Use of GNSS and ERA5 precipitable water vapor based standardized precipitation conversion index for drought monitoring in the Mediterranean coast:A first case study in Southern Spain

In this paper the Standardized Precipitation Conversion Index (SPCI), a PWV-based drought index, has been computed using GNSS and ERA5 PWV and its performance has been tested with respect to the Standardized Precipitation Evapotranspiration Index (SPEI) in Southern Spain. One of the climatic features of this area is the low correlation level between PWV and precipitation, in contrast with other areas in which SPCI has been previously tested. The GNSS-SPCI has been derived from validated ZTD time series estimated from local GNSS permanent stations’ data. All the needed meteorological values were derived from ERA5, excepting precipitation values and SPEI-SPI values which were extracted from a national high-resolution dataset.The resulting SPCI time series have shown high correlation coefficients with respect to the SPEI. The use of longer SPCI time series allowed by ERA5 model has provided the most coherent results, suggesting that the ERA5-PWV data can be interesting to overcome problems caused by the short timespan of GNSS time series in SPCI computation. In general, high correlation coefficients have been obtained compared to global results from previous studies. This shows that, even for regions with low correlation levels between PWV and precipitation, the SPCI can have an interesting potential for drought monitoring. The SPCI was found to perform better on higher timescales (12 and 24 months). The performance of SPCI has also been compared that of the SPI: SPCI is able to outperform SPI for the 24-month timescale for a limited geographical region. This supports that the inclusion of PWV data in drought monitoring indices could be promising and is worth keeping to be investigated

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

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

Levelling Profiles and a GPS Network to Monitor the Active Folding and Faulting Deformation in the Campo de Dalias (Betic Cordillera, Southeastern Spain)

The Campo de Dalias is an area with relevant seismicity associated to the active tectonic deformations of the southern boundary of the Betic Cordillera. A non-permanent GPS network was installed to monitor, for the first time, the fault- and fold-related activity. In addition, two high precision levelling profiles were measured twice over a one-year period across the Balanegra Fault, one of the most active faults recognized in the area. The absence of significant movement of the main fault surface suggests seismogenic behaviour. The possible recurrence interval may be between 100 and 300 y. The repetitive GPS and high precision levelling monitoring of the fault surface during a long time period may help us to determine future fault behaviour with regard to the existence (or not) of a creep component, the accumulation of elastic deformation before faulting, and implications of the fold-fault relationship

How Much Nubia‐Eurasia Convergence Is Accommodated by the NE End of the Eastern Betic Shear Zone (SE Spain)? Constraints From GPS Velocities

We present the first GPS‐derived geodetic observations from the NE end of the Eastern Betic Shear Zone obtained from the Bajo Segura GPS network (SE Spain). The network has 11 GPS sites and was sampled four times between 1999 and 2013. Despite the low signal‐to‐noise ratio of the residual velocities obtained, the velocities are nonzero at 95% confidence level. We postulate that the GPS data point to the partitioning of deformation into the NNW–SSE shortening and a N70E left‐lateral component. The maximum deformation rates are located along the two main active faults in the study area. The maximum shortening rates (north component) in the southern region of the Bajo Segura Basin vary from west to east, ranging from 0.2 to 0.7 mm/year along the Bajo Segura Fault Zone. On the northern border of the basin, along the Crevillente Fault Zone, left‐lateral displacement varies between 0.4 and 0.7 mm/year in the E‐W direction. The GPS‐based regional geodynamic models of the Western Mediterranean indicate that the residual shortening of the Eurasia‐Nubia plate convergence is accommodated in the eastern part of the Iberian Peninsula and the Algero‐Balearic Basin. Our results indicate that part of this residual deformation occurs at the NE end of the Eastern Betic Shear Zone, but significant deformation must be accommodated also to the north (External Betics) and to the south (Cartagena Basin and offshore area). We postulate that Eurasia‐Nubia plate convergence is transferred to the Eastern Betics because of the thin and rigid (potentially oceanic) crust of the Algero‐Balearic Basin, which acts as an indenter.This research was funded by the Spanish Ministry of Economy and Competitiveness (research project CGL2011‐30153‐C02‐02), University of Alicante (research project VIGROB053), University of Jaén (PAIUJA 2019/2020, CEACTierra), and RNM282 Research Group of Junta de Andalucía

A method to estimate the Ionospheric bias by using the new GNSS frequencies: an analysis of its theoretical accuracy in a PPP context

The modernization of the Global Positioning System (GPS)and the advent of the European Project Galileo will lead to a multifrequency Global Navigation Satellite System (GNSS). Single GNSS receiver observations could be used to estimate the ionospheric bias and smoothed pseudoranges which, in turn, can be exploited to better estimate the absolute position of the receiver and its clock correction. In fact, if we consider the satellite ephemerides and satellite clock corrections as perfect quantities (i. e. not affected by errors), the adjustment of GNSS observations is broken down into two parts. In addition, the least squares (LS) theory leads to a feasible adjustment in two steps, where covariance matrices can be explicitly written, studied and propagated from one step to the other, so that, a rigorous solution is finally obtained. This paper deals with the analytic representation of the above mentioned LS procedure and provides theoretical limits for the achievable accuracies of the parameter estimated considering different scenarios, including modernized GPS and Galileo systems. Furthermore, numerical tests with Galileo data simulated by GSSF (Galileo System Simulation Facility) have been carried out

The Bayesian approach applied to GPS ambiguity resolution. A mixture model for the discrete-real ambiguities alternative

The problem of phase ambiguity resolution in: global positioning system (GPS) theory is considered. The Bayesian approach is applied to this problem and, using Monte Carlo simulation to search over the integer candidates, a practical expression for, the Bayesian estimator is. obtained. The analysis of the integer grid points inside, the search ellipsoid and their evolution with time, while measurements are accumulated, leads to the development of a Bayesian theory based on, a mathematical mixture model for the ambiguity