Màster Oficial - Recursos Minerals i Riscos Geològics

URI permanent per a aquesta col·leccióhttps://hdl.handle.net/2445/47647

Treballs del màster de Recursos Minerals i Riscos Geològics és un màster conjunt entre la Universitat de Barcelona i la Universitat Autònoma de Barcelona, i ofereix dues especialitats: 1. Dinàmica Terrestre i Recursos Minerals i 2. Riscos Geològics.

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Desarrollo de proxies para identificar eventos de tormenta en sedimentos de playa basados en métodos indirectos no invasivos
(2025-06) Osorio Bermejo, Pablo; Benito Guillén, Jorge; Calafat Frau, Antoni
Coastal storms represent one of the most significant natural threats to sandy beaches, causing rapid morphological changes, sediment redistribution and damage to coastal infrastructure. Understanding the sedimentary imprint left by these events is crucial for improving coastal risk assessment and for designing effective adaptation strategies in a context of climate change and rising sea levels. Although traditional approaches have relied on direct sampling and destructive laboratory analyses, the potential of non- invasive geophysical methods to detect storm deposits remains underexplored. This study focuses on the northwestern Mediterranean coast, an area highly vulnerable to extreme weather events. Twenty sediment cores were collected along ten representative beaches of the Catalan coast. Each core was analyzed using high- resolution multisensor core logging (MSCL) and computed axial tomography (CAT) imaging. By combining physical parameters such as bulk density, porosity, P-wave velocity, magnetic susceptibility and acoustic impedance, this research establishes a robust multiproxy framework for identifying storm-induced sedimentary layers with high reliability. This integrated multiproxy approach enhances the distinction of storm-related layers compared to single-parameter analyses. The coherence among density, acoustic impedance, magnetic susceptibility and P-wave velocity provides solid evidence of abrupt compaction and sediment sorting caused by high-energy overwash processes. By validating this method in diverse coastal settings, the study demonstrates its practical value for coastal hazard assessment and resilience planning. This work highlights the applicability of indirect, non-destructive methods for storm deposit detection and provides a valuable basis for integrating sedimentological, geophysical and morphological data into comprehensive coastal risk management. The results contribute to a better understanding of past and future storm impacts, supporting more resilient coastal planning and adaptation measures. Overall, this methodology represents a step forward towards high-resolution, non-invasive reconstruction of storm histories in vulnerable coastal environments.
Cinemática de fallas y deformación con sistemas GNSS en la Cordillera Bética Oriental
(2024-06) Jacobo Quiñones, Noemi; Khazaradze, Giorgi; Martín Rojas, Iván; García Tortosa, Francisco Juan
The eastern Betic Cordillera (CBO) is one of the most seismically active areas of the Iberian Peninsula, as it accommodates part of the convergence between the Eurasian and Nubian plates. This project analyses the eastern sector of the ZCBO and the area to the south of it. In particular, the horizontal velocity field was derived by the analysis of both, the newly collected and previously available, GNSS data. From these data, the relative displacement velocity vectors with respect to a fixed Eurasian plate (obtained from the ITRF2014 model) have been calculated. These results have made it possible to distinguish a present-day crustal deformation oriented predominantly in the direction of NNW-SSE to NNE-SSW. These velocities reach their maximum of 1-2 mm/year in the southern sector of the study area, while in the western and north-eastern part, movements of ≈1 mm/year are observed. The northern area is deforming significantly slower, with velocities slightly above 0 mm/year. In addition, the rates of shortening or extensional movement and lateral displacement have been calculated for the selected three faults. On the Las Moreras fault, a shortening rate of 0.2±0.2 mm/year and a differential dextral movement of 0.3±0.2 mm/year are calculated. In the Carrascoy fault, the same rate of 0.2±0.3 mm/year is obtained for shortening and sinistral displacement. With respect to the Crevillente fault, a shortening velocity of 0.3±0.3 mm/year and a sinistral displacement movement of 0.6±0.3 mm/year are estimated. Finally, the strain rates were calculated from the obtained velocities, indicating that the area is being subjected to a notable predominance of the shortening regime, oriented N-NW, roughly parallel to the Nubia/Eurasia convergence direction, which reaches a maximum value of εmin= -20±2 nstrain/year in the SW sector of the study area. Similar magnitude shear strain rates can be observed in the southern region, coinciding with ZCBO.
Estudi neotectònic de l’àrea font dels sismes d’Os de Civís
(2023-06-22) Martín Castells, Jana; Echeverría, Anna; Frontera, Tànit; Ortuño Candela, Maria
Since 1st February 2021 there have been more than 630 earthquakes in the surroundings of Os de Civís (Alt Urgell, Spain), two of them reaching magnitudes up to Ml=3.8 and Ml=3.6. The absence of destructive earthquakes in the historic and instrumental record is reflected by the lack of neotectonics studies in this area, so the earthquakes source is unknown. However, the evidence of active faults close (<50km) to the study area and the trace of an E-W alpine thrust (Estaron thrust) crossing it, suggest that there could be a connection between the structure and the earthquakes. This study sets out two objectives to identify the seismic source of the earthquakes. On one hand, it is proposed to relocate the earthquakes available in the ICGC’s catalogue by using NonLinLoc, a non-linear location algorithm that provides reliable and complete solutions. The obtained locations would contribute to the knowledge of the seismic source in depth and also to enclose the study area. On the other hand, it is intended to elaborate a neotectonics map, considering elements and materials both affected or generated by tectonic deformation. This would allow to suggest a possible relation between the registered seismicity and its source. The obtained earthquake locations define an ESE dipping region that has been related to two NE-SW faults, interpreted as reactivated branches of the Estaron thrust. No unequivocal superficial rupture has been identified in the neotectonics study, but some displacement indicators have been seen in La Ginebrera region, as well as a scarp up to 35 m in the south slope of Bony de Trescull. The latter has been interpreted as a possible old rupture of another segment of the branch. The present study has been a first approach to the area. More investigation is need to be done, so different methods and studies are proposed for future research.
Nuevos datos paleosísmicos para la caracterización de un transecto completo en la Falla de Alhama de Murcia (SE España).
(2021) Ollé López, Marc; Masana, Eulàlia; Gómez Novell, Octavi
La Falla de Alhama de Murcia (FAM) es una de las principales fallas sismogénicas de la Zona de Cizalla de las Béticas Orientales (EBSZ). Entre Lorca y Totana, la falla se bifurca en múltiples ramas que se considera que se unen en profundidad y, por tanto, cada una tiene su propia contribución en cuanto a la historia sísmica y la tasa de deslizamiento de la falla principal. Un trabajo previo estudió la actividad de la falla realizando un análisis paleosísmico en cuatro de las cinco ramas más importantes de este sector y, por tanto, produciendo el primer transecto paleosísmico en la zona. Sin embargo, una rama adicional no se incluyó en el transecto debido a la falta de sitios paleosísmicos adecuados: la N2a-AMF. Este trabajo se ha centrado en esta rama inexplorada para analizar su potencial sísmico y obtener nuevos datos que permitan completar el transecto paleosísmico realizado previamente en esta zona (El Saltador-La Hoya), con el objetivo de contribuir a generar un modelo de peligrosidad sísmica más realista en la región. Realizamos un estudio geomorfológico detallado para mapear con precisión la N2a-AMF y seleccionar una ubicación adecuada para la excavación de una trinchera paleosísmica. También refinamos el mapeo de N2b-AMF (ya analizada en el estudio previo) para comprender mejor la relación entre ambas ramas y el push-up que delimitan. En la nueva trinchera, observamos evidencias sólidas de deformación recurrente (un mínimo de tres eventos morfogenéticos) en los sedimentos del Pleistoceno superior, lo que implica que N2a-AMF ha tenido actividad al menos durante ese periodo (dataciones en curso). Estos eventos habrían tenido lugar en el intervalo de tiempo estimado entre 82,4 ka y 39,2 ka, presentando una recurrencia mínima de 14,4 ka. Además, calculamos una tasa de desplazamiento vertical mínima de entre 0,010 y 0,011 mm/año para los últimos 82,4 ka.
La conca alta del Francolí i els seus molins: reconstrucció hidràulica de crescudes extraordinàries per l'anàlisi de freqüències dels cabals de crescuda
(2021) Poll Barrera, Laura; Furdada i Bellavista, Glòria; Tuset Mestre, Jordi; Balasch Solanes, J. Carles (Josep Carles)
[cat] Al llarg del darrer segle i mig la conca alta del riu Francolí ha estat afectada per quatre grans riuades de tipus flash flood. Aquestes riuades històriques han causat un gran nombre de danys materials i pèrdues de vides humanes. Aquest estudi pretén aportar coneixement sobre la freqüència i cabals amb què es produeixen aquestes riuades, útil per fer els mapes de perillositat i risc necessaris per a la planificació i gestió del territori. S’ha fet una recerca a la zona dels molins i limnimaques que s’hi troben a través de fonts bibliogràfiques i dades de camp. S’ha seleccionat i estudiat un tram on se situa el Molí del Celdoni i se n’ha reconstruït els cabals pic de les dues riuades més recents (1994 i 2019) utilitzant el software lliure Iber com a model hidràulic. Finalment s’ha recalculat els períodes de retorn tenint en compte les dades dels cabals sistemàtiques (aforaments) i no sistemàtiques (reconstruïts de les limnimarques històriques) per a períodes de retorn de baixa freqüència. Els resultats han estat per una banda una base de dades georeferenciada dels molins i les limnimarques que se situen a la capçalera de la conca del Francolí. Per l’altra banda, s’han estimat cabals pic de 380 m3/s per la riuada del 1994 amb un període de retorn inferior a 50 anys, d’acord amb l’anàlisi de freqüència. En canvi, per la riuada del 2019 s’han estimat cabals de 780 m3/s i corresponents a un període de retorn d’entre 50 i 100 anys. Aquest estudi mostra la importància de tenir en compte les dades no sistemàtiques, ja que i) redueixen els períodes de retorn i, ii) fan multiplicar per 8 els cabals obtinguts només amb dades sistemàtiques per els mateixos períodes de retorn.
Gestió d'una xarxa sísmica en temps real localitzada al Pirineu Oriental (La Cerdanya): relocalització hipocentral del període desembre 2019 - juny 2020 i anàlisis sismotectònic
(2020-09) Canari Bordoy, Ariadna; Ruíz, Mario; Ortuño Candela, Maria
Seismicity in the Eastern Pyrenees has shown moderate and diffuse over time. Although, there is evidence of catastrophic historical earthquakes and some of the events in the last decade that have caused considerable damage. This work shows the feasibility to obtain seismic data of best quality in the temporary seismic network installed on Cerdanya Neogene basin. The network has recorded local events that are added to the permanent seismic networks of the ICGC, IGN and RéNaSS distributed region, for the period between December of 2019 and June 2020. Seismic data processing has been performed using the Seiscomp3 seismological software package. A cortical velocity model has been created to improve the accuracy of the location, adjusted to the geology of the Cerdanya basin and the region around it. The catalogue contains 641 seismic events and 251 quarry blasts. The results of the study show that the locations of earthquakes have higher resolution (with vertical errors as low 1 km) in the Cerdanya when including the temporary network as a result of a denser network in this area. Also, it shows that seismicity of Eastern Pyrenees is concentrated in the north and easternmore areas. The recorded data has allowed to discuss the seismotectonic of the Cerdanya, Selva and Fenollet areas, where 202, 158 and 54 earthquakes have been identified, respectively. The hypocentres are distributed in depth from to surface to a maximum of 16 km. In particular, two areas show lineaments that could be related to individual structures: At Meranges (Cerdanya), the events could be grouped in two to three fault planes (dipping NW and SE) perpendicular to Cerdanya fault. In Santa Coloma, (Selva), the network has recorded a seismic cluster (main event 4,2 magnitude) that seems to follow a SE dipping structure. As showed in this study, seismic data in larger periods of time using temporary network could be key for improving the seismotectonic knowledge in some target seismic regions, benefiting the seismic hazard evaluation.
Reconstrucción del alud de febrero de 2018 en la carretera BV-4024, Coll de Pal, y definición y caracterización del correspondiente escenario de referencia de T100.
(2019-06) Andrade Fuentes, Carlos Alberto; Oller i Figueras, Pere; Furdada i Bellavista, Glòria
[eng] In mountain areas, natural phenomena such as avalanches generate risk when they affect infrastructures. On February 10, 2018, a wind slab avalanche triggered from an unknown release area, occurred within the “Zona de Alud RIT051”, which caused the temporary closure of the BV-4024 local road, on Coll de Pal, Catalonia, and therefore avoiding damage to vehicles in transit and their passengers. In order to facilitate a future risk management associated to the RIT051 avalanche, a 2-D simulation of the February 2018 snow avalanche and its T100 reference scenario was carried out. The snow avalanche module of free software IBER 2.5, still in development, was used. The February 2018 snow avalanche simulation was based on the analysis of the Allaus Control field data, the interpretation of 13 possible release zones and a nivological and meteorological analysis to determinate the return period (T). Despite of the simulation of the February 2018 avalanche was not completely successful on reconstructing the snow avalanche path and run-out zone, the results were considered consistent with recent damage to vegetation and representative of the event. The February 2018 snow avalanche was classified by a Size 2 (Canadian Snow Avalanche Size-Classification System) and would have a T among 15 and 20 years. The T100 snow avalanche simulation, designed and calibrated based on the February 2018 snow avalanche, set up a snow avalanche that, in its dense phase, would reach a maximum width and run-out distance of 115 and 594 m; respectively. The T100 snow avalanche would carry to 8140 m3 and reach a maximum speed of 25 m/s, just as the head reaches the BV-4024 local road, impacting with a dynamic pressure among 93.75 to 187.50 kPa. The T100 snow avalanche was classified by a Size 3, could be able to bury a car, destroy a small building or break trees. Measures such as snowpack-stabilizing and snowdrift control structures or avalanche guiding and deflecting structures can be considered, based on the present work, for future risk management. The simulation of both snow avalanches did not incorporate the existence of a less cohesive phase (powder component).
Estudio de los mecanismos que controlan la transición explosiva a efusiva de las erupciones de domo del complejo Teide-Pico Viejo.
(2019-06) Dorado García, Olaya; Martí i Molist, Joan, 1957-; Geyer Traver, Adelina
The Teide-Pico Viejo (PT-PV) stratovolcanoes constitute one of the major potentially active volcanic complexes in Europe. Traditionally, they have been considered to be non-explosive but recent studies have revealed that explosive activity of phonolitic magmas, including plinian and subplinian eruptions and generation of pyroclastic density currents, have also been significant. This explosive activity is mostly related to satellite dome vents, like the one studied in this work, Pico Cabras. Dome-forming eruptions usually present sudden transitions between explosive and effusive activity. A better knowledge of this type of eruptions and the main factors that controls these changes in eruptive styles are required to undertake a comprehensive volcanic hazard assessment of Tenerife Island. In this study, we conduct a petrological and mineral characterization of the different eruption phases of Pico Cabras with the aim of identifying the factors that control these changes in the volcanic activity. Using geothermobarometers, geohygrometers and comparing the results with experimental petrology data we present a model of a compositionally stratified magma chamber at 1 kbar±0.5kbar in which the differences in the eruptive styles are controled by the temperature and the amount of volatiles dissolved in the melt. The explosive phase is related to the upper part of the magma chamber at 725ºC±25ºC and 3,5-5 wt% H2O and the effusive phase with the main body of the chamber at 880ºC±30ºC and 2,5-3 wt% H2O. Also, we report for the first time the present of sodalite, a Cl-rich mineral, in recent PT-PV magmas. This mineral is an indicator of a significant amount of halogen gases within the fluid phase. The release of this kind of volatiles into the atmosphere (specially Cl and Br) have a direct impact on the ozone layer depletion.
Análisis de límites de detección y cálculo de volumen de desprendimientos en escarpes rocosos mediante datos LiDAR y fotogramétricos
(2019-07) Montaño Quintero, Maria Elena; Blanch Gorriz, Xabier; Guinau Sellés, Marta
[eng] This paper presents an analysis of the limits of detection and calculation of volume of rockfalls, through the use of LiDAR and photogrammetry. Also, part of the study, focuses on the comparison of two different instruments for the acquisition of photogrammetric data. The pilot study area is located at the Puigcercós cliff (Pallars Jussà). The behavior of this cliff, has been widely studied in preliminary investigations through the use of LiDAR technology. However, one of the limitations of this technique is the high cost of acquiring and processing the data and the temporary restrictions that this implies. The use of photogrammetry in this type of research, is not widely developed, however, offers the possibility of data acquisition at a much lower cost than the LiDAR. For this reason, it is to be determined the cost-benefit ratio of this technique, taking into account the high precision of the results obtained with LiDAR technology. For the analysis of the information, it is carried out: 1) Sensitivity analysis and 2) Quantitative analysis of the volumes of the rockfalls identified by means of the analysis of data acquired in different dates (2018 vs 2019). Through the observed results and the analysis of the calculations of volumes the rockfalls with photogrammetry, it is obtained that this technique provides results comparable to those obtained by LiDAR technology. Additionally, it is found that the use of better resolution photographic cameras for photogrammetry, does not necessarily imply contribution to a better definition of the geometries for the creation of optimum quality point clouds.
Áreas fuente de polvo desértico e impacto en la mortalidad en Ahvaz, SW de Irán
(2019-06) Gonzalez Romero, Adolfo; Querol Carceller, Xavier; Vilaplana, Joan Manuel
[eng] The city of Ahvaz is located in the SW of Iran and is considered one of the most polluted cities in the world by the World Health Organization. One of the causes is desert dust. The city is affected by desert dust from hot spot areas, such as Sahara, Sahel, the basins of Al-Batin, Al-Sahba, Al-Rimah, Tigris and Euphrates basins. The effect of atmospheric particulate matter (PM10 and PM2.5) on health has been studied in multiple articles throughout Europe, Asia and North America, but in Middle East and Africa are scarce. Accordingly, we aim at evaluating this effect in the city of Ahvaz. Data provided by the Department of Environmental and Occupational Hazards Control Research Center shows that the average levels of PM10 and PM2.5 reach 127 and 48 μg/m3 (2015-2018) and 96 and 94 % of the days exceed 50 and 25 μg/m3 for PM10 and PM2.5. After calculating the daily air mass back-trajectories reaching Ahvaz in the study period, and applying a cluster analysis, we were able to identify six dominant air mass transport trajectories (cluster) and the most common originates on the border between Syria and Iraq, followed by Saudi Arabia, Eastern Europe, Egypt, Algeria and Atlantic. The averaged levels of PM10, PM2.5 and PM10-PM2.5 (coarse fraction) for each cluster are very similar, which indicates that the major contribution of PM to the city is due to the closest source areas (independently of the cluster). The risk of daily mortality increases for each daily increment of 10 μg/m3 PM and is different for every cluster, with an increase from 0.5 to 2% (95% CI) for PM10, and from 0.8 to 2.7% (95% CI) for the coarse fraction, while for PM2.5 the effect is not statistically significant. The back-trajectories from Algeria and Egypt, that cross the region of Al-Basra, with high desert dust emissions and high anthropogenic pollution, are those having the greatest impact on mortality risk.
Millora metodològica per a la detecció i caracterització de despreniments amb dades de LiDAR Terrestre a la Muntanya de Montserrat
(2018-06) Garcia Badal, Miquel; Guinau Sellés, Marta; Blanch Gorriz, Xabier
[eng] In this work we present the results obtained in the implementation of a methodological improvement for the detection and characterization of rockfalls with Terrestrial LiDAR data in the Muntanya de Montserrat (Catalonia). The studies of detection of rockfalls with TLS carried out until now used a methodology with the Polyworks program, but this one has some important limitations, that are explained in detail in this work. The main constraint is the low accurate calculation of distances between scans, which leads to erroneous distances especially in areas of fracture or surfaces with large irregularities. The proposed new methodology (M3C2) consists of an algorithm that performs the comparison between scans and calculates the mean distance taking into account some neighbor points contained in a cylinder, which fit better with the real distance than with the method described above. The main objective of the work is to evaluate the implementation of the M3C2 tool with CloudCompare for the analysis of Terrestrial LiDAR (TLS) data with which it is expected to obtain an improvement in the detection, delimitation and calculation of volume of rockfalls on the Degotalls Nord rock cliff in Muntanya de Montserrat. The 93 rockfalls detected in this study highlight the permanent activity of rockfalls that occur on the wall of Degotalls N in Montserrat. Of these rockfalls, 74,19% have a volume of less than 0,1 m3, and the 25,81% are blocks of larger volume, easily detectable with other methodologies and even with visual inspection. The comparison of the results obtained in this study with those obtained in previous works is complex. In this work 55 rockfalls were detected which had not been detected in other studies. In previous works 113 rockfalls were detected, of which only 38 were detected in this study. 75 rockfalls were not detected with the new method but after an accurate inspection of the results they have been considered to be changes in vegetation rather than rockfalls. The volume obtained for 82.06% of the rockfalls detected in this study and also in previous works is higher than the volume previously obtained. The new method leads on a reduction in the volume in only 17.94% of the detected rockfalls. 3 rockfalls with volumes lower than 0.001m3 were detected, which was the lowest volume detected in the previous studies. In this work the lower threshold of detection was reduced to 0,0004 m3.
Present-day 3D GPS velocity field of the Iberian Peninsula and implications for seismic hazard
(2018-06) Pena Castellnou, Sara; Khazaradze, Giorgi
[eng] We present a 3D crustal deformation velocity field of the Iberian Peninsula based on the analysis of more than 400 continuous GPS station data from the last 3.3 years (2015-2018 interval) distributed throughout the Iberian Peninsula, northern Africa and southern France. We describe the procedures followed to obtain a combined uniform velocity solution from daily GPS data using GAMIT/GLOBK software. Until now the previously published studies have estimated the 2D horizontal velocity field of the study area, since the vertical component is more complicated to derive. Only the studies by Serpelloni et al. (2013) and Nguyen et al. (2016) have calculated the vertical rates of deformation in some limited areas of the peninsula. In the present work, we provide the main results in terms of the velocity vectors in horizontal and up/down directions. The calculated GPS velocities range from 0.0 to 4.5 mm/yr, in Eurasia fixed reference frame, indicating that the Iberian Peninsula presents a heterogeneous present-day crustal deformation field, which can be grouped into 7 distinct domains/blocks. Each domain is influenced by the geo-tectonic structural configuration of the Iberian Peninsula and by the proximity to the Iberia-Nubia plate boundary. The highest velocities, as well as the highest geodetic strain rates, are detected in the EBSZ and along the Iberia-Nubia plate boundary, areas with the highest seismicity rates. The obtained vertical GPS velocities are preliminary and a processing of extended time-series (from 2010 to present) and more careful treatment of various phenomena affecting the GPS vertical signal (e.g. ocean and tide loading) should be performed in order to better resolve them. However, when the rates of observed vertical rates are high (>10 mm/yr), our results do indicate real motions, for example a subsidence of 6 cm/yr in Guadalentín basin, caused by the groundwater extraction. This kind of information is useful for multi-risk analysis since it can provide information of ongoing uplift/subsidence motion, that can be caused by faults, landslides, sediment settlement and/or anthropogenic activities (e.g. groundwater withdrawal, mining).
Streambank erosion and channel widening: implications for flood hazard
(2017-07) Moraru, Adina; Ruiz-Villanueva, Virginia; Furdada i Bellavista, Glòria
[eng] As one of the most threatening geological hazards, flash floods have noteworthy geomorphic effects (e.g. erosional and depositional modifications of the pre-event channel), hence, the main aim of this study was to provide an understanding of geomorphic indicators controlling channel widening during flood events. Floods over the past fifteen years affecting the uppermost areas of selected European rivers have been compiled in a database, subsequently completed and homogenized. Initial channel widths of 1.3m (Swiss Alps) to 217.27m (Apennines) showed channel widenings of 2.8% (Austrian Alps) to ∼2000% (Apennines). Statistical analysis shows significant differences in channel widening among regions, depending on flood magnitude, catchment area, lateral confinement, and methodology used when gathering data. Slope gradient had great control over estimated hydraulic forces (i.e. stream power, stream power index, unit stream power) involved in river dynamics.
Evaluación del índice SL para la identificación de movimientos de ladera que afectan a la red de drenaje
(2017-07) Subiela Blanco, Guillem Bonaventura; Guinau Sellés, Marta
Many quantitative geomorphic parameters, like the Stream Length-Gradient (SL) index, have been demonstrated to be suitable for detecting anomalies on stream-profiles. These knickpoints are generally related to active tectonics, lithological changes and large landslides. This study aims to detect drainage areas affected by landslides using SL index in La Vall d’Àssua, Romadriu y La Vall de Tor basins (Catalan Axial Pyrenees). The methodology used consists of computing the SL index using Chi-Map script and then, applying a couple of ArcGIS Toolboxes to provide a better localisation of knickpoints. SL anomalies have been compared with the landslide inventory of La Vall d’Àssua basin, indicating a well-correlation between SL anomalies and landslides. Additionally, this geomorphic index provided the identification of 13 new mass movements which had not been described before. To conclude, this geomorphic parameter is a useful tool for the identification of drainage network areas affected by landslides, which allow focusing geomorphological studies on these areas for a better characterization of the landslides and the associated hazard and risk.
Análisis morfométrico cuantitativo para la caracterización tectónica del norte de Túnez
(2015-07) Camafort Blanco, Miquel; Rodríguez Ranero, César; Gràcia Mont, Eulàlia; Ortuño Candela, Maria
Northern Tunisia is characterized by low deformation rates and low to moderate seismicity. Although instrumental seismicity reaches maximum magnitudes of Mw 5.5, some historical earthquakes were described with catastrophic consequences in this region. Aiming to improve our knowledge of active tectonics in Tunisia, we carried out a quantitative morphometric analysis in the northwestern region. We applied different morphometric indices, like river profiles, knickpoint analysis, curves and hypsometric integrals and drainage pattern anomalies in order to differentiate between zones with high or low recent tectonic activity. These indices allow identifying uplift and subsidence zones, which we relate to fault activity. A selected sector was studied with a field campaign to test the results obtained with the quantitative analysis. During the field work we identified geological evidence of recent activity and a considerable seismogenic potential along El Alia-Teboursouk (ETF) and Dkhila (DF) faults. Geological evidence include fluvial terraces folded by faults, striated pebbles, wind gaps, clastic dikes, sand volcanoes, coseismic cracks, etc. To estimate the seismic potential of this region and obtain a first seismic hazard estimation, we interpreted fault segmentation affected by a potentially coseismic rupture. Then, we calculated earthquake magnitude expected for each segments using two empirical equations, which relate rupture length and maximum magnitude. Magnitude for each entire fault was also calculated to provide an upper bound. Our study provides evidence of active tectonics in this region, with potential magnitudes ranging from Mw 6 to 7.8. Although not reflected in the instrumental seismicity, our results support an important seismic hazard, evidenced by the several active tectonic structures identified and the two seismogenic faults described. The ETF fault could be responsible of one of the most debastating historical earthquakes in northern Tunisia that destroyed Utique in 412 A.D.
Predicción de aludes en el puerto de la Bonaigua: Análisis mediante árboles de clasificación (CART) de episodios de nevadas, actividad de aludes y patrones meteorológicos en el puerto de la Bonaigua (Val d’Aran)
(2016-07) Gorospe Alonso, Pablo; Moner, Ivan; Vilaplana, Joan Manuel
The highway C-28 is located in the Central Pyrenees and links the Aran valley with Catalonia along 20 km over the Bonaigua Pass. It constitutes a key access route for winter visitors. Most of the slopes affecting the road face to the south, with heights varying between 1600 and 2300 meters. The road runs through 58 avalanche paths of which 25 release frequently. Most of them are already capable to produce D2 or D3 avalanches, but in many places the road is carved in the hill side, what means that every single avalanche will certainly hit the road. We started from 12 years of meteorological and avalanche data collected by the local avalanche warning service of Aran Valley. Weather data were obtained from two automatic weather stations and a flowcapt, whereas avalanche activity was manually recorded in a GIS with a high level of detail. We selected 32 weather parameters including snow drift, time lagged, trend and categorical parameters and 137 avalanche days, in total. Using a classification tree method, we have developed a model to determine periods of significant avalanche activity in terms of the pre-defined avalanche day concept. The model is performed for the entire road in a combined analysis and also for three individual sections within the Pass. Results showed that time lagged conventional factors describing temperature and precipitation are more significant than the trend factors. Snow drift parameters segregated into prominent wind direction have not been found significant as solar radiation. A model for a single section with more homogeneous avalanche behavior allows us to highlight variables that were hidden in the general model applied for the overall highway.
Estudi dels esdeveniments sísmics no identificats corresponents a una àrea propera al Baix Camp (Tarragona)
(2016-07) Sánchez Serra, Cristina; Suriñach Cornet, Emma; Tapia, Mar
The aim of this study is to locate and interpret several undetermined events that have been undetected by seismological agencies and have only been recorded at the seismic station VAN2. Since these events were only recorded at one station, their localization can only be determined by the “location method with only a single station”. Moreover, this study seeks to test the validity of this unusual method with respect to the traditional location method. These undetermined events occurred in the Baix Camp area that is characterized by a moderate seismic activity and Quaternary active faults. After selecting the events, they are processed and analyzed with numerical algorithms in “Matlab” language. These programs allow us to study the frequency content of the events and to determine the first arrivals of the P and S waves. Subsequently, the “location method with only a single station” was applied to locate the undetermined events using an appropriate wave speed crustal model for the study area. To ratify this method, some determined seismic events from the “seismic series of Ametlla de Mar” were used. These events were localized with the “location method with only a single station” and the results were compared with the previous localizations from seismological agencies. Eight seismic events were located and the localization of five further events from the “seismic series of Ametlla de Mar” was confirmed. These thirteen seismic events are associated with the faults of the study area. Moreover, two additional events were identified as man-made events. Given the similarity of the locations of the events obtained by the two methods we can conclude that the “location method with only a single station” is a reliable method.
Modelització analògica de l’efecte topogràfic: limitacions d’un estudi pilot i resultats
(2016-07) Gómez Novell, Octavi; Ortuño Candela, Maria
The topographic effect causes seismic wave amplification on the top of the mountains. This amplification reportedly produces more damage on the infrastructures of these parts of the reliefs and for this reason this effect has been widely studied using mainly numerical and experimental approximations. However, it has never been studied using analogue modelling. This study aims to start pointing out the main issues and results of carrying out this type of modelling. Two gelatin analogue models have been made in order to achieve a correct scaling of crust’s elastic parameters and acoustic waves have been used in order to reproduce seismic Pwave propagation. Two experiments have been performed in the models allowing the observation of attenuation by geometrical spreading and topographic amplification in most of the acoustic signals. The experimental setup also affects the signals for some configurations producing anomalies in the attenuation and amplification tendencies. Measurements of the acceleration in the model’s surface have also been performed, but these don’t show any enhanced motions at the top of the relief. The amplification depends on the frequency of the acoustic waves, thus the waves with wavelengths more similar to the mountain’s length are the most amplified (12% to 28% of maximum amplification), which is in agreement with most of the studies. Nevertheless, the limitations of this study must be taken into account when it comes to relating the processes in the model with the natural ones. The absence of shear waves in the experimental runs and scaling problems, especially for the acoustic wave frequencies, constitute the main limitations of this study. However, the fact that some processes identified in the model actually occur in the nature, ensure the validity of the method at least from a qualitative perspective. Several improvements must be applied in this method in order to obtain better results and get more useful clues for the natural hazard assessment in the future.
Datación y caracterización de avenidas torrenciales mediante metodologías dendrogeomorfológicas en los Barrancos de Portainé y de Ramiosa (Pallars Sobirà, Lérida, España)
(2015-07) Fargas Gonzalez, Gerard-Ramon; Furdada i Bellavista, Glòria
En la vertiente norte del Pico del Orri, se localizan los barrancos de Portainé y Ramiosa. Estos barrancos y sus respectivas cuencas se encuentran en la comarca del Pallars Sobirà (Lleida). Los dos barrancos nombrados presentan una topografía, una geología y una geomorfología parecida. En el barranco de Portainé, des del 2008, precipitaciones no excepcionales han dado lugar a avenidas torrenciales prácticamente cada año, las cuales han producido daños en la carretera de acceso a la estación de esquí de Port Ainé y en la propia estación. En el barranco de la Ramiosa no se tiene constancia de que haya habido actividad de este tipo. Cabe decir que el registro de avenidas se inició en 2006, por lo que es un registro muy corto. Aplicando una metodología dendrogeomorfológica se pretende obtener información de eventos pasados, su frecuencia y magnitud, para integrarla en el análisis de los riesgos naturales. En el presente trabajo se pretende identificar, datar y caracterizar eventos torrenciales en los barrancos de Portainé y Ramiosa, comparar el comportamiento hidrológico de ambas cuencas y avanzar en el conocimiento del por qué del funcionamiento diferente.
Anàlisi de l’evolució de despreniments a partir de dades LiDAR a l’escarpament de Puigcercós (Pallars Jussà)
(2015-07) Blanch Gorriz, Xabier; Guinau Sellés, Marta; Royán Cordero, Manuel Jesús
Aquest treball presenta un anàlisi dels despreniments que es produeixen en un escarpament i que són detectats a partir de les dades LiDAR. Per realitzar-ho s’ha escanejat des del 2007 la àrea d’estudi pilot de Puigcercós (Pallars Jussà) on s’han detectat 4072 despreniments. Amb aquests despreniments detectats s’ha obtingut la relació magnitud freqüència que ha permès comparar l’escarpament amb altres moviments inventariats. També s’ha centrat part de l’estudi en analitzar els despreniments i la deformació en les àrees on s’han produït despreniments de grans dimensions, amb l’objectiu de detectar el comportament de l’escarpament després de que aquests es produeixin. A partir de les dades d’intensitat i de les dades d’RGB d’una fotografia s’han extret les litologies alhora que s’ha trobat quines d’aquestes litologies són més propenses a produir despreniments. Finalment, s’ha intentat buscar un patró estacional que permeti deduir si existeix alguna component climàtica que acceleri els despreniments. Tots aquests resultats s’han obtingut a partir de les dades LiDAR i s’han realitzat amb els objectius de caracteritzar millor l’escarpament estudiat i d’explorar tota la informació que ens aporten les dades LiDAR.

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