rotate2D: Rotate horizontal components of a seismic signal
In IRISSeismic: Classes and Methods for Seismic Data Analysis

rotate2D

R Documentation

Rotate horizontal components of a seismic signal

Description

The rotate2D() function rotates the two horizontal components of a seismic signal into Radial and Transverse components returned as a list of 2 Stream objects.

Usage

rotate2D(st1, st2, angle)

Arguments

`st1`	horizontal `Stream` from a channel set (channel name usually ending in "N", "E", "1", or "2")
`st2`	horizontal `Stream` from a channel set, complementary to st1
`angle`	angle (degrees) of the rotation

Details

The rotation web service returns Radial and Transverse seismic Streams, generated by rotating st1 and st2 by angle degrees.

The rotation service uses the following transformation matrix to change the output vectors for 2-D horizontal transformations

M_{2D} = ≤ft[ \begin{array}{cc} cos α & sin α \cr -sin α & cos α \end{array} \right]

≤ft[ \begin{array}{c} R \cr T \end{array} \right] = M_{2D} ≤ft[ \begin{array}{c} N \cr E \end{array} \right]

where :

   N and E represent data from the original (horizontal) orientations.
   R and T represent the Radial and Transverse components.
   \eqn{\alpha} is the azimuth angle measured clockwise from north.

Value

A list of two Stream objects stR and stT is returned.

Note

N and E are determined by the Stream @stats@azimuth values. If Stream @stats@azimuth values are not defined, st1 is assumed to be N and st2 is assumed to be E. Orthogonality is also assumed to be correct.