Re-establishing Canterbury earthquake affected boundaries in greater Christchurch

Guidance on meeting the requirements for cadastral survey datasets (CSDs) that are being prepared under the Cadastral Survey Rules 2021 (CSR 2021) to redefine parcel boundaries affected by the Canterbury earthquake sequence in greater Christchurch.

On this page

Overview

In the aftermath of the Darfield earthquake and subsequent aftershocks there were inconsistent approaches taken to redefining boundaries where the underlying land was subject to uniform block shift, deep-seated distortion, shear at fault rupture and surface layer distortion due to liquefaction. Rule 18 of the Rules for Cadastral Survey 2010 (RCS 2010) was introduced in November 2012 and confirmed that where deep-seated movement had distorted an existing boundary, that boundary must reflect that distortion. The rule also required that boundaries on land subject to uniform block shift must be re-established in terms of that block shift.

The earthquakes produced the first major incidence of liquefaction seen in recent history. The approach taken for defining boundaries affected by shallow surface movement was to reinstate these boundaries in their original positions relative to survey marks that retained the same relationship to each other as they held before the earthquakes. This approach resulted in many instances of reinstated boundaries being offset from occupation that had previously marked the boundary, which in turn led to a public loss of confidence in the cadastre.

The Canterbury Property Boundaries and Related Matters Act 2016 (CPB Act) was enacted to deal specifically with boundary movement resulting from the Canterbury earthquakes. This act stipulates that all boundaries within greater Christchurch are deemed to have moved with the movement of land caused by the Canterbury earthquakes, unless that movement was a landslip. Rule 20 was added to the RCS 2010 in April 2017 to specify requirements for cadastral surveys carried out under the CPB Act.

The requirements of rules 18 and 20 RCS 2010 have been combined into Part 8 Ground Movement (rules 108 to 111) of the CSR 2021. The provisions of the CPB Act are only applicable within the greater Christchurch area and not to the rest of New Zealand. Consequently, some ground movement rules in the CSR 2021 only apply to greater Christchurch.

This guideline relates to ground movement in greater Christchurch caused by the Canterbury earthquakes.

For information about dealing with other types of ground movement see the separate guideline

Key terms

Affected boundary - means a boundary where ground movement has distorted the land in excess of the relevant accuracy tolerances of the CSR 2021 and that has not been subsequently defined by survey and recorded in an approved CSD (r 108).

Approved interim survey – all surveys within greater Christchurch approved by LINZ in the period starting on 4 September 2010 and ending at the commencement of the CPB Act on 30 August 2016 (s 9(1) CPB Act).

Avulsion – where the change in the physical boundary between land and water was not gradual and imperceptible, but either sudden or perceptible as it was occurring.

Canterbury earthquakes – any earthquake in Canterbury in the period starting on 4 September 2010 and ending on 13 February 2022 and includes any aftershock in that period (s 4 CPB Act).

Canterbury earthquake movement - means the movement of land caused by the Canterbury earthquakes (whether the movement was horizontal or vertical, or both), unless the movement was a landslip, as defined under section 8(2) of the CPB Act (r 108).

Earthquake – the shaking and possible deformation of the earth’s surface resulting from the sudden release of locked parts along a fault line.

Disturbed survey mark – means an old survey mark that is in a different position from where it was originally placed, but does not include a change of position due to Canterbury earthquake movement or fault zone movement (schedule 2 CSR 2021).

Fault zone movement - means movement on a fault caused by the deformation of bedrock (r 108).

Greater Christchurch – defined under section 4 of the CPB Act as the districts of the Christchurch City Council, the Selwyn District Council and the Waimakariri District Council.
Section 4 of the CPB Act

Ground movement - means both deep-seated movement and/or shallow surface movement resulting from a natural event including landslip, earthquake, slumping, or surface flow.

Interim period - defined under section 4 of the CPB Act as meaning the period starting on 4 September 2010 and ending on the commencement of the CPB Act being 30 August 2016.
Section 4 of the CPB Act

Landslip – defined under section 4 of the CPB Act as the movement in greater Christchurch by way of falling, sliding, or flowing of materials that - (a) formed an integral part of the ground before the movement; but (b) had become loose material after the movement (other than by liquefaction).
Section 4 of the CPB Act

Lateral spreading - lateral spreading refers to landslides of saturated soil deposits that have a fluid-like flow down gentle slopes. These can be triggered by earthquake-induced liquefaction.

Liquefaction - earthquake liquefaction is the process by which saturated, unconsolidated soil sediment near the surface is converted into a suspension during strong and prolonged earthquake shaking. The effect on structures and buildings can be devastating and is a major contributor to urban seismic risk.

Shallow surface movement - movement that is shallow and limited to surface layers, such as that caused by liquefaction of soils or landslip.

Uniform block shift - consistent translation and rotation in a manner that maintains shape but not position or orientation.

Unproven mark – an old survey mark recorded on an approved survey under rule 18.3 RCS 2010 which had not been determined as being either disturbed or undisturbed. The mark type was commonly recorded on an approved interim survey where the mark had likely been affected by Canterbury earthquake ground movement but was not used to re-establish a boundary.

The Canterbury Property Boundaries and Related Matters Act 2016 (CPB Act)

The CPB Act came into force on 30 August 2016 and introduced new principles for re-establishing boundaries that are only applicable to greater Christchurch. It determined that the boundaries in greater Christchurch moved in terms of both shallow and deep-seated ground movement resulting from the Canterbury earthquakes. The CPB Act cannot be applied to earthquake events that occur outside of greater Christchurch or to ground movement events in greater Christchurch that occurred before 4 September 2010 or after 13 February 2022.

The purpose of the act under section 3 CPB Act is to:

  • provide certainty to surveying and titles in greater Christchurch following the Canterbury earthquakes
  • support the planning, rebuilding, and recovery of affected communities, including the repair and rebuilding of land, infrastructure, and other property in greater Christchurch
  • maintain public confidence in the cadastre.

Canterbury Property Boundaries and Related Matters Act 2016

Summary of Canterbury earthquake events

Sequence of events to date:

Event Date Magnitude Location
Darfield 2010 earthquake 4 September 2010 7.1 10km SE of Darfield
February 2011 earthquake 22 February 2011 6.2 10km SE of Christchurch
June 2011 earthquake 13 June 2011 6.0 10km SE of Christchurch
December 2011 earthquake 23 December 2011 5.9 10km E of Christchurch
Valentine’s Day 2016 earthquake 14 February 2016 5.7 Centred in sea 7km E of New Brighton

 

Darfield 2010 earthquake

Also known as the Greendale Fault rupture and the Greendale earthquake. The epicentre was 37km west of Christchurch and was at a relatively shallow depth of 10km. The green line that runs east-west on the map below is the Darfield earthquake fault trace. The east-west trending fault rupture, which occurred along a previously unknown fault line, extended to within 18km of Christchurch city. Analysis of the seismogram records indicate the main shock had primarily strike-slip (sideways) motion, which agrees with the observed 29km long surface fault rupture. Lateral shifts of 4 metres were visible along the surface of the fault rupture. Extensive liquefaction also occurred in east Christchurch and in Kaiapoi.

Greendale fault trace Canterbury

Figure 1: Map of Greendale fault trace

February 2011 earthquake

The magnitude 6.2 earthquake jolted Christchurch city at 12:51pm on 22 February 2011. The epicentre was close to Lyttelton Port about 10km southeast of Christchurch city, at a depth of about 5km. The earthquake was felt across the South Island and parts of the lower and central North Island. While the initial quake only lasted for approximately 10 seconds, the damage was severe because of the location and shallowness of the earthquake's focus in relation to Christchurch as well as previous earthquake damage. Christchurch's central city and eastern suburbs were badly affected. Significant soil liquefaction affected the eastern suburbs, producing around 400,000 tonnes of ejected silt. Liquefaction caused buildings and infrastructure to tilt or sink into the liquefied deposits. The Port Hills sustained extensive land damage in this earthquake including rock fall, small and large-scale landslides, and retaining wall failures.

June 2011 earthquake

The magnitude 6.0 earthquake struck at 2.20pm on 13 June 2011 producing ground accelerations of more than two times the force of gravity (g) in parts of the Port Hills and 0.4 g in the central business district (CBD). There was renewed liquefaction and further damage including partial collapse of already weakened buildings in the CBD. The earthquake was centred 10km southeast of the city within the aftershock zone of the February 2011 earthquake. It was on an approximately north to north-west to south to south-east oriented fault at right angles to the Port Hills fault. The aftershock pattern associated with this earthquake extended south across Banks Peninsula toward Akaroa.

December 2011 earthquake

A magnitude 5.8 earthquake struck east of Christchurch at 1:58pm on 23 December 2011 approximately 8km off the coast of New Brighton. This was followed by a magnitude 5.9 earthquake shortly afterwards at 3:18pm. These were further from built up areas, with slightly lower magnitudes and somewhat greater depth than the biggest shakes. Hence the effects were generally less damaging across most of the region than the previous main earthquakes. However, the location and direction of the fault meant that significant affects were observed in the north-eastern suburbs of Christchurch.

Valentine’s Day 2016 earthquake

On 14th February 2016, a magnitude 5.7 earthquake struck under the sea floor, 7km off the New Brighton coast at a depth of 15km. Most of the landslides generated by the earthquake were cliff collapses (technically called cliff-crest recession and debris avalanches) and boulder rolls (individual boulders bouncing down hills) on the steep cliffs between Redcliffs and Taylors Mistake.

Impact of the CPB Act on title

Under the Land Transfer Act 2017 (LTA 2017) a record of title describes the land in a way that directly or indirectly refers to a Deposited Plan (DP) CSD. The DP shows information enabling the owner (or a surveyor on behalf of the owner) to locate the land on the ground, including:

  • the land parcel in a scale diagram with an area
  • where the boundary markers have been placed (commonly wooden pegs)
  • the distances and bearings between those markers.

When a land transfer CSD is ‘approved’ as to survey, the Registrar-General of Land (RGL) is assured that the CSD correctly shows the extent of the land in relation to previous definitions of the land, and adjacent land. Based on this assurance, the RGL creates a new title and registers dealings in regard to the land. This is done without fear that any of the owner’s land has been omitted or the title inappropriately overlaps with property rights in another person’s land. Under the LTA 2017 the Crown guarantees ownership of the land as marked out on the ground as recorded by this DP. There is no Crown guarantee associated with a boundary defined in a survey office (SO) CSD. That is unless the definition of the boundary from the SO is recorded in the land transfer register (examples are where the SO boundary definition has been subsequently recorded in a DP CSD or where a SO legalisation CSD has resulted in a new record of title).

Under the CPB Act, boundaries are deemed to have moved with the movement of land caused by the Canterbury earthquakes (unless it is a landslip). This does not affect the validity of title for land registered under the LTA 2017. The land in a title will still be the land defined by undisturbed marks placed by the pre-earthquake survey and recorded on the pre-earthquake DP CSD — although the law recognises that where the marks have moved with earthquake movement, the boundaries will have moved accordingly.

The land might be of a different shape and area because of the movement of land and boundary marks. However, the CPB Act makes it clear the movement will not have created new overlaps or gaps that reduce certainty in the boundaries of interests in land and their relation to surrounding interests. In this regard title is still reliable.

As an example, Figure 2 shows the shape of Lot 1 DP 38048 is different because of earthquake movement (reflected by the change in location of the boundary points). The land (as moved) continues to be the same land (Lot 1 DP 38048) and affected by the same interests that existed before the movement. The title CB5B/261 continues as the record of ownership and interests. If further survey work is being undertaken, and the owner of Lot 1 DP 38048 wants a title that reflects the post–earthquake location of their boundaries, they will need to request a new title in terms of a deposited dataset prepared in line with the boundaries moved principle and the CPB Act.

Parcel of land before and after earthquake movement

Figure 2: Parcel of land before and after earthquake movement

Affected boundaries must reflect Canterbury earthquake movement in greater Christchurch

An affected boundary is defined in rule 108 as being a boundary where ground movement has distorted the land in excess of the relevant accuracy tolerances and that has not been subsequently defined by survey and recorded in an approved CSD. The applicable accuracy tolerances are set out in rule 27(1) (boundary points), rule 29(2) (water, water centreline and irregular boundaries), and rule 57 (permanent structure boundaries). Both horizontal and vertical boundaries can be affected by ground movement.

Rule 109(1) stipulates that all affected primary parcel boundaries must be defined by survey and ground marked, if practicable, unless they can be accepted under rule 15.

Rule 109(3) requires that boundaries being defined by survey in greater Christchurch must take into account Canterbury earthquake movement. Section 8 CPB Act confirms that the boundaries within greater Christchurch are deemed to have moved or to move with the movement of land caused by the Canterbury earthquakes, unless the movement was landslip. Where boundaries are identified as affected by Canterbury earthquake movement, then these boundaries must be defined by survey in terms of that movement, unless they can be accepted under rule 15 (r 109(1)).

Some affected boundaries may have changed orientation, been extended, compressed, or changed shape (distorted) as a result of Canterbury earthquake movement. When defining by survey, examples of redefining in terms of ground movement include:

  • the creation of new boundary points, new angles, in a right-line boundary
  • new bends in an irregular or water boundary
  • showing a difference in the shape of a permanent structure boundary
  • redefining the RLs of height-limited boundaries.

The following diagrams illustrate a number of scenarios where Canterbury earthquake movement has distorted existing parcel boundaries.

  • Pecked black line represents the boundary accuracy tolerance allowed by rule 27.
  • Pecked blue line represents the boundary in its pre-earthquake boundary location.
  • Solid blue line represents the old boundary in its post-earthquake boundary location.

Figure 3 below illustrates where the bend in the alignment of a right-line boundary is less than the accuracy tolerances which means it is not an affected boundary. In this example the pre-ground movement dimensions have been retained.

Boundary not affected by earthquake movement

Figure 3: Boundary within tolerances not an ‘affected boundary’

Figure 4 below illustrates an affected boundary where the surveyor has addressed the issue by creating a new boundary angle to reflect the impact of the earthquake ground movement on the boundary.

Affected boundary redefined with new boundary angle

Figure 4: Affected boundary redefined with new boundary angle

Figure 5 below illustrates where the surveyor has redefined an affected boundary to take into account stretching and rotation of the original boundary as witnessed by the new location of the old pre-earthquake boundary mark at the eastern end of the boundary. The movement of an old boundary point outside accuracy tolerances will also affect other boundaries that connect to that point. This is illustrated by the change in shape and location of the two eastern boundaries that ran north and south of the original boundary position.

Affected boundary redefined to account for stretching and rotation

Figure 5: Affected boundary redefined to account for stretching and rotation

Water and water centreline boundaries affected by Canterbury earthquake movement

An affected water boundary that is to be retained in its former position under rule 10(2) or (3), must be accepted (r 109(4)). The affected water boundary does not have to account for erosion and accretion that occurred prior to the ground movement.

Likewise, an affected water centre-line boundary that is to be retained in its former position under rule 11(2) must be accepted (r 109(5).

Where the affected boundaries are accepted under rules 109(4) and (5), the annotation “Boundary not surveyed since ground movement” must be added against the relevant boundary on the title diagram (r 104).

For further information on water and water centreline boundaries see the following guidelines:

New unit title and cross lease developments

If a new unit title or cross lease development is to be created over an existing primary parcel with affected underlying boundaries, then a new underlying parcel must be created before the development can deposit (r 110(4)(a)). All affected boundaries must be defined by survey (r 109(1)).

A new underlying parcel must also be created where any of the affected boundaries of the underlying parcel have already been redefined, but not recorded in the tenure system. An example of this is an affected boundary redefined in a boundary reinstatement Survey Office (SO) CSD.

A new development can be interpreted as where there is no existing unit title/cross lease development or where an existing development has been cancelled.

For registration under the LTA, creating a new underlying parcel requires a Land Transfer (LT) CSD defining the full extents of the underlying parcel. This CSD will need to be approved prior to the unit title/cross lease CSD being submitted.

Defining new non-primary parcel boundaries over affected underlying parcels

The requirements for new non-primary parcel boundaries are specified under rule 110 and only apply if the underlying parcel is not being created by the survey.

Under rule 110(2), an underlying parcel boundary affected by Canterbury earthquake movement with Class A or B boundaries must be defined by survey and marked, if practicable, if a new non-primary boundary coincides with or intersects it.

Note that rules 110(2) and 111 do not apply if the ground movement affecting the underlying parcel boundary is not caused by an earthquake in Canterbury during the period from 4 September 2010 to 13 February 2022. The provisions of rules 110(3) and 51(2) can be applied instead.

For more information see Defining non-primary parcels using the control network.

For registration under the LTA, the redefinition of an affected underlying primary parcel boundary would normally require a LT CSD defining the full extent of the underlying parcel and the issue of a new record of title.

Rule 111(1) provides a concession allowing for the partial redefinition and recording of some of the underlying parcel boundaries on a CSD that defines a non-primary parcel if:

  • the CSD does not include a new underlying parcel
  • the underlying parcel boundary has moved due to Canterbury earthquake movement, and
  • the redefinition of all the boundaries of the underlying parcel is not being recorded in the CSD.

The affected underlying boundaries redefined under rule 110(2), or already redefined in terms of earthquake movement on an approved CSD (including an approved SO CSD), may be recorded in the LT CSD that creates the new non-primary parcel. The deposit of this CSD will create a record of survey of the redefined underlying boundary in the register. The RGL will update the existing record of title to refer to the partial redefinition of the underlying parcel.

For example, a LT CSD may record a new easement parcel as well as the redefinition of an intersected or coincident underlying affected primary parcel boundary.

Rule 111 also applies to land held under other tenure systems, such as Crown land and Māori land. A Survey Office (SO) or Māori Land (ML) CSD would be used as appropriate.

Rule 111(2) sets out the additional information that must be depicted on the title diagram where the CSD records the redefinition of an underlying parcel boundary under rule 111(1).

The diagram must depict:

  • the underlying parcel appellation
  • all redefined underlying boundaries
  • the relationship between a redefined boundary and other underlying parcel boundaries, and
  • the annotation “Redefined boundary of [underlying parcel appellation]” on each redefined boundary.

To ensure users of the CSD are made aware of the two purposes of the survey (the redefined boundary and the new non-primary parcel), the words “and partial redefinition of [underlying parcel appellation]” must be included at the end of the dataset description (r 111(2)(e)).

The dual purpose of the survey should also be included in the survey report for the CSD (r 72(a)).

Figure 6 below illustrates rule 111 and shows:

  • new easement Area A
  • the redefinition of the affected northern boundary of Lot 1 DP 388041, and
  • the prior redefinition of the affected eastern boundary of Lot 1 recorded on SO 435687.
Easement A on Lot 1 DP 388041 and the partial redefinition of Lot 1 DP 388041

Figure 6: Easement A on Lot 1 DP 388041 and the partial redefinition of Lot 1 DP 388041

Figure 7 below shows:

  • new unit parcel PU 5
  • existing units PU 1 to PU 4
  • the redefinition of the affected northern boundary of Lot 1 DP 388041, and
  • the prior redefinition of the affected eastern boundary of Lot 1 recorded on SO 435687.

The western and southern boundaries are not affected.

Complete stage unit plan on Lot 1 DP 388041 and the partial redefinition of Lot 1 DP 388041

Figure 7: Complete stage unit plan on Lot 1 DP 388041 and the partial redefinition of Lot 1 DP 388041

Figure 8 below shows:

  • new cross lease Area 2 and new covenant Area A
  • the redefinition of the affected northern boundary of Lot 1 DP 388041, and
  • the prior redefinition of the affected eastern boundary of lot 1 recorded on SO 435687.

The other boundaries of Lot 1 that are coincident with Area A are not affected.

Area A on Lot 1 DP 388041 and the partial redefinition of Lot 1 DP 388041

Figure 8: Area A on Lot 1 DP 388041 and the partial redefinition of Lot 1 DP 388041

Height-limited boundaries

For height-limited boundaries where there has been uniform uplift or settlement of the ground surface over the full horizontal extent of the height restricted boundary, then the boundary is not an affected boundary. The boundary may have moved either upwards or downwards with the ground movement and any pre-ground movement reduced level (RL) defining the height-limited boundary may be no longer correct. A height-limited boundary may remain unaffected even where it has moved in a vertical direction that is different to vertical movement affecting related PRMs. If a potential RL change to an existing height-limited boundary is identified, then it is suggested advice should be sought from LINZ.

Where height-limited boundaries are recorded on an existing unit development then all reduced levels must be expressed in terms of the previously deposited CSD for the unit title development (r 62). The requirements for referencing a new height restricted boundary point are detailed in rule 61.

If an unofficial datum is used under rule 62(1), then one or more vertical control marks within 1000 m of a new height-limited boundary must be included in the survey (r 18(2)). If no vertical control mark exists within 1000m then a vertical control mark at any distance must be included in the survey (r 18(3)). The vertical control mark used must be provided with a reduced level in terms of the existing unit title development datum.

For further information see the guideline about Permanent reference marks and vertical control marks for height-limited boundaries

Ground marking and occupation information

Rule 109(1) requires each point on an affected primary parcel boundary to marked, if practicable.

A boundary reinstatement survey may be used to mark a boundary point that is on an affected boundary, but it must be a complex boundary reinstatement survey. (r 114(2)(b)).

For further information see the guideline about Complex boundary reinstatement and CSD requirements

An existing boundary mark that is deemed disturbed and no longer marks the boundary may be removed or driven below the surface under rule 37(1). Disturbed survey marks must be treated as a new survey mark. Where a survey mark is removed, the disturbed position must be recorded in the record of survey and survey diagram along with an annotation to indicate the mark has been removed (rr 80(1), (2), (5), 82(a), (b), (c) & 89(b)).

Occupation information in accordance with rule 81(2) must be provided in relation to any affected boundary points that are required to be marked by rule 109(1).

For further information see the guideline about Occupation and physical features

Survey reporting

Rule 6(a) requires a surveyor to 'gather all evidence relevant to the definition of the boundary and its boundary points' when defining a boundary by survey. Rule 72(i) requires information considered in reaching decisions made about defining an existing boundary by survey to be included in the survey report.

Examples of relevant evidence where there has been ground movement may include:

  • the condition of reference and boundary marks and the ground conditions immediately surrounding these marks
  • visible evidence of a fault trace, slump lines, or liquefaction of soils
  • broken or cracked fencing or kerbs or building foundations
  • visible evidence of repair to, or reinstatement of, occupational features damaged by soil liquefaction or fault trace
  • photographic evidence including historical aerial photographs or photographs taken immediately before and after the ground movement event
  • local knowledge from occupiers, neighbours, and present or past owners
  • Local Authority records
  • news media articles
  • engineering reports.

The survey report should include details of the investigations carried out to determine the type and nature of the ground movement. Factors such as historic movement in the locality, soil geology, seismic events, climate events and manmade earthworks could have had an influence on the ground movement.

For further information on reporting see the guideline about Content of a CSD – Survey report

Resources and tools for greater Christchurch

Geotechnical layers provided by the New Zealand Geotechnical database (NZGD) can be displayed in Google Earth to aid the identification of earthquake affected areas of greater Christchurch. This resource can be used to query the observed/measured effects of the earthquakes on Christchurch City and the surrounding areas.

The following layers provide useful information when establishing the effects of the Canterbury earthquakes:

  • liquefaction and lateral spreading
  • property observations Sept 2010, 22 Feb 2011 and 14 Feb 2016
  • observed ground crack locations
  • ground motion
  • Port Hills mass movement

To access the geo-technical data you need to request access to the New Zealand Geotechnical Database from the NZGD administrators.

New Zealand Geotechnical Database

Capture and linking requirements for greater Christchurch

Unproven marks

Unproven marks were permitted on CSDs completed during the interim period to record the location of an old mark that had likely been affected by ground movement and was not being used to define a boundary (r 18.3 RCS 2010). The unproven status of the mark was required to be annotated on the approved interim survey diagram of survey. Unproven marks were no longer permitted in greater Christchurch from 24 April 2017 when rule 20.2 RCS 2010 came into force. This stipulated that rule 18 RCS 2010 could no longer be applied to a cadastral survey in greater Christchurch.

In many cases the unproven mark may have been moved by Canterbury earthquake movement but did not mathematically agree with other surrounding pre-earthquake marks. Subsequent CSDs can re-evaluate the unproven old mark and confirm the mark as being reliable in terms of the CPB Act.

Existing unproven marks can be adopted on later CSDs but new unproven marks are not permitted for all of New Zealand under the CSR 2021.

Disturbed marks and linking

A disturbed mark in greater Christchurch excludes any change in position caused by Canterbury earthquake movement. For a survey mark to be called disturbed, it will need to be disturbed for reasons other than earthquake movement.

If a CSD includes an old mark that has shifted from its pre-earthquake location but is otherwise ‘undisturbed’ then the mark is correctly positioned and is to be linked to the existing node for that mark in Landonline.

Where an old boundary mark is determined as no longer correctly marking a boundary point, it is to be treated as a new non-boundary mark and not linked to any existing node.

A geodetic mark may have several post-earthquake nodes in Landonline. Newly measured observations should be linked to the most recent ‘disturbed’ mark.

Mark naming and linking

The following practices are to be used when recording and linking un-disturbed old marks, disturbed old marks, and adopted marks in greater Christchurch.

Un-disturbed old mark

Original survey mark name retained

Linking - Two options:

a) Preferred - Link to the corresponding original pre-earthquake node, even if there is a post-earthquake unproven node or approved interim survey disturbed node for the mark.

Un-disturbed old survey mark

Figure 9: Un-disturbed old survey mark

b) Prior linking practices have resulted in original pre-earthquake nodes being renamed with the unproven tag. Linking to these nodes will reinstate the original survey mark name.

Node with unproven tag

Figure 10: Node with unproven tag

Disturbed old mark

Two scenarios:

1. Old survey mark not previously deemed disturbed

New mark name assigned

Linking – Two options:

a) Only one node - Do not link.

Old survey mark deemed disturbed for the first time

Figure 11: Old survey mark deemed disturbed for the first time

b) Two nodes (i.e. original pre-earthquake and post-earthquake unproven) - Link to post-earthquake unproven node.

No further disturbance since unproven mark’s position observed

Figure 12: No further disturbance since unproven mark’s position observed

2. Old survey mark was found physically disturbed, and renamed, by approved interim survey

Approved interim survey mark name retained

Linking:

Link to approved interim survey disturbed mark node provided the mark has not been further disturbed by events other than earthquakes.

No further disturbance (except due to earthquakes) to observed mark position since found physically disturbed by approved interim survey (SO 488999)

Figure 13: No further disturbance (except due to earthquakes) to observed mark position since found physically disturbed by approved interim survey (SO 488999)

Adopted mark

Three scenarios:

1. Un-disturbed survey mark adopted

Original survey mark name retained

Linking - Two options:

a) Only one node (with or without unproven tag) – Link.

Only one node in Landonline

Figure 14: Only one node in Landonline

b) Two nodes (i.e. original pre-earthquake and post-earthquake unproven) - Link to original pre-earthquake node if an approved post-earthquake survey has deemed the mark to be un-disturbed.

Approved interim survey disturbed mark deemed un-disturbed by approved post-earthquake survey

Figure 15: Approved interim survey disturbed mark deemed un-disturbed by approved post-earthquake survey

2. Approved interim survey ‘disturbed’ mark adopted

Original survey mark name retained if a prior approved post-earthquake survey has deemed the survey mark to be un-disturbed

Linking - Two options:

a) An approved post-earthquake survey has deemed survey mark un-disturbed – Link to original pre-earthquake node.

Approved interim survey ‘disturbed’ mark deemed un-disturbed by approved post-earthquake survey

Figure 16: Approved interim survey ‘disturbed’ mark deemed un-disturbed by approved post-earthquake survey

b) Otherwise, the survey practice in use when the source survey was approved will determine which node to link to.

3. Unproven survey mark adopted

Unproven survey mark name retained

Linking:

Post-earthquake adoption source survey refers to the unproven mark and the new survey is not using this adopted mark for definition purposes – Link to unproven node.

Adopted unproven mark not used for definition

Figure 17: Adopted unproven mark not used for definition

Boundary conflicts in greater Christchurch resulting from approved interim surveys

Section 9 CPB Act recognises that some approved interim surveys did not define existing boundaries in terms of Canterbury earthquake movement, resulting in boundary conflicts.

For further information see Guidance for surveyors on boundary conflicts in greater Christchurch

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