Source code for openquake.hazardlib.gsim.fukushima_tanaka_1990

# -*- coding: utf-8 -*-
# vim: tabstop=4 shiftwidth=4 softtabstop=4
#
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#
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"""
Module exports :class:'FukushimaTanaka1990' and :class:
'FukushimaTanakaSite1990'
"""
import numpy as np
from scipy.constants import g


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


def _compute_distance_scaling(C, rrup, mag):
    """
    Returns the distance scaling term
    """
    rscale1 = rrup + C["c2"] * (10.0 ** (C["c3"] * mag))
    return -np.log10(rscale1) - (C["c4"] * rrup)


def _compute_magnitude_scaling(C, mag):
    """
    Returns the magnitude scaling term
    """
    return C["c1"] * mag + C["c5"]


def _compute_site_scaling(vs30, mean):
    """
    Scales the ground motions by increasing 40 % on NEHRP class D/E sites,
    and decreasing by 40 % on NEHRP class A/B sites
    """
    site_factor = np.ones(len(vs30), dtype=float)
    idx = vs30 <= 360.
    site_factor[idx] = 1.4
    idx = vs30 > 760.0
    site_factor[idx] = 0.6
    return np.log(np.exp(mean) * site_factor)


[docs]class FukushimaTanaka1990(GMPE): """ Implements the PGA GMPE of Fukushima and Tanaka (1990) Fukushima, Y. and Tanaka, T. (1990) A New Attenuation Relation for Peak Horizontal Acceleration of Strong Earthquake Ground Motion in Japan. Bulletin of the Seismological Society of America, 80(4), 757 - 783 """ #: The GMPE is derived from shallow earthquakes in California and Japan DEFINED_FOR_TECTONIC_REGION_TYPE = const.TRT.ACTIVE_SHALLOW_CRUST #: Supported intensity measure types are peak ground acceleration DEFINED_FOR_INTENSITY_MEASURE_TYPES = {PGA} #: Supported intensity measure component is the average horizontal #: component #: :attr:`openquake.hazardlib.const.IMC.AVERAGE_HORIZONTAL`, DEFINED_FOR_INTENSITY_MEASURE_COMPONENT = const.IMC.AVERAGE_HORIZONTAL #: Supported standard deviation types is total. DEFINED_FOR_STANDARD_DEVIATION_TYPES = {const.StdDev.TOTAL} #: Required site parameters. The GMPE was developed for an ''average'' #: site conditions. The authors specify that for rock sites the #: values should be lowered by 40 % and for soil site they should be #: raised by 40 %. For greatest consistencty the site condition is #: neglected currently but a site-dependent GMPE may be implemented #: inside a subclass. REQUIRES_SITES_PARAMETERS = set() #: Required rupture parameters are magnitude REQUIRES_RUPTURE_PARAMETERS = {'mag'} #: Required distance measure is rupture distance REQUIRES_DISTANCES = {'rrup'}
[docs] def compute(self, ctx, imts, mean, sig, tau, phi): """ See :meth:`superclass method <.base.GroundShakingIntensityModel.compute>` for spec of input and result values. """ for m, imt in enumerate(imts): C = self.COEFFS[imt] imean = (_compute_magnitude_scaling(C, ctx.mag) + _compute_distance_scaling(C, ctx.rrup, ctx.mag)) # Original GMPE returns log10 acceleration in cm/s/s # Converts to natural logarithm of g mean[m] = np.log((10.0 ** (imean - 2.0)) / g) if self.REQUIRES_SITES_PARAMETERS: # in subclass mean[m] = _compute_site_scaling(ctx.vs30, mean[m]) # Convert from common logarithm to natural logarithm sig[m] = np.log(10 ** C['sigma'])
COEFFS = CoeffsTable(sa_damping=5, table=""" IMT c1 c2 c3 c4 c5 sigma pga 0.41 0.032 0.41 0.0034 1.30 0.21 """)
[docs]class FukushimaTanakaSite1990(FukushimaTanaka1990): """ Implements the Fukushima and Tanaka (1990) model correcting for site class. The authors specify that the ground motions should be raised by 40 % on soft soil sites and reduced by 40 % on rock sites. The specific site classification is not known, so it is assumed that in this context "average" site conditions refer to NEHRP C, rock conditions to NEHRP A and B, and soft soil conditions to NEHRP D and E """ #: Input sites as vs30 although only three classes considered REQUIRES_SITES_PARAMETERS = {"vs30"}