Velocity field

The pyacs.vel_field package provides the Velocity_Field class to read, manipulate, and write velocity fields in GMT psvelo format. Each site is represented as a GMT_Point with position, velocity components (e.g. Ve, Vn), and uncertainties.

Full API reference: pyacs.vel_field

Backward compatibility: Velocity_Field is also available as Velocity_Field (pyacs.lib.vel_field is a thin wrapper that imports from pyacs.vel_field).

Velocity_Field class API

Full reference: pyacs.vel_field.Velocity_Field

The Velocity_Field class holds a collection of GMT_Point sites (lon, lat, Ve, Vn, uncertainties) and provides methods to read/write GMT psvelo files, subset sites, compute Euler poles, remove pole predictions, project along profiles, and estimate strain rates.

Summary of available methods

I/O

Method	Description
`read()`	Read a velocity field from a GMT psvelo file (class method).
`write()`	Write the velocity field to a GMT psvelo file.
`add_point()`	Append a GMT_Point to the field.
`remove_point()`	Remove a site by code.

Info and accessors

Method	Description
`info()`	Print basic information about the velocity field.
`print_info_site()`	Print information for one site by code.
`nsites()`	Return the number of sites.
`lcode()`	Return list of site codes.
`site()`	Return a GMT_Point by code.
`l_GMT_Point()`	Return the field as a list of GMT_Point instances.

Subset and transform

Method	Description
`subset()`	Return a new velocity field with a subset of sites (lonly / lexclude).
`radial()`	Return a field with radial and tangential components about a center.

Euler pole

Method	Description
`pole()`	Compute Euler pole from the velocity field (WLS or L1).
`calc_pole()`	Euler pole calculation for multiple plates; writes euler_sum.dat and per-plate outputs.
`substract_pole()`	Subtract (or add) the prediction of an Euler pole from the field.

Common sites and profile

Method	Description
`common()`	Return sites common to this field and a list of GMT_Points (e.g. from SINEX).
`proj_profile()`	Project velocity components along a great-circle profile.

Strain

Method	Description
`strain()`	Calculate strain rate from a list of site codes (velocity gradient tensor, principal axes, rotation).

API reference

Velocity field API

pyacs.vel_field