P-wave velocities and applied bed thickness and velocity changes for synthetic seismograms, ODP Leg 188 and Leg 119 sites

Synthetic seismograms provide a crucial link between lithologic variations within a drill hole and reflectors on seismic profiles crossing the site. In essence, they provide a ground-truth for the interpretation of seismic data. Using a combination of core and logging data, we created synthetic seismograms for Ocean Drilling Program Sites 1165 and 1166, drilled during Leg 188, and Site 742, drilled during Leg 119, all in Prydz Bay, Antarctica. Results from Site 1165 suggest that coring penetrated a target reflector initially thought to represent the onset of drift sedimentation, but the lithologic change across the boundary does not show a change from predrift to drift sediments. The origin of a shallow reflector packet in the seismic line across Site 1166 and a line connecting Sites 1166 and 742 was resolved into its constituent sources, as this reflector occurs in a region of large-scale, narrowly spaced impedance changes. Furthermore, Site 1166 was situated in a fluvio-deltaic system with widely variable geology, and bed thickness changes were estimated between the site and both seismic lines.

合成地震记录（Synthetic Seismograms）是连接钻孔内部岩性变化与穿过该观测点位的地震剖面反射层的关键纽带，本质上可为地震数据的解释提供实测真值。研究团队结合岩心与测井数据，为南极洲普里兹湾内的3个大洋钻探计划（Ocean Drilling Program, ODP）站位构建了合成地震记录，分别为188航次钻探的1165、1166站位，以及119航次钻探的742站位。1165站位的分析结果显示，取心作业穿透了最初被认为代表漂移沉积起始的目标反射层，但该界面上下的岩性变化并未体现出从漂移前沉积物到漂移沉积物的转变。穿过1166站位的地震测线以及连接1166与742站位的测线中，研究人员将一处浅层反射层组的成因解析为其各组成来源——因该反射层分布于大规模、窄间距波阻抗变化的区域内。此外，1166站位地处岩性差异显著的河流-三角洲体系中，研究人员估算了该站位与两条地震测线之间的层厚变化情况。