Source code for openquake.hazardlib.gsim.mcverry_2006

# -*- coding: utf-8 -*-
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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"""
Module exports :class:`McVerry2006Asc`, :class:`McVerry2006SInter`,
:class:`McVerry2006SSlab`, and :class:`McVerry2006Volc`..
"""
import numpy as np

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


[docs]class McVerry2006Asc(GMPE): """ Implements GMPE developed by G. McVerry, J. Zhao, N.A. Abrahamson, P. Somerville published as "New Zealand Acceleration Response Spectrum Attenuation Relations for Crustal and Subduction Zone Earthquakes", Bulletin of the New Zealand Society for Earthquake Engineering, v.39, no. 1, p. 1-58, March 2006. URL: http://www.nzsee.org.nz/db/Bulletin/Archive/39(1)0001.pdf Last accessed 10 September 2014. This class implements the GMPE for Active Shallow Crust earthquakes (Asc suffix). The GMPE distinguishes between rock (vs30 >= 760) and stiff soil (360 <= vs30 < 760) and soft soil (vs < 360) which equates to the New Zealand site class A and B (rock) and C,D and E (soil). The rake angle is also taken into account to distinguish between faulting mechanisms. A hanging-wall term is noted in the functional form of the model in the paper but is not used at present. Furthermore, a Rvolc (volcanic path distance) is noted in the functional form but this is not implemented in the McVerry2006Asc model, it is implemented in a seperate GMPE McVerry2006Volc where Rvol=Rrup as this is how it is implemented in the NZ Seismic Hazard Model (Stirling 2012) """ #: Supported tectonic region type for base class is 'active shallow crust' DEFINED_FOR_TECTONIC_REGION_TYPE = const.TRT.ACTIVE_SHALLOW_CRUST #: Supported intensity measure types are PGA and SA. PGA is assumed to #: have same coefficients as SA(0.00) DEFINED_FOR_INTENSITY_MEASURE_TYPES = set([ PGA, SA ]) #: Supported intensity measure component is the stronger of two #: horizontal components (see Section 6 paragraph 2, page 21) DEFINED_FOR_INTENSITY_MEASURE_COMPONENT = \ const.IMC.GREATER_OF_TWO_HORIZONTAL #: Supported standard deviation types are Inter, Intra and Total # (see equations 8-9 page 29) DEFINED_FOR_STANDARD_DEVIATION_TYPES = set([ const.StdDev.TOTAL, const.StdDev.INTER_EVENT, const.StdDev.INTRA_EVENT ]) #: The only site parameter is vs30 used to map to site class to distinguish # between rock, stiff soil and soft soil REQUIRES_SITES_PARAMETERS = set(('vs30', )) #: Required rupture parameters are magnitude, and rake and hypocentral # depth rake is for determining fault style flags. Hypo depth is for # subduction GMPEs REQUIRES_RUPTURE_PARAMETERS = set(('mag', 'rake', 'hypo_depth')) #: Required distance measure is RRup (paragraphy 3, page 26) which is # defined as nearest distance to the source. 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) # Compute SA with primed coeffs and PGA with both unprimed and # primed coeffs C = self.COEFFS_PRIMED[imt] C_PGA = self.COEFFS_PRIMED[PGA()] C_PGA_unprimed = self.COEFFS_UNPRIMED[PGA()] # Get S term to determine if consider site term is applied S = self._get_site_class(sites.vs30) # Abrahamson and Silva (1997) hanging wall term. This is not used # in the latest version of GMPE but is defined in functional form in # the paper so we keep it here as a placeholder f4HW = self._compute_f4(C, rup.mag, dists.rrup) # Flags for rake angles CN, CR = self._get_fault_mechanism_flags(rup.rake) # Get volcanic path distance which Rvol=0 for current implementation # of McVerry2006Asc, but kept here as placeholder for future use rvol = self._get_volcanic_path_distance(dists.rrup) # Get delta_C and delta_D terms for site class delta_C, delta_D = self._get_deltas(sites.vs30) # Compute lnPGA_ABCD primed lnPGAp_ABCD = self._compute_mean(C_PGA, S, rup.mag, dists.rrup, rvol, rup.hypo_depth, CN, CR, f4HW, delta_C, delta_D) # Compute lnPGA_ABCD unprimed lnPGA_ABCD = self._compute_mean(C_PGA_unprimed, S, rup.mag, dists.rrup, rvol, rup.hypo_depth, CN, CR, f4HW, delta_C, delta_D) # Compute lnSA_ABCD lnSAp_ABCD = self._compute_mean(C, S, rup.mag, dists.rrup, rvol, rup.hypo_depth, CN, CR, f4HW, delta_C, delta_D) # Stage 3: Equation 6 SA_ABCD(T). This is lnSA_ABCD # need to calculate final lnSA_ABCD from non-log values but return log mean = np.log(np.exp(lnSAp_ABCD) * (np.exp(lnPGA_ABCD) / np.exp(lnPGAp_ABCD))) # Compute standard deviations C_STD = self.COEFFS_STD[imt] stddevs = self._get_stddevs( C_STD, rup.mag, stddev_types, sites.vs30.size ) return mean, stddevs
def _compute_mean(self, C, S, mag, rrup, rvol, hypo_depth, CN, CR, f4HW, delta_C, delta_D): """ Compute mean value on site class A,B,C,D (equation 4) returns lnSA_ABCD """ # Stage 1: compute PGA_ABCD and PGA'_ABCD which are then used in # equation 6 # Equation 1 PGA unprimed version lnSA_AB = self._compute_mean_on_rock(C, mag, rrup, rvol, hypo_depth, CN, CR, f4HW) # Equation 4 PGA unprimed version lnSA_ABCD = lnSA_AB + S *\ self._compute_nonlinear_soil_term(C, lnSA_AB, delta_C, delta_D) return lnSA_ABCD def _compute_mean_on_rock(self, C, mag, rrup, rvol, hypo_depth, CN, CR, f4HW): """ Compute mean value on site class A/B (equation 1 on page 22) """ lnSA_AB = ( # line 1 of equation 1 C['c1'] + C['c4as'] * (mag - 6) + # line 2 C['c3as'] * (8.5 - mag) ** 2 + # line 3 C['c5'] * rrup + # line 3 and 4 (C['c8'] + C['c6as'] * (mag - 6)) * np.log((rrup ** 2 + C['c10as'] ** 2) ** 0.5) + # line 5 C['c46'] * rvol + # line 6 C['c32'] * CN + C['c33as'] * CR + f4HW ) return lnSA_AB def _compute_nonlinear_soil_term(self, C, lnSA_AB, delta_C, delta_D): """ Compute mean value on site class C/D (equation 4 on page 22 without the first term) """ lnSA_CD = ( # line 1 equation 4 without first term (lnSA_AB) C['c29'] * delta_C + # line 2 and 3 (C['c30as'] * np.log(np.exp(lnSA_AB) + 0.03) + C['c43']) * delta_D ) return lnSA_CD def _get_stddevs(self, C, mag, stddev_types, num_sites): """ Return standard deviation as defined on page 29 in equation 8a,b,c and 9. """ sigma_intra = np.zeros(num_sites) # interevent stddev tau = sigma_intra + C['tau'] # intraevent std (equations 8a-8c page 29) if mag < 5.0: sigma_intra += C['sigmaM6'] - C['sigSlope'] elif 5.0 <= mag < 7.0: sigma_intra += C['sigmaM6'] + C['sigSlope'] * (mag - 6) else: sigma_intra += C['sigmaM6'] + C['sigSlope'] std = [] for stddev_type in stddev_types: if stddev_type == const.StdDev.TOTAL: # equation 9 page 29 std += [np.sqrt(sigma_intra**2 + tau**2)] elif stddev_type == const.StdDev.INTRA_EVENT: std.append(sigma_intra) elif stddev_type == const.StdDev.INTER_EVENT: std.append(tau) return std def _get_site_class(self, vs30): """ Return site class flag (0 if vs30 => 760, that is rock, or 1 if vs30 < 760, that is deep soil) """ S = np.zeros_like(vs30) S[vs30 <= 760] = 1 return S def _get_volcanic_path_distance(self, rrup): """ Computes the path length in km through the Taupo Volcanic Zone NOTE: For the NZ Seismic Hazard Model this term is only used for sources with "Normal Volcanic" faulting type and the term is applied to the whole path length (i.e. rvol = rrup) In order to test the NSHM against OQ, the NSHM model approach is implemented here as a seperate GMPE for volcanic travel paths. For the crustal model of McVerry2006Asc rvol is always equal to 0 """ return 0 def _get_fault_mechanism_flags(self, rake): """ Return the fault mechanism flag CN and CR, page 23 CN = -1 for normal (-146<rake<-33), 0 otherwise CR = 0.5 for reverse-oblique (33<rake<66), 1 for reverse (67<rake<123) and 0 otherwise """ CN, CR = 0, 0 # Pure Normal: rake = -90 if rake > -147 and rake < -33: CN = -1 # Pure Reverse: rake = 90 if rake > 67 and rake < 123: CR = 1 # Pure Oblique Reverse: rake = 45 if rake > 33 and rake < 66: CR = 0.5 return CN, CR def _get_deltas(self, vs30): """ Return delta's for equation 4 delta_C = 1 for site class C (360<=Vs30<760), 0 otherwise delta_D = 1 for site class D (180<Vs30<360), 0 otherwise """ delta_C = np.zeros(len(vs30)) delta_C[(vs30 >= 360) & (vs30 < 760)] = 1 delta_D = np.zeros(len(vs30)) delta_D[vs30 < 360] = 1 return delta_C, delta_D def _compute_f4(self, C, mag, rrup): """ Abrahamson and Silva 1997 f4 term for hanging wall effects. This is in McVerry equation 1 but is not used (Section 6.1 page 27) Compute f4 term (eq. 7, 8, and 9, page 106) """ fhw_m = 0 fhw_r = np.zeros_like(rrup) if mag <= 5.5: fhw_m = 0 elif 5.5 < mag < 6.5: fhw_m = mag - 5.5 else: fhw_m = 1 idx = (rrup > 4) & (rrup <= 8) fhw_r[idx] = C['ca9'] * (rrup[idx] - 4.) / 4. idx = (rrup > 8) & (rrup <= 18) fhw_r[idx] = C['ca9'] idx = (rrup > 18) & (rrup <= 24) fhw_r[idx] = C['ca9'] * (1 - (rrup[idx] - 18.) / 7.) f4 = fhw_m * fhw_r # Not used in current implementation of McVerry 2006, but keep here # for future use (return f4) return 0 #: Coefficient table (table 3, page 108) COEFFS_PRIMED = CoeffsTable(sa_damping=5, table="""\ imt c1 c3as c4as c5 c6as c8 ca9 c10as c11 c12y c13y c15 c17 c18y c19y c20 c24 c29 c30as c32 c33as c43 c46 pga 0.18130 0.00000 -0.14400 -0.00846 0.17000 -0.75519 0.37000 5.60000 8.10697 1.41400 0.00000 -2.55200 -2.48795 1.78180 0.55400 0.01622 -0.41369 0.44307 -0.23000 0.20000 0.26000 -0.29648 -0.03301 0.075 1.36561 0.03000 -0.14400 -0.00889 0.17000 -0.94568 0.37000 5.58000 8.68782 1.41400 0.00000 -2.70700 -2.54215 1.78180 0.55400 0.01850 -0.48652 0.31139 -0.28000 0.20000 0.26000 -0.48366 -0.03452 0.10 1.77717 0.02800 -0.14400 -0.00837 0.17000 -1.01852 0.37000 5.50000 9.37929 1.41400 -0.00110 -2.65500 -2.60945 1.78180 0.55400 0.01740 -0.61973 0.34059 -0.28000 0.20000 0.26000 -0.43854 -0.03595 0.20 1.39535 -0.01380 -0.14400 -0.00940 0.17000 -0.78199 0.37000 5.10000 10.6148 1.41400 -0.00270 -2.52800 -2.70851 1.78180 0.55400 0.01542 -0.67672 0.37235 -0.24500 0.20000 0.26000 -0.29906 -0.03853 0.30 0.44591 -0.03600 -0.14400 -0.00987 0.17000 -0.56098 0.37000 4.80000 9.40776 1.41400 -0.00360 -2.45400 -2.47668 1.78180 0.55400 0.01278 -0.59339 0.56648 -0.19500 0.20000 0.19800 -0.05184 -0.03604 0.40 0.01645 -0.05180 -0.14400 -0.00923 0.17000 -0.51281 0.37000 4.52000 8.50343 1.41400 -0.00430 -2.40100 -2.36895 1.78180 0.55400 0.01426 -0.30579 0.69911 -0.16000 0.20000 0.15400 0.20301 -0.03364 0.50 0.14826 -0.06350 -0.14400 -0.00823 0.17000 -0.56716 0.37000 4.30000 8.46463 1.41400 -0.00480 -2.36000 -2.40630 1.78180 0.55400 0.01287 -0.24839 0.63188 -0.12100 0.20000 0.11900 0.37026 -0.03260 0.75 -0.21246 -0.08620 -0.14400 -0.00738 0.17000 -0.55384 0.33100 3.90000 7.30176 1.41400 -0.00570 -2.28600 -2.26512 1.78180 0.55400 0.01080 -0.01298 0.51577 -0.05000 0.20000 0.05700 0.73517 -0.02877 1.00 -0.10451 -0.10200 -0.14400 -0.00588 0.17000 -0.65892 0.28100 3.70000 7.08727 1.41400 -0.00640 -2.23400 -2.27668 1.78180 0.55400 0.00946 0.06672 0.34048 0.00000 0.20000 0.01300 0.87764 -0.02561 1.50 -0.48665 -0.12000 -0.14400 -0.00630 0.17000 -0.58222 0.21000 3.55000 6.93264 1.41400 -0.00730 -2.16000 -2.28347 1.78180 0.55400 0.00788 -0.02289 0.12468 0.04000 0.20000 -0.04900 0.75438 -0.02034 2.00 -0.77433 -0.12000 -0.14400 -0.00630 0.17000 -0.58222 0.16000 3.55000 6.64496 1.41400 -0.00730 -2.16000 -2.28347 1.78180 0.55400 0.00788 -0.02289 0.12468 0.04000 0.20000 -0.04900 0.75438 -0.02034 3.00 -1.30916 -0.17260 -0.14400 -0.00553 0.17000 -0.57009 0.08900 3.50000 5.05488 1.41400 -0.00890 -2.03300 -2.03050 1.78180 0.55400 -0.00265 -0.20537 0.14593 0.04000 0.20000 -0.15600 0.61545 -0.01673 """) COEFFS_UNPRIMED = CoeffsTable(sa_damping=5, table="""\ imt c1 c3as c4as c5 c6as c8 ca9 c10as c11 c12y c13y c15 c17 c18y c19y c20 c24 c29 c30as c32 c33as c43 c46 pga 0.28815 0.00000 -0.14400 -0.00967 0.17000 -0.70494 0.37000 5.60000 8.68354 1.41400 0.00000 -2.55200 -2.56727 1.78180 0.55400 0.01550 -0.50962 0.30206 -0.23000 0.20000 0.26000 -0.31769 -0.03279 0.075 1.36561 0.03000 -0.14400 -0.00889 0.17000 -0.94568 0.37000 5.58000 8.68782 1.41400 0.00000 -2.70700 -2.54215 1.78180 0.55400 0.01850 -0.48652 0.31139 -0.28000 0.20000 0.26000 -0.48366 -0.03452 0.10 1.77717 0.02800 -0.14400 -0.00837 0.17000 -1.01852 0.37000 5.50000 9.37929 1.41400 -0.00110 -2.65500 -2.60945 1.78180 0.55400 0.01740 -0.61973 0.34059 -0.28000 0.20000 0.26000 -0.43854 -0.03595 0.20 1.39535 -0.01380 -0.14400 -0.00940 0.17000 -0.78199 0.37000 5.10000 10.6148 1.41400 -0.00270 -2.52800 -2.70851 1.78180 0.55400 0.01542 -0.67672 0.37235 -0.24500 0.20000 0.26000 -0.29906 -0.03853 0.30 0.44591 -0.03600 -0.14400 -0.00987 0.17000 -0.56098 0.37000 4.80000 9.40776 1.41400 -0.00360 -2.45400 -2.47668 1.78180 0.55400 0.01278 -0.59339 0.56648 -0.19500 0.20000 0.19800 -0.05184 -0.03604 0.40 0.01645 -0.05180 -0.14400 -0.00923 0.17000 -0.51281 0.37000 4.52000 8.50343 1.41400 -0.00430 -2.40100 -2.36895 1.78180 0.55400 0.01426 -0.30579 0.69911 -0.16000 0.20000 0.15400 0.20301 -0.03364 0.50 0.14826 -0.06350 -0.14400 -0.00823 0.17000 -0.56716 0.37000 4.30000 8.46463 1.41400 -0.00480 -2.36000 -2.40630 1.78180 0.55400 0.01287 -0.24839 0.63188 -0.12100 0.20000 0.11900 0.37026 -0.03260 0.75 -0.21246 -0.08620 -0.14400 -0.00738 0.17000 -0.55384 0.33100 3.90000 7.30176 1.41400 -0.00570 -2.28600 -2.26512 1.78180 0.55400 0.01080 -0.01298 0.51577 -0.05000 0.20000 0.05700 0.73517 -0.02877 1.00 -0.10451 -0.10200 -0.14400 -0.00588 0.17000 -0.65892 0.28100 3.70000 7.08727 1.41400 -0.00640 -2.23400 -2.27668 1.78180 0.55400 0.00946 0.06672 0.34048 0.00000 0.20000 0.01300 0.87764 -0.02561 1.50 -0.48665 -0.12000 -0.14400 -0.00630 0.17000 -0.58222 0.21000 3.55000 6.93264 1.41400 -0.00730 -2.16000 -2.28347 1.78180 0.55400 0.00788 -0.02289 0.12468 0.04000 0.20000 -0.04900 0.75438 -0.02034 2.00 -0.77433 -0.12000 -0.14400 -0.00630 0.17000 -0.58222 0.16000 3.55000 6.64496 1.41400 -0.00730 -2.16000 -2.28347 1.78180 0.55400 0.00788 -0.02289 0.12468 0.04000 0.20000 -0.04900 0.75438 -0.02034 3.00 -1.30916 -0.17260 -0.14400 -0.00553 0.17000 -0.57009 0.08900 3.50000 5.05488 1.41400 -0.00890 -2.03300 -2.03050 1.78180 0.55400 -0.00265 -0.20537 0.14593 0.04000 0.20000 -0.15600 0.61545 -0.01673 """) #: Coefficient table for standard deviation calculation (table 4, page 109) COEFFS_STD = CoeffsTable(sa_damping=5, table="""\ imt sigmaM6 sigSlope tau pga 0.4865 -0.1261 0.2687 0.075 0.5281 -0.0970 0.3217 0.10 0.5398 -0.0673 0.3088 0.20 0.5703 -0.0243 0.2726 0.30 0.5505 -0.0861 0.2112 0.40 0.5627 -0.1405 0.2005 0.50 0.5680 -0.1444 0.1476 0.75 0.5562 -0.0932 0.1794 1.00 0.5629 -0.0749 0.2053 1.50 0.5394 -0.0056 0.2411 2.00 0.5394 -0.0056 0.2411 3.00 0.5701 0.0934 0.2406 """)
[docs]class McVerry2006SInter(McVerry2006Asc): """ Extend :class:`McVerry2006Asc` for Subduction Interface events (SInter) Implements GMPE developed by G. McVerry, J. Zhao, N.A. Abrahamson, P. Somerville published as "New Zealand Acceleration Response Spectrum Attenuation Relations for Crustal and Subduction Zone Earthquakes", Bulletin of the New Zealand Society for Earthquake Engineering, v.39, no. 1, p. 1-58, March 2006. URL: http://www.nzsee.org.nz/db/Bulletin/Archive/39(1)0001.pdf Last accessed 10 September 2014. This class implements the GMPE for Subduction Interface earthquakes (SInter suffix). The GMPE distinguishes between rock (vs30 >= 760) and deep soil (vs30 < 760) which equation to the New Zealand site class A and B (rock) and C,D and E (soil). The rake angle is also taken into account to distinguish between faulting mechanisms. A hanging-wall term is noted in the functional form of the model in the paper but is not used at present. """ DEFINED_FOR_TECTONIC_REGION_TYPE = const.TRT.SUBDUCTION_INTERFACE def _compute_mean_on_rock(self, C, mag, rrup, rvol, hypo_depth, CN, CR, f4HW): """ Compute mean value on site class A/B (equation 2 on page 22) """ # Define subduction flag (page 23) # SI=1 for subduction interface, 0 otherwise # DS=0 for subduction intraslab, 0 otherwise SI = 1 DS = 0 lnSA_AB = ( # line 1 and 2 of equation 2 C['c11'] + (C['c12y'] + (C['c15'] - C['c17']) * C['c19y']) * (mag - 6) + # line 3 C['c13y'] * (10 - mag) ** 3 + # line 4 C['c17'] * np.log(rrup + C['c18y'] * np.exp(C['c19y'] * mag)) + # line 5 C['c20'] * hypo_depth + C['c24'] * SI + # line 6 C['c46'] * rvol * (1 - DS) ) return lnSA_AB
[docs]class McVerry2006SSlab(McVerry2006Asc): """ Extend :class:`McVerry2006Asc` for Subduction Intraslab events (SSlab) Implements GMPE developed by G. McVerry, J. Zhao, N.A. Abrahamson, P. Somerville published as "New Zealand Acceleration Response Spectrum Attenuation Relations for Crustal and Subduction Zone Earthquakes", Bulletin of the New Zealand Society for Earthquake Engineering, v.39, no. 1, p. 1-58, March 2006. URL: http://www.nzsee.org.nz/db/Bulletin/Archive/39(1)0001.pdf Last accessed 10 September 2014. This class implements the GMPE for Subduction Intraslab earthquakes (SSlab suffix). The GMPE distinguishes between rock (vs30 >= 760) and deep soil (vs30 < 760) which equation to the New Zealand site class A and B (rock) and C,D and E (soil). The rake angle is also taken into account to distinguish between faulting mechanisms. A hanging-wall term is noted in the functional form of the model in the paper but is not used at present. """ DEFINED_FOR_TECTONIC_REGION_TYPE = const.TRT.SUBDUCTION_INTRASLAB def _compute_mean_on_rock(self, C, mag, rrup, rvol, hypo_depth, CN, CR, f4HW): """ Compute mean value on site class A/B (equation 2 on page 22) """ # Define subduction flag (page 23) # SI=1 for subduction interface, 0 otherwise # DS=1 for subduction intraslab, 0 otherwise SI = 0 DS = 1 lnSA_AB = ( # line 1 and 2 of equation 2 C['c11'] + (C['c12y'] + (C['c15'] - C['c17']) * C['c19y']) * (mag - 6) + # line 3 C['c13y'] * (10 - mag) ** 3 + # line 4 C['c17'] * np.log(rrup + C['c18y'] * np.exp(C['c19y'] * mag)) + # line 5 C['c20'] * hypo_depth + C['c24'] * SI + # line 6 C['c46'] * rvol * (1 - DS) ) return lnSA_AB
[docs]class McVerry2006Volc(McVerry2006Asc): """ Extend :class:`McVerry2006Asc` for earthquakes with Volcanic paths (Volc) Implements GMPE developed by G. McVerry, J. Zhao, N.A. Abrahamson, P. Somerville published as "New Zealand Acceleration Response Spectrum Attenuation Relations for Crustal and Subduction Zone Earthquakes", Bulletin of the New Zealand Society for Earthquake Engineering, v.39, no. 1, p. 1-58, March 2006. URL: http://www.nzsee.org.nz/db/Bulletin/Archive/39(1)0001.pdf Last accessed 10 September 2014. This class implements the GMPE for earthquakes with Volcanic paths The GMPE distinguishes between rock (vs30 >= 760) and deep soil (vs30 < 760) which equation to the New Zealand site class A and B (rock) and C,D and E (soil). The rake angle is also taken into account to distinguish between faulting mechanisms. A hanging-wall term is noted in the functional form of the model in the paper but is not used at present. rvolc is equal to rrup """ DEFINED_FOR_TECTONIC_REGION_TYPE = const.TRT.VOLCANIC def _get_volcanic_path_distance(self, rrup): """ Computes the path length in km through the Taupo Volcanic Zone NOTE: For the NZ Seismic Hazard Model this term is only used for sources with "Normal Volcanic" faulting type and the term is applied to the whole path length (i.e. rvol = rrup) In order to test the NSHM against OQ, the NSHM model approach is implemented here as a seperate GMPE for volcanic travel paths. For the crustal model of McVerry2006Asc rvol is always equal to 0 """ return rrup