Microevents produced by gas migration and expulsion at the seabed: A study based on sea bottom recordings from the Sea of Marmara

International audienceDifferent types of 4-component ocean bottom seismometers (OBS) were deployed for variable durations ranging from 1 week to about 4 months in 2007, over soft sediments covering the seafloor of the Tekirdag Basin (western part of the Sea of Marmara, Turkey). Non-seismic microevents were recorded by the geophones, but generally not by the hydrophones, except when the hydrophone is located less than a few tens of centimetres above the seafloor. The microevents are characterized by short durations of less than 0.8 s, by frequencies ranging between 4 and 30 Hz, and by highly variable amplitudes. In addition, no correlation between OBSs was observed, except for two OBSs, located 10 m apart. Interestingly, a swarm of ∼400 very similar microevents (based on principal component analysis) was recorded in less than one day by an OBS located in the close vicinity of an active, gas-prone fault cutting through the upper sedimentary layers. The presence of gas in superficial sediments, together with analogies with laboratory experiments, suggest that gas migration followed by the collapse of fluid-filled cavities or conduits could be the source of the observed microevents. This work shows that OBSs may provide valuable information to improve our understanding of natural degassing processes from the seafloor

Gas and seismicity within the Istanbul seismic gap

Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the “Istanbul seismic gap”) has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic- driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5–5 km depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro- seismicity (~M < 3) within the Istanbul offshore domain

Gas and seismicity within the Istanbul seismic gap

Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the “Istanbul seismic gap”) has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5–5 km depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro-seismicity (~M < 3) within the Istanbul offshore domain

Stability of SARS-CoV-2 spike antigens against mutations

Modern health care needs preventive vaccines and therapeutic treatments with stability against pathogen mutations to cope with current and future viral infections. At the beginning of the COVID-19 pandemic, our analytic and predictive tool identified a set of eight short SARS-CoV-2 S-spike protein epitopes that had the potential to persistently avoid mutation. Here a combination of genetic, Systems Biology and protein structure analyses confirm the stability of our identified epitopes against viral mutations. Remarkably, this research spans the whole period of the pandemic, during which 93.9% of the eight peptides remained invariable in the globally predominant 43 circulating variants, including Omicron. Likewise, the selected epitopes are conserved in 97% of all 1,514 known SARS-CoV-2 lineages. Finally, experimental analyses performed with these short peptides showed their specific immunoreactivity. This work opens a new perspective on the design of next-generation vaccines and antibody therapies that will remain reliable against future pathogen mutations.Dr. Lozano-Perez acknowledges the European Commission ERDF/FEDER Operational Program 'Murcia' CCI No. 2007ES161PO001 (Project No. 14-20/20). Miodrag Grbic acknowledges support from the NSERC Discovery grant (Canada). This work also has received funding from the Department of Education of the Basque Government via the Consolidated Research Group MATH MODE (IT1456-22). Besides, Ildefonso Martinez De la Fuente and Iker Malaina were supported by the UPV/EHU and Basque Center of Applied Mathematics, grant US21/27N

Study Procrastination, Achievement, And Academic Motivation In Web-Based And Blended Distance Learning

Growth in distance education is increasing the need to examine students\u27 learning strategies in distance and blended learning environments. Students\u27 cramming or spaced-review behaviors were measured and compared across delivery formats as well as examined related to course achievement and attitudes across a term. Although theory would predict that spaced study rather than last minute cramming would yield higher achievement, researchers report mixed findings in both areas. One hundred fifty-seven students in distance and blended course formats were blocked into 5 groups based on their cramming/spaced-review patterns a week prior to each of 3 posttests. Significant differences were observed in cramming/spaced-review behaviors between delivery formats and for achievement and attitudes. © 2005 Elsevier Inc. All rights reserved

Monitoring of gas emission in the Marmara Sea by the combined study of the Acoustic Bubble Detector and Ocean Bottom Seismometers

International audienceWe here present geophysical evidence of gas emission from the Sea of Marmara seafloor, recorded by an Acoustic Bubble Detector (BOB), deployed on the top of the Central High, giving insight on the temporal variations of the flow rates. The instrument insonified 24 sectors of 7 over several days, providing multiple passes for a given angular sector. The acquired data indicate that gas emissions are non-steady processes. Non-seismic micro events have also been identified on an ocean bottom seismometer (OBS) deployed at the same location as the BOB. These non-seismic micro-events have the same characteristics as the ones previously identified within the Tekirdag Basin, by a network of 4-component OBS: They were recorded by geophones, but generally not by the hydrophones, except when the hydrophone is located less than a few tens of cm above the seafloor. They are characterized by short durations of less than 0.6 seconds, by frequencies ranging between 5 and 30 Hz, and by highly variable amplitudes. In addition, no correlation was observed between OBSs. The presence of gas in superficial sediments, together with analogies with laboratory experiments, suggest that gas migration followed by the collapse of fluid-filled cavities or conduits could be the source of the observed micro-events. The present work combines the BOB recordings with the OBS recordings covering the whole North Marmara Trough. Our study shows that the monitoring of the gas emission by a multi parameter approach may provide valuable information to better understand the relationships between deformation and non-seismic transients related to degassing from the sub-seafloor layers near the fault zone

Towards Identifying School-level Factors Reducing Disciplinary Exclusions of American Indian/Alaska Native Students

Our study examined the relationship between the Native American community’s recommendations for improving outcomes for American Indian/Alaska Native (AI/AN) students and school level practices in Oregon. We merged data on teacher practices from the 2009 National Indian Education Study (NIES) with data reflecting disciplinary exclusions. Our unweighted sample consisted of 40 elementary schools, 40 middle schools, &lt;10 high schools, and 10 K-8/12 schools. Results indicated that the majority of teachers did not participate in recommended professional development nor did they integrate Native culture into instruction. Although correlations between participation in professional development and use of Native culture were significant, linear regression outcomes indicated no significant association between school level practices and disciplinary exclusion patterns of AI/AN students. Follow-up analyses of K-8/12 schools, which had the lowest rates of disciplinary exclusions for AI/AN students, indicated that greater AI/AN enrollment density was associated with lower out-of-school suspension rates. Based on our analyses and current efforts in Oregon to improve educational outcomes for AI/AN students we recommended greater emphasis on (a) disaggregating discipline data by student race, (b) meaningful collaboration between state departments of education and Native community leaders, (c) schools’ accountability for reaching out to Native parents and community members, and (d) sharing disaggregateddata with all relevant stakeholders