Sismicidad inducida en el yacimiento marino de gas Poseidón mediante el estudio de la sismicidad a largo plazo

El yacimiento de gas de Poseidón constituye uno de los campos de extracción de gas el cual se localiza en el Golfo de Cádiz. Esta zona presenta fallas sismogénicas con capacidad de generar terremotos. Es por ello que un estudio exhaustivo de la potencial sismicidad inducida por operaciones de extracción de gas permitirá avanzar en el estudio de potenciales terremotos que afecten a la zona de Huelva, Cádiz y extremo suroeste de Portugal. La energía sísmica anual liberada en el entorno cercano al almacenamiento (50 km) presenta una correlación positiva con la cantidad de gas producida según datos oficiales del Ministerio de Energía, Turismo y Agenda Digital. También se observa que dicha correlación depende de la cantidad producida al año. Con estos datos, es importante hacer un seguimiento al ser una de las zonas de mayor actividad sísmica de la Península Ibérica, con capacidad de disparar terremotos destructivos

Long-term induced seismicity at Poseidon off-shore gas field

El yacimiento de gas de Poseidón constituye uno de los campos de extracción de gas el cual se localiza en el Golfo de Cádiz. Esta zona presenta fallas sismogénicas con capacidad de generar terremotos. Es por ello que un estudio exhaustivo de la potencial sismicidad inducida por operaciones de extracción de gas permitirá avanzar en el estudio de potenciales terremotos que afecten a la zona de Huelva, Cádiz y extremo suroeste de Portugal. La energía sísmica anual liberada en el entorno cercano al almacenamiento (50 km) presenta una correlación positiva con la cantidad de gas producida según datos oficiales del Ministerio de Energía, Turismo y Agenda Digital. También se observa que dicha correlación depende de la cantidad producida al año. Con estos datos, es importante hacer un seguimiento al ser una de las zonas de mayor actividad sísmica de la Península Ibérica, con capacidad de disparar terremotos destructivos.The offshore field gas of Poseidon is located within the Gulf of Cadiz. This area is prone to large earthquakes, including the estimated epicentre of the great earthquake of Lisbon of 1755. In this sense, the study of the potential induced seismicity in this area is a key point to be addressed plus the role of induced earthquakes and large tectonic faults. We have found a positive correlation between the annual seismic energy released 50 km away of the gas field with the gas production (data provided by the Spanish Ministry of Energy).The long-term behaviour of the seismic energy and gas production indicates that induced seismicity was present during the period of extraction and reservoir depletion.Depto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEMinisterio de Economía y Competitividad (MINECO)/FEDERpu

Pulverized quartz clasts in gouge of the Alhama de Murcia fault (Spain): evidence for coseismic clast pulverization in a matrix deformed by frictional sliding

The fault gouge of the Alhama de Murcia fault (southeast Spain) shows a texture that resembles a mylonite, including a prominent foliation, S-C fabric, and isoclinal folds. It also embeds a large number of isolated pulverized quartz clasts (PQCs). Structural analysis indicates that the gouge fabric was mainly developed by slow frictional sliding along phyllosili- cate-lined Riedel shear bands during continued shearing. In contrast, the PQCs show tensile fracture network features that are typically reported in seismically pulverized rocks found along seismogenic faults. This suggests that quartz-clast pulverization was due to a transient dilatational mechanism rather than shearing. We propose that the PQCs are the result of a rapid confined stress drop related to transient tensile stresses during coseismic ruptures that interrupt creep faulting along the gouge zone. The present study suggests that there is probably a large amount of evidence for paleoseismicity in fault rocks that is currently overlookedThis research was supported by the Spanish Ministry of Economy and Competitiveness under the INTERGEO (CGL2013–47412-C2–1-P) and QUAKESTEP (CGL2017–83931-C3–1-P) project

Catalogue of the geological effects of earthquakes in Spain based on the ESI-07 macroseismic scale: A new database for seismic hazard analysis

This paper summarizes the content and scope of the “Catalogue of Earthquake Geological Effects in Spain”. The catalogue has been published by the Geological Survey of Spain (IGME) and constitutes the first official publication (in Spain) on seismic hazard containing geological information. The catalogue gathers the 51 stronger earthquakes that have occurred in Spain since the Neolithic period to the present and classifies earthquakes with geological or archaeological seismic records in paleoseismic, ancient, historical and instrumental earthquakes. The catalogue offers a variety of parametric information, quality indexes (Qe, Qi, Qg), and Environmental Seismic Intensity Scale (ESI-07) based description of environmental damage structured in individual “event files”. Sixteen of the 51 catalogued events present full information files (full event files), with individualized analyses of the geological and geoarchaeological data as well as graphic information with hybrid ESI-EMS intensity maps, ShakeMaps (seismic scenarios) and complementary kmz files (Google Earth) for each of the sixteen selected earthquakes; among which is the well-known AD 1755 Lisbon earthquake-tsunami. These selected earthquakes present individual environmental earthquake effects (EEE) or earthquake archaeoseismological effects (EAE) files for each catalogued effect containing specific site geo-information and graphic data (photos, graphs, maps, etc.). The second edition of the catalogue record 1027 EEEs and 187 EAEs, of which 322 effects have individual filesThis research was funded by the Spanish Research Project MINECO-FEDER CGL2015-67169-P (QTECSPAIN-USAL). This is contribution of the QTECT-AEQUA Working Group

Determinación de valores absolutos de paleoesfuerzos, basados en el maclado de la calcita, en el frente norte de la Sierra de Cameros (Cordillera Ibérica).

Calcite e-twin density (twins/mm) and percentage of calcite grains with one and two twin sets from sparry grains that fill microveins were used to precise the differential stress related with the inversion of the Cameros Basin, a Mesozoic sedimentary basin located in the northwestern part of Iberian Chain (Spain). The results obtained using techniques based on the percentage of twined grains yield better results that those techniques based on twin density. The deduced stress magnitudes fit well with the differential stress interval proposed for fold-thrust belt domains. Combination of twin data with rock mechanics data provides adequate estimations of differential stresses

An active tectonic field for CO2 storage management: the Hontomín onshore case study (Spain)

One of the concerns of underground CO2 onshore storage is the triggering of induced seismicity and fault reactivation by the pore pressure increasing. Hence, a comprehensive analysis of the tectonic parameters involved in the storage rock formation is mandatory for safety management operations. Unquestionably, active faults and seal faults depicting the storage bulk are relevant parameters to be considered. However, there is a lack of analysis of the active tectonic strain field affecting these faults during the CO2 storage monitoring. The advantage of reconstructing the tectonic field is the possibility to determine the strain trajectories and describing the fault patterns affecting the reservoir rock. In this work, we adapt a methodology of systematic geostructural analysis to underground CO2 storage, based on the calculation of the strain field from kinematics indicators on the fault planes (ey and ex for the maximum and minimum horizontal shortening, respectively). This methodology is based on a statistical analysis of individual strain tensor solutions obtained from fresh outcrops from the Triassic to the Miocene. Consequently, we have collected 447 fault data in 32 field stations located within a 20 km radius. The understanding of the fault sets’ role for underground fluid circulation can also be established, helping further analysis of CO2 leakage and seepage. We have applied this methodology to Hontomín onshore CO2 storage facilities (central Spain). The geology of the area and the number of high-quality outcrops made this site a good candidate for studying the strain field from kinematics fault analysis. The results indicate a strike-slip tectonic regime with maximum horizontal shortening with a 160 and 50◦ E trend for the local regime, which activates NE–SW strike-slip faults. A regional extensional tectonic field was also recognized with a N–S trend, which activates N–S extensional faults, and NNE–SSW and NNW– SSE strike-slip faults, measured in the Cretaceous limestone on top of the Hontomín facilities. Monitoring these faults within the reservoir is suggested in addition to the possibility of obtaining a focal mechanism solutions for microearthquakes (M < 3)This work has been partially supported by the European Project ENOS: ENabling Onshore CO2 Storage in Europe, H2020 Project ID: 653718 and the Spanish project 3GEO, CGL2017-83931-C3-2-P, MICIU-FEDE

Criterios geomorfológicos sobre actividad tectónica reciente a lo largo de la Costa Recta, Isla Decepción (Antártida Occidental)

Several active tectonic evidences are observed along Costa Recta, located eastward of Deception Island (western Antarctica): marine terraces and fluvial streams cutting a relict glacier. The height of both landforms decrease southward from Macaroni Point, appointing to a tilt movement across a fault plane. Fault planes were measured at Macaroni Point and Baily Head, with a main NNWSSE orientation, similar to the Costa Recta strike. From several scales o f measure, the orientation of the beach was established in two principal segments: N168QE, and N173QE. On the other hand, the beach and glacier dynamics and sedimentary deposits were studied. According to the morpho-tectonic analysis, we conclude that the Costa Recta beach is a retreat scarp of a submarine fault oriented NNW-SSE and located in the Bransfield Strait, although a geophysical study o f the marine bottom is needed to map the fault trace in an accurate way

Present day kynematic model of the Caribbean Plate in the boundary with the North American and Cocos plates

Este trabajo propone un modelo cinemático en la zona más occidental de la Placa Caribe, en los límites con la Placa Norteamericana y la Placa de Cocos. Para ello se ha realizado un análisis cluster de la sismicidad presente en la zona en función de: 1) su distribución espacial y 2) de la dirección de máximo acortamiento horizontal (ey), obtenidas del análisis de las construcciones de sus mecanismos focales mediante métodos de análisis poblacional de fallas. En total, se han considerado 57 de los 488 sismos con construcción del mecanismo focal situados en la zona. Los resultados obtenidos, tanto de los tensores, como de las trayectorias de deformación sugieren un modelo caracterizado por la rotación de ey en los límites de esta placa con la Placa Norteamérica y en la zona del Arco Volcánico Centroamericano. Esta rotación es congruente con un movimiento lateral hacia el ESE del área más occidental de la Placa Caribe, produciendo una extensión asociada a este movimiento en la zona central del Bloque de Chortis. Este modelo corrobora la existencia de un bloque tectónico costero en la Placa Caribe independiente del Bloque de Chortis (Forearc Sliver).This work proposes a present day kinematic tectonic model for the western part of the Caribbean Plate in relationship at its boundary with the North American and Cocos plates. We have performed the following cluster analysis of the instrumental seismicity within the area: 1) the spatial distribution of focal mechanism solutions and 2) the orientation of the maximum horizontal shortening (ey). Both studies come from the analysis of focal mechanisms by using the fault population technique. From the original available 488 earthquakes with focal mechanism (HCMT online database), we have considered 57 of them according to several criteria. Our results show a clockwise rotation of the ey trajectory across the boundary between Caribbean and North American plates and the Central American Volcanic Arc. This rotation agrees with a lateral tectonic movement towards ESE of the Chortis Block (Caribbean Plate). Furthermore, this model corroborates the existence of a coastal tectonic block within the Caribbean Plate that it is independent from the Chortis Block.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEMinisterio de Educación y Cienciapu

Speleoseismology and palaeoseismicity of Benis Cave (Murcia, SE Spain): coseismic effects of the 1999 Mula earthquake (mb 4.8)

This work describes the coseismic ceiling block collapse within Benis Cave (−213 m; Murcia, SE Spain), associated with the 1999 Mula earthquake (mb=4.8, MSK VII). The collapse occurred at −156 m into the Earthquake Hall, and as a consequence one small gallery became blind. We studied the geology, topography and active tectonic structures relevant to the cave. In addition, we carried out a seismotectonic analysis of the focal mechanism solutions, and also a fault population analysis on slickensides measured in fault planes in the cave. The stress and strain regime is interpreted as being congruent with the palaeoseismic evidence, and agrees with the fault kinematics established for cave galleries developed within fault planes and growth anomalies of coral flowstone. Our analysis suggests that one active segment (NNE–SSW) determined the morphology and topography of the Benis Cave, where strong to moderate palaeoearthquakes (6≤M≤7) took place. As a consequence of this intense seismic activity a small gallery collapsed. A new palaeoseismic structure, or seismothem, has been recognized, namely the effect of palaeoearthquakes affecting the pattern of development of the spatial coral flowstone distribution located at the bottom of the cave