Units and coordinates

Units

All units are SI units. Location in m, Seismic moment in Nm.

Coordinates

We assume a right-handed Cartesian coordinate system where \(x_1, x_2, x_3\) are North, East, Down. Azimuth is in degree east of north (\(x_1 \rightarrow x_2\)) and plunge in degree down from horizontal (\((x_1,x_2) \rightarrow x_3\)).

Time and space coordinates are relative to an arbitrary origin.

Time measurements are required to tie time shifts of seismic traces to an absolute reference frame and can be useful when importing and exporting seismic traces. They are not required for moment tensor calculation.