Source code for openquake.hazardlib.gsim.munson_thurber_1997

# -*- coding: utf-8 -*-
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"""
Module exports :class:`MunsonThurber1997`
               :class:`MunsonThurber1997Vector`.
"""
import numpy as np

from openquake.hazardlib.gsim.base import GMPE
from openquake.hazardlib import const
from openquake.hazardlib.imt import PGA


class MunsonThurber1997(GMPE):
    """
    Implements GMPE developed by Clifford G. Munson and Clifford H. Thurber
    and published as "Analysis of the Attenuation of Strong Ground Motion
    on the Island of Hawaii" (1997, Bulletin of the Seismological Society
    of America, Vol. 87, No. 4, pp. 954-960).
    """

    #: Supported tectonic region type is volcanic,
    #: see paragraph 'Introduction', page 99.
    DEFINED_FOR_TECTONIC_REGION_TYPE = const.TRT.VOLCANIC

    #: Supported intensity measure types is spectral acceleration,
    #: see table 3, pag. 110
    DEFINED_FOR_INTENSITY_MEASURE_TYPES = set([PGA])

    #: Supported intensity measure component is maximum horizontal
    #: :attr:`~openquake.hazardlib.const.IMC.VECTORIAL`,
    DEFINED_FOR_INTENSITY_MEASURE_COMPONENT = const.IMC.HORIZONTAL

    #: Supported standard deviation type is total
    DEFINED_FOR_STANDARD_DEVIATION_TYPES = set([
        const.StdDev.TOTAL
    ])

    #: Required site parameters is Vs30.
    #: See paragraph 'Predictor Variables', pag 103
    REQUIRES_SITES_PARAMETERS = set(('vs30', ))

    #: Required rupture parameter is magnitude
    REQUIRES_RUPTURE_PARAMETERS = set(('mag', ))

    #: Required distance measure is hypocentral distance
    #: see page 18 in Atkinson and Boore's manuscript
    REQUIRES_DISTANCES = set(('rjb', ))

    def get_mean_and_stddevs(self, sites, rup, dists, imt, stddev_types):
        """
        See :meth:`superclass method
        <.base.GroundShakingIntensityModel.get_mean_and_stddevs>`
        for spec of input and result values.
        """

        # Distance term
        R = np.sqrt(dists.rjb ** 2 + 11.29 ** 2)

        # Magnitude term
        M = rup.mag - 6

        # Site term only distinguishes between lava and ash;
        # since ash sites have Vs30 in the range 60-200m/s,
        # we use this upper value as class separator
        S = np.zeros(R.shape)
        S[sites.vs30 <= 200] = 1

        # Mean ground motion (log10)
        mean = (0.518 + 0.387*M - np.log10(R) - 0.00256*R + 0.335*S)

        # Converting to natural log
        mean /= np.log10(np.e)

        # Check for standard deviation type
        assert all(stddev_type in self.DEFINED_FOR_STANDARD_DEVIATION_TYPES
                   for stddev_type in stddev_types)

        # Constant (total) standard deviation
        stddevs = [0.237/np.log10(np.e) + np.zeros(R.shape)]

        return mean, stddevs


class MunsonThurber1997Vector(MunsonThurber1997):
    """
    Modification of the original base class to correct mean ground motion
    to geometric mean of horizontal components (Beyer and Bommer, 2006)
    """

    #: Supported intensity measure component is geometric mean of horizontal
    #: :attr:`~openquake.hazardlib.const.IMC.VECTORIAL`,
    DEFINED_FOR_INTENSITY_MEASURE_COMPONENT = const.IMC.VECTORIAL

    def get_mean_and_stddevs(self, sites, rup, dists, imt, stddev_types):
        mean, stddevs = super().get_mean_and_stddevs(sites, rup, dists,
                                                     imt, stddev_types)

        # Conversion to geometric mean of horizontal components
        # using the coefficient in Beyer and Bommer, 2006
        mean += np.log(1.1)

        return mean, stddevs