Publication Date:
2013-03-22
Description:
Continuous observational monitoring of a study site in eastern Christchurch, New Zealand, following the 2010 M w 7.1 Darfield earthquake has recorded ten distinct liquefaction episodes in the mainshock–aftershock sequence. Three nearby accelerometers allow calibration between the geological expressions of liquefaction and the intensity of earthquake-induced surface ground motion at the site. Sand blow formation was generated by M w 5.2–7.1 earthquakes with M w 7.5–normalized peak ground accelerations (PGA 7.5 ) of ≥ 0.057 g (acceleration due to gravity). Silt drapes between successive sand blow deposits provide markers for delineating distinct liquefaction-inducing earthquakes in the geologic record. However, erosion quickly modifies the surface of sand blows into alluvial and aeolian forms that complicate geologic diagnosis. The two feeder-dike generations identified in subsurface investigations significantly underrepresent the number of liquefaction-inducing earthquakes due to extensive dike reactivation. New constitutive equations enable PGA 7.5 variations to be estimated from the thickness and areal extent of sand blows.
Print ISSN:
0091-7613
Electronic ISSN:
1943-2682
Topics:
Geosciences
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