Source code for openquake.hazardlib.gsim.convertito_2012

# The Hazard Library
# Copyright (C) 2014 GEM Foundation
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
"""
Module exports :class:'ConvertitoEtAl2012Geysers'
"""
from __future__ import division
import numpy as np
# standard acceleration of gravity in m/s**2
from scipy.constants import g


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


class ConvertitoEtAl2012Geysers(GMPE):
    """
    Implements the PGA GMPE for Induced Seismicity in the Geysers Geothermal
    field, published in Convertito, V., Maercklin, N., Sharma, N., and Zollo,
    A. (2012) From Induced Seismicity to Direct Time-Dependent Seismic
    Hazard. Bulletin of the Seismological Society of America, 102(6),
    2563 - 2573
    """
    #: The GMPE is derived from induced earthquakes in the Geysers Geothermal
    #: field
    DEFINED_FOR_TECTONIC_REGION_TYPE = const.TRT.GEOTHERMAL

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

    #: Supported intensity measure component is the larger of two components
    DEFINED_FOR_INTENSITY_MEASURE_COMPONENT = \
        const.IMC.GREATER_OF_TWO_HORIZONTAL

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

    #: Required site parameters. The GMPE was developed for two site conditions
    #: "with" and "without" site effect. No information is given regarding
    #: the soil conditions, so we assume "with site effect" to correspond
    #: to NEHRP Classes C, D or E (i.e. Vs30 < 760), and "without site effect"
    #: to corresponse to NEHRP Classes A and B (i.e. Vs30 >= 760)
    REQUIRES_SITES_PARAMETERS = set(('vs30',))

    #: Required rupture parameters are magnitude
    REQUIRES_RUPTURE_PARAMETERS = set(('mag', ))

    #: Required distance measure is hypocentral distance
    REQUIRES_DISTANCES = set(('rhypo',))

    #: GMPE not tested against independent implementation so raise
    #: not verified warning
    non_verified = True

    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_magnitude_scaling(C, rup.mag) +
                self._compute_distance_scaling(C, dists.rhypo) +
                self._compute_site_scaling(C, sites.vs30))
        # Original GMPE returns log acceleration in m/s/s
        # Converts to natural logarithm of g
        mean = np.log(np.exp(mean) / g)
        stddevs = self._compute_stddevs(C, dists.rhypo.shape, stddev_types)
        return mean, stddevs

    def _compute_magnitude_scaling(self, C, mag):
        """
        Returns the magnitude scaling term
        """
        return C["a"] + (C["b"] * mag)

    def _compute_distance_scaling(self, C, rhypo):
        """
        Returns the distance scaling term accounting for geometric and
        anelastic attenuation
        """
        return C["c"] * np.log(np.sqrt((rhypo ** 2.) + (C["h"] ** 2.))) +\
            (C["d"] * rhypo)

    def _compute_site_scaling(self, C, vs30):
        """
        Returns the site scaling term as a simple coefficient
        """
        site_term = np.zeros(len(vs30), dtype=float)
        # For soil sites add on the site coefficient
        site_term[vs30 < 760.0] = C["e"]
        return site_term

    def _compute_stddevs(self, C, num_sites, stddev_types):
        """
        Return total standard deviation.
        """
        stddevs = []
        for _ in stddev_types:
            stddevs.append(np.zeros(num_sites) + C["sigma"])
        return stddevs

    COEFFS = CoeffsTable(sa_damping=5, table="""
    IMT        a      b       c      d    h      e  sigma
    pga   -2.268  1.276  -3.528  0.053  3.5  0.218  0.324
    """)