A continuous map of near-surface S-wave attenuation in New Zealand

• Published in: Geophysical journal international Vol. 213; no. 1; pp. 408 - 425
• Main Authors: Van Houtte, Chris, Ktenidou, Olga-Joan, Larkin, Tam, Holden, Caroline
• Format: Journal Article
• Language: English
• Published: Oxford University Press (OUP) 01.04.2018
• Subjects: Sciences of the Universe; Seismic attenuation; Site effects; Body waves; Earthquake ground motions; Earthquake hazards
• ISSN: 0956-540X; 1365-246X
• DOI: 10.1093/gji/ggx559

Quantifying the near-surface attenuation of seismic waves at a given location can be important for seismic hazard analysis of high-frequency ground motion. This study calculates the site attenuation parameter, κ0, at 41 seismograph locations in New Zealand. Combined with results of a previous study, a total of 46 κ0 values are available across New Zealand. The results compare well with previous t* studies, revealing high attenuation in the volcanic arc and forearc ranges, and low attenuation in the South Island. However, for site-specific seismic hazard analyses, there is a need to calculate κ0 at locations away from a seismograph location. For these situations, it is common to infer κ0 from weak correlations with the shear wave velocity in the top 30 m, VS30, or to adopt an indicative regional value. This study attempts to improve on this practice. Geostatistical models of the station-specific κ0 data are developed, and continuous maps are derived using ordinary kriging. The obtained κ0 maps can provide a median κ0 and its uncertainty for any location in New Zealand, which may be useful for future site-specific seismic hazard analyses.