Source code for openquake.hazardlib.gsim.geomatrix_1993

# -*- coding: utf-8 -*-
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#
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"""
Module exports :class:`Geomatrix1993SSlabNSHMP2008`.
"""
from __future__ import division

import numpy as np

from openquake.hazardlib.gsim.base import CoeffsTable, GMPE
from openquake.hazardlib import const
from openquake.hazardlib.imt import PGA, SA


class Geomatrix1993SSlabNSHMP2008(GMPE):
    """
    Implements GMPE for subduction intraslab events developed by Geomatrix
    Consultants, Inc., 1993, "Seismic margin earthquake for the Trojan site:
    Final unpublished report prepared for Portland General Electric Trojan
    Nuclear Plant", Ranier, Oregon.

    This class implements the equation as coded in the subroutine ``getGeom``
    in the ``hazgridXnga2.f`` Fortran code available at:
    http://earthquake.usgs.gov/hazards/products/conterminous/2008/software/

    Coefficients are given for the B/C site conditions.
    """
    #: Supported tectonic region type is subduction intraslab
    DEFINED_FOR_TECTONIC_REGION_TYPE = const.TRT.SUBDUCTION_INTRASLAB

    #: Supported intensity measure types are spectral acceleration,
    #: and peak ground acceleration
    DEFINED_FOR_INTENSITY_MEASURE_TYPES = set([
        PGA,
        SA
    ])

    #: Supported intensity measure component is the geometric mean of
    #: two horizontal components
    DEFINED_FOR_INTENSITY_MEASURE_COMPONENT = const.IMC.AVERAGE_HORIZONTAL

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

    #: No site parameters required
    REQUIRES_SITES_PARAMETERS = set()

    #: Required rupture parameters are magnitude and top of rupture depth
    REQUIRES_RUPTURE_PARAMETERS = set(('mag', 'ztor'))

    #: Required distance measure is rrup (closest distance to rupture)
    REQUIRES_DISTANCES = set(('rrup', ))

    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.
        """
        assert all(stddev_type in self.DEFINED_FOR_STANDARD_DEVIATION_TYPES
                   for stddev_type in stddev_types)

        C = self.COEFFS[imt]

        mean = self._compute_mean(C, rup.mag, rup.ztor, dists.rrup)
        stddevs = self._compute_stddevs(
            C, rup.mag, dists.rrup.shape, stddev_types
        )

        return mean, stddevs

    def _compute_mean(self, C, mag, ztor, rrup):
        """
        Compute mean value as in ``subroutine getGeom`` in ``hazgridXnga2.f``
        """
        gc0 = 0.2418
        ci = 0.3846
        gch = 0.00607
        g4 = 1.7818
        ge = 0.554
        gm = 1.414

        mean = (
            gc0 + ci + ztor * gch + C['gc1'] +
            gm * mag + C['gc2'] * (10 - mag) ** 3 +
            C['gc3'] * np.log(rrup + g4 * np.exp(ge * mag))
        )

        return mean

    def _compute_stddevs(self, C, mag, num_sites, stddev_types):
        """
        Return total standard deviation.
        """
        std_total = C['gc4'] + C['gc5'] * np.minimum(8., mag)

        stddevs = []
        for _ in stddev_types:
            stddevs.append(np.zeros(num_sites) + std_total)

        return stddevs

    #: Coefficient table obtained from coefficient arrays and variables
    #: defined in subroutine getGeom in hazgridXnga2.f
    COEFFS = CoeffsTable(sa_damping=5, table="""\
    IMT   gc1      gc2      gc3      gc4    gc5
    pga   0.0      0.0     -2.556    1.45  -0.1
    0.1   1.1880  -0.0011  -2.6550   1.45  -0.1
    0.2   0.722   -0.0027  -2.528    1.45  -0.1
    0.3   0.246   -0.0036  -2.454    1.45  -0.1
    0.5  -0.4     -0.0048  -2.36     1.45  -0.1
    1.0  -1.736   -0.0064  -2.234    1.45  -0.1
    2.0  -3.3280  -0.0080  -2.107    1.55  -0.1
    3.0  -4.511   -0.0089  -2.033    1.65  -0.1
    """)