Source code for openquake.hazardlib.gsim.fukushima_tanaka_1990

# -*- coding: utf-8 -*-
# vim: tabstop=4 shiftwidth=4 softtabstop=4
#
# Copyright (C) 2014-2017 GEM Foundation
#
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"""
Module exports :class:'FukushimaTanaka1990' and :class:
'FukushimaTanakaSite1990'
"""
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


[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 = set([ 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 = set([ 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 = set(('mag', )) #: Required distance measure is rupture distance REQUIRES_DISTANCES = set(('rrup',))
[docs] 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] imean = (self._compute_magnitude_scaling(C, rup.mag) + self._compute_distance_scaling(C, dists.rrup, rup.mag)) # Original GMPE returns log10 acceleration in cm/s/s # Converts to natural logarithm of g mean = np.log((10.0 ** (imean - 2.0)) / g) istddevs = self._compute_stddevs( C, dists.rrup.shape, stddev_types ) # Convert from common logarithm to natural logarithm stddevs = np.log(10 ** np.array(istddevs)) return mean, stddevs
def _compute_magnitude_scaling(self, C, mag): """ Returns the magnitude scaling term """ return C["c1"] * mag + C["c5"] def _compute_distance_scaling(self, 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_stddevs(self, C, num_sites, stddev_types): """ Return total standard deviation. """ std_total = C['sigma'] stddevs = [] for _ in stddev_types: stddevs.append(np.zeros(num_sites) + std_total) return stddevs 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 = set(("vs30",))
[docs] 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] imean = (self._compute_magnitude_scaling(C, rup.mag) + self._compute_distance_scaling(C, dists.rrup, rup.mag)) # Original GMPE returns log10 acceleration in cm/s/s # Converts to natural logarithm of g mean = np.log((10.0 ** (imean - 2.0)) / g) mean = self._compute_site_scaling(sites.vs30, mean) istddevs = self._compute_stddevs( C, dists.rrup.shape, stddev_types ) # Convert from common logarithm to natural logarithm stddevs = np.log(10 ** np.array(istddevs)) return mean, stddevs
def _compute_site_scaling(self, 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)