PSI Ground Motion in Northumberland and Durham, UK · 2021. 5. 25. · Northumberland: PSI data used in the study •Processed by FugroNPA Ltd •ERS descending PSI data (1995 –

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Terrafirma: a Pan-European Terrain motion hazard information service

www.terrafirma.eu.com

PSI Ground Motion in Northumberland and Durham, UK

Luke Bateson and David Lawrence, BGS.

Harry McCormack and Richard Burren, FNPA.

[email protected]

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Terrafirma: A Pan-European Terrain Motion Hazard Information Service

Outline

• Introduction to the area of interest

• The PS data used in the study

• Interpretation case studies – ERS PSI

• Difference between ERS and Envisat PSI

• Interpretation of Envisat motions

• Conclusions

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Introduction to the area of interest – Location

• Long history of coal mining

• Dating back to Roman times

• Last active mine closed in 2005

• 20+ coal seams mined underground

• Extensive opencast mining

• Working of deeper coal led to the need to pump mine water

• Recent years – reduction in pumping and recovery of mine water levels

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Introduction to the area of interest – Bedrock Geology

• Oldest Strata; Stainmore formation in NW

• Youngest Strata; Zechestein Group in SE

• Coal measures; Mudstones, Ironstones, Sandstones and Coal

• Coal measures dip to the east (<10°)

• Faults within the Coal Measures

• Typical displacements 25 m or less

• can be up to 170m

1:625 000 Scale 1:50 000 Scale

Northern England thloeiitic Dyke-swarm

Mull Dyke-swarm

Roker Formation

Ford Formation - Reef

Ford Formation

Seaham Formation

Yellow Sand Formation

Pennine Upper Coal Measures

Sandstone in Pennine Upper Coal Measures

Pennine Middle Coal Measures

Sandstone in Pennine Middle Coal Measures

Pennine Lower Coal Measures

Stainmore Formation

Igneous rocks

Sedimentary rocks

Carboniferous

Permian

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Northumberland: PSI data used in the study

• Processed by FugroNPA Ltd

• ERS descending PSI data (1995 – 2000)

• 50 ERS scenes

• 19 April 1995 to 14th December 2000

• 115 555PS points identified

• Overall average annual motion of +0.407mm/yr

• ENVISAT descending PSI data (2002 – 2008)

• 21 ENVISAT scenes

• 3rd December 2002 to the 7th October 2008

• 71899 PS points identified

• Overall average annual motion rate of +2.47mm/yr

• ERS Ascending DifSAR data (1992 – 2000)

• ENVISAT Ascending DifSAR data (2002 – 2009)

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ERS / Envisat PSI Results

ERS descending PSI: 1995 - 2000

Envisat descending PSI: 2002 - 2008

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MOTION RELATING TO FAULTING

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Comparison of ERS PSI with major faults

• Motion appears to be constrained by the faulting

• Faults are accommodating motion caused by another factor.

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Comparison of Envisat PSI with major faults

• Envisat motion and major faults

• Fewer areas of motion now appear to be constrained by the faulting

• A more regional explanation for the uplift to the south of Newcastle?

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TEAM VALLEY

Case Study…….Compressible sediments

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Compressible sediments in the Team Valley

ERS 1995 – 2000 Building weight causes

compression

ENVISAT 2002 – 2008 Influx of water causes uplift?

Cyclical shrink

swell trend?

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Compressible sediments in the Team Valley

ERS 1995 – 2000Building weight causes

compression

• Deep in-filled valley• Loading of ground• Sealing of ground• Possible pumping• Lead to ‘drying out’ of sediments

A A

A

B

B

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HOUGHTON-LE-SPRING

ERS Motion - Case Study……..Mining related subsidence or water abstraction?

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Houghton-Le-Spring

• Complex subsidence pattern shown in the ERS data

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Houghton-Le-Spring

• Field observations of cavities and fissures in Houghton-le-Spring (purple stars and red lines)

• PSI shows differential motion across fault

• Field observations show fissures and cavities opening due to motion associated with the fault

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Northumberland: Value added product results

Houghton-Le-Spring

• Mine abandonment plans:

• area worked until 1981,

• mining was pillar and stall

• areas of underground water

• Did a combination of

these lead to motion,

which was accommodated

by the faults?

Approximate line of fissures on previous slide

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SITES OF ABANDONED MINING

Case Studies

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Ryhope Colliery (ERS 95-2000) – Non-linear subsidence

1859 - 1966

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Envisat PSI Motions

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Northumberland: Overall change between processing periods

ERS 1995-2000

• Differences confirmed by DifSAR and separate PSI and SBAS studies

• Overall change

• Most subsiding areas in 95-00 are uplifting in 02-08

• Dramatic change mainly related to mine water pumping regimes

ENVISAT 2002-2008

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Northumberland: Overall change between processing periods

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Mine Water Recovery - Envisat

Westoe minewater

monitoring point

Boldon

minewater

monitoring

point

Wearmouth

minewater

monitoring point

Minewater recovery

blocks

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Conclusions

• PSI ground motion is related to:

• Thickness of superficial deposits

• Fault locations

• Ground water pumping and minewater recovery

• Spatial association to abandoned mines – but no temporal association

• Envisat PSI does not detect small scale motions related to pillar collapse

• but no PSI directly over the area of motion and slight discrepancy in dates

• Subsidence seen in ERS data is likely to be a result of the complex relationship between

1. pumping of the ground water to prevent flooding of mine workings

2. general groundwater abstraction

3. accommodation of motion by the faults, fissures and joints in the area.

Documents

PSI Ground Motion in Northumberland and Durham, UK · 2021. 5. 25. · Northumberland: PSI data used in the study •Processed by FugroNPA Ltd •ERS descending PSI data (1995 –