Liquefaction Assessment Study Level of Detail:https://www.building.govt.nz/building-code-compliance/geotechnical-educationLevel A - Basic Desktop AssessmentConsiders only the most basic information about geology, groundwater and seismic hazard to assess the potential for liquefaction to occur. This has been completed as a simple ‘desktop study’, based on existing information (geological and topographic maps) and local knowledge.Residual uncertainty: The primary focus is identification of land where there is a high degree of certainty that Liquefaction Damage is Unlikely. For other areas, substantial uncertainty will likely remain regarding the level of risk.Level B - Calibrated desktop assessmentA high-level ‘calibration’ of geological/geomorphic maps. Qualitative assessment of a small number of subsurface investigations provides a better understanding of liquefaction susceptibility and triggering for the mapped deposits and underlying ground profile.Residual uncertainty: Because of the limited amount of subsurface ground information, significant uncertainty remains regarding the level of liquefaction-related risk, how it varies across each mapped area, and the delineation of boundaries between different areasVariabilityThere is considerable uncertainty involved in estimating liquefaction-induced ground damage. These categories are intended to provide a general indication of the damage that might typically be expected. However there can be wide variation in land performance, even where ground conditions appear to be similar, with damage in some cases being much greater or less than inferred from the damage category.Description of uncertaintiesThis assessment has been made at a broad scale across the entire Auckland Council territorial authority area and is intended to approximately describe the typical range of liquefaction across neighborhood-sized areas. It is not intended to precisely describe liquefaction at individual property scale. This information is general in nature, and more detailed site-specific liquefaction assessment will be required for some purposes (e.g. for design of building foundations).Liquefaction CategoryDescription Liquefaction Category is Undetermined A liquefaction vulnerability category has not been assigned at this stage, either because a liquefaction assessment has not been undertaken for this area, or there is not enough information to determine the appropriate category with the required level of confidence. Liquefaction Damage is Unlikely There is a probability of more than 85 percent that liquefaction-induced ground damage will be None to Minor for 500-year shaking. At this stage there is not enough information to distinguish between Very Low and Low. More detailed assessment would be required to assign a more specific liquefaction category. Liquefaction Damage is Possible There is a probability of more than 15 percent that liquefaction-induced ground damage will be Minor to Moderate (or more) for 500-year shaking. At this stage there is not enough information to distinguish between Medium and High. More detailed assessment would be required to assign a more specific liquefaction category. Very Low Liquefaction VulnerabilityThere is a probability of more than 99 percent that liquefaction-induced ground damage will be None to Minor for 500-year shaking. Low Liquefaction Vulnerability There is a probability of more than 85 percent that liquefaction-induced ground damage will be None to Minor for 500-year shaking. Medium Liquefaction Vulnerability There is a probability of more than 50 percent that liquefaction-induced ground damage will be: Minor to Moderate (or less) for 500-year shaking; and None to Minor for 100-year shaking. High Liquefaction Vulnerability There is a probability of more than 50 percent that liquefaction-induced ground damage will be: Moderate to Severe for 500-year shaking; and/or Minor to Moderate (or more) for 100-year shaking. Terms of use:It is important to recognize that these maps are prepared to a city-wide scale and are not intended to provide assessment specific to any one property. Nor does it replace the need for site-specific investigations required for land and building development processes under the Resource Management Act and Building Act.The maps are prepared based on an assessment of natural ground conditions and therefore do not take into account the influence of recent human activities that may influence liquefaction response (i.e. earthworks, ground improvement, foundation design), unless specifically stated within the technical reports. As such, degree of land damage may be less than predicted for a given property where liquefaction risk was addressed during landform or building foundation design.
