# -*- coding: utf-8 -*-
"""
Velocity model class.
"""
from pathlib import Path
import numpy as np
from .velocity_layer import VelocityLayer, evaluate_velocity_at
from . import _DEFAULT_VALUES
[docs]class VelocityModel(object):
[docs] def __init__(self, model_name, radius_of_planet, min_radius, max_radius,
moho_depth, cmb_depth, iocb_depth, is_spherical,
layers=None):
"""
Object for storing a seismic planet model.
:type model_name: str
:param model_name: name of the velocity model.
:type radius_of_planet: float
:param radius_of_planet: reference radius (km), usually radius of the
planet.
:type min_radius: float
:param min_radius: Minimum radius of the model (km).
:type max_radius: float
:param max_radius: Maximum radius of the model (km).
:type moho_depth: float
:param moho_depth: Depth (km) of the Moho. It can be input from
velocity model (``*.nd``) or should be explicitly set. For phase
naming, the tau model will choose the closest first order
discontinuity.
:type cmb_depth: float
:param cmb_depth: Depth (km) of the CMB (core mantle boundary). It can
be input from velocity model (``*.nd``) or should be explicitly
set.
:type iocb_depth: float
:param iocb_depth: Depth (km) of the IOCB (inner core-outer core
boundary). It can be input from velocity model (``*.nd``) or should
be explicitly set.
:type is_spherical: bool
:param is_spherical: Is this a spherical model? Defaults to true.
:type layers: list
:param layers: The layers of the model.
"""
self.model_name = model_name
self.radius_of_planet = radius_of_planet
self.moho_depth = moho_depth
self.cmb_depth = cmb_depth
self.iocb_depth = iocb_depth
self.min_radius = min_radius
self.max_radius = max_radius
self.is_spherical = is_spherical
self.layers = np.array(layers if layers is not None else [],
dtype=VelocityLayer)
[docs] def __len__(self):
return len(self.layers)
[docs] def is_discontinuity(self, depth):
return np.any(self.get_discontinuity_depths() == depth)
[docs] def get_discontinuity_depths(self):
"""
Return the depths of discontinuities within the velocity model.
:rtype: :class:`~numpy.ndarray`
"""
above = self.layers[:-1]
below = self.layers[1:]
mask = np.logical_or(
above['bot_p_velocity'] != below['top_p_velocity'],
above['bot_s_velocity'] != below['top_s_velocity'])
discontinuities = np.empty((mask != 0).sum() + 2)
discontinuities[0] = self.layers[0]['top_depth']
discontinuities[1:-1] = above[mask]['bot_depth']
discontinuities[-1] = self.layers[-1]['bot_depth']
return discontinuities
[docs] def layer_number_above(self, depth):
"""
Find the layer containing the given depth(s).
Note this returns the upper layer if the depth happens to be at a layer
boundary.
.. seealso:: :meth:`layer_number_below`
:param depth: The depth to find, in km.
:type depth: :class:`float` or :class:`~numpy.ndarray`
:returns: The layer number for the specified depth.
:rtype: :class:`int` or :class:`~numpy.ndarray` (dtype = :class:`int`,
shape equivalent to ``depth``)
"""
depth = np.atleast_1d(depth)
layer = np.logical_and(
self.layers['top_depth'][np.newaxis, :] < depth[:, np.newaxis],
depth[:, np.newaxis] <= self.layers['bot_depth'][np.newaxis, :])
layer = np.where(layer)[-1]
if len(layer):
return layer
else:
raise LookupError("No such layer.")
[docs] def layer_number_below(self, depth):
"""
Find the layer containing the given depth(s).
Note this returns the lower layer if the depth happens to be at a layer
boundary.
.. seealso:: :meth:`layer_number_above`
:param depth: The depth to find, in km.
:type depth: :class:`float` or :class:`~numpy.ndarray`
:returns: The layer number for the specified depth.
:rtype: :class:`int` or :class:`~numpy.ndarray` (dtype = :class:`int`,
shape equivalent to ``depth``)
"""
depth = np.atleast_1d(depth)
layer = np.logical_and(
self.layers['top_depth'][np.newaxis, :] <= depth[:, np.newaxis],
depth[:, np.newaxis] < self.layers['bot_depth'][np.newaxis, :])
layer = np.where(layer)[-1]
if len(layer):
return layer
else:
raise LookupError("No such layer.")
[docs] def evaluate_above(self, depth, prop):
"""
Return the value of the given material property at the given depth(s).
Note this returns the value at the bottom of the upper layer if the
depth happens to be at a layer boundary.
.. seealso:: :meth:`evaluate_below`
:param depth: The depth to find, in km.
:type depth: :class:`float` or :class:`~numpy.ndarray`
: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 (in g/cm^3)
:type prop: str
:returns: The value of the given material property
:rtype: :class:`float` or :class:`~numpy.ndarray` (dtype =
:class:`float`, shape equivalent to ``depth``)
"""
layer = self.layers[self.layer_number_above(depth)]
return evaluate_velocity_at(layer, depth, prop)
[docs] def evaluate_below(self, depth, prop):
"""
Return the value of the given material property at the given depth(s).
Note this returns the value at the top of the lower layer if the depth
happens to be at a layer boundary.
.. seealso:: :meth:`evaluate_below`
:param depth: The depth to find, in km.
:type depth: :class:`float` or :class:`~numpy.ndarray`
: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 (in g/cm^3)
:type prop: str
:returns: the value of the given material property
:rtype: :class:`float` or :class:`~numpy.ndarray` (dtype =
:class:`float`, shape equivalent to ``depth``)
"""
layer = self.layers[self.layer_number_below(depth)]
return evaluate_velocity_at(layer, depth, prop)
[docs] def depth_at_top(self, layer):
"""
Return the depth at the top of the given layer.
.. seealso:: :meth:`depth_at_bottom`
:param layer: The layer number
:type layer: :class:`int` or :class:`~numpy.ndarray`
:returns: The depth of the top, in km.
:rtype: :class:`float` or :class:`~numpy.ndarray` (dtype =
:class:`float`, shape equivalent to ``layer``)
"""
layer = self.layers[layer]
return layer['top_depth']
[docs] def depth_at_bottom(self, layer):
"""
Return the depth at the bottom of the given layer.
.. seealso:: :meth:`depth_at_top`
:param layer: The layer number
:type layer: :class:`int` or :class:`~numpy.ndarray`
:returns: The depth of the bottom, in km.
:rtype: :class:`float` or :class:`~numpy.ndarray` (dtype =
:class:`float`, shape equivalent to ``layer``)
"""
layer = self.layers[layer]
return layer['bot_depth']
[docs] def validate(self):
"""
Perform internal consistency checks on the velocity model.
:returns: True if the model is consistent.
:raises ValueError: If the model is inconsistent.
"""
# Is radius_of_planet positive?
if self.radius_of_planet <= 0.0:
raise ValueError("Radius of the planet is not positive: %f" % (
self.radius_of_planet, ))
# Is moho_depth non-negative?
if self.moho_depth < 0.0:
raise ValueError("moho_depth is not non-negative: %f" % (
self.moho_depth, ))
# Is cmb_depth >= moho_depth?
if self.cmb_depth < self.moho_depth:
raise ValueError("cmb_depth (%f) < moho_depth (%f)" % (
self.cmb_depth,
self.moho_depth))
# Is cmb_depth non-negative?
if self.cmb_depth < 0.0:
raise ValueError("cmb_depth is negative: %f" % (
self.cmb_depth, ))
# Is iocb_depth >= cmb_depth?
if self.iocb_depth < self.cmb_depth:
raise ValueError("iocb_depth (%f) < cmb_depth (%f)" % (
self.iocb_depth,
self.cmb_depth))
# Is iocb_depth non-negative?
if self.iocb_depth < 0.0:
raise ValueError("iocb_depth is negative: %f" % (
self.iocb_depth, ))
# Is min_radius non-negative?
if self.min_radius < 0.0:
raise ValueError("min_radius is not non-negative: %f " % (
self.min_radius, ))
# Is max_radius non-negative?
if self.max_radius <= 0.0:
raise ValueError("max_radius is not positive: %f" % (
self.max_radius, ))
# Is max_radius > min_radius?
if self.max_radius <= self.min_radius:
raise ValueError("max_radius (%f) <= min_radius (%f)" % (
self.max_radius,
self.min_radius))
# Check for gaps
gaps = self.layers[:-1]['bot_depth'] != self.layers[1:]['top_depth']
gaps = np.where(gaps)[0]
if gaps.size:
msg = ("There is a gap in the velocity model between layer(s) %s "
"and %s.\n%s" % (gaps, gaps + 1, self.layers[gaps]))
raise ValueError(msg)
# Check for zero thickness
probs = self.layers['bot_depth'] == self.layers['top_depth']
probs = np.where(probs)[0]
if probs.size:
msg = ("There is a zero thickness layer in the velocity model at "
"layer(s) %s\n%s" % (probs, self.layers[probs]))
raise ValueError(msg)
# Check for negative P velocity
probs = np.logical_or(self.layers['top_p_velocity'] <= 0.0,
self.layers['bot_p_velocity'] <= 0.0)
probs = np.where(probs)[0]
if probs.size:
msg = ("There is a negative P velocity layer in the velocity "
"model at layer(s) %s\n%s" % (probs, self.layers[probs]))
raise ValueError(msg)
# Check for negative S velocity
probs = np.logical_or(self.layers['top_s_velocity'] < 0.0,
self.layers['bot_s_velocity'] < 0.0)
probs = np.where(probs)[0]
if probs.size:
msg = ("There is a negative S velocity layer in the velocity "
"model at layer(s) %s\n%s" % (probs, self.layers[probs]))
raise ValueError(msg)
# Check for zero P velocity
probs = np.logical_or(
np.logical_and(self.layers['top_p_velocity'] != 0.0,
self.layers['bot_p_velocity'] == 0.0),
np.logical_and(self.layers['top_p_velocity'] == 0.0,
self.layers['bot_p_velocity'] != 0.0))
probs = np.where(probs)[0]
if probs.size:
msg = ("There is a layer that goes to zero P velocity (top or "
"bottom) without a discontinuity in the velocity model at "
"layer(s) %s\nThis would cause a divide by zero within "
"this depth range. Try making the velocity small, followed "
"by a discontinuity to zero velocity.\n%s")
raise ValueError(msg % (probs, self.layers[probs]))
# Check for negative S velocity
probs = np.logical_or(
np.logical_and(self.layers['top_s_velocity'] != 0.0,
self.layers['bot_s_velocity'] == 0.0),
np.logical_and(self.layers['top_s_velocity'] == 0.0,
self.layers['bot_s_velocity'] != 0.0))
# This warning will always pop up for the top layer even
# in IASP91, therefore ignore it.
probs = np.logical_and(probs, self.layers['top_depth'] != 0)
probs = np.where(probs)[0]
if probs.size:
msg = ("There is a layer that goes to zero S velocity (top or "
"bottom) without a discontinuity in the velocity model at "
"layer(s) %s\nThis would cause a divide by zero within "
"this depth range. Try making the velocity small, followed "
"by a discontinuity to zero velocity.\n%s")
raise ValueError(msg % (probs, self.layers[probs]))
return True
[docs] def __str__(self):
desc = "model_name=" + str(self.model_name) + "\n" + \
"\n radius_of_planet=" + str(
self.radius_of_planet) + "\n moho_depth=" + \
str(self.moho_depth) + \
"\n cmb_depth=" + str(self.cmb_depth) + "\n iocb_depth=" + \
str(self.iocb_depth) + "\n min_radius=" + str(
self.min_radius) + "\n max_radius=" + str(self.max_radius) + \
"\n spherical=" + str(self.is_spherical)
return desc
[docs] @classmethod
def read_velocity_file(cls, filename):
"""
Read in a velocity file.
The type of file is determined from the file name (changed from the
Java!).
:param filename: The name of the file to read.
:type filename: str
:raises NotImplementedError: If the file extension is ``.nd``.
:raises ValueError: If the file extension is not ``.tvel``.
"""
if filename.endswith(".nd"):
v_mod = cls.read_nd_file(filename)
elif filename.endswith(".tvel"):
v_mod = cls.read_tvel_file(filename)
else:
raise ValueError("File type could not be determined, please "
"rename your file to end with .tvel or .nd")
v_mod.fix_discontinuity_depths()
return v_mod
[docs] @classmethod
def read_tvel_file(cls, filename):
"""
Read in a velocity model from a "tvel" ASCII text file.
The name of the model file for model "modelname" should be
"modelname.tvel". The format of the file is::
comment line - generally info about the P velocity model
comment line - generally info about the S velocity model
depth pVel sVel Density
depth pVel sVel Density
The velocities are assumed to be linear between sample points. Because
this type of model file doesn't give complete information we make the
following assumptions:
* ``modelname`` - from the filename, with ".tvel" dropped if present
* ``radius_of_planet`` - the largest depth in the model
* ``meanDensity`` - 5517.0
* ``G`` - 6.67e-11
Comments using ``#`` are also allowed.
:param filename: The name of the file to read.
:type filename: str
:raises ValueError: If model file is in error.
"""
# Read all lines in the file. Each Layer needs top and bottom values,
# i.e. info from two lines.
data = np.genfromtxt(filename, skip_header=2, comments='#')
# Check if density is present.
if data.shape[1] < 4:
raise ValueError("Top density not specified.")
# Check that relative speed are sane.
mask = data[:, 2] > data[:, 1]
if np.any(mask):
raise ValueError(
"S velocity is greater than the P velocity\n" +
str(data[mask]))
layers = np.empty(data.shape[0] - 1, dtype=VelocityLayer)
layers['top_depth'] = data[:-1, 0]
layers['bot_depth'] = data[1:, 0]
layers['top_p_velocity'] = data[:-1, 1]
layers['bot_p_velocity'] = data[1:, 1]
layers['top_s_velocity'] = data[:-1, 2]
layers['bot_s_velocity'] = data[1:, 2]
layers['top_density'] = data[:-1, 3]
layers['bot_density'] = data[1:, 3]
# We do not at present support varying attenuation
layers['top_qp'].fill(_DEFAULT_VALUES["qp"])
layers['bot_qp'].fill(_DEFAULT_VALUES["qp"])
layers['top_qs'].fill(_DEFAULT_VALUES["qs"])
layers['bot_qs'].fill(_DEFAULT_VALUES["qs"])
# Don't use zero thickness layers; first order discontinuities are
# taken care of by storing top and bottom depths.
mask = layers['top_depth'] == layers['bot_depth']
layers = layers[~mask]
# tvel files cannot have named discontinuities so it is really only
# useful for Earth models. The exact radius is derived from the tvel
# file, the depth of discontinuities are fixed.
min_radius = 0
max_radius = data[-1, 0]
radius_of_planet = data[-1, 0]
model_name = Path(Path(filename).name[0]).suffix
return VelocityModel(
model_name=model_name,
radius_of_planet=radius_of_planet,
min_radius=min_radius,
max_radius=max_radius,
moho_depth=_DEFAULT_VALUES["default_moho"],
cmb_depth=_DEFAULT_VALUES["default_cmb"],
iocb_depth=_DEFAULT_VALUES["default_iocb"],
is_spherical=True,
layers=layers)
[docs] @classmethod
def read_nd_file(cls, filename):
"""
Read in a velocity model from a "nd" ASCII text file.
This method reads in a velocity model from a "nd" ASCII text file, the
format used by Xgbm. The name of the model file for model "modelname"
should be "modelname.nd".
The format of the file is:
depth pVel sVel Density Qp Qs
depth pVel sVel Density Qp Qs
. . . with each major boundary separated with a line with "mantle",
"outer-core" or "inner-core". "moho", "cmb" and "icocb" are allowed
as synonyms respectively.
This feature makes phase interpretation much easier to
code. Also, as they are not needed for travel time calculations, the
density, Qp and Qs may be omitted.
The velocities are assumed to be linear between sample points. Because
this type of model file doesn't give complete information we make the
following assumptions:
modelname - from the filename, with ".nd" dropped, if present
radius_of_planet - the largest depth in the model
Comments are allowed. # signifies that the rest of the
line is a comment. If # is the first character in a line, the line is
ignored
:param filename: The name of the file to read.
:type filename: str
:raises ValueError: If model file is in error.
"""
moho_depth = _DEFAULT_VALUES["default_moho"]
cmb_depth = _DEFAULT_VALUES["default_cmb"]
iocb_depth = _DEFAULT_VALUES["default_iocb"]
# Read all lines from file to enable identifying top and bottom values
# for each layer and find named discontinuities if present
with open(filename) as modfile:
lines = modfile.readlines()
# Loop through to fill data array and locate named discontinuities
ii = 0
for line in lines:
# Strip off anything after '#'
line = line.split('#')[0].split()
if not line: # Skip empty or comment lines
continue
if ii == 0:
data = []
for item in line:
data.append(float(item))
data = np.array(data)
ii = ii + 1
else:
if len(line) == 1: # Named discontinuity
dc_name = line[0].lower()
if dc_name in ("mantle", "moho"):
moho_depth = data[ii - 1, 0]
elif dc_name in ("outer-core", "cmb"):
cmb_depth = data[ii - 1, 0]
elif dc_name in ("inner-core", "iocb"):
iocb_depth = data[ii - 1, 0]
else:
raise ValueError("Unrecognized discontinuity name: " +
str(line[0]))
else:
row = []
for item in line:
row.append(float(item))
data = np.vstack((data, np.array(row)))
ii = ii + 1
# Check if density is present.
if data.shape[1] < 4:
raise ValueError("Top density not specified.")
# Check that relative speed are sane.
mask = data[:, 2] > data[:, 1]
if np.any(mask):
raise ValueError(
"S velocity is greater than the P velocity\n" +
str(data[mask]))
layers = np.empty(data.shape[0] - 1, dtype=VelocityLayer)
layers['top_depth'] = data[:-1, 0]
layers['bot_depth'] = data[1:, 0]
layers['top_p_velocity'] = data[:-1, 1]
layers['bot_p_velocity'] = data[1:, 1]
layers['top_s_velocity'] = data[:-1, 2]
layers['bot_s_velocity'] = data[1:, 2]
layers['top_density'] = data[:-1, 3]
layers['bot_density'] = data[1:, 3]
# We do not at present support varying attenuation
layers['top_qp'].fill(_DEFAULT_VALUES["qp"])
layers['bot_qp'].fill(_DEFAULT_VALUES["qp"])
layers['top_qs'].fill(_DEFAULT_VALUES["qs"])
layers['bot_qs'].fill(_DEFAULT_VALUES["qs"])
# Don't use zero thickness layers; first order discontinuities are
# taken care of by storing top and bottom depths.
mask = layers['top_depth'] == layers['bot_depth']
layers = layers[~mask]
radius_of_planet = data[-1, 0]
max_radius = data[-1, 0]
model_name = Path(Path(filename).name).suffix[0]
# I assume that this is a whole planet model
# so the maximum depth == maximum radius == planet radius.
return VelocityModel(
model_name=model_name,
radius_of_planet=radius_of_planet,
min_radius=0, max_radius=max_radius,
moho_depth=moho_depth, cmb_depth=cmb_depth, iocb_depth=iocb_depth,
is_spherical=True, layers=layers)
[docs] def fix_discontinuity_depths(self):
"""
Reset depths of major discontinuities.
The depths are set to match those existing in the input velocity model.
The initial values are set such that if there is no discontinuity
within the top 100 km then the Moho is set to 0.0. Similarly, if there
are no discontinuities at all then the CMB is set to the radius of the
planet. Similarly for the IOCB, except it must be a fluid to solid
boundary and deeper than 100 km to avoid problems with shallower fluid
layers, e.g., oceans.
"""
moho_min = 65.0
cmb_min = self.radius_of_planet
iocb_min = self.radius_of_planet - 100.0
change_made = False
temp_moho_depth = 0.0
temp_cmb_depth = self.radius_of_planet
temp_iocb_depth = self.radius_of_planet
above = self.layers[:-1]
below = self.layers[1:]
# Only look for discontinuities:
mask = np.logical_or(
above['bot_p_velocity'] != below['top_p_velocity'],
above['bot_s_velocity'] != below['top_s_velocity'])
# Find discontinuity closest to current Moho
moho_diff = np.abs(self.moho_depth - above['bot_depth'])
moho_diff[~mask] = moho_min
moho = np.argmin(moho_diff)
if moho_diff[moho] < moho_min:
temp_moho_depth = above[moho]['bot_depth']
# Find discontinuity closest to current CMB
cmb_diff = np.abs(self.cmb_depth - above['bot_depth'])
cmb_diff[~mask] = cmb_min
cmb = np.argmin(cmb_diff)
# don't set cmb to be same as moho, unless fixed
if (cmb_diff[cmb] < cmb_min
and above[cmb]['bot_depth'] > temp_moho_depth):
temp_cmb_depth = above[cmb]['bot_depth']
cmb_min = np.abs(self.cmb_depth - above[cmb]['bot_depth'])
# Find discontinuity closest to current IOCB
iocb_diff = self.iocb_depth - above['bot_depth']
iocb_diff[~mask] = iocb_min
# IOCB must transition from S==0 to S!=0
iocb_diff[above['bot_s_velocity'] != 0.0] = iocb_min
iocb_diff[below['top_s_velocity'] <= 0.0] = iocb_min
iocb = np.argmin(iocb_diff)
if iocb_diff[iocb] < iocb_min:
temp_iocb_depth = above[iocb]['bot_depth']
iocb_min = np.abs(self.iocb_depth - above[iocb]['bot_depth'])
# may need to set named discon to center of planet
# in case of degenerate model without a core
# final is bottommost layer, so
# final['bot_depth'] == radius of planet
final = below[-1]
if (final['bot_depth'] > temp_moho_depth and
np.abs(self.cmb_depth - final['bot_depth']) < cmb_min):
temp_cmb_depth = final['bot_depth']
cmb_min = np.abs(self.cmb_depth - final['bot_depth'])
# iocb is either below a fluid layer or is equal to cmb
# or center of planet
if (final['bot_depth'] == temp_cmb_depth or
(final['bot_s_velocity'] == 0.0 and
temp_iocb_depth == temp_cmb_depth)):
temp_iocb_depth = final['bot_depth']
iocb_min = np.abs(self.iocb_depth - final['bot_depth'])
if self.moho_depth != temp_moho_depth \
or self.cmb_depth != temp_cmb_depth \
or self.iocb_depth != temp_iocb_depth:
change_made = True
self.moho_depth = temp_moho_depth
self.cmb_depth = temp_cmb_depth
self.iocb_depth = (temp_iocb_depth
if temp_cmb_depth != temp_iocb_depth
else self.radius_of_planet)
return change_made