Implement creation of Surface Waveforms group

[baagaard-usgs]

SurfaceWaveforms [group]

SURFACE_NAME.EVENTID.LABEL [group]

• SURFACE_NAME: Name of simply connected surface, e.g., ground_surface
• EVENTID: Event id matching event in QuakeML
• LABEL: User-specified label for waveforms

Vertices [dataset]

Attributes

• coordinate_system (Need to specify georeferenced coordinate system. Proj supports proj parameters, EPSG codes, and WKT)

Coordinates of vertices (points) defining the surface. Dataset dimensions are [num_points, 3]. Components are x, y, z.

Cells [dataset]

Attributes

• cell_shape [triangle, quadrilateral]

Zero-based array of how vertices are connected into cells (sometimes called connectivity arrays). Dataset is [num_cells, num_corners], where num_corners is the number of vertices in a cell (3 for triangles, 4 for quadrilaterals).

The coordinates of a cells corners are vertices[cells[i,0],:], vertices[cells[i,1],:], ...

FIELD [dataset]

• FIELD: Name of field (Displacement, Velocity, or Acceleration)

Attributes

• units (i.e., m, m/s, m/s**2)

Dataset is [num_time, num_points, 3]. This ordering means the slowest varying index is time, consistent with the dataset being saved in [num_points, 3] hyperslabs. Field components should be x, y, z, consistent with the coordinate system.