Finite-difference approximation of wave equation: a study case of the SIMA velocity model

Synthetic seismograms enable to model the theoretical seismic response of the Earth interior due to different structural features and changes in the physical properties of crust and mantle. This approximation provides a best understanding of the real seismic data recorded in field experiments. In this paper, we are showing the development and application of a new scheme based on a multi-order explicit finite-difference algorithm for acoustic waves in a 2D heterogeneous media. The results of the modeling are compared with the seismic data acquired within the SIMA project providing new insight about the internal structure of the subsurface allowing improving the velocity model obtained in previous works.Peer Reviewe

FROM THE ATLAS TO THE RIF A CRUSTAL SEISMIC IMAGE ACROSS MOROCCO

The velocity structure of the crust and the geometry of the Moho across Morocco has been the main target of two recently acquired wide-angle seismic reflection transects. One is the SIMA experiment which provided seismic constraints beneath the Atlas Mountains and the second has been the RIFSEIS experiment which sampled the RIF orogen. Jointly these controlled source wide-angle seismic reflection data results in an almost 700 km, seismic profile going from the the Sahara craton across the High and Middle Atlas and Rif Mountain till the Gibraltar-Arc (Alboran). Current work on the interpretation of the seismic data-set is based on forward modeling, ray-tracing, as well as low fold wide-angle stacking. The data has resulted in a detailed crustal structure and velocity model for the Atlas Mountains and a 700 km transect revealing the irregular topography of the Moho beneath these two mountain orogens. Results indicate that the High Atlas features a moderate crustal thickness and that shortening is resolved at depth through a crustal root where the Saharan crust under-thrusts below the Moroccan crust, defining a lower crust imbrication which locally places the Moho boundary at, approximately, 40 km depth. The P-wave velocity model is characterized, in averaged, by relatively low velocities. These low deep crustal velocities together with other geophysical observables such as: conductivity estimates derived from Mt measurements; moderate Bouguer gravity anomaly; surface exposures of recent alkaline volcanics; lead the interpretation to propose that partial melts are currently emplaced in the deep crustal levels and in the upper mantle. The Moho discontinuity defines a crust which is in average relatively thin beneath the Atlas which is almost a 4000 m high orogenic belt. The resulting model supports existence of mantle upwelling as a possible mechanism that contributes, significantly, to maintain the High Atlas topographyPeer Reviewe

Homeostatic Response to Three Years of Experimental Warming Suggests High Intrinsic Natural Resistance in the Páramos to Warming in the Short Term

Páramos, tropical alpine ecosystems, host one of the world s most diverse alpine floras, account for the largest water reservoirs in the Andes, and some of the largest soil carbon pools worldwide. It is of global importance to understand the future of this extremely carbon-rich ecosystem in a warmer world and its role on global climate feedbacks. This study presents the result of the first in situ warming experiment in two Colombian páramos using Open-Top Chambers. We evaluated the response to warming of several ecosystem carbon balance-related processes, including decomposition, soil respiration, photosynthesis, plant productivity, and vegetation structure after 3 years of warming. We found that OTCs are an efficient warming method in the páramo, increasing mean air temperature by 1.7°C and mean daytime temperature by 3.4°C. The maximum air temperature differences between OTC and control was 23.1°C. Soil temperature increased only by 0.1°C. After 3 years of warming using 20 OTC (10 per páramo) in a randomized block design, we found no evidence that warming increased CO2 emissions from soil respiration, nor did it increase decomposition rate, photosynthesis or productivity in the two páramos studied. However, total C and N in the soil and vegetation structure are slowly changing as result of warming and changes are site dependent. In Sumapaz, shrubs, and graminoids cover increased in response to warming while in Matarredonda we observed an increase in lichen cover. Whether this change in vegetation might influence the carbon sequestration potential of the páramo needs to be further evaluated. Our results suggest that páramos ecosystems can resist an increase in temperature with no significant alteration of ecosystem carbon balance related processes in the short term. However, the long-term effect of warming could depend on the vegetation changes and how these changes alter the microbial soil composition and soil processes. The differential response among páramos suggest that the response to warming could be highly dependent on the initial conditions and therefore we urgently need more warming experiments in páramos to understand how specific site characteristics will affect their response to warming and their role in global climate feedbacks. © Copyright © 2021 Lasso, Matheus-Arbeláez, Gallery, Garzón-López, Cruz, Leon-Garcia, Aragón, Ayarza-Páez and Curiel Yuste.Special thanks to David Campos, Fabian Salgado, Luis Fernando Rojas, Ewen Dano, Jorge Acosta, Juliana Portilla, and Michelle Guevara that helped with field and lab work. We would like to thank the Sabogal family for allowing the establishment of the OTC and collection of samples in the p?ramo ?Parque Ecol?gico Matarredonda? and to the Lieutenant Colonel Edgar Riveira, Commander of the High Mountain Battalion No. 1 in Sumapaz and all the commanders that follow him and who provided us with accommodation and food in the battalion as well as logistic support in all our field campaigns. Thanks to all the soldiers who always enthusiastically helped us in the field work in Sumapaz. This research was also supported by the Basque Government through the BERC 2018?2021 program, and by the Spanish Ministry of Science, Innovation and Universities through the BC3 Mar?a de Maeztu excellence accreditation (MDM-2017-0714). Funding. Funding for this research comes from the ?Patrimonio Aut?nomo Fondo Nacional de Financiamiento para la Ciencia, la Tecnolog?a y la Innovaci?n Francisco Jos? de Caldas?Colciencias,? grant number 120471451294, granted by Colciencias (today?s Colombian Ministry of Science, Technology and Innovation), from Eloisa Lasso?s FAPA (Fondo de Apoyo para Profesores Asistentes) grant number P12.160422.001 from the Universidad de los Andes, and from the Research Fund to support faculty programs at the Faculty of Sciences at the Universidad de los Andes grant number INV-2019-84-1805

Basement structure of the Hontomín CO2 Geological storage facility (Burgos, Spain): integration of microgravity & 3D seismic reflection data

The structure of the Hontomín CO2 geological storage research facility has been addressed combining 3D seismic reflection data, borehole information and microgravity data. The integrated interpretation constrains the basement structural setting geometry and that of the sedimentary succession. The study unravels the deep structure and topography of the basement and quantifies the thickness of the Triassic Keuper evaporites. We describe a half-graben setting filled with Keuper evaporites (up to 2000 m) forming an extensional forced fold. Three set of faults are identified with two main fault systems compartmentalizing the area into three differentiated blocks. These faults have been interpreted to be reactivated normal faults that have led to the formation of the Hontomín dome.The datasets in this work have been funded by Fundación Ciudad de la Energía (Spanish Government, www.ciuden.es) and by the European Union through the “European Energy Programme for Recovery” and the Compostilla OXYCFB300 project. Dr. Juan Alcalde is currently funded by NERC grant NE/M007251/1.Peer Reviewe

Conocimientos para la enseñanza del número en Educadoras de Párvulos en Formación Docente Inicial: Constructo, instrumentos e intervención

El trabajo propone un constructo sobre el conocimiento docente que incluye el conocimiento de la educadora sobre lógica, número, etapas del aprendizaje del niño y organización de la enseñanza. Se diseñó un instrumento para medir este conocimiento. Se diseñó y aplicó un curso de enseñanza de la matemática, particularmente del número. El curso se basó en metodologías que integran teoría-práctica en la formación inicial: análisis de videos, estudio de caso y estudio de clase. Se usó un enfoque mixto, un diseño cuasi experimental con pre y post test, mapas conceptuales y entrevistas; constatándose diferencias significativas a favor del curso. El estudio provee un marco conceptual y metodologías para la formación docente en enseñanza de la matemática en Educación Parvularia

Reflection Seismic Imaging for Mineral Exploration in the Sotiel-Coronada Area, Southwest Spain

Near Surface Geoscience Conference & Exhibition Online 2020This work explores the first results of the seismic data acquired in the Sotiel-Coronada mine as part of the SIT4ME (Seismic Imaging Techniques for Mineral Exploration) project. In this experiment, a multi-source seismic data-set was acquired at the end of 2018 in the Sotiel- Coronada area of the Iberian Pyrite Belt (IPB) (southwest Spain). In the seismic experiment presented, 653 seismic receivers were deployed distributed in a pseudo 3D grid and six crooked lines across the study area. The sensors recorded c. 900 vibration points produced by a 32 Tn vibrotruck. Here, we present the stack results of the 2D seismic sections. Data from over 100 wells have been incorporating to aid in the structural interpretation. The preliminary interpretation reveals the complexity of this highly faulted ore-bearing area. Correlations between well log data information and 2D seismic profiles, suggest the location of a potentially mineralized area. The SIT4ME project has been funded by EIT Raw Materials (17024)

Basement structure of the Hontomín CO2 Geological storage facility (Burgos, Spain): integration of microgravity & 3D seismic reflection data

The structure of the Hontomín CO2 geological storage research facility has been addressed combining 3D seismic reflection data, borehole information and microgravity data. The integrated interpretation constrains the basement structural setting geometry and that of the sedimentary succession. The study unravels the deep structure and topography of the basement and quantifies the thickness of the Triassic Keuper evaporites. We describe a half-grabensetting filled with Keuper evaporites (up to 2000 m) forming an extensional forced fold. Three set of faults are identified with two main fault systems compartmentalizing the area into three differentiated blocks. These faults have been interpreted to be reactivated normal faults that have led to the formation of the Hontomín dome.The datasets in this work have been funded by Fundación Ciudad de la Energía (Spanish Government, www.ciuden.es) and by the European Union throughthe “European Energy Programme for Recovery” and the Compostilla OXYCFB300 project. Dr. Juan Alcalde is currently funded by NERC grant NE/M007251/1.Peer Reviewe

The Crust beneath Morocco: From the surface topography to the upper mantle a 700 km long seismic section across Morocco.

The most characteristic topographic features of Morocco are the Atlas Mountains and the Rif Coordillera. These two orogenic belts are the response of different geodynamic processes acting at lithospheric scale caused by a complex plate interaction. Both are located within the diffuse plate boundary zone separating Africa and Europe. The boundary zone is characterized by a relatively broad zone of deformation that includes mountain chains in southern Iberia, the Betics and in Morocco, the Rif Cordillera, separated by the Alboran basin. The zone delineates an arcuate arc system known as the Gibraltar arc. The area is characterized by a relatively large amount of earthquake activity at various depths and with a broad spectra of focal mechanisms. Within the last decade a large international effort have been devoted to the area. The topic has fostered a strong collaborations between Spanish and international research teams form Europe and USA. Key multi-seismic projects have been developed that aim to constrain the structure, composition and tectonic scenario from south of the Atlas to the Betics, across the Rif cordillera and the Alboran basin. The multidisciplinary research program included: natural source (earthquakes) recording with temporal deployments of broad band (BB) instrumentation and, controlled source seismic acquisition experiments where, spatially dense recording of wide-angle seismic reflection shot gathers were acquired. The natural source experiments consisted on a transect from Merzouga across the Gibraltar Arc and into the Iberian Peninsula (until south of Toledo) and, a nearly regular grid of BB. The controlled source data-sets were able to constrain the crustal structure and provide seismic P-wave propagation velocity models from the coast across the Rif and the Atlas. From south to north the crust features a relatively moderate crustal root beneath the Middle Atlas which can reach 40 km clearly differing from the 35 km thickness value observed at both sides of this root. Travel time inversion results position the crustal root just south of the High Atlas defining a thrusted mantle wedge and, also a limited crustal imbrication is suggested in the Middle Atlas. The most surprising feature is a prominent and unexpected crustal root (over 50 km) located beneath the external Rif and identified by both the wide-angle data and receiver function studies. To the east of this feature the crust thins rapidly by 20 km across the Nekkor fault zone, suggested to be related to the sharp change in crustal thickness. On shore-offshore recording of marine shots reveal further complexities in the transition to the Alboran basin. The low values of the Bouguer gravity anomalies beneath the Rif Cordillera are consistent with the crustal models derived from the new seismic data. The detailed knowledge on the crustal structure achieved by this high resolution imaging geophysical techniques is an asset to evaluate the earthquake and potential tsunami hazard for the coasts of North Africa and western Europe.This work has been primarily funded by the Spanish MEC project CGL2007–63889. Additional funding was provided by projects CGL2010–15416, CSD2006-00041, and CGL2009–09727 (Spain), CGL2008–03474-E, 07- TOPO_EUROPE_FP-006 (ESF Eurocores) and EAR-0808939 (US, NSF).Peer Reviewe

From the surface Topography to the Upper mantle beneath Central-Iberian-Zone. The ALCUDIA Seismic Experiments

American Geophysical Union, Fall Meeting 15-19 December, 2014, San FranciscoMulti-seismic experiments acquired across the central and southern part of the Iberian Peninsula provide a new insight into the structure and nature of the lithosphere beneath these areas. Normal incidence and wide-angle seismic reflection data acquired in the area resolve the internal architecture and constrain the distribution of the physical properties along an almost 280 km long transect that samples the major tectonic domains of the Central Iberian Zone (CIZ) and the associated suture (e.g., the Central Unit, CU). A high quality image, ~230 km long, down to 45 km depth (~15 s TWTT) is provided by the normal incidence data set. Based on the reflectivity characteristics, the image can be divided into an upper and mid-lower crust, ~13 km and ~18 km thick, respectively. The wide-angle seismic transect extended the crustal section towards the north across the Madrid Basin. This, latter data set also sample the CIZ until the CU. This is ~280 km long profile which provides very strong constraints on the distribution of physical properties (P wave and S wave velocities, Poisson's ratio) of the upper lithosphere. The PiP and PmP seismic phases constrain two discontinuities: the brittle to ductile discontinuity at ~13-19 km and the Moho boundary at ~31-35.5 km. Currently both appear to act as decoupling surfaces and are interpreted to represent levels of lithological/rheological variations. The internal structure of the Moho is further discussed taking into account the characteristics of the PmP reflections. Furthermore, low fold wide-angle P and S wave stacks reveal a marked crust-mantle transition which is most probably 5-6 km thick and relatively complex structure. The geometrical relationships of this structure with the crustal fabrics of the normal incidence image suggest that the Moho is most probably a result of the re-equilibration and/or other lithospheric processes active after the Variscan collision

Is it possible to retrieve Moho reflections from high-frequency autocorrelations of ambient noise?

[EN]This presentation describes the process to retrieve Moho reflections from autocorrelation of seismic noise dat