NHRP / Hazard themes / Geological Hazards / Seismology / Seismology Highlights 2014-15

Seismology Highlights 2014-15



♦ Contest 2012 ('NZ Natural Hazards')

Drs Kate Clark and Ursula Cochran culminated their contest project ‘Improved forecasting for large-great earthquakes…’ with town hall meetings in Franz Josef, Hokitika and Christchurch. The public feedback from their presentations was enthusiastic and reinforced that the engagement component cannot be overlooked.  In recognition of its value, public engagement has become forefront to new research initiatives funded by MBIE and is a key part of Platform’s forward-looking work.  

♦ Lessons learned from Christchurch (non-contest) 

Rethinking Probabilistic seismic hazard analysis (PSHA) through ensemble modelling (Project leader: Matt Gerstenberger).  The GNS-led research team have developed a time-dependent seismic hazard model for the Canterbury region that estimates the amount of earthquake shaking in the region for the next 50 years. For this model, the team developed a hybrid source model that captured time-dependence on three different time scales, from short- to long-term. Additionally, a logic tree was used to combine the McVerry (2006) Ground Motion Prediction Equation (GMPE) with the more recently developed Bradley (2010) GMPE to quantify differences between these two models.

Now the aim of the research is to draft a new long-term National Seismic Hazard Model using an ensemble approach that takes account of outputs from a range of existing GNS Science research. Precedence has been given to understanding how to integrate source model information for a range of time scales - from paleoseismic (thousands of years) to short-term (years) and sources (e.g., faults, earthquake catalogue) into a 50-year model appropriate for earthquake building code and to better understand uncertainty in hazard estimates, including that in predicted ground shaking.  Link to PSHA Workshop, Te Papa, Wellington, 2-4 Nov 2015.

Results from this project will be a key input to NZ building design standards, updates to the NZ bridge manual, and standards for construction of base isolated buildings.  There are good international linkages on this project with USGS, SCEC, and overseas universities.  EU REAKT is conducting physics-based forecast modelling on the Canterbury sequence using resource provided by the NZ Testing Centre infrastructure. 

♦ East coast hazards: Slow slip events & tsunami earthquakes

Slow slip event. GeoNet’s continuous GPS network in NZ has enabled the detection of ‘silent earthquakes’ or slow-slip events at the North Island's Hikurangi subduction zone. In 2013 and 2014, slow slip events were recorded offshore Kapiti, Hawke’s Bay and Gisborne.  These movements in themselves don't pose any risk to people, but they are a major part of how the tectonic plates move in a subduction zone. If we better understand slow-slip events, we should better understand the earthquake potential of the Hikurangi subduction zone.

Stuart Henrys (GNS Science) and others are part of the HOBITSS programme to further investigate the slow slip events offshore Gisborne. HOBITSS or ‘Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip’ is an international endeavour with wide NZ involvement.  Earlier in the year, Stephen Bannister was invited to Japan to give a keynote presentation on "Slow slip events and seismicity behaviour on the Hikurangi subduction zone."  Charles Williams (GNS Science) with USA colleague Laura Wallace presented work about NZ slow slip events at the annual meeting of the Southern California Earthquake Centre. Link to Radio NZ interview on HOBITSS

Tsunami Earthquake. Early in the reporting year, GNS scientists William Power, Caroline Holden and Xiaoming Wang spoke to media about the mystery behind the 1947 Gisborne tsunami where waves up to 10 metres followed seemingly small earthquakes.  Power’s team determined that undersea volcanoes situated along the Hikurangi trough on the Pacific platehave the potential to contribute to seismic activity as ‘sticking points’ when subducted or pushed under the Australian plate.  These findings identify a new category of hazard called a ‘tsunami earthquake’ which is characterised by longer duration, slow moving events – earthquakes that are described as ‘not strongly felt. Link to Radio NZ interview

Current advice from civil defence along the East Coast is to develop an action plan and to self-evacuate if there is a strong earthquake or if there is an earthquake that goes on for more than a minute – to include the possibility of these slower tsunami-generating events. Platform researchers from Geological Hazards and Societal Resilience teams are providing advice to the East Coast LAB (Life at the Boundary) initiative and are contributing to tsunami evacuation plans for Napier and Hawke’s Bay.

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Last updated 16 Dec 2015