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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.

In precise point positioning (PPP), the ionospheric delay is corrected in a first-order approximation from GPS dual-frequency observations, which should eliminate almost completely the ionosphere as a source of error. However, sudden plasma density variations can adversely affect the GPS signal, degrading accuracy and reliability of positioning techniques. The occurrence of plasma density irregularities is frequent at equatorial latitudes and is reflected in large total electron content (TEC) variations. We study the relation between large changes in the rate of TEC (ROT) and positioning errors in singleepoch PPP. At equatorial latitudes and during post-sunset hours, the estimated altitudes contain errors of several meters for a single-epoch position determination, and latitude and longitude estimates are also degraded. These results have been corroborated by the online CSRS-PPP (NRCan) program. Moreover, abrupt changes in the satellite geometry have been discarded as possible cause of such errors, suggesting an apparent relation between the occurrence of large ROT and degraded position estimates.

Intense disturbances in the ionosphere may produce perturbations in Global Navigation Satellite Systems (GNSS) radio signals that in the most severe cases produce receiver tracking problems, which in turn impact on GNSS positioning accuracy. In this paper we present a case study related to the sudden increase in total electron content (SITEC) induced by the X17.2 solar flare that occurred on 28 October 2003. This is the largest SITEC ever recorded by means of the rate of change of total electron content. A solar radio burst (SRB) occurred in the same period which caused GNSS signal fading and in some cases complete signal loss. Although SITEC contribution to the signal noise cannot be separated from that of SRB, in this paper we show that accuracy degradation may happen in kinematic precise point positioning (PPP) in several stations of the sunlit hemisphere when 30 s sampling rate data are analyzed. The observed errors in the position are the result of the difficulties that cycle slip (CS) detection strategies have to deal with the observables that have been affected by the SITEC.