A model for the attenuation of peak ground acceleration in New Zealand earthquakes based on seismograph and accelerograph data

A combination of weak-motion velocity data from seismographs and strong-motion acceleration data from accelerographs has been used to model the attenuation of peak ground acceleration (PGA) in New Zealand earthquakes. The resulting model extends the PGA attenuation model of Zhao, Dowrick and McVerry [30] to include the variability of rock strength, and also describes the unusually high attenuation in the volcanic zone of the North Island of New Zealand. Strong-rock sites were found to experience lower PGAs than either weak rock or soil sites for magnitudes below M W 7, and the apparent degree of amplification on going from strong rock to weak rock or soil decreased as the magnitude increased from M W 5 to M W 7. At magnitude 7 the PGAs were very similar for all site classes for source distances up to 100 km. When extrapolated to magnitudes beyond the maximum of the data, M W 7.4, the model predicted that PGAs for strong rock sites were greater than for weak rock or soil sites. The so-called whole Taupo Volcanic Zone was found to provide a good boundary for the zone of high attenuation in the volcanic region of the North Island. The high attenuation was successfully modelled as a simple function of the length of travel path through the zone of high attenuation. Over the effective maximum volcanic path length of about 70 km the extra attenuation resulted in a factor of ten reduction in PGA compared with non-volcanic paths of the same length.

[1]  R. Abercrombie,et al.  Strong motion modelling of the 1993 Tikokino earthquake, southern Hawke's Bay, New Zealand , 1998 .

[2]  Michael McWilliams,et al.  Volcanic and structural evolution of Taupo Volcanic Zone, New Zealand: a review , 1995 .

[3]  D. J. Dowrick,et al.  Attenuation of peak ground accelerations in New Zealand earthquakes , 1997 .

[4]  S. B. Hodder.  Computer processing of New Zealand strong-motion accelerograms , 1983 .

[5]  M. Yetton.  The probability and consequences of the next alpine fault earthquake, South Island, New Zealand , 2000 .

[6]  N. Abrahamson,et al.  Empirical Response Spectral Attenuation Relations for Shallow Crustal Earthquakes , 1997 .

[7]  Roger D. Borcherdt,et al.  Estimates of Site-Dependent Response Spectra for Design (Methodology and Justification) , 1994 .

[8]  N. Abrahamson,et al.  Magnitude-dependent variance of peak ground acceleration , 1995, Bulletin of the Seismological Society of America.

[9]  Kenneth W. Campbell,et al.  Empirical Near-Source Attenuation Relationships for Horizontal and Vertical Components of Peak Ground Acceleration, Peak Ground Velocity, and Pseudo-Absolute Acceleration Response Spectra , 1997 .

[10]  David M. Boore,et al.  Peak horizontal acceleration and velocity from strong motion records including records from the 1979 Imperial Valley, California, earthquake , 1981 .

[11]  Kenneth W. Campbell,et al.  Near-source attenuation of peak horizontal acceleration , 1981 .

[12]  A. Haines.  A local magnitude scale for New Zealand earthquakes , 1981 .

[13]  R. I. Skinner,et al.  Accelerograph calibration and accelerogram correction , 1973 .

[14]  David J. Dowrick,et al.  Attenuation of modified mercalli intensity in New Zealand earthquakes , 1999 .

[15]  W. D. Smith,et al.  A development in the modelling of far-field intensities for New Zealand earthquakes , 1995 .