4.97 McVerry et al. (2000)

• Ground-motion model for crustal earthquakes is (using form from Abrahamson and Silva (1997), see Section 4.79):
  
  Also add on hanging wall term, see Section 4.79. Subscript AS denotes those coefficients from Abrahamson and Silva (1997). Three parts of equation within {…} are for site conditions MA/SA, Class B and Class C respectively. PGA_WA′ is the predicted PGA (SA′(0)) for weak rock category. CN = -1 for normal mechanism and 0 otherwise. CR = 0.5 for reverse/oblique, 1.0 for reverse and 0 otherwise. Ground-motion model for subduction zone earthquakes is (using form from Youngs et al. (1997), see Section 4.83):
  
  Subscript Y denotes those coefficients from Youngs et al. (1997). Three parts of equation within {…} are for site conditions MA/SA, Class B and Class C respectively. SI = 1 for subduction interface and 0 otherwise. DS = 1 for deep slab and 0 otherwise. r_VOL is length of path that lies in the volcanic zone.
• Response parameter is acceleration for 5% damping.
• Use four site conditions (mostly based on geological descriptions rather than measured shear-wave velocity):

  WA

  Weak rock sites, or sites with soil layer of thickness ≤ 3m overlying weak rock.

  MA/SA

  Moderate-strength or strong rock sites, or sites with soil layer of thickness ≤ 3m overlying moderate-strength or strong rock.

  Class B

  Intermediate soil sites or sites with soil layer of thickness > 3m overlying rock.

  Class C

  Flexible or deep soil sites with natural periods > 0.6s.

  Justify soil categories using statistical studies of residuals at early stage. Exclude response spectra from very soft soil sites (V _s < 150m∕s for depths of ≳ 10m).

• Use data for PGA equation from Zhao et al. (1997), see Section 2.152.
• Exclude records from bases of buildings with >4 storeys.
• Use less records for long periods because noise.
• Lack of data prevent development of robust model purely from NZ data. Plot residuals of predicted response using published attenuation relations (base models) for other areas to find relations which gave good representations of NZ data. Then modify some coefficients to improve match; imposing constraints so that the selected models control behaviour at short distances where NZ data lacking. Require crustal and subduction zone expressions for rock sites to match magnitude dependence of base models at r = 0km. Constrain coefficients that occur nonlinearly and nonlinear site response coefficient for Class C to base model values.
• Find anelastic attenuation term and additive terms for shallow slab earthquakes for subduction earthquakes not statistically significant. Also differences in attenuation rates for shallow slab, deep slab and interface earthquakes not statistically significant.
• Exclude deep slab earthquakes because of high attenuation in mantle; note equation should not be used for such earthquakes.
• Different attenuation rate for site category MA/SA because of magnitude dependence apparent in residuals for simpler model.
• Eliminate nonlinear site response term for Class B because find unacceptable (positive) values of coefficient and constraining to negative values produces poorer fit.
• Predicted PGA (SA′(0)) from response spectrum set of records considerably smaller than those, SA(0), from the complete PGA set of records. Thus scale SA′(T) by ratio SA(0)∕SA′(0).
• Standard error has a magnitude dependent intra-event component and a magnitude independent inter-event component.
• Note lack of data for large magnitude subduction zone earthquakes and large magnitude near source data for crustal earthquakes.
• Do not give coefficients, only predictions.