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# 2D seismic ray travel-time modeling (fatiando.seismic.ttime2d)¶

Calculate travel-times of seismic waves in 2D.

fatiando.seismic.ttime2d.straight(cells, prop, srcs, recs, velocity=None, par=False)[source]

Calculate the travel times inside a mesh of square cells between source and receiver pairs assuming the rays are straight lines (no refraction or reflection).

Note

Don’t care about the units as long they are compatible.

For a homogeneous model, cells can be a list with only one big cell.

Parameters:

• cells
:

The velocity model to use to trace the straight rays. Cells must have the physical property given in parameter prop. This will be used as the velocity of each cell. (cells can also be a SquareMesh)

• prop
: str

Which physical property of the cells to use as velocity. Normaly one would choose 'vp' or 'vs'

• srcs
: list fo lists

List with [x, y] coordinate pairs of the wave sources.

• recs
: list fo lists

List with [x, y] coordinate pairs of the receivers sources

• velocity
: float or None

If not None, will use this value instead of the prop of cells as the velocity. Useful when building sensitivity matrices (use velocity = 1).

• par
: True or False

If True, will run the calculations in parallel using all the cores available. Not recommended for Jacobian matrix building!

srcs and recs are lists of source-receiver pairs. Each source in srcs is associated with the corresponding receiver in recs for a given travel time.

For example:

>>> # One source was recorded at 3 receivers.
>>> # The medium is homogeneous and can be
>>> # represented by a single Square
>>> from fatiando.mesher import Square
>>> cells = [Square([0, 10, 0, 10], {'vp':2})]
>>> src = (5, 0)
>>> srcs = [src, src, src]
>>> recs = [(0, 0), (5, 10), (10, 0)]
>>> print straight(cells, 'vp', srcs, recs)
[ 2.5  5.   2.5]


Returns:

• times
: array

The total times each ray took to get from a source to a receiver (in compatible units with prop)