The autumn 1919 Torremendo (Jacarilla) earthquake series (SE Spain)

On 10th September 1919 several slightly damaging earthquakes struck the towns of Torremendo, Jacarilla (near Alicante, SE-Spain) and others nearby. Available magnitude estimations for the largest two events of the series are M = 5 approx. They were earthquakes of moderate size and they occurred in a region where similar magnitude earthquakes, thoroughly studied, occurred recently (1999 Mula; 2002 Bullas; 2005 La Paca; 2011 Lorca). This makes these events of interest for a better definition of the regional seismicity. We study their sources from the analysis of the available contemporary seismograms and related documents. A total of 23 seismograms from 9 seismic stations have been collected and digitized. These seismograms contain records for the two main events and several aftershocks of the earthquake series. Finally 44 files, corresponding to 44 recorded single component records from the different events have been processed. The events have been relocated and their magnitudes recalculated. Also, original macroseismic information for these events was recovered. A macroseismic evaluation of the series has been performed. Intensity data points have been recalculated and macroseismic location and magnitude obtained. We conclude that these are the largest earthquakes occurred in the region since the beginning of instrumental recording, with Mw = 5.5 for the largest shock, and that the available data could be compatible with a thrust mechanism related to blind faults in the Bajo Segura region.This research was partly funded through projects PTDC/CTEGIX/ 122262/2010 from Portuguese FCT and CGL2012-31472 from Spanish DGI/MEyC

Seismic hazard in Andalucia region (Southern Spain)

The global objective of the SISMOSAN Project has been to provide a general seismic risk assessment of Andalusian region (Southern Spain) associated with the ground motions expected for a return period of 475 years. The project was financed by Civil Defence of Andalusia and its results will be applied to the definition of regional emergency plans. We present here the study and main results of the first phase of the project, aimed at evaluating seismic hazard. In contrast to most of the previous studies in the region, which were performed for peak ground accelerations (PGA) making use of Intensity-to-PGA relationships, hazard was here calculated in terms of magnitude and using published spectral ground-motion models. Moreover, we have considered distinct models for the Atlantic earthquakes, since the attenuation of those motions seem to be slower, as evidenced by the extensive macroseismic areas of the 1755, 1969 and 2007 earthquakes. A comprehensive revision of the seismic catalogue, as well as of the seismogenic models proposed for the region (including those for North Africa, which is part of the influence area) has been done. In a first step, seismic hazard was evaluated at generic rock sites covering the entire region, using a seismic catalogue homogenized to moment magnitude and considering attenuation models in terms of PGA and spectral ordinates (SA). A Probabilistic Seismic Hazard Assessment (PSHA) methodology was followed using a logic tree, in order to constrain the epistemic uncertainty, including two nodes for different options of zonification and attenuation models. In a second step, a geotechnical characterization of the whole region has been carried out, mainly inferred from geological maps and refined with on-site data, which are combined with rock acceleration estimates, in order to compose hazard maps that incorporate local soil effects

Archivo online de datos macrosísmicos de la península Ibérica

An application has been adopted to visualize macroseismic data of the Iberian Peninsula. Three institutions, Institut Geològic de Catalunya (IGC), Instituto Geográfico Nacional (IGN), from Spain and Instituto de Meteorologia from Portugal have already implemented in their web sites with information on the most important earthquakes. A computer programe (MIDOP, Macroseismic Intensity Data Online Publisher) was created by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) in order to easily allow theobtention of Earthquake listing and geographical distribution of intensity data points through a web page

Informe del sismo de Lorca del 11 de mayo de 2011

En la reciente historia sísmica de España, desde el terremoto de 1956 en Albolote (Granada) con once muertos y el de 1969 al SW del Cabo San Vicente con cuatro, el terremoto de Lorca de 11 de mayo de 2011 (magnitud 5.1) ha vuelto a ser especialmente importante por haber ocasionado nueve víctimas mortales. El movimiento sísmico, localizado muy próximo a la ciudad de Lorca, ha afectado directamente a más de 90.000 personas, que han sufrido sus consecuencias al registrarse con una intensidad de grado VII en la escala europea EMS, lo que ha motivado daños notables en las viviendas. El presente informe trata de reflejar las características del terremoto y de su serie de réplicas, recogiendo los trabajos que han desarrollado diferentes equipos de investigación, tanto previos al terremoto como posteriores. El estudio describe los aspectos científicos y técnicos de mayor interés, desde la historia sísmica de la zona hasta el comportamiento de las edificaciones de la ciudad de Lorca. Asimismo, se acompaña de un encuadre geológico de la zona y de las características de la falla de Alhama de Murcia, responsable de la ocurrencia del terremoto. Como consecuencia de los terremotos que hubo la misma zona en el año 2005, precedidos por un apreciable nivel de actividad sísmica en los años 1999 y 2002, la región de Murcia fue objeto del proyecto RISMUR, cofinanciado por el Instituto Geográfico Nacional y en el que participaron los redactores de este informe. Algunos de los aspectos de este proyecto, en concreto los relativos a la peligrosidad sísmica han sido incluidos, incidiendo en los resultados que se obtuvieron en la ciudad de Lorca. El informe va acompañado al final de una serie de conclusiones en relación con cada uno de los temas tratados, resaltando aquellos aspectos que se deberán tener en cuenta en futuros proyectos, a fin de mejorar por un lado el conocimiento de la sismicidad y peligrosidad sísmica y por otro para la adecuación de la normativa sismorresistente.Peer reviewe

Sismicidad histórica de la Península Ibérica

Los terremotos más destructivos que han afectado a la península Ibérica han sucedido antes del siglo XX, durante el llamado periodo histórico. Los estudios de sismicidad se consideran por lo tanto absolutamente necesarios, ya que permiten conocer las principales características de este periodo y representan una herramienta de gran valor en los estudios de peligrosidad y riesgo sísmico. En este trabajo se realiza un análisis sobre la evaluación de los datos macrosismicos, de la distribución espacial y temporal de los terremotos y de los daños producidos. Asimismo, los nuevos mapas de información macrosísmica obtenidos han permitido estimar la energía liberada mediante el cálculo de la magnitud

Optimización de parámetros de localización para distintos tipos de redes sísmicas : aplicación a la Peninsula Ibérica

A partir de los datos suministrados por la red sísmica nacional y el dispositivo sísmico de Sonseca sobre terremotos próximos y lejanos, se han desarrollado diferentes tecnicas con objeto de determinar sus parámetros de localización. La metodología esta basada en la configuración de redes sísmicas de tipo antena, donde los sismos se producen a distancias muy alejadas en relación con el diámetro de la red. Los resultados permiten establecer una serie de criterios para la configuración y geometría de redes sísmicas y desarrollo de sistemas de detección y alerta de eventos sísmicos

Terremotos y Edificios. Una historia común

Los documentos confeccionados como consecuencia de algunos de los terremotos más importantes ocurridos en épocas históricas (siglos XVI a XIX), permiten observar la evolución que ha tenido el conocimiento de las técnicas constructivas y urbanísticas de las ciudades. También iban acompañados de teorías sobre la causa y origen de los terremotos, basadas algunas en ideas sobrenaturales que con el tiempo se fueron modificando hacia planteamientos más científicos. Los informes sobre los terremotos ocurridos iban reflejando las diferentes hipótesis que justificaban los daños ocasionados y aportaban soluciones muy específicas, como la búsqueda de un nuevo emplazamiento, las características del terreno, el proyecto urbanístico, la ejecución de la construcción o la elección de los materiales. Asimismo, a finales del siglo XIX, se redactan reglamentos constructivos con criterios legales, que pueden considerarse como los antecedentes de la actual normativa

The impact of Tsunamis on the island of Majorca induced by North Algerian seismic sources

The north of Algeria is the main earthquake-related tsunami generation zone that threatens the Balearic Islands. In this work we review the major seismic series of the area -the 1980 El Asnam and the 2003 Boumerdes- Zemmouri earthquakes- in order to obtain a probable worst characteristic earthquake rupture. We estimate rupture dimensions of 55 km × 16 km, reaching the fault plane a depth of 13 km. The dip and rake have been taken as constants, with values of 50° and 90° respectively, while the strike is adjusted to the local tectonic structure. With these characteristics a magnitude MW= 7.3 earthquake is obtained for an average slip of 4 metres; these values being reasonable for the seismotectonics of the area. Nine sources along the northern coast of Algeria have been proposed, some of them have been mapped offshore and others that are less known are probable continuations of onshore structures. Based on numerical simulations the tsunami impacts of the nine potential events on Majorca have been studied. Catastrophic tsunamis cannot be triggered from these sources in the Balearic Islands. However, wave elevations up to 2 m can generate flooding in low areas and wave amplifications in bays and harbours that can be damaging, as witnessed in historical events

The 7 June 2007 mbLg 4.2 escopete earthquake : An event with significant ground motion in a stable zone (Central Iberian Peninsula)

An earthquake occurred on 7 June 2007 at 01h:42m:09.5s (UTC) with geographical coordinates 40°.41N, 2°.98W and magnitude mbLg = 4.2 according to the Seismic national network (RSN) of Madrid's Instituto Geográfico Nacional (IGN). The epicenter was located close to the town of Escopete, where the earthquake was felt with intensity IV, waking up inhabitants and causing widespread alarm. Historically, rare but similar events have been felt in the area, near the towns of Pastrana (1922) and Duron (1982). Nevertheless, this part of Iberia experiences very low seismic activity. The earthquake with the largest magnitude recorded to date by the RSN since the mid-1920s was 4.1. Due to low seismicity values, the hazard map of the Norma de la Construcción Sismorresistente Española (Spanish seismic building code; NCSE-02) establishes a basic acceleration value of less than 0.04 g, which is the threshold value for the application of the earthquake-resistant building code. However, this value was exceeded in strong-motion recordings during the 2007 event. An important consideration is the existence of two nuclear power plants in the Guadalajara administrative province: José Cabrera and Trillo. Strong-motion instruments at the José Cabrera nuclear power plant (JCNPP) recorded a peak ground acceleration (PGA) value of 0.07g. This is the first acceleration recording made from central Iberia and also one of the highest values read from instruments to date for the whole of the Iberian peninsula. This paper presents an overview of the results of our multidisciplinary analysis of the earthquake, which we researched in terms of its regional and local tectonic setting, local seismicity, focal mechanics, strong-motion records, and macroseismic effects.Universidad Complutense de MadridMinisterio de Educación y CienciaDepto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu