Source code for openquake.hazardlib.gsim.somerville_2001

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"""
Module exports :class:`SomervilleEtAl2001NSHMP2008`.
"""
import numpy as np

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


def _compute_mean(C, mag, rjb):
    """
    Compute and return mean value (table 8, page 8)
    """
    d1 = np.sqrt(50. ** 2 + 6. ** 2)
    d = np.sqrt(rjb ** 2 + 6 ** 2)

    mean = np.zeros_like(rjb)

    mean += (
        C['a1'] + C['a2'] * (mag - 6.4) +
        C['a7'] * (8.5 - mag) ** 2
    )

    idx = rjb < 50.
    mean[idx] += (
        C['a3'] * np.log(d[idx]) +
        C['a4'] * (mag[idx] - 6.4) * np.log(d[idx]) +
        C['a5'] * rjb[idx]
    )

    idx = rjb >= 50.
    mean[idx] += (
        C['a3'] * np.log(d1) +
        C['a4'] * (mag[idx] - 6.4) * np.log(d[idx]) +
        C['a5'] * rjb[idx] + C['a6'] * (np.log(d[idx]) - np.log(d1))
    )

    return mean


[docs]class SomervilleEtAl2001NSHMP2008(GMPE): """ Implements GMPE developed by P. Somerville, N. Collins, N. Abrahamson, R. Graves, and C. Saika and documented in "GROUND MOTION ATTENUATION RELATIONS FOR THE CENTRAL AND EASTERN UNITED STATES" (Final report, June 30, 2001: Report to U.S. Geological Survey for award 99HQGR0098). This GMPE is used by the National Seismic Hazard Mapping Project (NSHMP) for the 2008 US hazard model. Document available at: http://earthquake.usgs.gov/hazards/products/conterminous/2002/99HQGR0098.pdf This class replicates the algorithm for the Somerville et. al. 2001 GMPE as coded in the subroutine ``getSomer`` 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 stable continental crust, #: given that the equations have been derived for central and eastern #: north America DEFINED_FOR_TECTONIC_REGION_TYPE = const.TRT.STABLE_CONTINENTAL #: Supported intensity measure types are spectral acceleration, #: and peak ground acceleration DEFINED_FOR_INTENSITY_MEASURE_TYPES = {PGA, SA} #: Supported intensity measure component is the geometric mean of #: two : horizontal components #: attr:`~openquake.hazardlib.const.IMC.AVERAGE_HORIZONTAL`, DEFINED_FOR_INTENSITY_MEASURE_COMPONENT = const.IMC.AVERAGE_HORIZONTAL #: Supported standard deviation type is only total. DEFINED_FOR_STANDARD_DEVIATION_TYPES = {const.StdDev.TOTAL} #: No site parameters required REQUIRES_SITES_PARAMETERS = set() #: Required rupture parameter is only magnitude (Mw). REQUIRES_RUPTURE_PARAMETERS = {'mag'} #: Required distance measure is rjb REQUIRES_DISTANCES = {'rjb'} #: Shear-wave velocity for reference soil conditions in [m s-1] DEFINED_FOR_REFERENCE_VELOCITY = 760.
[docs] def compute(self, ctx: np.recarray, 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] mean[m] = clip_mean(imt, _compute_mean(C, ctx.mag, ctx.rjb)) sig[m] = C['sigma']
#: Coefficient table obtained from coefficient arrays (a1, a2, a3, a4, #: a5, a6, a7, sig0) defined in subroutine getSomer in hazgridXnga2.f COEFFS = CoeffsTable(sa_damping=5, table="""\ IMT a1 a2 a3 a4 a5 a6 a7 sigma pga 0.658 0.805 -0.679 0.0861 -0.00498 -0.477 0.0 0.587 0.1 1.442 0.805 -0.679 0.0861 -0.00498 -0.477 0.0 0.595 0.2 1.358 0.805 -0.679 0.0861 -0.00498 -0.477 0.0 0.611 0.3 1.2353 0.805 -0.67023 0.0861 -0.0048045 -0.523792 -0.030298 0.6057 0.5 0.8532 0.805 -0.671792 0.0861 -0.00442189 -0.605213 -0.0640237 0.6242 1.0 -0.0143 0.805 -0.696 0.0861 -0.00362 -0.755 -0.102 0.693 2.0 -0.9497 0.805 -0.728 0.0861 -0.00221 -0.946 -0.140 0.824 """)