Natural Hazards Update - No.5 2003
Future hazards research plans
Proposed research relationships.
Much of the research by GNS and NIWA that ultimately provides natural hazard information is funded by the Foundation for Research, Science & Technology (FRST). FRST required new research proposals to be submitted this year, and asked for a change in the balance of work on hazard reduction and research to assist readiness, response, and recovery from hazard events. NIWA and GNS took this opportunity to re-evaluate their current research portfolios, discuss proposed directions with end users and potential collaborators, build on the relationships created with the establishment of the Natural Hazards Centre, and prepare new proposals that significantly increased the collaboration.
This process resulted in four closely linked proposals, led by GNS and NIWA, that included a significant number of other collaborators from the university and private sectors. The combined proposals aim to provide an all-hazards approach to (i) the provision of risk assessment information for hazard reduction (GNS and NIWA Hazards), (ii) forecasting tools to provide information to assist readiness and response during emergencies (Forecasting), and (iii) the social, economic, and Maori research to underpin increasing community resilience and recovery (Resilience). The proposals are taking a big-picture approach by targeting all significant hazards, and assembling national teams, supported by the models, computational capability, monitoring networks, and databases needed to provide national coverage.
New initiatives include more focus on an all-hazard risk assessment approach; a combined approach to hazard forecasting incorporating new models; an all-hazards approach to social and economic impacts and effects on Maori; new approaches to the uniform communication of hazard information, risk, probabilities, and uncertainty; and a new focus on community impediments to the uptake of hazard information.
Insurance risk and climate change
Graph showing a climate shift.
The insurance industry has a real need to understand the risk implications of the likely changes to our climate. Already, the global re-insurance sector is very conscious of the rise in the losses due to damage caused by natural hazard events worldwide over the past two decades. To help IAG NZ (incorporating the NZI & State brands) gain a fuller appreciation of the likely changes in risk over the next 50 years, Drs Warren Gray and Rob Bell (NIWA) joined with Bruce Thomas (Swiss Re), Jeff Patchett (IAG NZ Ltd), Tony Coleman (IAG, Australia), and Brendan Morris (Environment Waikato) to give presentations on climate change effects on weather and coastal hazards. The IAG NZ risk analysts and business managers present were all keen to garner a better understanding of the often-vaunted climate change scenarios and what it will mean for underwriting in the future.
Dr Gray talked about the implications of climate change for the “hazardous” end of the climate variability spectrum and discussed how global climate change implications for the average climate could be interpreted. For example, a 1 °C increase in temperature implies not only that the rain is likely to be 8% more intense (as a result of the increased water holding capacity of warmer air), but that the extra heat released in the formation of that extra rain would further intensify storms, leading to a positive feedback. Recent climate change models also predict an increase in the temperature contrasts between the pole and equator in our region. This is an energy source for our weather systems, and could lead to more storms, more vigorous storms, or both.
Natural hazards in winter 2003
Landslides |
Coastal hazards |
Weather extremes |
Weather extremes - Rainfall |
Floods and droughts |
Earthquakes and volcanic activity |
Data sources for these maps: GeoNet, NIWA, MetService, Regional Councils
Tsunami hits the Chathams
The area where the village was pre 1868.
On 15 August 1868, some hours after a powerful earthquake off Chile, a tsunami struck the Chatham Islands. The first wave washed into the huts of a Maori village on the northwest coast of the main island. People rushed to higher ground before the much higher second wave arrived 10 minutes later. The entire village and several other houses, huts, and boats were totally destroyed, and one person was drowned. No lives were lost on mainland New Zealand, but the tsunami caused dramatic ebbing and flowing of waters, damaged harbour facilities, and scoured beaches.
Spotlight on ...
Large earthquake strikes Fiordland
Earthquake scars
Totara Park, Upper Hutt.
Just after midnight on Thursday, 21 August, one of the largest earthquakes ever in Fiordland occurred near the northern tip of Secretary Island, at the mouth of Doubtful Sound. It was of magnitude 7.1, and was felt most strongly in Te Anau and Manapouri, although these places are both about 70 km from the epicentre. Had the earthquake been closer to any populated area, much damage would have resulted. It was felt over most of the South Island, and even at a few places in the lower North Island.
Tectonics
In the Fiordland region, the Australian and Pacific plates are converging obliquely, and the Australian plate is subducting beneath the coast in a southeasterly direction. Large earthquakes from 1938 to 1988 have occurred within both the subducted and overlying plates. In contrast, the magnitude 6.4 Doubtful Sound earthquake of 1989 and the magnitude 6.8 Secretary Island earthquake of 1993 represent motion between the plates at shallow depth. The larger earthquake of 21 August has continued this trend. An important aspect of this most recent earthquake is how it has in turn affected the stress regime in the overlying plate, particularly on the nearby strands of the Alpine Fault.
GPS results
In February 2001, GPS measurements were made at sites throughout Fiordland by a joint University of Otago–GNS team. A number of these sites in the epicentral region were reoccupied between 29 August and 3 September, and a model of the displacements that had occurred in the earthquake was produced. All GPS observations of displacement were used in a least-squares procedure to determine the best fitting fault plane and source parameters. The maximum vertical motion measured was 13 cm of subsidence, though the model predicts only 9.5 cm. At most other stations the modelled vertical displacement agrees with the observations to better than 1–1.5 cm.
Landslides and ground damage
The earthquake was felt very strongly over much of Otago and Southland, and caused minor, but sometimes spectacular, damage throughout the region, with items thrown off shelves in Te Anau and Queenstown, and minor cracking to some concrete structures. So far more than 2100 claims for damage have been received by EQC. Landslide damage was very extensive and widespread throughout the mountainous and the unpopulated epicentral region, 50–70 km west of Te Anau. More than 400 landslides were triggered by the earthquake. Landslides ranged from small debris flows involving a few trees and a few tens of cubic metres of soil, to large debris slides and rock falls running 1000 m downhill.
Tsunami
A small tsunami about 20 cm high was generated by the earthquake and recorded on the tide gauges at Port Jackson, and also in Australia. This height is consistent with having been caused by the modelled uplift offshore. A larger localised tsunami generated by a landslide in Gold Arm of Charles Sound affected an area of about 0.45 km2 on the opposite bank. Seiching caused by the earthquake was observed in Lake Manapouri.
Land use planning on or close to active faults – guidelines for planners
A guide has been developed to provide direction on land use planning approaches for land on or close to active faults to assist regional and district planners in New Zealand.
The guide contains basic principles for planning approaches, easy-to-understand information about earthquakes, fault rupture, fault hazard maps, and ideas for developing suitable policy in areas subject to fault rupture, along with a few tricky exercises to test your knowledge.
The aim of the guidelines is to help local authorities minimise the hazard risk and the time it takes for individuals, communities, and the government to recover from fault rupture.
A range of professionals with expertise and interest in land use issues and hazard risk reduction contributed to developing the guidelines, including the Institute of Geological & Nuclear Sciences, Ministry for the Environment, Geological Society of NZ, NZ Society of Earthquake Engineering, BRANZ, and the Earthquake Commission.
A copy of the guideline document “Planning for development of land on or close to active faults – an interim guideline to assist resource management planners in New Zealand” is available at www.qualityplanning.org.nz.
Coasts and Ports Australasian Conference 2003
Coastal hazards management and case studies featured at the Coasts and Ports Australasian Conference 2003 that was held in Auckland in September. This biennial conference was also the venue for the 16th Australasian Coastal and Ocean Engineering Conference, the 9th Australasian Port and Harbour Conference, and the annual NZ Coastal Society Conference. The conference attracted 350 delegates from 10 countries, and there were 180 technical papers addressing engineering, scientific, planning, and resource management issues of the coastal zone. The theme of “Coastal development: a quest for excellence” inspired a range of papers on coastal hazards, covering wave climate assessments, coastal setbacks, guidance notes, coastal planning, coastal protection, design of port structures, cliff and beach erosion, design of cyclone shelters, and storm frequencies.
The abstracts will be made available on the NZ Coastal Society website and the CD-Rom of proceedings can be purchased through the same site: www.cae.canterbury.ac.nz/nzcs/About.htm
The next conference is in Adelaide in 2005.