# -*- coding: utf-8 -*-
"""
Functionality for dealing with a single velocity layer.
"""
import numpy as np
#: The VelocityLayer dtype stores a single layer. An entire velocity model is
#: implemented as an array of layers. The elements are:
#:
#: * ``top_depth``: The top depth of the layer.
#: * ``bot_depth``: The bottom depth of the layer.
#: * ``top_p_velocity``: The compressional (P) wave velocity at the top.
#: * ``bot_p_velocity``: The compressional (P) wave velocity at the bottom.
#: * ``top_s_velocity``: The shear (S) wave velocity at the top.
#: * ``bot_s_velocity``: The shear (S) wave velocity at the bottom.
#: * ``top_density``: The density at the top.
#: * ``bot_density``: The density at the bottom.
#: * ``top_qp``: The P wave attenuation at the top.
#: * ``bot_qp``: The P wave attenuation at the bottom.
#: * ``top_qs``: The S wave attenuation at the top.
#: * ``bot_qs``: The S wave attenuation at the bottom.
VelocityLayer = np.dtype([
('top_depth', np.float_),
('bot_depth', np.float_),
('top_p_velocity', np.float_),
('bot_p_velocity', np.float_),
('top_s_velocity', np.float_),
('bot_s_velocity', np.float_),
('top_density', np.float_),
('bot_density', np.float_),
('top_qp', np.float_),
('bot_qp', np.float_),
('top_qs', np.float_),
('bot_qs', np.float_),
])
[docs]def evaluate_velocity_at_bottom(layer, prop):
"""
Evaluate material properties at bottom of a velocity layer.
.. seealso:: :func:`evaluate_velocity_at_top`, :func:`evaluate_velocity_at`
:param layer: The velocity layer to use for evaluation.
:type layer: :class:`~numpy.ndarray`,
dtype = :py:const:`~obspy.taup.velocity_layer.VelocityLayer`
:param prop: The material property to evaluate. One of:
* ``p``
Compressional (P) velocity (km/s)
* ``s``
Shear (S) velocity (km/s)
* ``r`` or ``d``
Density (g/cm^3)
:type prop: str
:returns: The value of the material property requested.
:rtype: :class:`~numpy.ndarray` (dtype = :class:`float`, shape equivalent
to ``layer``)
"""
prop = prop.lower()
if prop == "p":
return layer['bot_p_velocity']
elif prop == "s":
return layer['bot_s_velocity']
elif prop in "rd":
return layer['bot_density']
raise ValueError("Unknown material property, use p, s, or d.")
[docs]def evaluate_velocity_at_top(layer, prop):
"""
Evaluate material properties at top of a velocity layer.
.. seealso:: :func:`evaluate_velocity_at_bottom`,
:func:`evaluate_velocity_at`
:param layer: The velocity layer to use for evaluation.
:type layer: :class:`~numpy.ndarray`,
dtype = :py:class:`~obspy.taup.velocity_layer.VelocityLayer`
:param prop: The material property to evaluate. One of:
* ``p``
Compressional (P) velocity (km/s)
* ``s``
Shear (S) velocity (km/s)
* ``r`` or ``d``
Density (g/cm^3)
:type prop: str
:returns: The value of the material property requested.
:rtype: :class:`~numpy.ndarray` (dtype = :class:`float`, shape equivalent
to ``layer``)
"""
prop = prop.lower()
if prop == "p":
return layer['top_p_velocity']
elif prop == "s":
return layer['top_s_velocity']
elif prop in "rd":
return layer['top_density']
raise ValueError("Unknown material property, use p, s, or d.")
[docs]def evaluate_velocity_at(layer, depth, prop):
"""
Evaluate material properties at some depth in a velocity layer.
.. seealso:: :func:`evaluate_velocity_at_top`,
:func:`evaluate_velocity_at_bottom`
:param layer: The velocity layer to use for evaluation.
:type layer: :class:`~numpy.ndarray`,
dtype = :py:class:`~obspy.taup.velocity_layer.VelocityLayer`
:param depth: The depth at which the material property should be
evaluated. Must be within the bounds of the layer or results will be
undefined.
:type depth: float
:param prop: The material property to evaluate. One of:
* ``p``
Compressional (P) velocity (km/s)
* ``s``
Shear (S) velocity (km/s)
* ``r`` or ``d``
Density (g/cm^3)
:type prop: str
:returns: The value of the material property requested.
:rtype: :class:`~numpy.ndarray` (dtype = :class:`float`, shape equivalent
to ``layer``)
"""
thick = layer['bot_depth'] - layer['top_depth']
prop = prop.lower()
if prop == "p":
slope = (layer['bot_p_velocity'] - layer['top_p_velocity']) / thick
return slope * (depth - layer['top_depth']) + layer['top_p_velocity']
elif prop == "s":
slope = (layer['bot_s_velocity'] - layer['top_s_velocity']) / thick
return slope * (depth - layer['top_depth']) + layer['top_s_velocity']
elif prop in "rd":
slope = (layer['bot_density'] - layer['top_density']) / thick
return slope * (depth - layer['top_depth']) + layer['top_density']
raise ValueError("Unknown material property, use p, s, or d.")