Abstract.Recently acquired swath-bathymetry data and high-resolution seismic reflection profiles offshore Adra (Almería, Spain) reveal the surficial expression of a NW-SE trending 20 km-long fault, which we termed the Adra Fault. Seismic imaging across the structure depicts a subvertical fault reaching the seafloor surface and slightly dipping to the NE showing an along-axis structural variability. Our new data suggest normal displacement of the uppermost units with probably a lateral component. Radiocarbon dating of a gravity core located in the area indicates that seafloor sediments are of Holocene age, suggesting present-day tectonic activity. The NE Alboran Sea area is characterized by significant low-magnitude earthquakes and by historical records of moderate magnitude, such as the M w = 6.1 1910 Adra Earthquake. The location, dimension and kinematics of the Adra Fault agree with the fault solution and magnitude of the 1910 Adra Earthquake, whose moment tensor analysis indicates normal-dextral motion. The fault seismic parameters indicate that the Adra Fault is a potential source of large magnitude (M w ≤ 6.5) earthquakes, which represents an unreported seismic hazard for the neighbouring coastal areas.

Abstract. Coastal areas are highly exposed to natural hazards associated with the sea. In all cases where there is historical evidence for devastating tsunamis, as is the case of the southern coasts of the Iberian Peninsula, there is a need for quantitative hazard tsunami assessment to support spatial planning. Also, local authorities must be able to act towards the population protection in a preemptive way, to inform "what to do" and "where to go" and in an alarm, to make people aware of the incoming danger. With this in mind, we investigated the inundation extent, run-up and water depths, of a 1755-like event on the region of Huelva, located on the Spanish southwestern coast, one of the regions that was affected in the past by several high energy events, as proved by historical documents and sedimentological data. Modelling was made with a slightly modified version of the COMCOT (Cornell Multi-grid Coupled Tsunami Model) code. Sensitivity tests were performed for a single source in order to understand the relevance and influence of the source parameters in the inundation extent and the fundamental impact parameters. We show that a 1755-like event will have a dramatic impact in a large area close to Huelva inundating an area between 82 and 92 km 2 and reaching maximum run-up around 5 m. In this sense our results show that small variations on the characteristics of the tsunami source are not too significant for the impact assessment. We show that the maximum flow depth and the maximum run-up increase with the average slip on the source, while the strike of the fault is not a critical factor as Huelva is significantly far away from the potential sources identified up to now. We also show that the maximum flow depth within the inundated area is very dependent on the tidal level, while maximum run-up is less affected, as a consequence of the complex morphology of the area.Correspondence to:

S U M M A R YLg records analysis and numerical modelling of Lg propagation are used to find out to what extent this phase can be seen as a marker of unidentified structural anomalies in the crust. This study is based on Lg propagation through the Pyrenean range from earthquakes located in Spain.We have first evaluated the mean value of the S-wave quality factor for central Spain. We have computed simultaneously the seismic station responses and the source functions. The correction for propagation effects, assuming a homogeneous attenuation and the theoretical calculation of the Lg excitation, lead to the seismic moment of each event. The moment magnitude obtained correlates well with the magnitude proposed by the local networks. This gives a confirmation of the Q model in the low-frequency range (1-5 Hz). As we intended to compare traces of different Spanish earthquakes recorded in France at different epicentral distances, we had to make amplitudes independent of propagation and source effects. Therefore, we corrected the spectral amplitudes for geometrical spreading, anelastic attenuation and normalized them to equal seismic moment.We then plotted the records as a function of group velocity, in order to make up a fan profile along the Pyrenean axis. The resulting section reveals that in the central and the eastern parts of the range, neither the North Pyrenean Fault, nor the Moho jump deduced from seismic-refraction experiments and vertical seismics, seem to affect Lg propagation. However, there is an extinction of the Lg phase in the western part of the chain. The lateral extent of this area is correlated with a zone of positive gravity anomaly, probably linked to the presence of dense material of mantle origin. A numerical simulation in the low-frequency band indicates that the Moho topography inferred from deep seismic soundings does not explain the strength of the observed attenuation. Ray-tracing seismograms show that, at high frequency, the conclusion is the same. The attenuation effect due to lateral variation of structure should not be so strong. We, therefore, think that attenuation of guided waves is not due to large-scale geometry effects, but is due to local properties of the crustal materials, possibly apparent attenuation due to scattering on small-scale heterogeneities.

Abstract. El Salvador is the smallest and most densely populated country in Central America; its coast has an approximate length of 320 km, 29 municipalities and more than 700 000 inhabitants. In El Salvador there were 15 recorded tsunamis between 1859 and 2012, 3 of them causing damages and resulting in hundreds of victims. Hazard assessment is commonly based on propagation numerical models for earthquake-generated tsunamis and can be approached through both probabilistic and deterministic methods. A deterministic approximation has been applied in this study as it provides essential information for coastal planning and management. The objective of the research was twofold: on the one hand the characterization of the threat over the entire coast of El Salvador, and on the other the computation of flooding maps for the three main localities of the Salvadorian coast. For the latter we developed high-resolution flooding models. For the former, due to the extension of the coastal area, we computed maximum elevation maps, and from the elevation in the near shore we computed an estimation of the run-up and the flooded area using empirical relations. We have considered local sources located in the Middle America Trench, characterized seismotectonically, and distant sources in the rest of Pacific Basin, using historical and recent earthquakes and tsunamis. We used a hybrid finite differencesfinite volumes numerical model in this work, based on the linear and non-linear shallow water equations, to simulate a total of 24 earthquake-generated tsunami scenarios. Our results show that at the western Salvadorian coast, run-up values higher than 5 m are common, while in the eastern area, approximately from La Libertad to the Gulf of Fonseca, the run-up values are lower. The more exposed areas to flooding are the lowlands in the Lempa River delta and the Barra de Santiago Western Plains. The results of the empirical approximation used for the whole country are similar to the results obtained with the high-resolution numerical modelling, being a good and fast approximation to obtain preliminary tsunami hazard estimations. In Acajutla and La Libertad, both important tourism centres being actively developed, flooding depths between 2 and 4 m are frequent, accompanied with high and very high person instability hazard. Inside the Gulf of Fonseca the impact of the waves is almost negligible.