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Greywacke: subjectively stunning, frictionally fascinating, and societally relevant

A seminar by Otago Geology alumna Dr Carolyn Boulton – Te Herenga Waka - Victoria University of Wellington.

Across New Zealand, multiple historical earthquakes have ruptured faults within Torlesse Supergroup greywacke. Yet, because of its (undeserved) reputation as ugly and monotonous, few researchers have investigated its mechanical properties.

In this research, hydrothermal friction experiments were conducted on greywacke psammite and argillite across a wide range of crustal conditions (T=50°C to 600°C and σn’=75 MPa).

Results reveal that at T= 250°C to 450°C, both greywacke lithologies are frictionally strong (mu=0.6-0.8) and unstable; these conditions correspond to the hypocentral depths of the 2010 Mw 7.1 Darfield (~10 km depth) and 2016 Mw 7.8 Kaikōura (~13 km depth) earthquakes. At T≤200°C, argillite is weaker (m=0.32-0.53) than psammite (m=0.55-0.65) and more stable.

We hypothesise that the argillite’s low friction coefficient at shallow depths promotes complex multi-fault earthquakes and earthquake sequences.

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Date Wednesday, 11 May 2022
Time 1:00pm - 2:00pm
Audience Future students,Parents,Public,Undergraduate students,Postgraduate students,Staff,Alumni
Event Category Sciences
Event Type Seminar
LocationOnline via Zoom
Contact NameJack Williams

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