QuakeCoRE Flagship 2 The National Liquefaction Database Matt Ogden ME Student UoA

Introduction My background Overview of the project Objectives Title of this project is the Scrutiny of Simplified Triggering Procedures and has been divided into three major parts. First – Liquefaction mapping from NZ Earthquakes and Evaluation of the Prediction Methods, Second – Supplementary Field Testing for Site Characterisation, and Third – Liquefaction Testing of Characteristic New Zealand soils. My research largely deals with the first part, and is supervised by Liam, and assisted by two forth year UoA engineering students. As we know the current methods for predicting liquefaction rely on simplified empirical methods derived from case histories of liquefaction and no-liquefaction. They work well in clean sands however their efficacy diminishes as we introduce things such a fines correction, effects of interbedded layering for example, leading to over-prediction. To further evaluate the empirical methods we need observations which have been identified in at least 13 recent earthquakes. These have largely been compiled through different researchers but they do not exist in one database. So the first part of my work has been to create a database of known observations of liquefaction from a selection of historic earthquakes which ill talk to in the coming slides.

QuakeCoRE Liquefaction Database The Database Edgecumbe 1987 Events What is being captured Napier 1931 QuakeCoRE Liquefaction Database Liquefaction – Sand boils, ejecta. Key events in which liquefaction has been observed have been included in the database. Drop down shows our targeted events. My research focuses particularly on the West Coast and the 7.8 1929 Murchison and 7.2 1968 Inangahua earthquakes, which have been researched heavily by John Berrill and various masters students in the past. The two fourth year engineering students are targeting the Wairarapa events in the 1800’s. Kaikoura and the CES were accurately mapped and the Kaikoura dataset has been added to this database. Edgecumbe 1987, Nick Mellsop and Sarahs work from last year has also been uploaded and when ready, we will upload observations from the 1931 Napier earthquake. In the database we are capturing observations of liquefaction which are taken as sand boils, ejecta, lateral spreading, ground distortion and ground cracking from prior research or accounts from earthquakes. In some cases, it is the effect of liquefaction on structures which provides the evidence e.g. differential settlement of foundations. We are also trying to capture, if possible, cases where no liquefaction was observed, as this forms one half of the empirical triggering equations. Lateral spreading No observations

Example – specific entry Developed a web-interface to readily upload observations and save back to the database. This table shows the fields we are capturing for a specific entry on the west coast. Talk to the different fields.

Positive observation 1968 Insights Observations which can be further analysed given availability of geotech data on the NZGD. Develop predictive models based on geomorphology, groundwater, shake maps then compare against actual observations. No observation 1968. Confirmation of geomorphic conditions for liquefaction – young Holocene loosely consolidated alluvial and fluvial deposits. Potential for more case histories as more geotechnical data is published to the NZGD. Resolution and accuracy, captured in the database. Specific interesting cases such as Westport where there were observations north of Orowaiti Road but not south. We can compare against geomporhic map from previous study, this suggests finer estuarine deposits liquefied in 1968 but the more dense alluvial deposits south of Orowaiti road did not. Blenheim

Next steps – Greymouth and Westport Groundwater Iterative process Develop groundwater models Obtain further investigations for analyses Estimation of PGAs from events Begin scrutinising simplified methodology Where it works well? Where it doesn’t? In what cases can we apply it? Dealing with over-prediction? Geotech data Outline the upcoming steps. Develop regional groundwater models Comprehensive collation of geotech data over regions.