Otago scientist on first Japan fault-zone expedition

Thursday 22 March 2012

Otago scientist on first Japan fault-zone expedition

University of Otago geologist Dr Virginia Toy has been selected to travel on board the scientific drilling vessel Chikyu when it departs next month to explore, for the first time, the undersea fault that slipped to generate the devastating Tohuku-Oki earthquake off the coast near Sendai, Japan,in March last year.

The earthquake fault caused displacement of the sea floor off the Coast of Japan of 50 metres horizontally, and 10 metres vertically – the “biggest measured surface displacement I know of,” says Dr Toy.

The resulting tsunami is estimated to have killed some 23,000 people and the M 9.0 quake has since been named one of the five most powerful quakes to shake the earth since 1900.
Dr Toy is the only representative of New Zealand and Australia on this Integrated Ocean Drilling Programme (IODP) expedition, which departs from the port of Shimizu, South of Tokyo, on April 1. She joins some 28 scientists from ten other countries.

“My role is to look at the micro-structure of the earthquake fault rocks. I then hope to make a comparison between samples that can be recovered from the fault area that slipped off Japan to generate this earthquake with the samples from New Zealand’s Alpine Fault zone,” she says.

Dr Toy is one of the Principal Investigators organising a land-based drilling project, the Alpine Fault – Deep Fault Drilling Project (DFDP), which aims to investigate the active Alpine Fault zone through drilling to a depth of 1.5km in early 2013.

Dr Toy says she is delighted to be chosen for the expedition, and excited at the opportunities to learn more using the state-of-the-art equipment aboard the Chikyu – a 210 metre long research vessel. The opportunity to work on this well-equipped ship will be very useful when putting together a similar lab to support the DFDP.

“I’m honoured to be allowed to participate and be able to advance the knowledge of this event that affected so many people’s lives. For New Zealand, we will be providing important information about earthquake source mechanics that will be used to refine the New Zealand National Seismic Hazard Model so that we can make better designs for buildings and infrastructure, and also for better civil defence planning,” she says.

The main goal of the project is to understand the Japan fault slip by sampling the fault rock, and to take temperature measurements over the next few years, in order to estimate the frictional stress on the fault during the earthquake.

“It is very important to put the temperature monitoring equipment in place within 2 years of the earthquake to measure this, and so this project has been fast-tracked by IODP. Furthermore, scientists have never seen samples of a fault that has moved such a large amount during a recent earthquake,” says Dr Toy.

The expedition will last nearly two months, finishing on 24 May. Dr Toy will provide regular updates on the progress of the expedition via the following Otago Geology Department website: http://www.otago.ac.nz/geology/news/jfast/index.html.

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