Explaining Creep-Like Deformation in the Marmara Sea: Results from AVO-Derived Vp/Vs and Pore Pressure Analysis

Recent studies suggest that high pore pressures have caused seafloor creep-like deformation and slope failure in the Marmara Sea (e.g. Shillington et al., 2012). Stratigraphic analysis provides evidence for creep-like deformation in Marmara Sea sediments, however, no detailed quantitative geophysical analysis has been conducted to determine whether elevated fluid pressures exist in the Marmara Sea sediments today, or if these sediments are potentially near-critically stressed. If fluid pressures are high and the sediments are close to failure, only minor ground accelerations from earthquakes along the active Northern Anatolian Fault might trigger failure. For this study, I use high resolution multichannel 2D seismic data collected in the Marmara Sea to estimate indirectly P-wave and S-wave velocities that I then use to detect both possible gas accumulations and zones of high pore pressure. Specifically, I integrate interval P-wave velocities (using Dix equation), rock physics models, and Amplitude Versus Offset (AVO) methods to estimate Vs velocities. With Vp and Vs constrained, I then estimate where elevated fluid pressures in shallow (\u3c500 \u3embsf) sediment might exist in sediments on the southern margin of the Marmara Sea where pressure-driven creep-like deformation is hypothesized. I first characterize using forward models what normal versus overpressured AVO and Vp/Vs response should be like in the environment. Then, I compare model predictions with observations in a zone where creep-like deformation exists. The final product provides evidence for both if and where elevated pore pressure likely exists along the zone of noted sediment creep. I conclude by noting how sediment mineralogy and sedimentation rates likely play an important role in characterizing pore pressure evolution along this margin

Explaining Creep-Like Deformation in the Marmara Sea: Results from AVO-Derived Vp/Vs and Pore Pressure Analysis

Recent studies suggest that high pore pressures have caused seafloor creep-like deformation and slope failure in the Marmara Sea (e.g. Shillington et al., 2012). Stratigraphic analysis provides evidence for creep-like deformation in Marmara Sea sediments, however, no detailed quantitative geophysical analysis has been conducted to determine whether elevated fluid pressures exist in the Marmara Sea sediments today, or if these sediments are potentially near-critically stressed. If fluid pressures are high and the sediments are close to failure, only minor ground accelerations from earthquakes along the active Northern Anatolian Fault might trigger failure. For this study, I use high resolution multichannel 2D seismic data collected in the Marmara Sea to estimate indirectly P-wave and S-wave velocities that I then use to detect both possible gas accumulations and zones of high pore pressure. Specifically, I integrate interval P-wave velocities (using Dix equation), rock physics models, and Amplitude Versus Offset (AVO) methods to estimate Vs velocities. With Vp and Vs constrained, I then estimate where elevated fluid pressures in shallow (\u3c500 \u3embsf) sediment might exist in sediments on the southern margin of the Marmara Sea where pressure-driven creep-like deformation is hypothesized. I first characterize using forward models what normal versus overpressured AVO and Vp/Vs response should be like in the environment. Then, I compare model predictions with observations in a zone where creep-like deformation exists. The final product provides evidence for both if and where elevated pore pressure likely exists along the zone of noted sediment creep. I conclude by noting how sediment mineralogy and sedimentation rates likely play an important role in characterizing pore pressure evolution along this margin

Incidence and severity of retinopathy of prematurity in Turkey

Background: The purpose of this study was to estimate the current incidence of retinopathy of prematurity (ROP) and the need for treatment in preterm infants in Turkey. Methods: The study included preterm infants who had been screened for ROP between 2011 and 2013 in 49 neonatal intensive care units. Infants with birth weight (BW) ≤1500 g or ≤32 weeks' gestational age and those with BW >1500 g or >32 weeks' GA with an unstable clinical course were included. The incidence of any ROP or severe ROP and treatment modalities were determined. Results: The study population included 15 745 preterm infants: 11 803 (75%) with GA ≤32 weeks, and 3942 (25%) with GA >32 weeks. Overall, 30% were found to have any stage of ROP, and 5% had severe ROP. Severe ROP was diagnosed in 8.2% of infants with BW ≤1500 g and 0.6% of infants with BW >1500 g. Of all infants diagnosed with ROP, 16.5% needed laser photocoagulation, and 20 patients born at >32 weeks' GA required this treatment modality. Vitroretinal surgery was performed in 28 infants with severe ROP: 23 with GA ≤28 weeks and 5 with GA 29-32 weeks. Conclusions: The findings of our study have the important implication that more mature babies are at risk of severe ROP requiring treatment. An effective programme for detecting and treating ROP should be established in Turkey