Structural features in the cores recovered during Leg 187 are summarized on the HRVCDs. For each section, more detailed structural information, such as the apparent and true orientations of veins and fractures and crosscutting relationships, is described and sketched on a separate structural geology description form (e.g., Fig. F4). With reference to the structural geology checklist (Table T2), observations are recorded to a structural log spreadsheet (Fig. F5) (see the "Supplementary Materials" contents list).
Descriptions and structural measurements were based on observations of the working half of the core. We followed the procedures used for the description of hard rocks in the "Explanatory Notes" chapter of the Leg 153 Initial Reports volume (see Cannat, Karson, Miller, et al., 1995).
All the structural features were recorded (in centimeters) relative to core-section depths from the top of the core section. Depth is defined as the point at which the structure intersects the center of the cut face of the working half of the core, as detailed in figure 15A in Cannat, Karson, Miller, et al. (1995).
Apparent fault displacements were recorded as they appear on the cut face of the archive half of the core and the ends of broken pieces. Displacements seen on the core face were treated as components of dip-slip movement, either normal or reverse. Displacements of features visible on the upper and lower surfaces of core pieces were treated as components of strike slip and termed sinistral or dextral. Displacements were measured parallel to the trace of the fault between displaced planar markers. Additional cuts and slickenside orientations were incorporated wherever possible to differentiate between apparent dip-slip, oblique-slip, and strike-slip displacements.
Structures were oriented using the techniques outlined during Legs 131 (Taira, Hill, Firth, et al., 1991) and 153 (Cannat, Karson, Miller, et al., 1995). Our assumption is that the core axis is always vertical within a horizontal slice of the core. Pseudonorth (000°) is defined as 90° to the cut face of the archive core; the right side is designated 270° and the left side is 090° (Fig. F6).