shakelib.conversions.imt.newmark_hall_1982

class shakelib.conversions.imt.newmark_hall_1982.NewmarkHall1982[source]

Bases: shakelib.conversions.convert_imt.IMTConverter

Class for conversion between PGA and PSA10 by Newmark and Hall (1982).

  • PSA10 stands for spectral acceleration with oscillator period of 1.0 sec

  • PGV is peak ground velocity.

The conversion factor is 37.27*2.54. Note that 2.54 is the conversion factor to convert from cm/s to in/s and 37.27 is derived from SA(f) = 1.65*(2*pi*V*f)/386.09, where:

  • SA(f) is spectral acceleration at frequency f (in g)

  • f is the frequency of interest

  • V is the velocity

  • 1.65 is the N&H amplification factor for velocity at 5% damping

  • 386.09 is the acceleration of gravity in inches per second per g

The sigma factor was computed from an average sigma value determined by plotting PGV/PSA10 versus Distance for earthquakes with magnitudes greater than or equal to 5.0.

References

Newmark, N. M., & Hall, W. J. (1982). Earthquake spectra and design. Earthquake Engineering Research Institute, El Cerrito, California.

convertAmps(imt_in, imt_out, imt)[source]

Returns an array of converted IMT amplitude values.

Parameters:

  • imt_in (str) – OQ intensity measure type. Same as type as the input values defined by the imt variable.

  • imt_out (str) – OQ intensity measure type that the values will be converted to.

  • imt (OpenQuake IMT) – The intensity measurements of the input ground motions. Valid IMTs are PGV, and SA.

Returns:

Numpy array of amps converted from imt_in to imt_out.

Return type:

array

Raises:

ValueError – If not a valid conversion.

convertSigmas(imt_in, imt_out, sigma)[source]

Convert standard deviation to natural log units.

Parameters:

  • imt_in (str) – OQ intensity measure type. Same as type as the input values defined by the imt variable.

  • imt_out (str) – OQ intensity measure type that the values will be converted to.

  • sigma (array) – Numpy array or float of standard deviation of PGV from a GMPE; units must be natural log.

Returns:

Converted standard deviations with natural log units.

Return type:

array

getLnSigma()[source]
Returns:

The the estimate of the logarithmic standard deviation of the PGV

predicted by Newmark and Hall (1982).

Return type:

float