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Ambient seismic noise acquired in the Cerdanya Basin (Eastern Pyrenees) is used to assess the capability of different methodologies to map the geometry of a small-scale sedimentary basin. We present results based on a 1-year long broad-band deployment covering a large part of the Eastern Pyrenees and a 2-months long high-density deployment covering the basin with interstation distances around 1.5 km. The explored techniques include autocorrelations, ambient noise Rayleigh wave tomography, horizontal to vertical spectra ratio, and band-pass filtered ambient noise amplitude mapping. The basement depth estimations retrieved from each of these approaches, based on independent datasets and different implicit assumptions, are consistent, showing that the deeper part of the basin is located in its central part, reaching depths of 600-700 m close to the Têt Fault trace bounding the Cerdanya Basin to the NE. The results from the different methodologies have an overall consistency, although significant differences appear in some zones. The results show also that when high-density seismic data are available, mapping the ambient noise amplitude in a selected frequency band is a valid tool to quickly map the sedimentary 3D geometry. Besides this methodological aspect, our results help to improve the geological characterization of the Cerdanya Basin and will provide further constraints to refine the seismic risk maps of an area of relevant touristic and economic activity., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

The Extended Hubbard Hamiltonian used by the Condensed Matter community is nothing but a simplified version of the Pariser, Parr and Pople Hamiltonian, well established in the Quantum Chemistry community as a powerful tool to describe the electronic structure of {\pi}-conjugated planar Polycyclic Aromatic Hydrocarbons (PAH). We show that whenever the interaction potential is non-local, unphysical charge inhomogeneities may show up in finite systems, provided that electrons are not neutralized by the ion charges. Increasing the system size does not solve the problem when the potential has an infinite range, and for finite range potentials these charge inhomogeneities become slowly less important as the potential range decreases and/or the system size increases. Dimensionality does also play a major role. Examples in bi-dimensional systems, such as planar PAH and graphene, are discussed to some extent.

The South Pyrenean fold-and-thrust belt triangle zone developed above Eocene to Oligocene foreland evaporitic levels. The triangle zone, Oligocene in age, dies eastwards and westwards where the thrust front becomes south-directed and emergent. The eastern and western terminations of the triangle zone coincide with the edges of the evaporitic basins. The frontal thrust wedge defines abrupt changes in trend related to the depositional orientation of evaporitic limits: the NE-SW Suria Anticline, the NW-SE Sanaiija Anticline and the E-W Barbastro-Balaguer Anticline. The thrust wedge is formed commonly at pinch-outs of salt without changes in structural level, although in some localities the thrust wedge developed above a thrust ramp geometry. Constrained timing and structural evolution of the foreland fold-and-thrust belt indicate the existence of northern and previous thrust wedges located at the Oliana and Puig-reig anticlines and the Sanaiija Anticline that have been abandoned as deformation progressed southward. Frontal thrust wedges were incorporated into the triangle zone which widened as new frontal thrust wedges developed forwards, at the southern edge of higher evaporitic levels. The exposed example is well understood because of continuous field exposures, syntectonic sedimentary relationships and new, good quality seismic profiles as well as subsurface control from oil and potash exploration wells., La zone triangulaire de la zone de plissement et de chevauchement des Pyrenees australes s'est developpee au-dessus des niveaux evaporitiques d'avant-pays d'age s'echelonnant de l'Eocene a I'Oligocene. La zone triangulaire, d'age Oligocene, s'estompe vers I'est et I'ouest la Oll le chevauchement frontal se dirige vers le sud et emerge. Les extremites est et ouest de la zone triangulaire correspondent aux marges des bassins evaporitiques. Le prisme a chevauchement frontal definit les changements abrupts de direction relatifs a I'orientation des depots des limites evaporitiques : l'anticlinal NE-SO Suria, I'anticlinal NO-SE Sanaiija et I'anticlinal E-O Barbastro-Balaguer. Le prisme de chevauchement est forme habituellement aux retrecissements de sel sans changement de niveau structural, meme si pour certains emplacements les prismes de chevauchement se sont developpes au-dessus de la geometrie de rampe de chevauchement. Les contraintes de temps et de l'evolution anticlinale de la zone de plissement et de chevauchement de l'avant-pays indiquent la presence de prismes de chevauchement au nord et anterieurs situes aux anticlinaux Oliana et Puig-reig et a l'anticlinal Sanaiija qui ont ete abandonnes a mesure que la deformation se depla, This project has been partially financed by DGICYT PB 91-0805 and PB 91-0252 and by the Comissionat per Universitats i Recerca de la Generalitat de Catalunya, Grup de Qualitat GRQ94-1048.

Devastating earthquakes like the 1944 San Juan earthquake reflect active deformation in western Argentina. Although the earthquake caused considerable damage to San Juan, the source of the earthquake remains uncertain. Potential source faults occur in the thin-skinned fold-and-thrust belt Precordillera province and in the thick-skinned Sierras Pampeanas province, to the west and east, respectively of Sierra de Villicum, a thrust sheet in the eastern Precordillera northwest of San Juan. Sierra de Villicum is a west-vergent thrust sheet bound on the northwest by the Villicum thrust, which juxtaposes a southeast dipping panel of Cambro-Ordovician and Neogene strata in the hanging wall with Neogene red beds in the footwall. A series of Late Pleistocene fluvial terraces developed across the Villicum thrust show no evidence of active fold or fault deformation. Terraces are deformed by active folds and faults in the middle of the southeastern flank of the Sierra de Villicum thrust sheet. A southeast-facing, southwest-plunging monocline characterizes the Neogene red beds in the region of active folding. Co- and post-seismic surface rupture along roughly 6 km of the La Laja fault in 1944 occurred in the limb of the monocline. Evidence that surface deformation in the 1944 earthquake was dominated by folding includes terrace´s fold geometry, which is consistent with kink-band models for fold growth, and bedding-fault relationships that indicate that the La Laja fault is a flexural slip fault. A blind basement reverse fault model for the earthquake source and for active deformation reconciles the zone of terrace deformation, coseismic surface rupture on the La Laja fault, refolding of the Villicum thrust sheet, a basement arch between the Precordillera and eastern Precordillera, and microseismicity that extends northwestward from a depth of ~5 km beneath Sierra de Villicum to ~35 km depth. Maximum horizontal shortening rate is estimated to be ~3.0 mmyr-1 from the terrace fold model and correlation of the terraces with dated terraces located to the southwest of the study area. Basement rocks beneath Cerro Salinas, another eastern Precordillera thrust sheet to the southwest, are also characterized by an east-facing monoclinal geometry, which suggests that blind thrust faulting on east-vergent basement faults represents a significant, underappreciated seismic hazard in western Argentina., La deformación activa en el oeste de Argentina está reflejada por terremotos devastadores como el sismo de San Juan en 1944. Aunque el terremoto causó un daño considerable a San Juan, la fuente del terremoto permanecía incierta. Fuentes potenciales de falla ocurren en las fajas plegadas y corridas adyacentes, la epidérmica de la Precordillera o la faja de basamento de Sierras Pampeanas, al oeste y este respectivamente de la sierra de Villicum, una lámina de corrimiento de la Precordillera Oriental, ubicada al noroeste de la provincia de San Juan. La sierra de Villicum es una lámina de corrimiento limitada al oeste por el corrimiento de Villicum, que yustapone un panel de estratos cambro-ordovícicos y neógenos de la pared colgante, con estratos rojos neógenos en la pared yaciente. Una serie de terrazas fluviales desarrolladas a través del corrimiento de Villicum no tienen evidencia activa de plegamiento o falla. Las terrazas están deformadas por fallas y pliegues activos en el medio del flanco sudeste de la lámina de corrimiento de la sierra de Villicum. La región de replegamiento activo está caracterizada por un monoclinal buzante al sudoeste de estratos neógenos que inclinan al sudeste. Rupturas superficiales cosísmicas y postsísmicas de la falla de La Laja ocurrieron en 1944 a lo largo de aproximadamente 6 km en el limbo del monoclinal. La evidencia de deformación superficial en el terremoto de 1944 estuvo dominada por plegamiento, incluido el de terrazas con geometría de pliegues, las que son consistentes con modelos de kink-bands para pliegues de crecimiento y con relaciones de fallas de estratificación que indican que la falla de La Laja es una falla por flexo deslizamiento. Un modelo de falla inversa ciega en el basamento para la fuente del terremoto y para la deformación activa, reconcilia la deformación en la zona de terrazas, la ruptura superficial cosísmica en la falla de La Laja, el repliegue de la lámina de corrimiento de Villicum, el arqueamiento del basamento entre la Precordillera y la Precordillera Oriental y la sismicidad que se extiende en profundidad hacia el noroeste desde ~5 km a unos ~35 km por debajo de la sierra de Villicum. La tasa de acortamiento horizontal máximo es estimada en unos ~3,0 mm por año a partir del modelo de plegamiento de terraza y su correlación con las terrazas datadas ubicadas al sudoeste del área estudiada. Rocas de basamento por debajo del cerro Salinas, una lámina de corrimiento de las Sierras Pampeanas ubicada al sudoeste de la región estudiada, también está caracterizada por una geometría monoclinal inclinada al este, que sugiere que fallas inversas ciegas en fallas de basamento con vergencia oriental representan un riesgo sísmico significativo, pero subvalorado en el oeste de Argentina., AJM was supported by U.S NSF grants EAR- 0232603and EAR-0409443 and a Research Equipment Reserve Fund grant from Oregon State University. We thank Repsol-YPF S.A. for providing us with the seismic line and for the permission to publish it (Fig. 13). J.V. was partially supported by 99AR0010 CSIC-CONICET project and Grups de Recerca Consolidats (II Pla de Recerca de Catalunya) Projects 1997 SGR 00020.