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"""
Module :mod:`openquake.hmtk.seismicity.max_magnitude.kijko_sellevol` defines
the Kijko & Sellevol algorithm for maximum magnitude
"""
import warnings
import numpy as np
from math import fabs
from scipy.integrate import quad
from openquake.hmtk.seismicity.max_magnitude.base import (
BaseMaximumMagnitude,
MAX_MAGNITUDE_METHODS,
_get_observed_mmax,
_get_magnitude_vector_properties,
)
[docs]def check_config(config, data):
"""Checks that the config file contains all required parameters
:param dict config:
Configuration file
:returns:
Configuration file with all correct parameters
"""
if "tolerance" not in config.keys() or not config["tolerance"]:
config["tolerance"] = 1e-5
if not config.get("maximum_iterations", None):
config["maximum_iterations"] = 1000
mmin_obs = np.min(data["magnitude"])
if config.get("input_mmin", 0) < mmin_obs:
config["input_mmin"] = mmin_obs
if fabs(config["b-value"]) < 1e-7:
config["b-value"] = 1e-7
return config
[docs]@MAX_MAGNITUDE_METHODS.add(
"get_mmax",
**{
"input_mmin": lambda cat: np.min(cat.data["magnitude"]),
"input_mmax": lambda cat: cat.data["magnitude"][
np.argmax(cat.data["magnitude"])
],
"input_mmax_uncertainty": lambda cat: cat.get_observed_mmax_sigma(0.2),
"b-value": 1e-7,
"maximum_iterations": 1000,
"tolerance": 1e-5,
},
)
class KijkoSellevolFixedb(BaseMaximumMagnitude):
"""
Implements Kijko and Sellevol estimator for maximim magnitude assuming
a fixed b-value. Coded from description in Kijko (2004):
Kijko, A. (2004), ..., Pure & Applied Geophysics,
"""
[docs] def get_mmax(self, catalogue, config):
"""
Calculates Maximum magnitude
:param catalogue:
Earthquake catalogue as instance of :class:
openquake.hmtk.seismicity.catalogue.Catalogue
:param dict config:
Configuration file for algorithm, contains the attributes:
* 'b-value': b-value (positive float)
* 'input_mmin': Minimum magnitude for integral (if less than
minimum observed magnitude, will be overwritten by
minimum observed magnitude)
* 'tolerance': Tolerance of stabilising of iterator
* 'maximum_interations': Maximum number of iterations
:returns: **mmax** Maximum magnitude and **mmax_sig** corresponding
uncertainty
"""
config = check_config(config, catalogue.data)
obsmax, obsmaxsig = _get_observed_mmax(catalogue.data, config)
mmin = config["input_mmin"]
beta = config["b-value"] * np.log(10.0)
neq, mmin = _get_magnitude_vector_properties(catalogue.data, config)
mmax = np.copy(obsmax)
d_t = np.inf
iterator = 0
print(mmin, mmax, neq, beta)
while d_t > config["tolerance"]:
delta = quad(
self._ks_intfunc, mmin, mmax, args=(neq, mmax, mmin, beta)
)[0]
tmmax = obsmax + delta
d_t = np.abs(tmmax - mmax)
mmax = np.copy(tmmax)
iterator += 1
if iterator > config["maximum_iterations"]:
print(
"Kijko-Sellevol estimator reached "
"maximum # of iterations"
)
d_t = -np.inf
return mmax.item(), np.sqrt(obsmaxsig**2.0 + delta**2.0)
def _ks_intfunc(self, mval, neq, mmax, mmin, beta):
"""Integral function inside Kijko-Sellevol estimator
(Eq. 6 in Kijko, 2004)
:param float mval:
Magnitude value
:param float neq:
Number of earthquakes
:param float mmax:
Maximum Magnitude
:param float mmin:
Minimum Magnitude
:param float beta:
Beta-value of the distribution
:returns:
Integrand of Kijko-Sellevol estimator
"""
if mmin >= mmax:
raise ValueError(
"Maximum magnitude smaller than minimum magnitude"
" in Kijko & Sellevol (Fixed-b) integral"
)
func1 = 1.0 - np.exp(-beta * (mval - mmin))
if np.fabs(beta) > 1e-3:
func1 = (func1 / (1.0 - np.exp(-beta * (mmax - mmin)))) ** neq
else:
warnings.warn("beta is lower or equal to 0", RuntimeWarning)
return func1
