Caracterización de acuíferos mediante testificación geofísica e imágenes 3D en los sondeos de investigación Almera-1 y Almera-2, en el entorno urbano de la ciudad de Barcelona

Logging, borehole imaging and monitoring carried out in the scientific boreholes Almera-1 and Almera-2 in the Pedralbes campus of the University of Barcelona has allowed us to identify three preferential groundwater flow paths. Geophysical logging data combined with groundwater monitoring levels allowed us to identify three high permeable zones in the boreholes. Logging data combined with core analysis were used to characterize the aquifers lithology and petrophysical properties. We compared the groundwater measured levels and the rainfall in the area to identify and characterize aquifer dynamics and potential relationships between the variations in groundwater levels and the rainfalls.Proyecto: PNIDI-CGL2010-21568Peer Reviewe

Scientific drilling in the campus: Almera-1 borehole, unraveling urban subsurface geology in Barcelona (Spain).

Almera-1 borehole was drilled to provide a borehole geophysical logging and downhole monitoring research and training facility. Also a main objective was the exploration of the urban subsurface geology adjacent to the Institute of Earth Sciences Jaume Almera (CSIC) in Barcelona the University of Barcelona Pedralbes. Wireline drilling continuous coring was successfully applied to recover cores from the entire section (214m). Since 2011 Almera-1 hole has been extensively used for slim hole logging, coring and monitoring. Total depth was reached after drilling a Quaternary to Paleozoic section. The upper section of Almera-1 hole is cased with PVC and the lowermost is an open hole section within the Paleozoic section. A complete set of geophysical logging measurements and oriented borehole images was acquired with CSIC own slim hole logging equipment both in open hole mode and through the PVC casing. Logging measurements were acquired over the entire section. Open hole measurements included acoustic and optical imaging, spectral natural gamma ray, full wave acoustic logging, magnetic susceptibility, hydrochemical-temperature logs and fluid sampling. Through casing (PVC casing) measurements included spectral gamma ray logging, full wave sonic and acoustic televiewerPeer Reviewe

Tomografía sísmica vertical inversa 2.5D alrededor del sondeo científico Almera-1, ICTJA-CSIC, Barcelona

En 2011 junto al Instituto de Ciencias de la Tierra Jaume Almera-CSIC, en Barcelona, se perforó un sondeo científico con el objeto de disponer de una infraestructura destinada a la investigación con sondas de testificación geofísica, monitorización de sondeos, la formación especializada y también para la exploración del subsuelo urbano. La extracción de testigo continuo y un completo estudio mediante sondas de testificación geofísica del ICTJA-CSIC, permitieron caracterizar la sección geológica, estructuras atravesadas y características hidrogeológicas en el sondeo Almera-1. Se presentan aquí los resultados obtenidos en una exploración sísmica de la estructura en el entorno del sondeo y el reconocimiento de la estructura en la que está emplazado el mismo. En este contexto se planteó una tomografía sísmica vertical inversa pseudo-3D (o 2.5D), cuyo dispositivo experimental, metodología y resultados son objeto de este trabajo. Se define la estructura en el entorno del sondeo y se establece una correlación entre las respuestas geofísicas y los distintos tramos de materiales reconocidos en el subsuelo.Peer Reviewe

On the connection of fractures with clays and fluids in the accretionary prism of the Nankai Trough at Site C0002, NanTroSEIZE IODP Expedition 338/348. Borehole images and log interpretation results

International Ocean Discovery Program IODP has extensively used the D/V Chikyu to drill the Kumano portion of the Nankai Trough. (IODP) Expeditions 338 and 348 of the NanTroSEIZE project drilled deep into the inner accretionary prism south of the Kii Peninsula collecting a suite of LWD data, including natural gamma ray, electrical resistivity logs and borehole images, suitable to characterize structures (fractures and faults) inside the accretionary prism. Both expeditions drilled into the accretionary prism at Site C0002: Hole C0002F (Expedition 338) was drilled down to 2004.5 mbsf, Hole C0002P (Expedition 348) reached a depth of 3058.8 mbsf. Structural interpretation and analysis of logging-while-drilling data in the deep inner prism revealed intense deformation of a generally homogenous bedding that dips steeply and are intersected by faults and fractures. The interpretation of the images of both Hole C0002F and Hole C0002P reveals distinct areas of intense fracturing and faulting within a very clay-dominated lithology. Faults are undobutedly interpreted on C0002P images. The relationship between fractures, faults and the changes in clay mineralogy from cutting sample analyses is analyzed to characterize potential connection between these features in the accretionary prismM.J. Jurado research supported by PNIDI- CGL2009-13405, CGL2010-21568, and ACI2008-0773 projects.Peer Reviewe

IODP Expedition 338: NanTroSEIZE stage 3: NanTroSEIZE plate boundary deep riser 2

The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is designed to investigate fault mechanics and seismogenesis along a subduction megathrust, with objectives that include characterizing fault slip, strain accumulation, fault and wall rock composition, fault architecture, and state variables throughout an active plate boundary system. Integrated Ocean Drilling Program (IODP) Expedition 338 was planned to extend and case riser Hole C0002F from 856 to 3600 meters below the seafloor (m b.s.f.). Riser operations extended the hole to 2005.5mb.s.f., collecting logging-while-drilling (LWD) and measurement-while-drilling, mud gas, and cuttings data. Results reveal two lithologic units within the inner wedge of the accretionary prism that are separated by a prominent fault zone at ¿ 1640mb.s.f. Due to damage to the riser during unfavorable winds and strong currents, riser operations were suspended, and Hole C0002F left for re-entry during future riser drilling operations. Contingency riserless operations included coring at the forearc basin site (C0002) and at two slope basin sites (C0021 and C0022), and LWD at one input site (C0012) and at three slope basin sites (C0018, C0021 and C0022). Cores and logs from these sites comprehensively characterize the alteration stage of the oceanic basement input to the subduction zone, the early stage of Kumano Basin evolution, gas hydrates in the forearc basin, and recent activity of the shallow megasplay fault zone system and associated submarine landslides. © Author(s) 2014.Peer Reviewe

FAM-1 Borehole: first results from the scientific drilling of the Alhama de Murcia Fault, Betic Cordillera, Spain

We present the preliminary results of the borehole FAM-1 a 175 m depth scientific drilling of the Alhama de Murcia fault. The borehole was drilled close to La Torrecilla rambla three km SW of Lorca where the fault zone shearing is more concentrated and it is dominated by well-developed clay rich fault gouge. To select the drilling point and to perform a prognosis of it, three trenches were excavated crossing the fault zone that allowed us to determine the detailed 3D structure of the fault zone. We have collected more than 100 m of unaltered high quality fault rock to be studied using mineralogical and microtectonic analysis, and geomechanical testing that will improve the knowledge of the influence of tectonic microfabric and mineralogy in the seismogenic behavior of the AMF. The borehole FAM-1 and the seismic monitoring borehole FamSis-1 constitute the first stage of a future geological-geophysical observatory for monitoring the activity of the AMF.This research is part of the INTERGEO project: CGL2013-47412-C2-1-P.Peer Reviewe

Deformation of the Nankai Trough inner accretionary prism: The role of inherited structures

Accretionary prisms commonly grow seaward, with the strata of the inner prism consisting of older, previously accreted outer prism rocks overlain by thick fore-arc basin strata. We focus on the Nankai Trough inner accretionary prism using three-dimensional (3-D) seismic data and logging data from the Integrated Ocean Drilling Program (IODP). We update the 3-D seismic volume using well velocity data to better constrain deeper horizons. Interpretation of these horizons reveals multiple folds with axial surfaces that strike near parallel to modern outer prism thrust faults, and we interpret that these folds formed as a result of thrust faulting. Reactivation of one inner prism thrust fault continued until at least ∼0.44 Ma, after the modern fore-arc basin formed, indicating that the inner prism had continued deformation until that time. Structural restorations of these folded seismic horizons demonstrate that ∼580 m of slip occurred on this steeply dipping reactivated thrust after fore-arc basin formation. Structural interpretation and analysis of logging-while-drilling data, including borehole images, in the deep inner prism revealed intense deformation of a generally homogenous lithology characterized by bedding that dips steeply (60°–90°), intersected by faults and fractures that have a range of dips and densities. Our study of the deep Kumano Basin provides new insights into the structure of the inner prism and reveals that although the inner prism has partially preserved inherited outer prism structures, these older folds and faults are steeply rotated and cut by multiple fracture populations during subsequent deformation.Funding for this research was provided by the National Science Foundation (grant OCE-0451790) and a U.S. Science Support Program Post-Expedition Award.Peer reviewe

Investigating active faults in SE Iberia: borehole and surface seismic monitoring

Monitoring seismic signal associated to active faults in SE Iberia was undertaken by the installation of 3-component geophone strings in boreholes and also on the surface, close to active faults located in Torreperogil-Sabiote area and Baza basin. Our instrumentation was installed in existing hydrogeological and geotechnical boreholes for continuous monitoring of low intensity seismic activity during 8 months. Borehole geophone strings consisting of 8 receivers of 3-component, with 15Hz of natural frequency, spaced 6 m at depth were used. The main purpose of continuous monitoring of the seismic signal in the subsurface was to record the high frequencies of the seismic data and to investigate and eventually characterize fault creep and seismic noise related to deformation and fault movements in seismically active areas. The dataset recorded included a series of low magnitude earthquakes and is being analyzed to identify and characterize seismic events. A 3G GSM module was used together with the acquisition system in order to guarantee remote access to check the acquired data quality and to control the acquisition parameters. Also, the remote access allowed us to pre-process the data 'in situ' and to perform only selective transmission of the most relevant files. Because of the isolated and remote locations of some of the monitoring stations, proprietary software was developed to avoid the possible losses of communication between the acquisition system and remote control computer. In this contribution we present the most relevant features of the acquisition and methodology implemented for this acquisition, first results of the field experiment and data processing and advantages of the on site pre-processing management and remote operation of the acquisition system. This system is being applied to other active fault zones in the area.Peer Reviewe

Maar-diatreme infill features recorded in borehole imaging

Oriented borehole images recorded with an ultrasonic acoustic televiewer and continuous coring recovery has allowed the characterization of different facies and volcanic processes involved in the infill of a maar-diatreme volcano type. Maar-diatremes are associated with strong explosions throughout most of their development, focused along feeder dikes and generally attributed to magma-water interaction. In the case study of Camp dels Ninots maar-diatreme (Girona, Spain) we have recognized four facies types located in the center of the maar-diatreme: volcanic ash, phreatomagmatic breccia with lithics and juveniles, vesicular pyroclasts (scoria), massive basalt or welded pyroclastic fragments. Ultrasonic televiewer images allow to characterize the different volcanic facies, since they display a different degree of reflectivity and textures. Other features such as fracturing and grain size can be directly measured on the images.Projects 2014-100575 from Departament de Cultura de and SGR2014-901 from AGAUR (both from Generalitat de Catalunya) financed the drilling campaigns.Peer Reviewe

Nasal cannula use during polysomnography in children aged under three with suspected sleep apnea

Acord transformatiu CRUE-CSICObjective: Early diagnosis of obstructive sleep apnea (OSA) in children is important. The use of a nasal cannula as an airflow sensor during polysomnography has not been evaluated in younger children. The study aims to evaluate the use of nasal cannula in detecting respiratory events in children under three with suspected OSA during daytime nap studies. Methods: A total of 185 patients were prospectively included. Respiratory events were scored using nasal cannula alone, thermistor alone, and both methods simultaneously as the airflow sensor. Agreement and diagnostic accuracy were assessed. Results: One hundred and seventy-two children were finally analyzed and 110 (64.0%) presented OSA. Total sleep time with an uninterpretable signal was longer with the nasal cannula than with the thermistor (17.8% vs 1.9%; p < 0.001), and was associated with poor sensor tolerance and adenotonsillar hypertrophy. In the estimation of the apnea-hypopnea index, the nasal cannula showed lower agreement than the thermistor with the joint use of the two sensors (intraclass correlation coefficient: 0.79 vs 0.996 with thermistor). Compared with the thermistor, the nasal cannula presented lower sensitivity for detecting OSA (82.7% vs 95.5%) and a lower negative predictive value (76.5% vs 92.4%). Overall, fewer children were diagnosed with severe OSA with the nasal cannula (19.8% vs 30.8% with the thermistor, and 32.6% with both). Conclusions: In children under the age of three, the ability of the nasal cannula to detect obstructive events was relatively low. Therefore, other non-invasive measurements for identifying respiratory events during sleep may be of additional value