Crustal velocity and strain rate fields in the Balearic Islands based on continuous GPS time series from the XGAIB network (2010-2013)

In this paper, we present a first estimation, using the GIPSY-OASIS software, of the crustal velocity and strain rate fields in the Balearic Islands (Spain), based on continuous GPS observations from the XGAIB network spanning the period 2010-2013. The XGAIB network consists of nine permanent, widely distributed stations that have operated continuously since 2010. In this paper, we describe the XGAIB network and the CGPS data processing and present our principle results in terms of the position time series and velocities of all of the sites, which were observed for more than three and a half years. In addition, strain tensors were estimated from the velocity field to obtain the first realistic crustal deformation model of the archipelago. The strains exhibit gradual variation across the Balearic Islands, from WNW-ESE extension in the southwest (Ibiza and Formentera) to NW-SE compression in the northeast (Menorca). These results constitute an advance in our knowledge of the tectonics of the western Mediterranean region.This research was partly funded by the Spanish Ministry of Science and Innovation through the AYA2010-15501, CGL2011-30153-C02-02 and CSD2006-0041 projects (European Regional Development Fund-ERDF)

The Padul normal fault activity constrained by GPS data: Brittle extension orthogonal to folding in the central Betic Cordillera

The Padul Fault is located in the Central Betic Cordillera, formed in the framework of the NW-SE Eurasian-African plate convergence. In the Internal Zone, large E-W to NE-SW folds of western Sierra Nevada accommodated the greatest NW-SE shortening and uplift of the cordillera. However, GPS networks reveal a present-day dominant E-W to NE-SW extensional setting at surface. The Padul Fault is the most relevant and best exposed active normal fault that accommodates most of the NE-SW extension of the Central Betics. This WSW-wards dipping fault, formed by several segments of up to 7 km maximum length, favored the uplift of the Sierra Nevada footwall away from the Padul graben hanging wall. A non-permanent GPS network installed in 1999 constrains an average horizontal extensional rate of 0.5 mm/yr in N66°E direction. The fault length suggests that a (maximum) 6 magnitude earthquake may be expected, but the absence of instrumental or historical seismic events would indicate that fault activity occurs at least partially by creep. Striae on fault surfaces evidence normal-sinistral kinematics, suggesting that the Padul Fault may have been a main transfer fault of the westernmost end of the Sierra Nevada antiform. Nevertheless, GPS results evidence: (1) shortening in the Sierra Nevada antiform is in its latest stages, and (2) the present-day fault shows normal with minor oblique dextral displacements. The recent change in Padul fault kinematics will be related to the present-day dominance of the ENE-WSW regional extension versus ~ NNW-SSE shortening that produced the uplift and northwestwards displacement of Sierra Nevada antiform. This region illustrates the importance of heterogeneous brittle extensional tectonics in the latest uplift stages of compressional orogens, as well as the interaction of folding during the development of faults at shallow crustal levels.This research was funded by PAIUJA 2017/2018, UJA2016/00086/001 project, CGL2016-80687-R AEI/FEDER, UE project and RNM148 and RNM282 research groups of Junta de Andalucía

The Campo de Dalias GNSS Network Unveils the Interaction between Roll-Back and Indentation Tectonics in the Gibraltar Arc

The Gibraltar Arc includes the Betic and Rif Cordilleras surrounding the Alboran Sea; it is formed at the northwest–southeast Eurasia–Nubia convergent plate boundary in the westernmost Mediterranean. Since 2006, the Campo de Dalias GNSS network has monitored active tectonic deformation of the most seismically active area on the north coast of the Alboran Sea. Our results show that the residual deformation rates with respect to Eurasia range from 1.7 to 3.0 mm/year; roughly homogenous west-southwestward displacements of the northern sites occur, while the southern sites evidence irregular displacements towards the west and northwest. This deformation pattern supports simultaneous east-northeast–west-southwest extension, accommodated by normal and oblique faults, and north-northwest–south-southeast shortening that develops east-northeast–west-southwest folds. Moreover, the GNSS results point to dextral creep of the main northwest–southeast Balanegra Fault. These GNNS results thus reveal, for the first time, present-day interaction of the roll-back tectonics of the Rif–Gibraltar–Betic slab in the western part of the Gibraltar Arc with the indentation tectonics affecting the eastern and southern areas, providing new insights for improving tectonic models of arcuate orogens.Junta de Andalucia; European Regional Development Fund; grant numbers: AGORA P18-RT-3275, PAPEL B-RNM-301-UGR18. Programa Operativo FEDER-Andalucia 2014–2020 Project ref. 1263446; University of Jaén; CEACTEMA; grant number: POAIUJA 21/22. Junta de Andalucía (Andalusian Board); grant numbers: RNM-148, RNM-282, RNM-370. V.T.S. was supported by the FPU PhD grant (16/04038)

La Zona de Falla del Bajo Segura: cabalgamiento activo “ciego” en la Cordillera Bética oriental

The Bajo Segura Fault Zone, located at the NE end of the Eastern Betic Shear Zone, has been the site of some of the most intense seismic activity on the Iberian Peninsula in the historical and instrumental time periods. This structure is an active blind fault that does not show any surface rupture. It is characterised by a set of ENE-WSW trending blind thrust faults that offset the Triassic basement and cause active folding of the Upper Miocene-Quaternary sedimentary cover. The main active structures of this fault zone are two ENE-WSW striking reverse blind faults, the Torremendo and the Bajo Segura Faults, and several secondary NW-SE striking dextral faults (San Miguel de Salinas, Torrevieja and Guardamar Faults). These structures continue offshore to the east. From geological, geomorphological and geodetic data, we obtain fault slip rates between 0.2 and 0.4 mm/yr, whereas other authors have proposed higher values ranging between 0.75 and 1 mm/yr. The fault zone can generate earthquakes with maximum estimated magnitudes (Mw) from 6.6 to 7.1 and has approximate recurrence intervals between 4.500 and 21.500 years.La Zona de Falla del Bajo Segura, localizada en el extremo NE de la Zona de Cizalla de la Bética Oriental, es una de las estructuras tectónicas de la Península Ibérica con mayor actividad sísmica asociada durante el periodo histórico e instrumental. Es una zona de falla ciega, sin ruptura en superficie, caracterizada por varios pliegues que deforman las rocas sedimentarias de edad Mioceno Superior a Cuaternario. Su traza principal tiene varios segmentos aproximadamente paralelos entre sí de dirección ENE-WSW entre los que destacan la Falla del Bajo Segura y la Falla de Torremendo. Además, tiene asociadas varias fallas de transferencia dextrorsas de dirección NW-SE (San Miguel de Salinas, Torrevieja y Guardamar). Estas fallas ENE-WSW y NW-SE tienen su continuidad hacia el este, en el Mar Mediterráneo. Algunos marcadores geológicos y geomorfológicos junto con un perfil de nivelación de alta precisión, han permitido obtener tasas de desplazamiento que varían entre 0.2 y 0.4 mm/año, aunque otros autores han propuesto valores más altos de entre 0.75 y 1 mm/año. A partir de estas tasas de desplazamiento y de la cartografía de la zona de falla, se estima que la máxima magnitud Mw varía entre 6.6 y 7.1 con periodos de recurrencia aproximados entre 4.500 y 21.500 años.Financial support for this work was provided by the research projects CGL2011-30153-C02-02, FASEGEO (CGL2009-09726), EVENT (CGL 2006-12861-C02-02) and SHAKE (CGL 2011-30005-C02-02) and Acciones Complementarias EVENT-SHELF (CTM 2008-03346-E/MAR) and SPARKER (CTM 2008-03208-E/MAR)

Insights of Active Extension Within a Collisional Orogen From GNSS (Central Betic Cordillera, S Spain)

The coexistence of shortening and extensional tectonic regimes is a common feature in orogenic belts. The westernmost end of the Western Mediterranean is an area undergoing shortening related to the 5 mm/yr NNW‒SSE convergence of the Nubia and Eurasia Plates. In this region, the Central Betic Cordillera shows a regional ENE‒WSW extension. Here, we present GNSS-derived geodetic data along a 170 km-long transect orthogonal to the main active normal faults of the Central Betic Cordillera. Our data indicate that the total extension rate along the Central Betic Cordillera is 2.0 ± 0.3 mm/yr. Extension is accommodated in the eastern (0.8 ± 0.3 mm/yr in the Guadix-Baza Basin) and western (1.3 ± 0.3 mm/yr in the Granada Basin) parts of the Central Betic Cordillera, while no extension is recorded in the central part of the study area. Moreover, our data permit us to quantify, for the first time, short-term fault slip rates of the Granada Fault System, which is one of the main seismogenic sources of the Iberian Peninsula. We deduce a fault slip rate of ∼1.3 ± 0.3 mm/yr for the whole Granada Basin, with 0.9 ± 0.3 mm/yr being accommodated in the Granada Fault System and 0.4 ± 0.3 mm/yr being accommodated in the southwestern sector of the Granada Basin, where no active faults have been previously described at the surface. The heterogeneous extension in the Central Betic Cordillera could be accommodated by shallow high-angle normal faults that merge with a detachment at depth. Part of the active extension could be derived from gravitational instability because of underlying over-thickened crust.This research was funded by the Generalitat Valenciana (Valencian Regional Government, Research project AICO/2021/196), Spanish Ministry of Science, Innovation and University (Research Projects RTI2018-100737-B-I00 and PID2021-127967NB-I00), the University of Alicante (Research Project VIGROB053), the University of Jaén (POAIUJA 2021–2022, CEACTEMA and Programa Operativo FEDER Andalucía, 2014–2020—call made by UJA, 2018, Ref. 1263446), P18-RT-3275 (Junta de Andalucía/FEDER), and the Junta de Andalucía regional government (RNM282 and RNM 148 research groups). The Institut Cartogràfic Valencià, Agencia Valenciana de Seguridad y Respuesta a las Emergencias (Generalitat Valenciana), Consorcio Provincial para el Servicio de Prevención y Extinción de Incendios y Salvamento de Alicante, Excelentísimas Diputaciones Provinciales de Alicante y Castellón, and the Ayuntamiento de Almoradí also provided partial funding

Crustal velocity field in Baza and Galera faults: A new estimation from GPS position time series in 2009 - 2018 time span

The Baza and Galera faults are two active geologic structures located in the central area of the Betic Cordillera (Southern Spain). The goal of our research is to constrain the activity of this faults from high quality GPS measurements to obtain precise deformation rates. In 2008 a GPS survey – mode network was installed to monitor this area. In previous works, we presented a velocity field based on the analysis of some GPS campaigns. Here we show the new results computed from nine GPS campaigns in the timespan 2009-2018. The measurements were done in September 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2017 and 2018. The data process and analysis were performed in Precise Point Positioning by using GIPSYX 1.6 software. GIPSY is a GNSS-inferred positioning software developed by the Jet Propulsion Laboratory. Then, the new estimation of the crustal velocity field is computed from the IGb14 time series by SARI software. The model applied to the original time series, using weighted least squares, consists of an intercept, a site rate and an offset to account for an antenna change. The error term is composed of white noise and temporally correlated random error. The colored noise is described by a random-walk process. We have assumed a typical magnitude for this process of 1.0 mm/√yr. Finally, we discuss the implications of the new results for the tectonic setting and seismic hazard assessment of this key tectonic area of the Betic Cordillera.This work has been funded by Programa Operativo FEDER Andalucía 2014-2020 - call made by University of Jaen in 2018, Ref. 1263446, POAIUJA 2021/2022, CEACTEMA, and RNM148 and RNM282 research groups of Junta de Andalucía

The Campo de Dalias GNSS Network Unveils the Interaction between Roll-Back and Indentation Tectonics in the Gibraltar Arc

12 pages, 7 figures, 1 table.-- Data Availability Statement: The data are included in Table 1 of this paperThe Gibraltar Arc includes the Betic and Rif Cordilleras surrounding the Alboran Sea; it is formed at the northwest–southeast Eurasia–Nubia convergent plate boundary in the westernmost Mediterranean. Since 2006, the Campo de Dalias GNSS network has monitored active tectonic deformation of the most seismically active area on the north coast of the Alboran Sea. Our results show that the residual deformation rates with respect to Eurasia range from 1.7 to 3.0 mm/year; roughly homogenous west-southwestward displacements of the northern sites occur, while the southern sites evidence irregular displacements towards the west and northwest. This deformation pattern supports simultaneous east-northeast–west-southwest extension, accommodated by normal and oblique faults, and north-northwest–south-southeast shortening that develops east-northeast–west-southwest folds. Moreover, the GNSS results point to dextral creep of the main northwest–southeast Balanegra Fault. These GNNS results thus reveal, for the first time, present-day interaction of the roll-back tectonics of the Rif–Gibraltar–Betic slab in the western part of the Gibraltar Arc with the indentation tectonics affecting the eastern and southern areas, providing new insights for improving tectonic models of arcuate orogensJunta de Andalucia; European Regional Development Fund; grant numbers: AGORA P18-RT-3275, PAPEL B-RNM-301-UGR18. Programa Operativo FEDER-Andalucia 2014–2020 Project ref. 1263446; University of Jaén; CEACTEMA; grant number: POAIUJA 21/22. Junta de Andalucía (Andalusian Board); grant numbers: RNM-148, RNM-282, RNM-370. V.T.S. was supported by the FPU PhD grant (16/04038)With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)Peer reviewe

Fold and fault activity in the Campo de Dalias from GNSS networks

IV Reunión Ibérica sobre Fallas Activas y Paleosismología, del 7 al 10 de septiembre de 2022 en Teruel.-- 3 pages, 1 figure, 1 table[EN] The Campo de Dalias GNSS network monitors since 2006 the active tectonic deformation of the most seismic area on the boundary of the Alboran Sea and the Betic Cordillera. The residual deformation rates determined with respect to Eurasia range from 1.7 to 3.0 mm/yr. The displacements are roughly homogenous towards WSW of the northern sites while the southern sites evidence irregular displacements towards the W and NW. This deformation pattern supports simultaneous NNWSSE shortening that develops ENE-WSW folds and ENE-WSW extension, accommodated by normal and oblique faults. Moreover, the GNSS results point to dextral kinematics of the main NW-SE Balanegra Fault, that was previously considered as a normal fault. These GNSS results thus reveal, for the first time, present-day interaction of the roll-back tectonics of the Rif-Gibraltar-Betics slab in the western part of the Gibraltar Arc with the indentation tectonics affecting the eastern and southern areas, providing new insights for seismic hazard studies in this region[ES] La red GNSS del Campo de Dalias monitoriza desde 2006 la deformación tectónica activa de la zona con mayor sismicidad del límite entre la Cordillera Bética y el Mar de Alborán. Las velocidades de deformación residuales calculadas con respecto a Eurasia oscilan entre 1,7 y 3,0 mm/año. Los desplazamientos son aproximadamente homogéneos hacia el OSO de las estaciones del norte, mientras que las estaciones del sur evidencian desplazamientos irregulares hacia el O y el NO. Este patrón de deformación indica el acortamiento NNO-SSE que desarrolla pliegues ENE-OSO simultáneo a la extensión ENEOSO, acomodada por fallas normales y oblicuas. Además, los resultados de la red GNSS indican un salto dextro de la falla de Balanegra, con orientación NO-SE, que había sido considerada anteriormente como una falla normal. Las redes GNSS revelan, por primera vez, la interacción actual de la tectónica de roll-back asociada a la subducción Rif-Gibraltar-Bética en la parte occidental del Arco de Gibraltar y la tectónica de indentación que afecta a las zonas oriental y meridional del Mar de Alborán. Además, proporciona nuevos datos para los estudios de peligrosidad sísmica en esta regiónJunta de Andalucía; FEDER: AGORA P18-RT-3275, PAPEL B-RNM-301-UGR18; Programa Operativo FEDER-Andalucía 2014–2020 1263446; Universidad de Jaén. CEACTEMA. POAIUJA 21/22, Junta de Andalucía. RNM-148, RNM-282, RNM-370; V.T.S. FPU (16/04038)Peer reviewe

GPS deformation rates in the Bajo Segura basin (Eastern Betic Cordillera)

En este trabajo hemos cuantificado las tasas de deformación actual de la cuenca del Bajo Segura (NE del corredor de cizalla de la Bética oriental), a partir del análisis de una red GPS con 11 vértices geodésicos. Se han analizado los datos de cuatro campañas GPS entre junio de 1999 y enero de 2013, que han sido procesados con la versión 6.2 del software GIPSY-OASIS. Este software utiliza la técnica de posicionamiento puntual de precisión conocido por las siglas PPP. Se observa un acortamiento ~N-S en toda la cuenca de mayor magnitud en el sur, en la zona de falla del Bajo Segura, con valores que varían de oeste a este entre 0,73 y 0,24 mm/año. En el borde septentrional de la cuenca, en la zona de falla de Crevillente, los valores de acortamiento N-S son menores. Sin embargo, en esta falla se ha observado un movimiento lateral sinistrorso que, en la componente E-O, varía entre 0,44 y 0,75 mm/año.We estimate the present deformation rates of the Bajo Segura Basin (NE end of the Eastern Betic shear zone), from the analysis of a GPS network with 11 sites. We analyze the data from four observation campaigns carried out between June 1999 and January 2013.We used the 6.2 version of GIPSYOASIS software to process GPS data in Precise Point Positioning mode (PPP). It is observed a ~N-S shortening in the whole basin, higher in the south, along the Bajo Segura fault zone, with rates varying from West to East between 0.73 and 0.24 mm/yr. In the northern border of the basin, along the Crevillente fault zone, N-S deformation rates are lower. However, it is observed a left-lateral movement of this fault zone varying between 0.44 and 0.75 mm/yr in the E-W direction.Este trabajo ha sido financiado por los proyectos del Ministerio de Economía y Competitividad AYA2010-15501 y CGL2011-30153-C02-02 y por el proyecto CSD2006-0041 (European Regional Development Fund-ERDF)

Geodetic fault slip rates on active faults in the Baza sub-Basin (SE Spain): Insights for seismic hazard assessment

One of the most significant parameters for seismic hazard assessment analyses is the fault slip rate. The combination of both geological (long-term) and geodetic (short-term) data offers a more complete characterization of the seismic potential of active faults. Moreover, geodetic data are also a helpful tool for the analysis of geodynamic processes. In this work, we present the results of a local GPS network from the Baza sub-Basin (SE Spain). This network, which includes six sites, was established in 2008 and has been observed for seven years. For the first time, we obtain short-term slip rates for the two active faults in this area. For the normal Baza Fault, we estimate slip rates ranging between 0.3 ± 0.3 mm/yr and 1.3 ± 0.4 mm/yr. For the strike-slip Galera Fault, we quantify the slip rate as 0.5 ± 0.3 mm/yr. Our GPS study shows a discrepancy for the Baza Fault between the short-term slip rates and previously reported long-term rates. This discrepancy indicates that the fault could be presently in a period with a displacement rate higher than the mean of the magnitude 6 seismic cycle. Moreover, the velocity vectors that we obtained also show the regional tectonic significance of the Baza Fault, as this structure accommodates one-third of the regional extension of the Central Betic Cordillera. Our GPS-related slip rates form the basis for future seismic hazard analysis in this area. Our results have further implications, as they indicate that the Baza and Galera Faults are kinematically coherent and they divide the Baza sub-Basin into two tectonic blocks. This points to a likely physical link between the Baza and Galera Faults; hence, a potential complex rupture involving both faults should be considered in future seismic hazard assessment studies.We acknowledge the comments of Editor Prof. Irina M. Artemieva and two anonymous reviewers, which significantly improved the quality of this paper. This research was funded by the Spanish Ministry of Science, Innovation and University (Research Projects: RTI2018-100737-BI00 and CGL2016-80687-R), the University of Alicante (Research Project: VIGROB053), the University of Jaén (PAIUJA 2019-2020 and Programa Operativo FEDER Andalucía 2014-2020 - call made by UJA 2018), the University of Granada (B-RNM-301-UGR18) and the Junta de Andalucía regional government (RNM148, RNM282, and RNM370 and P18-RT-3275 research groups). We thank all observers who collected the data of survey-mode GPS measurements