caa a22 4500 445364858 CHVBK 20180317142927.0 cr unu---uuuuu 170323e20110901xx s 000 0 eng 10.1007/s11001-011-9122-4 doi (NATIONALLICENCE)springer-10.1007/s11001-011-9122-4 Lateral continuity of basement seismic reflections in 15Ma ultrafast-spreading crust at ODP Site 1256 [Elektronische Daten] [Sreeja Nag, Stephen Swift] The Ocean Drilling Program (ODP) initiated drilling at Site 1256D in the Guatemala Basin, about 1,000km off the East Pacific Rise to penetrate plutonic rocks, anticipated to be relatively shallow in this region, formed at an ultra-fast spreading rate. IODP Expedition E312 successfully drilled into gabbros at ~1,150m in basement. Multi-channel seismic traces show weak laterally coherent sub-basement reflections at borehole depths. Synthetic reflectivity seismograms were computed using a Ricker wavelet and impedance profiles from borehole sonic logs. These seismograms show significant sub-basement amplitude peaks. A zero-offset vertical seismic profile, shot on E312, was processed to investigate the authenticity of these reflections and their relationship to borehole geology. A dual scheme of the median filtering and F-K dip filtering was used. Tests with synthetic seismograms indicate the approach is effective at reasonable SNR levels. Downgoing energy is clearly identified but negligible upgoing energy is visible over random noise. These results indicate that lava flows and igneous contacts in upper ocean crust have significant topography on lateral scales less than the Fresnel Zone (~300m) due to igneous and tectonic processes. Springer Science+Business Media B.V., 2011 East pacific rise nationallicence Vertical seismic profiling nationallicence Nag Sreeja Engineering Systems Division, Massachusetts Institute of Technology, 02139, Cambridge, MA, USA aut Swift Stephen Department of Geology and Geophysics, MS#24, Woods Hole Oceanographic Institution, 02543, Woods Hole, MA, USA aut Marine Geophysical Research Springer Netherlands 32/3(2011-09-01), 429-439 0025-3235 32:3<429 2011 32 11001 https://doi.org/10.1007/s11001-011-9122-4 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11001-011-9122-4 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Nag Sreeja Engineering Systems Division, Massachusetts Institute of Technology, 02139, Cambridge, MA, USA aut NATIONALLICENCE 700 1- Swift Stephen Department of Geology and Geophysics, MS#24, Woods Hole Oceanographic Institution, 02543, Woods Hole, MA, USA aut NATIONALLICENCE 773 0- Marine Geophysical Research Springer Netherlands 32/3(2011-09-01), 429-439 0025-3235 32:3<429 2011 32 11001 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer