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Research Papers, Lincoln University

Liquefaction features and the geologic environment in which they formed were carefully studied at two sites near Lincoln in southwest Christchurch. We undertook geomorphic mapping, excavated trenches, and obtained hand cores in areas with surficial evidence for liquefaction and areas where no surficial evidence for liquefaction was present at two sites (Hardwick and Marchand). The liquefaction features identified include (1) sand blows (singular and aligned along linear fissures), (2) blisters or injections of subhorizontal dikes into the topsoil, (3) dikes related to the blows and blisters, and (4) a collapse structure. The spatial distribution of these surface liquefaction features correlates strongly with the ridges of scroll bars in meander settings. In addition, we discovered paleoliquefaction features, including several dikes and a sand blow, in excavations at the sites of modern liquefaction. The paleoliquefaction event at the Hardwick site is dated at A.D. 908-1336, and the one at the Marchand site is dated at A.D. 1017-1840 (95% confidence intervals of probability density functions obtained by Bayesian analysis). If both events are the same, given proximity of the sites, the time of the event is A.D. 1019-1337. If they are not, the one at the Marchand site could have been much younger. Taking into account a preliminary liquefaction-triggering threshold of equivalent peak ground acceleration for an Mw 7.5 event (PGA7:5) of 0:07g, existing magnitude-bounded relations for paleoliquefaction, and the timing of the paleoearthquakes and the potential PGA7:5 estimated for regional faults, we propose that the Porters Pass fault, Alpine fault, or the subduction zone faults are the most likely sources that could have triggered liquefaction at the study sites. There are other nearby regional faults that may have been the source, but there is no paleoseismic data with which to make the temporal link.

Images, UC QuakeStudies

A digitally manipulated image of Michael Parekowhai's scuplture 'On First Looking into Chapman's Homer' on Madras Street. The photographer comments, "One of the two bulls on pianos by Michael Parekowhai called 'On First Looking into Chapman's Homer'. They have been placed on the site of a building that was demolished after earthquake damage.

Videos, UC QuakeStudies

Aerial footage of a site in Avondale where several liquefaction remediation options are being tested. Gelignite explosives have been buried throughout the site. These will be set off to simulate liquefaction caused by an earthquake. The result, if successful, will help EQC protect people's houses from future earthquakes, and settle land claims. The video was recorded using a drone aircraft.

Videos, UC QuakeStudies

A video of a tour of the Christchurch central city Red Zone. The video shows footage of the Edmond's Band Rotunda, Gloucester Street, the CTV building site, Poplar Lane, the McKenzie & Willis building, High Street, Lichfield Street, Colombo Street, Cathedral Square, and ChristChurch Cathedral.