DOCSLIB.ORG

The Canterbury Earthquakes: Scientific Answers to Critical Questions

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Canterbury Earthquakes: Scientific Answers to Critical Questions OFFICE OF THE PRIME MINISTER’S SCIENCE ADVISORY COMMITTEE The Canterbury Earthquakes: Scientific answers to critical questions The Canterbury region has had six months of unexpected and extremely difficult challenges as a result of a sequence of damaging and deadly earthquakes and the associated aftershocks. The result is significant uncertainty within the public about why the February 22 aftershock was so damaging and deadly compared to the larger magnitude event on September 4, 2010. In order to provide information on these and other questions, the Royal Society of New Zealand, together with the Office of the Prime Minister’s Science Advisory Committee, has convened a group of earthquake science experts including those from the Natural Hazards Research Platform, a collaborative research consortia hosted by GNS Science, to provide answers to critical questions based on current best scientific information and knowledge. An enormous scientific effort is underway but it is difficult to define all of the critical attributes of an earthquake quickly after the event. As a result, our understanding of these earthquakes will improve and much more information will become available to be used in further scientific analyses and advice in the weeks and months ahead. The information below is provided for the purpose of improved understanding of the science relating to the Canterbury earthquakes. Prediction Why didn’t scientists know about the faults that caused the two earthquakes? Prior to September 4th, there were no surface signs of the Greendale Fault or the fault that generated the Lyttelton aftershock and there was no evidence for seismicity on these faults (i.e. ‘foreshocks’). Seismic surveys have located some ‘hidden’ faults across parts of the Canterbury Plains, but these particular regions had not been surveyed for this purpose. An oil-gas seismic survey had been carried out but did not reveal any convincing evidence for the presence of the Greendale Fault. Following September 4th, there was significant aftershock activity in the area of the Lyttelton Fault and around many faults in the region but there was no clear indication that a larger earthquake was imminent there. It was predicted that aftershocks from the September 2010 earthquake might reach magnitude 6, and some smaller aftershocks had already occurred under Christchurch city. Why wasn’t some warning given about the possibility of a big and damaging aftershock under the city? Warnings were given over the risks from large aftershocks1. The prediction of aftershocks of approximately magnitude 6 is based on statistical analysis of historical earthquakes (Bath’s Law), 1 http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10671602 1 | Page which states “the average difference in magnitude between a mainshock and its largest aftershock is 1.2, regardless of the mainshock magnitude”. A quick survey of some of New Zealand’s largest historical earthquakes conforms to this average, although there is significant variability. The 6.3 aftershock is not outside the average range. The isolated and smaller aftershocks that occurred under the city CBD do not necessitate the presence of a larger fault capable of generating larger earthquakes, however this is possible. Seismic and aerial surveys are targeting this area in the near future to provide constraints on the geometry, extent, and magnitude potential of a fault under the city. Why did the February aftershock occur so long after the September 2010 earthquake? It is not unusual to have a 6 month gap between a magnitude 7.1 earthquake and a 6.3 aftershock. How predictable was the 22 February quake - and what was the influence of the moon and the tides; do more earthquakes happen at night? Despite substantial scientific effort, the specific timing, location, or magnitude of earthquakes cannot be predicted. Although it is not possible to reliably predict individual earthquakes, it is possible and routine to identify areas and times of higher or lower earthquake activity based on models of crustal stresses and faulting. In addition, on the basis of observations of past earthquakes, it is possible to expect a series of aftershocks after an earthquake which follows a general and decreasing pattern, but there is always some level of unpredictability as to their timing, location and severity. For this reason, it is not possible to give specific predictions about aftershocks in terms of severity, location and timing. Recent popularized ‘predictions’ regarding the Canterbury earthquakes and their relationship to phases of the moon are not scientifically correct. Although there is some evidence that the moon can sometimes influence very small earth tremors, there is no credible evidence linking the moon to medium or large earthquakes. There is no relationship between the time of day and the frequency of earthquakes. More earthquakes will be felt at night only because people are in bed or at rest and thus have more contact with the ground, making them more sensitive to feeling the ground movement during earthquakes. Are the recent natural disasters in Queensland, Japan and New Zealand linked in any way? No. The Canterbury earthquakes are in no way related to the flooding events in Queensland or the massive earthquake in Japan. Facts Why was the magnitude 6.3 earthquake able to cause so much more destruction in the CBD and Christchurch suburbs than the magnitude 7.1 quake last September? The main reason was that the earthquake was so close to Christchurch. Although the total energy released by the 22 February 6.3 aftershock was only about 1/20 of the energy from last 2 | Page September’s magnitude 7.1 event, the 6.3 event was much closer to the Christchurch CBD (~6 km to the SE) than the 7.1 earthquake (~44 km W of Christchurch CBD) so a greater percentage of the total energy released from the 6.3 earthquake hit Christchurch itself (See Figures 1 -3). Seismic energy spreads out away from an earthquake and at the same time is absorbed by the Earth. Damage generally decreases with increasing distance from the earthquake. In September the region with very high ground accelerations (comparable to those felt in the CBD in February) was near Hororata and Greendale, away from major population centres. In the Christchurch CBD, the ground accelerations produced by the February magnitude 6.3 earthquake were 3-4 times greater than during the 7.1 earthquake; in the eastern suburbs they were about 6 times greater2. In summary, it was the closeness of the earthquake to the city and its shallowness that led to the increased destruction. Overall the levels of ground shaking in the CBD during the magnitude 6.3 earthquake were consistent with ground shaking observed for other similar-sized earthquakes elsewhere in the world. Figure 1: Graphic showing location of main shock, aftershocks above magnitude 3, and fault ruptures in Canterbury. Graphic by Rob Langridge and William Ries, GNS Science. 2 USGS http://earthquake.usgs.gov/learn/topics/NewZealand2011_slides.ppt 3 | Page Figure 2: Christchurch Earthquake Population Exposure showing the extent of earthquake ground shaking (represented in colour) overlain on population density (represented as height of vertical bars) at a grid size of 1 km2. The colour key is based on the Mercalli scale, which is a measure of shaking, and explains how sever the ground shaking is for each colour. (Source: USGS) 4 | Page Figure 3a and 3b: Comparisons of the ground accelerations in the Christchurch CBD between the 2011 Christchurch and 2010 Darfield earthquake. Left to right, the recordings are arranged roughly in increasing distance from the epicenter of the earthquake on 22 February 2011 Was the Christchurch magnitude 6.3 earthquake an aftershock? Yes. The term ‘aftershock’ refers to an earthquake that is smaller in magnitude than the preceding main shock, part of the sequence of earthquakes that closely follows the main shock in time, and in the region influenced by changes in crustal stress levels due to the main shock. The M 6.3 earthquake fits all of these criteria and is therefore considered an aftershock. What is liquefaction and what causes it? Liquefaction is the term used to describe when some soils behave more like a liquid than a solid during the shaking from an earthquake. During an earthquake the soil particles are rearranged and compacted, forcing out water onto the surface, creating sand volcanoes or sand boils, water fountains and surface cracking (See Figure 3). Along with liquefaction, lateral spread can also occur, which is when the liquefied soil flows in to lower areas such as river channels, under the force of gravity. 5 | Page Figure 4: A representation of the liquefaction process (source: Environment Canterbury) After liquefaction, does the ground ever stabilise again? The risks from liquefaction will remain. Strength-depth profiles under some parts of Christchurch indicate up to 9m of ‘liquefiable’ material. Immediately following some of the largest aftershocks from the 7.1 earthquake, liquefaction reappeared in the same areas. During the 6.3 earthquake, liquefaction was widespread and vents continued to surge during the aftershocks immediately following this event. Although some ground settlement may occur, the large reservoir of liquefiable material and these examples suggest that similar characteristics of ground shaking are likely to result in similar amounts of liquefaction in the future. Have new faults appeared under Christchurch after these earthquakes? It is not yet known. All aftershocks are earthquakes and most earthquakes occur on faults. There has been some aftershock activity under Christchurch, however this activity has occurred on small faults that may not be connected. In order to better understand the extent of faults under the city, further seismic studies are required. Are the faults around Christchurch a southern extension of the Marlborough Fault Zone? No.
Load more

Recommended publications
  • Regional Overview
    Air, land and water in the Wellington region – state and trends Regional overview This summary highlights the key findings from State of the Environment monitoring we carry out of natural resources across the Wellington region. It is drawn from eight technical reports which give the full picture of the health of the Wellington region’s air, land, fresh waters and coast. The reports, published every five years, are based on environmental monitoring and investigations over the past five to ten years (and longer for some resources). The findings are informing the current review of Greater Wellington’s regional plans – the ‘rule books’ for ensuring our region’s natural resources are sustainably managed. These plans are now more than ten years old and we are developing a new integrated plan. Community input to the review is critical – you can find out how to have a say on the back page. How do we measure the health of the region’s air, land and water resources? Regional councils have a legal responsibility under section 35 of the Resource Management Act 1991 to monitor the state of the environment – this essentially means tracking the quality and quantity of the region’s natural resources over time. Greater Wellington does this through long-term monitoring programmes across the region focusing on: ● Air quality at 6 locations ● Soil quality (118 sites under a range of different land uses) and stability ● Rainfall (at 50 sites) and river flows/levels (at 45 sites) ● Groundwater levels (at 146 sites) and quality (at 71 sites) ● Water quality at popular river and beach recreation spots (100 sites) ● River/stream water quality and ecosystem health (at 55 sites) ● The health of selected estuaries and our two harbours Measuring river flow We also carry out short-term investigations where our routine monitoring identifies gaps or potential problems, such as poor air or water quality.
    [Show full text]
  • Using Campaign GPS Data to Model Slip Rates on the Alpine Fault
    New Zealand Journal of Geology and Geophysics ISSN: 0028-8306 (Print) 1175-8791 (Online) Journal homepage: http://www.tandfonline.com/loi/tnzg20 A geodetic study of the Alpine Fault through South Westland: using campaign GPS data to model slip rates on the Alpine Fault Chris J. Page, Paul H. Denys & Chris F. Pearson To cite this article: Chris J. Page, Paul H. Denys & Chris F. Pearson (2018): A geodetic study of the Alpine Fault through South Westland: using campaign GPS data to model slip rates on the Alpine Fault, New Zealand Journal of Geology and Geophysics, DOI: 10.1080/00288306.2018.1494006 To link to this article: https://doi.org/10.1080/00288306.2018.1494006 View supplementary material Published online: 09 Aug 2018. Submit your article to this journal View Crossmark data Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=tnzg20 NEW ZEALAND JOURNAL OF GEOLOGY AND GEOPHYSICS https://doi.org/10.1080/00288306.2018.1494006 RESEARCH ARTICLE A geodetic study of the Alpine Fault through South Westland: using campaign GPS data to model slip rates on the Alpine Fault Chris J. Page, Paul H. Denys and Chris F. Pearson School of Surveying, University of Otago, Dunedin, New Zealand ABSTRACT ARTICLE HISTORY Although the Alpine Fault has been studied extensively, there have been few geodetic studies Received 11 December 2017 in South Westland. We include a series of new geodetic measurements from sites across the Accepted 25 June 2018 Haast Pass and preliminary results from a recently established network, the Cascade array KEYWORDS that extends from the Arawhata River to Lake McKerrow, a region that previously had few Alpine Fault; slip rates; South geodetic measurements.
    [Show full text]
  • Tectonic Setting Seismic Hazard Epicentral Region
    U.S. DEPARTMENT OF THE INTERIOR EARTHQUAKE SUMMARY MAP U.S. GEOLOGICAL SURVEY Prepared in cooperation with the M8.0 Samoa Islands Region Earthquake of 29 September 2009 Global Seismographic Network M a r s Epicentral Region h a M A R S H A L L l I S TL A eN DcS tonic Setting l 174° 176° 178° 180° 178° 176° 174° 172° 170° 168° 166° C e n t r a l 160° 170° I 180° 170° 160° 150° s l a P a c i f i c K M e l a n e s i a n n L NORTH a d B a s i n i p B a s i n s n Chris tmas Island i H e BISMARCK n C g I R N s PLATE a l B R I TA i G E I s E W N T R 0° m a 0° N E R N e i n P A C I F I C 10° 10° C a H l T d b r s a e r C P L A T E n t E g I D n e i s A o Z l M e a t u r SOUTH n R r a c d E K I R I B A T I s F s K g o BISMARCK l a p a PLATE P A C I F I C G a Solomon Islands P L A T E S O L O M O N T U V A L U V I T Y I S L A N D S A Z TR FUTUNA PLATE 12° 12° S EN O U C BALMORAL C 10° T H H o 10° S O REEF o WOODLARK L Santa k O M Cruz PLATE I PLATE O N T RE N C H Sam sl Is lands oa I NIUAFO'OU a N s n C o r a l S e a S A M O A lan d SOLOMON SEA O ds PLATE s T U B a s i n R A M E R I C A N (N A PLATE T M H .
    [Show full text]
  • Mylonitization Temperatures and Geothermal Gradient from Ti-In
    Solid Earth Discuss., https://doi.org/10.5194/se-2018-12 Manuscript under review for journal Solid Earth Discussion started: 7 March 2018 c Author(s) 2018. CC BY 4.0 License. Constraints on Alpine Fault (New Zealand) Mylonitization Temperatures and Geothermal Gradient from Ti-in-quartz Thermobarometry Steven Kidder1, Virginia Toy2, Dave Prior2, Tim Little3, Colin MacRae 4 5 1Department of Earth and Atmospheric Science, City College New York, New York, 10031, USA 2Department of Geology, University of Otago, Dunedin, New Zealand 3School of Geography, Environment and Earth Sciences, Victoria University of Wellington, Wellington, New Zealand 4CSIRO Mineral Resources, Microbeam Laboratory, Private Bag 10, 3169 Clayton South, Victoria, Australia Correspondence to: Steven B. Kidder ([email protected]) 10 Abstract. We constrain the thermal state of the central Alpine Fault using approximately 750 Ti-in-quartz SIMS analyses from a suite of variably deformed mylonites. Ti-in-quartz concentrations span more than an order of magnitude from 0.24 to ~5 ppm, suggesting recrystallization of quartz over a 300° range in temperature. Most Ti-in-quartz concentrations in mylonites, protomylonites, and the Alpine Schist protolith are between 2 and 4 ppm and do not vary as a function of grain size or bulk rock composition. Analyses of 30 large, inferred-remnant quartz grains (>250 µm), as well as late, cross-cutting, chlorite-bearing 15 quartz veins also reveal restricted Ti concentrations of 2-4 ppm. These results indicate that the vast majority of Alpine Fault mylonitization occurred within a restricted zone of pressure-temperature conditions where 2-4 ppm Ti-in-quartz concentrations are stable.
    [Show full text]
  • Geophysical Structure of the Southern Alps Orogen, South Island, New Zealand
    Regional Geophysics chapter 15/04/2007 1 GEOPHYSICAL STRUCTURE OF THE SOUTHERN ALPS OROGEN, SOUTH ISLAND, NEW ZEALAND. F J Davey1, D Eberhart-Phillips2, M D Kohler3, S Bannister1, G Caldwell1, S Henrys1, M Scherwath4, T Stern5, and H van Avendonk6 1GNS Science, Gracefield, Lower Hutt, New Zealand, [email protected] 2GNS Science, Dunedin, New Zealand 3Center for Embedded Networked Sensing, University of California, Los Angeles, California, USA 4Leibniz-Institute of Marine Sciences, IFM-GEOMAR, Kiel, Germany 5School of Earth Sciences, Victoria University of Wellington, Wellington, New Zealand 6Institute of Geophysics, University of Texas, Austin, Texas, USA ABSTRACT The central part of the South Island of New Zealand is a product of the transpressive continental collision of the Pacific and Australian plates during the past 5 million years, prior to which the plate boundary was largely transcurrent for over 10 My. Subduction occurs at the north (west dipping) and south (east dipping) of South Island. The deformation is largely accommodated by the ramping up of the Pacific plate over the Australian plate and near-symmetric mantle shortening. The initial asymmetric crustal deformation may be the result of an initial difference in lithospheric strength or an inherited suture resulting from earlier plate motions. Delamination of the Pacific plate occurs resulting in the uplift and exposure of mid- crustal rocks at the plate boundary fault (Alpine fault) to form a foreland mountain chain. In addition, an asymmetric crustal root (additional 8 - 17 km) is formed, with an underlying mantle downwarp. The crustal root, which thickens southwards, comprises the delaminated lower crust and a thickened overlying middle crust.
    [Show full text]
  • Constraints on Alpine Fault (New Zealand) Mylonitization Temperatures and the Geothermal Gradient from Ti-In-Quartz Thermobarometry
    Solid Earth, 9, 1123–1139, 2018 https://doi.org/10.5194/se-9-1123-2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Constraints on Alpine Fault (New Zealand) mylonitization temperatures and the geothermal gradient from Ti-in-quartz thermobarometry Steven B. Kidder1, Virginia G. Toy2, David J. Prior2, Timothy A. Little3, Ashfaq Khan1, and Colin MacRae4 1Department of Earth and Atmospheric Science, City College New York, New York, 10031, USA 2Department of Geology, University of Otago, Dunedin, New Zealand 3School of Geography, Environment and Earth Sciences, Victoria University of Wellington, Wellington, New Zealand 4CSIRO Mineral Resources, Microbeam Laboratory, Private Bag 10, 3169 Clayton South, Victoria, Australia Correspondence: Steven B. Kidder ([email protected]) Received: 22 February 2018 – Discussion started: 7 March 2018 Revised: 28 August 2018 – Accepted: 3 September 2018 – Published: 25 September 2018 Abstract. We constrain the thermal state of the central when more fault-proximal parts of the fault were deforming Alpine Fault using approximately 750 Ti-in-quartz sec- exclusively by brittle processes. ondary ion mass spectrometer (SIMS) analyses from a suite of variably deformed mylonites. Ti-in-quartz concentrations span more than 1 order of magnitude from 0.24 to ∼ 5 ppm, suggesting recrystallization of quartz over a 300 ◦C range in 1 Introduction temperature. Most Ti-in-quartz concentrations in mylonites, protomylonites, and the Alpine Schist protolith are between The Alpine Fault is the major structure of the Pacific– 2 and 4 ppm and do not vary as a function of grain size Australian plate boundary through New Zealand’s South Is- or bulk rock composition.
    [Show full text]
  • GEOTECHNICAL RECONNAISSANCE of the 2011 CHRISTCHURCH, NEW ZEALAND EARTHQUAKE Version 1: 15 August 2011
    GEOTECHNICAL RECONNAISSANCE OF THE 2011 CHRISTCHURCH, NEW ZEALAND EARTHQUAKE Version 1: 15 August 2011 (photograph by Gillian Needham) EDITORS Misko Cubrinovski – NZ Lead (University of Canterbury, Christchurch, New Zealand) Russell A. Green – US Lead (Virginia Tech, Blacksburg, VA, USA) Liam Wotherspoon (University of Auckland, Auckland, New Zealand) CONTRIBUTING AUTHORS (alphabetical order) John Allen – (TRI/Environmental, Inc., Austin, TX, USA) Brendon Bradley – (University of Canterbury, Christchurch, New Zealand) Aaron Bradshaw – (University of Rhode Island, Kingston, RI, USA) Jonathan Bray – (UC Berkeley, Berkeley, CA, USA) Misko Cubrinovski – (University of Canterbury, Christchurch, New Zealand) Greg DePascale – (Fugro/WLA, Christchurch, New Zealand) Russell A. Green – (Virginia Tech, Blacksburg, VA, USA) Rolando Orense – (University of Auckland, Auckland, New Zealand) Thomas O’Rourke – (Cornell University, Ithaca, NY, USA) Michael Pender – (University of Auckland, Auckland, New Zealand) Glenn Rix – (Georgia Tech, Atlanta, GA, USA) Donald Wells – (AMEC Geomatrix, Oakland, CA, USA) Clint Wood – (University of Arkansas, Fayetteville, AR, USA) Liam Wotherspoon – (University of Auckland, Auckland, New Zealand) OTHER CONTRIBUTORS (alphabetical order) Brady Cox – (University of Arkansas, Fayetteville, AR, USA) Duncan Henderson – (University of Canterbury, Christchurch, New Zealand) Lucas Hogan – (University of Auckland, Auckland, New Zealand) Patrick Kailey – (University of Canterbury, Christchurch, New Zealand) Sam Lasley – (Virginia Tech, Blacksburg, VA, USA) Kelly Robinson – (University of Canterbury, Christchurch, New Zealand) Merrick Taylor – (University of Canterbury, Christchurch, New Zealand) Anna Winkley – (University of Canterbury, Christchurch, New Zealand) Josh Zupan – (University of California at Berkeley, Berkeley, CA, USA) TABLE OF CONTENTS 1.0 INTRODUCTION 2.0 SEISMOLOGICAL ASPECTS 3.0 GEOLOGICAL ASPECTS 4.0 LIQUEFACTION AND LATERAL SPREADING 5.0 IMPROVED GROUND 6.0 STOPBANKS 7.0 BRIDGES 8.0 LIFELINES 9.0 LANDSLIDES AND ROCKFALLS 1.
    [Show full text]
  • Presentation of September 4, 2010 Canterbury Earthquake
    Presentation of September 4, 2010 Canterbury Earthquake William Godwin, PG, CEG AEG Vice President, 2019-20 Webinar – May 6, 2020 Introduction ► This presentation is on the 2010 Mw 7.1 Canterbury Earthquake. The earthquake occurred as I was traveling from San Francisco to Auckland, New Zealand to attend the IAEG Congress. Upon arrival I was asked to join the Geotechnical Extreme Events Reconnaissance (GEER) team to document damage from the event in the Christchurch area of the South Island. Little did I know that another smaller (Mw 6.2), yet deadlier earthquake would strike 5 months later in close to the same area. Introduction ► The purpose of the GEER is to observe and record earthquake induced phenomena and impacts to infrastructure before evidence is removed or altered as part of cleanup efforts. ► The reconnaissance was conducted by a joint USA-NZ-Japan team with the main funding for the USA contingent coming from GEER and partial support from PEER and EERI. ► This presentation includes my photographs from Sept. 8-10 supplemented with a few photos and observations noted in the GEER report, Nov. 2010. I also describe other seismic events from 2011-16. Sept 4th Darfield Earthquake ► At 4:35 am on September 4th NZ Standard Time (16:35 Sept 3rd UTC) the rupture of a previously unrecognized strike-slip fault (Greendale Fault) beneath the Canterbury Plains of New Zealand’s South Island produced a Mw 7.1 earthquake that caused widespread damage throughout the region. Surprisingly only two people were seriously injured, with approximately 100 total injuries. This compares with 185 deaths in the 2011 event Canterbury Earthquake Sequence Greendale Fault Rupture Characteristics Epicenter (focal) depth: 10.8km Tectonic Setting Ground Motion (pga) Geographical Setting Preliminary Observations ► Rock Avalanche, Castle Rock Reserve, Littleton, Christchurch ► Fault Offset, Telegraph Rd at Grange Rd.
    [Show full text]
  • Employment Analysis Report
    Employment Analysis October 2020 Wellington Regional Growth Framework | 0 Introduction Ka ora te wai If the water is healthy Purpose of this report More detailed work, than has been undertaken in the Ka ora te whenua the land will be nourished The purpose of this report is to summarise existing Framework, will need to be undertaken to Ka ora te whenua If the land is nourished research and data to assist with regional spatial understand in more detail: Ka ora te tangata the people will be provided planning. No new analysis has been undertaken. This 1. How many jobs do we expect in each for report should be read as an input into other work, geographical area as of 2050? and not as a final conclusion on the spatial direction 2. What change is that from the current situation? for the Framework or as policy for any of the partner Mo te iti - mo te rahi For the little - for the large 3. What type of jobs are they? organisations. 4. What do we need to do to make this change? 1 As outlined in the Foundation Report for the This report builds upon the Foundation Report to Wellington Regional Growth Framework (the 2 provide background information to assist in analysing Framework), employment in the region is employment patterns and information and concentrated in central Wellington and a significant determine what changes may/could occur with number of commuters travel into central Wellington regards to employment and the Framework. from other parts of the region for employment. A key direction during development of the Regional employment is dominated by knowledge- Framework with regards to employment has been to based sector employment.
    [Show full text]
  • GPH 333 Canterbury Eartquakes Research Paper
    The Canterbury Tales: How Neogene Shortening and Brittle Shear Failure Cause the Reactivation of Inherited and New Fault Systems underneath the Canterbury Plains, New Zealand Andrew J Pugh Abstract Two notable earthquakes occurred in Canterbury, New Zealand between September 2010 and February 2011. The first in Darfield Mw 7.1 and Christchurch Mw 6.2 devastated the region along a previously unknown right-lateral strike-slip fault. The fault lies southeast of the Alpine Transform with an enigmatic motion that does not comply with the expected sense of slip in other parts of the region. To date no conclusive answers has been brought forth to explain the reasons behind a near east-west strike-slip fault in this area. Many hypotheses exist with the most likely being that an evolving stress field is reactivating inherited high angles faults and, through brittle deformation, new fault systems are being created. The Greendale Fault is important to study because of the potential catastrophic impact of a large earthquake given that 12.5% of New Zealand’s total population calls the Canterbury region home. By examining the kinematic mechanisms responsible for the Greendale Fault using InSAR, LiDAR, and Stress modeling, this paper seeks to gain a better understanding on what caused this fault to suddenly rupture in an area of relatively “quiet” activity. Introduction Between September 2010 and February 2011 two large earthquakes occurred along a previously unknown strike-slip fault east of Christchurch, New Zealand. It is not so much a surprise that these earthquakes happened but the nature of them. In other words, the two events that will be discussed, Darfield and Christchurch, occurred on a right-lateral strike-slip fault.
    [Show full text]
  • Variability in Single Event Slip and Recurrence Intervals for Large
    Variability of single event slip and recurrence intervals for large magnitude paleoearthquakes on New Zealand’s active faults A. Nicol R. Robinson R. J. Van Dissen A. Harvison GNS Science Report 2012/41 December 2012 BIBLIOGRAPHIC REFERENCE Nicol, A.; Robinson, R.; Van Dissen, R. J.; Harvison, A. 2012. Variability of single event slip and recurrence intervals for large magnitude paleoearthquakes on New Zealand’s active faults, GNS Science Report 2012/41. 57 p. A. Nicol, GNS Science, PO Box 30368, Lower Hutt 5040, New Zealand R. Robinson, PO Box 30368, Lower Hutt 5040, New Zealand R. J. Van Dissen, PO Box 30368, Lower Hutt 5040, New Zealand A. Harvison, PO Box 30368, Lower Hutt 5040, New Zealand © Institute of Geological and Nuclear Sciences Limited, 2012 ISSN 1177-2425 ISBN 978-1-972192-29-0 CONTENTS LAYMANS ABSTRACT ....................................................................................................... IV TECHNICAL ABSTRACT ..................................................................................................... V KEYWORDS ......................................................................................................................... V 1.0 INTRODUCTION ........................................................................................................ 1 2.0 GEOLOGICAL EARTHQUAKES ................................................................................ 2 2.1 Data Sources ................................................................................................................. 2 2.2
    [Show full text]
  • Paleoseismology of the 2010 Mw 7.1 Darfield (Canterbury) Earthquake Source, Greendale Fault, New Zealand
    BIBLIOGRAPHIC REFERENCE Hornblow, S.; Nicol, A.; Quigley, M.; Van Dissen, R. J. 2014. Paleoseismology of the 2010 Mw 7.1 Darfield (Canterbury) earthquake source, Greendale Fault, New Zealand, GNS Science Report 2014/26. 27 p. S. Hornblow, Department of Geological Sciences, University of Canterbury, Christchurch, New Zealand A. Nicol, GNS Science, GNS Science, PO Box 30368, Lower Hutt, New Zealand M. Quigley, Department of Geological Sciences, University of Canterbury, Christchurch, New Zealand R. J. Van Dissen, GNS Science, GNS Science, PO Box 30368, Lower Hutt, New Zealand © Institute of Geological and Nuclear Sciences Limited, 2014 ISSN 1177-2425 (Print) ISSN 2350-3424 (Online) ISBN 978-1-927278-50-5 CONTENTS LAYMAN’S ABSTRACT ....................................................................................................... III TECHNICAL ABSTRACT .................................................................................................... IV KEYWORDS ........................................................................................................................ IV 1.0 INTRODUCTION ........................................................................................................ 1 2.0 TECTONIC, GEOLOGIC AND GEOMORPHIC SETTING .......................................... 4 3.0 GEOMETRY AND SLIP OF THE DARFIELD EARTHQUAKE RUPTURE ................. 6 4.0 FAULT TRENCHING .................................................................................................. 7 4.1 HIGHFIELD ROAD ..............................................................................................
    [Show full text]