslides within an individual grid cell. The results illustrate the importance of terrain roughness and soil type as key factors within the model — using only these two variables the analysis returned a significance level of 89.4%. The results obtained from the model within the GIS were then used to produce a map of relative landslide susceptibility.