Points and areas prone to earthquake-induced landslides in the CARM. Base information for Civil Protection

Se presenta un trabajo de aplicación para la definición de posibles escenarios de catástrofe sísmica, donde deben de incorporarse los movimientos de ladera, como información de base para la última revisión del Plan Especial de Protección Civil ante el Riesgo Sísmico en la Región de Murcia (SISMIMUR). Para ello se ha confeccionado un inventario adecuado y un mapa a escala 1:200.000 que contiene los puntos y zonas más susceptibles a este tipo de fenómenos inducidos por los terremotos en la CARM que pueden afectar a núcleos urbanos, infraestructuras lineales (carreteras y ferrocarriles), balsas mineras, cursos de agua y cuerpos de agua (embalses y lagos). En el análisis solo se han seleccionado los puntos definidos como desprendimientos s.l., tipología predominante en la zona de estudio y de mayores efectos de cara al escenario de la catástrofe sísmica posible. Aunque en la mayoría de las infraestructuras evaluadas están alejadas de movimientos de ladera inventariados, hay núcleos de población importantes como Lorca, Águilas o Caravaca de la Cruz, entre otras, así como algunos tramos del creciente entramado urbano del litoral murciano con zonas de susceptibilidad alta. El tramo más susceptible sería el situado en la carretera RM-520, entre Archena y Abarán.In this work, we present a methodology to define potential seismic scenarios including seismic-induced landslides as background information for the latest revision of the “Plan Especial de Protección Civil ante el Riesgo Sísmico en la Región de Murcia (SISMIMUR)”. We first made an adequate inventory and a map at 1:200,000 scale containing the points and areas more susceptible to this type of seismic-induced effects in the CARM which may affect urban areas, lifelines(roads and railways), tailing dams, waterways and bodies of water (reservoirs and lakes). For this analysis, only points defined as rockfalls s.l. have been selected, since they are the predominant type of landslide in the area and it is associated to the greatest effects regarding a potential seismic scenario. Although most of the infrastructures evaluated are far from the inventoried landslides, some areas with high susceptibility have been identified near major population centers, such as Lorca, Águilas, Caravaca de la Cruz, etc., and near of some growing urban fabric areas located along the Murcia province coast. According to this study, the most vulnerable section would be located in the RM-520 road between Archena and Abarán

Regional subsidence modelling in Murcia city (SE Spain) using 1-D vertical finite element analysis and 2-D interpolation of ground surface displacements

Subsidence is a hazard that may have natural or anthropogenic origin causing important economic losses. The area of Murcia city (SE Spain) has been affected by subsidence due to groundwater overexploitation since the year 1992. The main observed historical piezometric level declines occurred in the periods 1982–1984, 1992–1995 and 2004–2008 and showed a close correlation with the temporal evolution of ground displacements. Since 2008, the pressure recovery in the aquifer has led to an uplift of the ground surface that has been detected by the extensometers. In the present work an elastic hydro-mechanical finite element code has been used to compute the subsidence time series for 24 geotechnical boreholes, prescribing the measured groundwater table evolution. The achieved results have been compared with the displacements estimated through an advanced DInSAR technique and measured by the extensometers. These spatio-temporal comparisons have showed that, in spite of the limited geomechanical data available, the model has turned out to satisfactorily reproduce the subsidence phenomenon affecting Murcia City. The model will allow the prediction of future induced deformations and the consequences of any piezometric level variation in the study area.This work has been supported by the Spanish Ministry of Economy and Competitiveness and EU FEDER funds under projects ESP2013-47780-C2-2-R and TEC2011-28201-C02-02 and by the project 15224/PI/10 from the Regional Agency of Science and Technology in Murcia. The European Space Agency (ESA) Terrafirma project funded all the SAR data processing with the SPN technique

Geometrical and geotechnical characterization of the earth fissures appeared in the Guadalentín Valley (southeastern Spain) after the September 2012 flooding

Two earth fissures appeared in Murcia province (southeastern Spain) after the flood occurred because of a heavy downpour on 28 September 2012. In this area, located within the Guadalentín Valley, up to 212 L m−2 was reported that day. More than 200 agricultural exploitations were destroyed by the flooding, with a devastating effect on many infrastructures, such as a main A-7 highway bridge that collapsed in this event. The earth fissures appeared after this flooding in the towns of Puerto Lumbreras and Totana. The first fissure showed a straight-line direction approximately parallel to the main geological structures of the Guadalentín Valley. The total length of the fissure was 400 m and was 2 to 3 m in depth. The soil in the fissure is classified as a low-plasticity silt with some sand and clay, ML, according to the Unified Soil Classification System. From the sieve and hydrometer tests, the percentage of silt in these samples was between 48 % and 68 %, the clay content between 12 % and 30 % and the sand content between 2 % and 40 %. The plasticity index was smaller than 9.2 for all the samples. To evaluate the piping and internal erosion susceptibility of the soil, pinhole, crumb and geochemical tests were done on the collected samples. A result of non-dispersive soil was obtained from crumb and pinhole tests. Nevertheless, the pH, sodium adsorption ratio and exchangeable sodium percentage tests showed that some samples could be affected by the dispersion of the soil. Also, the collapsible potential of the soil was studied, showing negative results for all the samples except for that collected at the southern end of the fissure, which showed a medium to high potential. Concerning the Totana fissure, it appeared with different branches and holes instead of as a rectilinear pattern. The total length of the fissure was 190 m, with the soil characterized as a silty soil. Lastly, INSAR data, GPS, GPR and land subsidence maps were used to study the possible origin of these fissures.This research has been supported by the Spanish Ministry of Economy and Competitiveness, the State Agency of Research and the European Funds for Regional Development (grant no. TEC2017-85244-C2-1-P), UNESCO (grant no. ICGP641), the Universidad de Alicante (grant no. GRE17-11), and the Universidad de Alicante (grant no. GRE18-15)

Application of multi-sensor advanced DInSAR analysis to severe land subsidence recognition: Alto Guadalentín Basin (Spain)

Multi-sensor advanced DInSAR analyses have been performed and compared with two GPS station measurements, in order to evaluate the land subsidence evolution in a 20-year period, in the Alto Guadalentín Basin where the highest rate of man-induced subsidence (> 10 cm yr−1) of Europe had been detected. The control mechanisms have been examined comparing the advanced DInSAR data with conditioning and triggering factors (i.e. isobaths of Plio-Quaternary deposits, soft soil thickness and piezometric level).This work is financially supported by the DORIS project (Ground Deformation Risk Scenarios: an Advanced Assessment Service) funded by the EC-GMES-FP7 initiative (Grant Agreement 423 no. 242212). ALOS PALSAR images were provided by the project JAXA-1209. Part of this work is supported by the Spanish Government under project TEC2011-28201-C02-02 and TIN2014-55413-C2-2-P and by the project 15224/PI/10 from the Regional Agency of Science and Technology in Murcia. Additional funding was obtained from the Spanish Research Program through the projects AYA2010-17448, ESP2013-47780-C2-1-R and ESP2013-47780-C2-2-Rand by the Ministry of Education, Culture and Sport through the project PRX14/00100

Radar interferometry techniques for the study of ground subsidence phenomena: a review of practical issues through cases in Spain

Subsidence related to multiple natural and human-induced processes affects an increasing number of areas worldwide. Although this phenomenon may involve surface deformation with 3D displacement components, negative vertical movement, either progressive or episodic, tends to dominate. Over the last decades, differential SAR interferometry (DInSAR) has become a very useful remote sensing tool for accurately measuring the spatial and temporal evolution of surface displacements over broad areas. This work discusses the main advantages and limitations of addressing active subsidence phenomena by means of DInSAR techniques from an end-user point of view. Special attention is paid to the spatial and temporal resolution, the precision of the measurements, and the usefulness of the data. The presented analysis is focused on DInSAR results exploitation of various ground subsidence phenomena (groundwater withdrawal, soil compaction, mining subsidence, evaporite dissolution subsidence, and volcanic deformation) with different displacement patterns in a selection of subsidence areas in Spain. Finally, a cost comparative study is performed for the different techniques applied.The different research areas included in this paper has been supported by the projects: CGL2005-05500-C02, CGL2008-06426-C01-01/BTE, AYA2 010-17448, IPT-2011-1234-310000, TEC-2008-06764, ACOMP/2010/082, AGL2009-08931/AGR, 2012GA-LC-036, 2003-03-4.3-I-014, CGL2006-05415, BEST-2011/225, CGL2010-16775, TEC2011-28201, 2012GA-LC-021 and the Banting Postdoctoral Fellowship to PJG

Contribución de la interferometría SAR diferencial (InSAR) al estudio de la subsidencia del terreno de la Vega Media del Segura (Murcia): experiencias y tendencias futuras

XVII Congreso de la Asociación Española de Teledetección. Murcia 3-7 octubre 2017La Vega Media del Segura (VMS) se localiza en el sector este de la Cordillera Bética. El valle está relleno por sedimentos recientes (Holoceno-Plioceno) potencialmente deformables que han sido depositados por la acción de los ríos Segura y Guadalentín. La extracción de agua subterránea de los niveles permeables que constituyen el acuífero conlleva la consolidación de los materiales deformables, dando lugar a asientos de la superficie del terreno. La Interferometría SAR diferencial (InSAR) es una técnica remota que permite monitorizar de forma efectiva y precisa amplias extensiones del territorio. En este trabajo se describe las diferentes experiencias llevadas a cabo por los autores en la VMS, que han permitido avanzar en el entendimiento del funcionamiento hidrogeológico del acuífero para la comprensión del comportamiento geomecánico del subsuelo, así como para monitorizar los desplazamientos del terreno desde el año 1994 usando imágenes ERS, ENVISAT y TerraSAR-X, contribuyendo de forma efectiva al estudio, caracterización y modelización del fenómeno. Por último, se describen las tareas futuras a desarrollar haciendo uso de nuevos sensores SAR con el fin de asegurar la continuidad de la información disponible para el estudio de este fenómeno a lo largo del tiempo.Departamento de Ingeniería Civil, Universidad de Alicante, EspañaGeohazards InSAR Laboratory and Modeling Group, Instituto Geológico y Minero de España, EspañaDepartamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Universidad de Alicante, EspañaDepartamento de Teoria Senyal i Comunicacions, Universitat Politècnica de Catalunya, EspañaDepartment of Earth Sciences, Environment and Resources, University of Naples, EspañaDares Technology, Barcelona, Españ

Análisis de los aspectos geotécnicos en depósitos sedimentarios recientes con vistas a la microzonación sísmica : aplicación a la ciudad de Murcia

La microzonación sísmica representa la plasmación en un mapa de todos o alguno de los conocimientos existentes sobre la respuesta del terreno, las estructuras y la interacción entre ambos, como consecuencia de la acción producida por un terremoto en un emplazamiento concreto. Desde de la 2ª Guerra Mundial, se han venido desarrollando lenta y con escasa cobertura este tipo de estudios en algunas partes del mundo. Las incertidumbres del fenómeno, junto con la extensa variabilidad del marco geológico de las zonas de riesgo sísmico reseñables en el mundo, además de problemas económicos por el alto coste de ejecución de estos estudios, han hecho que no existan métodos rigurosos y fiables que aborden muchos de los aspectos involucrados en una microzonación sísmica. No obstante, las investigaciones en este campo son cada vez más abundantes como así lo constatan los congresos sismológicos y de ingeniería sísmica, y ha aumentado de forma significativa la disponibilidad de registros acelerográficos que, aunque todavía insuficientes, son muy importantes para cualquier análisis racional sobre respuesta sísmica del terreno de cierto detalle en un sitio concreto. La evolución y mejora de las técnicas de microzonación sísmica estarán siempre condicionadas por los avances en el conocimiento de muchas disciplinas como la dinámica de suelos, la modelización dela respuesta del terreno y de las estructuras, los estudios de peligrosidad sísmica regional, la investigación en mecanismos focales, la realización de campañas de geofísica regional y local, sin contar con temas de urbanismo, arquitectura y económicos. Todo ello hace, que dada la elevada incertidumbre en las investigaciones sobre caracterización de focos sísmicos y zonas de trayectoria que pueden influir en el sitio de emplazamiento, propicie que la mayoría de los estudios de microzonación sísmica se centren fundamentalmente en la caracterización de la propagación de ondas sísmicas en el ámbito cercano al emplazamiento partiendo de un input sísmico, estimado como consecuencia de la trayectoria y foco de la onda sísmica, que sirve de entrada en el modelo de respuesta para los distintos sitios. Actualmente, son muchos los proyectos de investigación en el mundo que buscan ir acotando las limitaciones de este campo. Sin embargo, la mayoría de estas investigaciones se basan en métodos que a priori se consideran más rápidos y baratos frente a los que necesitan un amplio contenido en datos y análisis mecánico/geotécnico ante terremotos de los materiales encontrados. La presente tesis pretende analizar los aspectos geotécnicos relacionados con los depósitos sedimentarios recientes con una perspectiva orientada a la necesidad de incorporar este tipo de datos que, por lo general, suele ser escasamente contemplada o usada de forma eficiente en los estudios de microzonación sísmica. Se ha ceñido el análisis de respuesta a ver la influencia de parámetros como laVs, espesor y secuencias de capas, pesos unitarios, curvas de materiales (G/Gmax-γ y D-γ) y la posición del nivel freático en aquellas situaciones relacionadas con comportamientos del terreno de baja-media deformación. No siendo objeto de esta tesis, los efectos de media y alta deformación en dichos depósitos recientes (licuefacción o inestabilidades de ladera). Se ha seleccionado la ciudad de Murcia como zona piloto para la validación de esta tesis, por localizarse sobre depósitos fluviales del río Segura y estar encuadrada en un área de potencialidad sísmica de las Cordilleras Béticas. Se ha realizado una discusión de todos aquellos aspectos geotécnicos más relevantes en relación a los antecedentes en la zona de estudio y su influencia geotécnica en la respuesta sísmica. Se exponen además las implicaciones de los mismos en la microzonación sísmica, sus carencias y limitaciones para la configuración de escenarios y se señalan las futuras líneas de investigación en este campo. ----------ABSTRACT---------- Seismic microzonation maps consist on the representation of all or any of the existing knowledges about the response of the ground, structures and interaction between them, due to the action of an earthquake at a particular location. Since the WW, these studies have been developing slowly and partially in some parts of the world.The uncertainties of the phenomenon, along with the great variability of the geological settings of the notable seismic risk areas in the world, plus economic drawbacks because of the high execution costs of these studies, have been the main reasons for not to have rigorous and reliable methods to address many of the issues involved in a seismic microzoning. However, research in this field is becoming more abundant, as evidenced by holding of congresses on seismology and earthquake engineering,and the availability of acceleration records has significantly increased, what, although still in sufficient, is very important for any rational analysis of the seismic ground response with some detail at a particular site.The development and improvement of seismic microzoning techniques will always be conditioned by the advances in the knowledge of many disciplines such as soil dynamics, modeling of the ground/structure response, regional seismic hazard studies, focal mechanisms research, regional and local geophysical investigations, etc., not taking into account issues of urbanism, architecture and economic. All this implies that, given the high uncertainty on the characterization of seismic sources and areas of experience that can influence the site, most of the seismic microzonation studies focus mainly on the characterization of the seismic waves propagation in the area near to the site, based on seismic input, estimated from the path and focus of the seismic wave, which serves as input to the response model for the different sites. Currently, many research projects in the world look to reduce the limitations in these fields. However,most of them are based on methods that, a priori, are faster and cheaper compared to those that need a comprehensive data content and a mechanical/geotechnical analysis of the materials in relation to earthquakes..This thesis aims to analyze the geotechnical aspects of recent sedimentary soil deposits, oriented to the need to incorporate this type of data, often poorly considered or used inefficiently, in seismic microzonation studies. The analysis has been limited to study the influence of parameters such as Vs,thickness and sequence of the layers, unit weights, curves (G/Gmax and D-γ-γ) of the materials and position of the water table in those situations related to the behaviour of soils with low-medium deformation. It is not subject of this thesis the study of the effects of medium and high deformation in these recent deposits (e.g. liquefaction or slope instabilities). It has been selected the city of Murcia asa pilot area for validation of this thesis, as it is located on the Segura river deposits in an area of seismic potential of the Andalusian Betic mountain range. A discussion of those most relevant geotechnical aspects is carried out, in relation to the study area’s background and the geotechnical influence on the seismic response. Also their implications in seismic micro-zoning are discussed, and their shortcomings and limitations for configuring scenarios are presented, and future research lines in this field are proposed

Análisis de los aspectos geotécnicos en depósitos sedimentarios recientes con vistas a la microzonación sísmica : aplicación a la ciudad de Murcia

La microzonación sísmica representa la plasmación en un mapa de todos o alguno de los conocimientos existentes sobre la respuesta del terreno, las estructuras y la interacción entre ambos, como consecuencia de la acción producida por un terremoto en un emplazamiento concreto. Desde de la 2ª Guerra Mundial, se han venido desarrollando lenta y con escasa cobertura este tipo de estudios en algunas partes del mundo. Las incertidumbres del fenómeno, junto con la extensa variabilidad del marco geológico de las zonas de riesgo sísmico reseñables en el mundo, además de problemas económicos por el alto coste de ejecución de estos estudios, han hecho que no existan métodos rigurosos y fiables que aborden muchos de los aspectos involucrados en una microzonación sísmica. No obstante, las investigaciones en este campo son cada vez más abundantes como así lo constatan los congresos sismológicos y de ingeniería sísmica, y ha aumentado de forma significativa la disponibilidad de registros acelerográficos que, aunque todavía insuficientes, son muy importantes para cualquier análisis racional sobre respuesta sísmica del terreno de cierto detalle en un sitio concreto. La evolución y mejora de las técnicas de microzonación sísmica estarán siempre condicionadas por los avances en el conocimiento de muchas disciplinas como la dinámica de suelos, la modelización dela respuesta del terreno y de las estructuras, los estudios de peligrosidad sísmica regional, la investigación en mecanismos focales, la realización de campañas de geofísica regional y local, sin contar con temas de urbanismo, arquitectura y económicos. Todo ello hace, que dada la elevada incertidumbre en las investigaciones sobre caracterización de focos sísmicos y zonas de trayectoria que pueden influir en el sitio de emplazamiento, propicie que la mayoría de los estudios de microzonación sísmica se centren fundamentalmente en la caracterización de la propagación de ondas sísmicas en el ámbito cercano al emplazamiento partiendo de un input sísmico, estimado como consecuencia de la trayectoria y foco de la onda sísmica, que sirve de entrada en el modelo de respuesta para los distintos sitios. Actualmente, son muchos los proyectos de investigación en el mundo que buscan ir acotando las limitaciones de este campo. Sin embargo, la mayoría de estas investigaciones se basan en métodos que a priori se consideran más rápidos y baratos frente a los que necesitan un amplio contenido en datos y análisis mecánico/geotécnico ante terremotos de los materiales encontrados. La presente tesis pretende analizar los aspectos geotécnicos relacionados con los depósitos sedimentarios recientes con una perspectiva orientada a la necesidad de incorporar este tipo de datos que, por lo general, suele ser escasamente contemplada o usada de forma eficiente en los estudios de microzonación sísmica. Se ha ceñido el análisis de respuesta a ver la influencia de parámetros como laVs, espesor y secuencias de capas, pesos unitarios, curvas de materiales (G/Gmax-γ y D-γ) y la posición del nivel freático en aquellas situaciones relacionadas con comportamientos del terreno de baja-media deformación. No siendo objeto de esta tesis, los efectos de media y alta deformación en dichos depósitos recientes (licuefacción o inestabilidades de ladera). Se ha seleccionado la ciudad de Murcia como zona piloto para la validación de esta tesis, por localizarse sobre depósitos fluviales del río Segura y estar encuadrada en un área de potencialidad sísmica de las Cordilleras Béticas. Se ha realizado una discusión de todos aquellos aspectos geotécnicos más relevantes en relación a los antecedentes en la zona de estudio y su influencia geotécnica en la respuesta sísmica. Se exponen además las implicaciones de los mismos en la microzonación sísmica, sus carencias y limitaciones para la configuración de escenarios y se señalan las futuras líneas de investigación en este campo. ----------ABSTRACT---------- Seismic microzonation maps consist on the representation of all or any of the existing knowledges about the response of the ground, structures and interaction between them, due to the action of an earthquake at a particular location. Since the WW, these studies have been developing slowly and partially in some parts of the world.The uncertainties of the phenomenon, along with the great variability of the geological settings of the notable seismic risk areas in the world, plus economic drawbacks because of the high execution costs of these studies, have been the main reasons for not to have rigorous and reliable methods to address many of the issues involved in a seismic microzoning. However, research in this field is becoming more abundant, as evidenced by holding of congresses on seismology and earthquake engineering,and the availability of acceleration records has significantly increased, what, although still in sufficient, is very important for any rational analysis of the seismic ground response with some detail at a particular site.The development and improvement of seismic microzoning techniques will always be conditioned by the advances in the knowledge of many disciplines such as soil dynamics, modeling of the ground/structure response, regional seismic hazard studies, focal mechanisms research, regional and local geophysical investigations, etc., not taking into account issues of urbanism, architecture and economic. All this implies that, given the high uncertainty on the characterization of seismic sources and areas of experience that can influence the site, most of the seismic microzonation studies focus mainly on the characterization of the seismic waves propagation in the area near to the site, based on seismic input, estimated from the path and focus of the seismic wave, which serves as input to the response model for the different sites. Currently, many research projects in the world look to reduce the limitations in these fields. However,most of them are based on methods that, a priori, are faster and cheaper compared to those that need a comprehensive data content and a mechanical/geotechnical analysis of the materials in relation to earthquakes..This thesis aims to analyze the geotechnical aspects of recent sedimentary soil deposits, oriented to the need to incorporate this type of data, often poorly considered or used inefficiently, in seismic microzonation studies. The analysis has been limited to study the influence of parameters such as Vs,thickness and sequence of the layers, unit weights, curves (G/Gmax and D-γ-γ) of the materials and position of the water table in those situations related to the behaviour of soils with low-medium deformation. It is not subject of this thesis the study of the effects of medium and high deformation in these recent deposits (e.g. liquefaction or slope instabilities). It has been selected the city of Murcia asa pilot area for validation of this thesis, as it is located on the Segura river deposits in an area of seismic potential of the Andalusian Betic mountain range. A discussion of those most relevant geotechnical aspects is carried out, in relation to the study area’s background and the geotechnical influence on the seismic response. Also their implications in seismic micro-zoning are discussed, and their shortcomings and limitations for configuring scenarios are presented, and future research lines in this field are proposed

Advanced interpretation of subsidence in Murcia (SE Spain) using A-DInSAR data – modelling and validation

Subsidence is a natural hazard that affects wide areas in the world causing important economic costs annually. This phenomenon has occurred in the metropolitan area of Murcia City (SE Spain) as a result of groundwater overexploitation. In this work aquifer system subsidence is investigated using an advanced differential SAR interferometry remote sensing technique (A-DInSAR) called Stable Point Network (SPN). The SPN derived displacement results, mainly the velocity displacement maps and the time series of the displacement, reveal that in the period 2004–2008 the rate of subsidence in Murcia metropolitan area doubled with respect to the previous period from 1995 to 2005. The acceleration of the deformation phenomenon is explained by the drought period started in 2006. The comparison of the temporal evolution of the displacements measured with the extensometers and the SPN technique shows an average absolute error of 3.9±3.8 mm. Finally, results from a finite element model developed to simulate the recorded time history subsidence from known water table height changes compares well with the SPN displacement time series estimations. This result demonstrates the potential of A-DInSAR techniques to validate subsidence prediction models as an alternative to using instrumental ground based techniques for validation.The European Space Agency (ESA) Terrafirma project has funded all the SAR data processing with the SPN technique as well as the subsidence interpretation and modelling work presented above. Additionally, this work has been partially financed by the Spanish Geological and Mining Institute (IGME) with the collaboration of the Regional Government of Murcia and the universities of Alicante (UA) and Rey Juan Carlos (URJC). This work has been also supported by the Spanish Ministry of Science and Research (MICINN) and EU FEDER under project TEC2008-06764-C02-02