Sharma et al. 2009

class openquake.hazardlib.gsim.sharma_2009.SharmaEtAl2009

Implements GMPE of Sharma et al. (2009). This GMPE is intended for the Indian Himalayas but is based on data from both Zagros in Iran and the Himalayas. The combination of these two regions is motivated by the sparsity of near field data. Seismotectonic similarity is supposed based on both regions being continental collision zones, and in spite of the lack of subduction in Zagros.

Note that Figure 7-9 of Sharma et al. (2009) are in error (Sharma, personal communication). This implementation is verified against test vector obtained from lead author.

Support for PGA has been added by assuming it to be equal to the spectral acceleration at 0.04 s. This is assumed by the authors in the captions for Figures 11-13 anyway.

Reference:

Sharma, M. L., Douglas, J., Bungum, H., and Kotadia, J. (2009). Ground-motion prediction equations based on data from the Himalayan and Zagros regions. Journal of Earthquake Engineering, 13(8):1191–1210.

COEFFS = <openquake.hazardlib.gsim.base.CoeffsTable object>

Coefficients taken from Table 2, p. 1202. Note that “In this article, only the coefficients for a subset of these periods [between 0.04 and 2.5 s] are reported” and the damping is 5% (Sharma et al., 2009, p. 1200).

CONSTS = {'b4': 15.0}

“After trials with different values b4 was fixed to be 15km for all periods.” (Sharma et al., 2009, p. 1201)

DEFINED_FOR_INTENSITY_MEASURE_COMPONENT = 'Average horizontal'

Supported intensity measure component is the geometric mean of two horizontal components AVERAGE_HORIZONTAL, see p. 1200.

DEFINED_FOR_INTENSITY_MEASURE_TYPES = set([<class 'openquake.hazardlib.imt.SA'>, <class 'openquake.hazardlib.imt.PGA'>])

Set of intensity measure types this GSIM can calculate. A set should contain classes from module openquake.hazardlib.imt.

DEFINED_FOR_STANDARD_DEVIATION_TYPES = set(['Total'])

Only total standard deviation is supported, see Table 2, p. 1202.

DEFINED_FOR_TECTONIC_REGION_TYPE = 'Active Shallow Crust'

Supported tectonic region type is ‘active shallow crust’ however as inndicated the introduction the tectonics of the Himalayas have a “great range of focal depths” (Sharma et al., 2009, p. 1192).

NEHRP_BC_BOUNDARY = 760.0

Sharma et al. (2009) does not use VS30 so no threshhold is given. A value of 760 m/s was selected. This is consistent with openquake.hazardlib.gsim.atkinson_boore_2003, corresponds to NEHRP class A/B, and is close to the threshhold for Eurocode 8 Class 8 (800 m/s).

RAKE_THRESH = 30.0

Rake threshhold of 30 degrees was selected, same as openquake.hazardlib.gsim.boore_atkinson_2008 and openquake.hazardlib.gsim.campbell_bozorgnia_2008. Contrast with 45 degree threshhold used by 30 degree threshhold used in openquake.hazardlib.gsim.zhao_2006.

REQUIRES_DISTANCES = set(['rjb'])

Required distance measure is Joyner-Boore distance, see p. 1200

REQUIRES_RUPTURE_PARAMETERS = set(['rake', 'mag'])

Required rupture parameters are magnitude and rake, see equation (1) on p. 1200. Rake is used to distinguish between reverse and strike-slip faulting, and to detect mis-application of GMPE to normal faulting.

REQUIRES_SITES_PARAMETERS = set(['vs30'])

Required site parameter Vs30 is used to set binary rock/soil classification dummy variable, see equation (1) on p. 1200.

get_fault_type_dummy_variables(rup)

Fault-type classification dummy variable based on rup.rake.

“H is 1 for a strike-slip mechanism and 0 for a reverse mechanism” (p. 1201).

Note:

UserWarning is raised if mechanism is determined to be normal faulting, since as summarized in Table 2 on p. 1197 the data used for regression included only reverse and stike-slip events.

get_mean_and_stddevs(sites, rup, dists, imt, stddev_types)

See superclass method for specification of input and result values.

get_site_type_dummy_variables(sites)

Binary rock/soil classification dummy variable based on sites.vs30.

“S is 1 for a rock site and 0 otherwise” (p. 1201).